CHAPTER II REVIEW OF LITERATURE Although the scope of the present study is limited to the evaluation of the field performance of selected F 1 hybrid progenies of arabica coffee and molecular characterization of few interspecific hybrids, an exhaustive review has been made covering all important aspects related to coffee crop, a journey since its detection as a stimulating beverage to its current economic significance both in producing as well as consuming countries, in order to present a comprehensive status of research on coffee. 2.1. Coffee legendry and origin Human settlement in Ethiopia is very ancient; some of the earliest ancestors of the human species have been discovered here. Most of the commercially cultivated species of coffees have originated in the Abyssinian region of Ethiopia. There was a custom using coffee seeds as symbol of brother-hood that signified the blood relation among the community. People observed that two seeds present in the coffee fruit were of the same size and shape and tightly bound by the outer coating of the fruit and perhaps for this reason, they intended to shape their custom in similar fashion. Often, people leaving on strenuous and extensive journey carry some coffee beans (seeds) so that it could be chewed when felt tired and thirsty. Africans were not used to plant coffee for their own purpose with their own hands, instead the visitors to their place were requested to perform this task as a sign of close companionship and high regard (Haarar, 1956). There are several species of coffee grown in Africa but how coffee reached Arab is uncertain. In Arab, coffee plant was introduced as a garden plant at higher altitudes possibly due to attraction of its scented flowers by the Arabian kings. Coffee grown in Arabia later, became popular with the name Arabica that had the morphological features totally different from that grown in Abyssinia (in Africa). The wild plant of Coffea arabica was first 10
discovered during 850AD as an indigenous coffee species of Ethiopia and it was found in cultivation in Arabian colony of Harar. As per the Chevalier publication (1929) it is believed that the Arabian coffee first began its cultivation in Arabia during the fourteenth century. Even, up to the beginning of the seventeenth century nowhere, in the world Arabica coffee was under cultivation. Between 15 th and 16 th century, coffee was used in the form of beverages prepared through extraction from ripe fruits and roasted beans were realized by the Arabians. Coffee was called as Kahwa or Kahwe in Arabia. It is said that the preparation and consumption of Coffee liquor by roasting and grinding of beans first started in Persia the neighboring country of Arabia. Later, coffee spread to many parts of the world for commercial cultivation. It is whispered that again from Arabia coffee was introduced to Ethiopia and became popular as Arabica coffee and later classified as C. arabica (Clifford, 1985). 2.2 The spiritual affinity of coffee Coffee was discovered when a shepherd named Kaladi noticed the dramatic actions of his goats that after eating berries of the bush situated nearby a Monastery on the bank of Red Sea they became excited and started prancing. This stimulating power of the berries in the goatherd was curiously observed by a Priest of the Monastery. He collected some fruits of that plant and prepared a beverage out of those fruits after roasting. He served the liquor to his brethren. This resulted in keeping them more vigilant as well as spick and span during the night prayer. In another instance, a priest Ali Bin Omer who was exiled to the hills of the Yemen realized the stimulating effect of the decoction prepared from the beans of the plant which had white and fragrant flowers. He carried the seeds of the plant with him on the pilgrimage to Mecca and treated some pilgrims suffering from a spate of prickle. For this noble cause, Ali Bin Omer was privileged with the better position as the patron saint (Clifford, 1985). 11
The ancient legend indicates that coffee was introduced by Prophet Mohammed when he was ailing, he prayed to Allah. The angel Gabriel descended there along with Holy Koran and a beverage as black as Kaaba of Mecca. The beverage gave him enormous strength and recovery from illness. Although no documentary proof is available on introduction of coffee to Arabia, a conversation written by an Arabian Sheikh in 1566 reports that a Mollah named Djmaleddin Abou Elfrager introduced coffee into Arabia from Abyssinia during 15 th Century. In India too, coffee was introduced by Baba Budan hailing from Chikmagalur district of Karnataka. Whilehe was on a pilgrimage to Mecca, he brought seven seeds of coffee wrapped around his belly to India and sowed these seeds near his cottage in Chikmagalur. Later, the plants raised out of these seven seeds gradually took the shape of coffee plantations in India. (Lakshmi, 2004). Keeping in view the above legends, one can assume that the coffee of the recent days is not merely an ordinary coffee instead a Sacred Coffee Seed that has tied the several countries in one knot of unity for its cultivation, promotion and consumption so as to lead on the path of prosperity and happiness. 2.3. Botanical classification Classification: Kingdom: Division: Class: Order: Family: Genus: Species: Plantae Tracheophyta Magnoliopsida Gentianales Rubiaceae Coffea arabica, canephora, liberica and several others belonging to genus Coffea Binomial Name: Coffea arabica L. 12
2.4. Coffea species: Coffee belongs to the botanical family Rubiaceae, which has some 500 genera and over 6,000 species. Most are tropical trees and shrubs which grow in the lower storey of forests. Other members of the family include the gardenias and plants which yield quinine and other useful substances, but Coffea is by far the most important member of the family having economic significance. The genus Coffea consists of between 25 and 100 species that have a tropical distribution within Africa and Madagascar, including many of the adjacent Indian Ocean islands. Based on the Chevalier (1947) taxonomic work, there are 65 species but among these 24 are placed in other genera. The attempts were made by the several workers to classify genus Coffea based ondistinct phenotypic characteristicssuch as bush size, leaf area, flower numbers, fruit size and color, seed size and shape. Cramer (1957) studied the genus Coffea for several years and could identify about 100 true species and some more species were expected to be present. Charrier (1978) listed 56 species available in Madagascar and Mascarenes. Among these, few were not with distinct characters and commented that the true members of genus Coffea were not found in outside Africa, Madagascar and Mascarenes. There are only three economically important cultivated coffee species: Coffea arabica L; Coffea canephora Pierre ex. Froehn and Coffea liberica Bull ex. Hiern,. In its wild state the coffee bush is an evergreen shrub 8-10 m high, with small white flowers that have a strong jasmine-like scent. There are several genotypic and phenotypic dissimilarities in C. arabica and C. canephora which differentiate these two commercially cultivated species from each other (Clifford, 1985) as shown below. 13
Important characteristic features of arabica and robusta coffee Characters Arabica Robusta Year of species description 1753 1895 Chromosomes (2n) 44 22 Time required for ripening after flowering 9 months 10-11 months Blossom after rain irregular Rain affected ripe fruits fall stay Yield (kg beans/ha) 1500-3000 2300-4000 Root system deep shallow Pollination Self-pollinated Cross-compatible Optimum annual temperature 15-24 C 24-30 C Optimal rainfall 1500-2000 mm 2000-3000 mm Growth optimum 1000-2000 m 0-700 m Hemileia vastatrix susceptible resistant Koleroga susceptible tolerant Nematodes susceptible resistant Tracheomycosis resistant susceptible Coffee berry disease susceptible resistant Caffeine content of beans 0.8-1.4% 1.7-4.0% Size of bean bold smaller Liquor characteristics superior quality inferior in taste Since, Coffea was first correctly described, by Linnaeus in the mid 18th century, some botanists have failed to agree on a precise classification system. Accuracy in the number of species in the genus is still contentious because, some of discrepancies arose in species description during 20 th century (Charrier and Eskes, 2004). There are at least 25 major species, probably, all indigenous to tropical Africa and certain islands in the Indian Ocean, notably Madagascar. Difficulties in classification and in designation of a plant as a true member of the Coffea genus arise because of the great variation in the plants and seeds. All 14
species of Coffea are woody, but they range from small shrubs to large trees over 10 metres tall; the leaves can be yellowish, dark green, bronze or tinged with purple (Wrigley, 1988). The comprehensive work done on classification of the world coffees by the Chevalier (1940, 1942, 1947) was highly recognized and followed. The entire genus Coffea he subdivided into four sections namely; Paracoffea, Argocoffea, Mascarocoffea and Eucoffea. 2.5. Plant morphology and growth habit Coffee is a perennial bush with evergreen foliage, glossy appearance. The main stem is hard and vertically growing along with two vegetative buds on each internode situated in opposite direction. These buds lie in the leaf axils and give rise to horizontal shoot growth (Plagiotropic shoots) called primary branches. Primary branches produce secondary and then tertiary and lateral branches. There are three types of branches based on its angle of projection from the main stem namely; erect, semi-erect and drooping type. The plants with erect branching habit develop spreading type vigorous bushes whereas, drooping type branches on the plants produce compact bushes that occupy lesser area than the spreading ones. The plants with semi-erect type branching pattern are ideal for commercial cultivation. In addition to this, some shoots arise from the main stem of the coffee plant and grow vertically; they are termed as suckers (Orthotropic shoots) and capable of forming a new bush by producing primary and secondary branches. In general, these types of shoots are removed at early stage of growth to reduce the loss of nutrients through these suckers. The orthotropic shoots are also utilized for vegetative propagation. 2.6. Cultivated species of Coffea The two species of Coffea with economic importance are Coffea arabica L. (Arabica coffee) which accounts for over 70% of world production and Coffea canephora Pierre ex Froehner (Robusta coffee). Other species grown on a much smaller scale are Coffea liberica Bull ex Hiern (Liberica coffee), Coffea dewevrei De Wild.(Excelsa coffee) and 15
Coffea abeokutae Cramer. Apart from the species, there are several others which come under genus Coffea with diploid behaviour and possessing valuable traits of low caffeine content, drought hardiness, nematode resistance and good cup quality. These characters can preferably be exploited in coffee breeding (Haarer, 1962) 2.7. Coffea arabica - Arabica coffee Coffea arabica was first described by Linnaeus in 1753. The best known varieties are 'Typica' and 'Bourbon'. Many different strains and cultivars have evolved from these lines such as Caturra (Brazil, Colombia), Mundo Novo (Brazil), Tipo (Central America), dwarf San Ramon and the Jamaican Blue Mountain. It is a species of self-fertile nature and often produces true breeding lines through single plant selection and multiplication (Van der Vossen, 2000). Arabica species produces the plants having large bush with dark-green foliage comparatively smaller than robusta variety. Having four sets of chromosomes, it is genetically different from other coffee species which contain two sets. Coffea arabica prefers higher altitudes ranging from 500-2500MSL for considerably vigorous plant growth, higher yield potential and superior bean and cup quality as compared to the varieties grown at lower elevation (Willson, 1999). Arabica being an allotetraploid (2n=44) with inbreeding behavior produces compact bush, grey to light brown bark, abundant branches laden with dark green foliage.the sweet-scented pentamerous flowers are associated with white color tendency of corolla. Blossom in arabica generally occurs within 9-10 days after the receipt of blossom showers and sets round or oblong shaped fruits of 10-12 numbers per cluster. There are two flat seeds so called the coffee beans and mature in 7 to 9 months. In some cases instead of two flat beans only one bean develops and forms single oval shape seed termed as a peaberry (Wintngens, 2004). Saikia and Srinivasan(1992) selected seven cultivars of arabica coffee at four different locations in North-Eastern region to study the fruit abnormality pattern. No significant 16
difference was noticed between the cultivars for the fruits containing peaberry while, variation between the location and year of observation for all the four parameters on fruits was recorded. Amaravenmathy and Srinivasan, (2007) studied the fertility status in thirty five new arabica accessions established at CRSS, Chettalli, Kodagu, Karnataka by collecting the fruit samples randomly from the field. The results indicated low fruit abnormality ranging from 0-8 percent in most of the accessions while highest of 21.4 percent was observed in Tafarikela variety. Often, bearing in arabica begins from 3 rd to 4 th year after planting in the field and after 5-7 years the crop is stabilized in normal course. Caffeine content in the range of 0.5 percent to 1.8 percent has been observed in arabica. In general, the cup quality of arabica is better than any other commercially grown coffee species (Wrigley, 1988). Arabica coffee is usually prone to attack of pests and diseases; therefore, introgression of resistant genes is a major goal of plant breeding programmers. It is grown throughout Latin America, in Central and East Africa, in India and to some extent in Indonesia (Clifford, 1985). 2.8. Coffea canephora - Robusta coffee Coffea canephora is regarded as a species of low lying areas that is suited for elevations in 1000MSL at an latitude of 10 N and 10 S of equator (Willson, 1999). Warm temperature and high level of humidity is believed to be the ideal environmental requirement for good growth and production but is prone to adverse effect in cold conditions (Illy and Viani, 1995). Robusta coffee is said to be the native of Belgian Congo and in 1895, it was collected by Emile Laurent from the basin of Congo River and studied thereafter, it was named by Pierre in 1897 (Wrigley, 1988). The term 'robusta' is actually the name of a widely grown variety of this species with robust plant growth. It is one of the diploid species available in the form of a shrub or small 17
tree that grows up to 10 meters in height, with a shallow root system and characterized by its thick stem, large-pale-green leaves present on thick primary and secondary branches. Flowers are produced in axils of the leaves and bloom as white-scented and pentamerous flowers in a cluster of 40-60 numbers, even higher on 7 th to 8 th day of blossom rain during summer season (Shanmugavellu et al., 2002). It sets the fruits due to cross-pollination of the flowers from the other plants having compatible pollens. The fruits are rounded and take up to 11 months to mature; the seeds are oval in shape and smaller than those of C. arabica (Anonymous, 2000). The inferior liquor quality and higher caffeine level in the beans as compared to arabica are some of the distinct characteristics of robusta (Wrigley, 1988). The resistance to the major insect-pest (white stem borer) and diseases (coffee leaf rust) is one of the desirable features being utilized in coffee breeding. Robusta coffee is grown in West and Central Africa, throughout South-East Asia and to some extent in Brazil, where it is known as Conillon (Van der Vossen, 2000). 2.9. Coffea liberica - Liberica coffee Liberica coffee grows as a strong tree, up to 18 metres in height, with large leathery leaves. The fruits and seeds (beans) are also bigger in size than the robusta or arabica beans.. Liberica coffee is grown in Malaysia and in West Africa, but only very small quantities are traded as its flavour characteristics is low (Wrigley, 1988). Liberica readily hybridizes with C.arabica and the hybrids so generated are found to produce superior quality of coffee. It has also the ability to cross with C. dewevrei of excelsa group and C. canephora (Haarer, 1956). Several other wild species of Coffea are used locally and have significance in coffee improvement by crossbreeding. These include Coffea eugenioides, Coffea bengalensis Roxb., Coffea dewevrei De Wild. & Durand. (excelsa coffee),coffea racemosa Lour. (inhambane coffee), Coffea stenophylla G. Don (Leone coffee) and Coffea zanguebariae Lour. (Zanzibar coffee). Coffea congensis Froehn. is a distinct species originated from the rain forests of 18
Central Africa and morphologically resembles C. arabica and C. canephora. Fruits are smaller in size with protruded navel and good cup quality characters. This species is being utilized in breeding by several coffee producing counties to produce congensis x robusta hybrids (Congusta variety) for commercial cultivation (Srinivasan, 1996 and Srinivasan et al., 1999). 2.10. Genetic diversity The investigation on genetic relationships of the Coffea species was confined to Erythrocoffea. Thereafter, more emphasis was given to the studies related to cross-ability and chromosomal homology among the Coffea species especially in Brazil (Carvalho and Monaco, 1968), India (Vishveshwara, 1975), Madagascar (Charrier, 1978) and in Ivory Coast (Capot, 1972 and Louarn, 1982). Very recently, coffee scientists have shown more interest to establish the facts about coffee evolution by studying biochemical and serological relation of coffee taxa using biotechnological tools (Lashermes, 1995, 2000). The considerable amount of variation has been recorded within the genus Coffea The maternal effect has been observed to be very significant between the species for the period between flowering and fruit ripening. Crossing the species within one group of Coffea was found easier when C. canephora and C. congensis belonging to the same subsection Erythrocoffea were used in the crosses. Similarly, a good result was anticipated from the crosses between C. liberica and C. eugenioides evenly, between C. dewevrei and C. stenophylla. Beside this, the other species Psilanthopsis kapakata is compatible with C. canephora and C. eugenioides. Success rate has been much better when C. eugenioides was crossed with all the diploid species than with C. canephora (Carvalho and Monaco, 1967). The F 1 hybrids derived from the crosses of diploid species were found to have significant correlation between 11 bivalents chromosomes and fertility. C. canephora and 19
C. congensis exhibited normal chromosomal pairing and good fertility in the hybrid progeny in spite of their morphological and ecological differences. Genetically divergent population was thought to be the result of effective geographical isolation caused by genetic drift and selection pressure. In East African coffee too similar trend was observed (Leroy, 1982;Hamon et al., 1984). In another case, C. canephora, C. liberica and C. eugenioides exhibited genetic divergence in partial congruity. The F 1 hybrids of these three species indicated reduction in chromosome pairing during meiosis and 40-50 percent of the pollen mother cells had eleven bivalents. Apart from this, the genetic effect was apparent on the chromosome pairing and hybrid fertility with inter-specific crosses of C. liberica x C. canephora (Louarn, 1980). The Mascarocoffea series also showed the same level of genetic divergence. A large variation was noticed in the weak and sterile F 1 hybrids of C. canephora and section of Mascarocoffea. The situation was quite different in case of C. eugenioides that generated considerably higher number of fertile F 1 progeny. Furat & Uzun(2010) estimated agro-morphological variation in 103 landraces of sesame germplasm using 21 morphologic and agronomic descriptors for characterization and identification of genetic diversity in Turkey. Seventeen morphologic and agronomic traits exhibited high degree of variation while, four characters namely; branching pattern, flower color, shattering and indeterminate growth habit were found to be monomorphic. The characters such as days to emergence, flowering and capsule initiation and seed yield were the major determinants of the genetic diversity in the collection. Cluster analysis indicated that diversity in agro-morphological characters could mainly be due to varied agro-climatic conditions. 20
2.11. Coffee cytology Cytology is the science of living cells that deals with the composition of somatic cell, its components and functions and decides the quantum, quality and mode of transmission of somatic substances from the parents to the progeny. Coffee is the plant that is highly sensitive to the environmental changes and possesses the ability to withstand adverse circumstances. Beside the prominent attributes of the genus Coffea for huge range of morphological variation between the species, there is wide adaptability to the various environmental situations (Wrigley, 1988). The basic investigations on coffee genetics have been carried out at Institute of Agronomy, Campinas, Sao Paulo, Brazil since 1933 by Krug, Carvalho and Mendes with 25 varieties belonging to genus Coffea. Their cytological examination confirmed that C. arabica was an allotetraploid (2n=44) chromosomes while most other species are diploid (2n=22). The study also revealed that the other form of C. arabica bullata had two type of plants containing 66 and 88 chromosomes respectively (Krug, 1936) and C. arabica monosperma was a diploid or di haploid material with 2n=22. These are sterile forms of coffee regenerated due to abnormal meiosis otherwise, commercially cultivated varieties of arabica have 2n=44 chromosomes (Mendes and Bacchi, 1940). Krug, (1937) and Mendes, (1946) the evolution of these forms of arabica either because of fusion of unreduced gametes or doubling of chromosome numbers. In India, these Bullata and Monosperma types of plants have been exposed by many research workers (Narasimhaswamy1946), Vishveshwara, 1960 and Chinnappa, 1969). To study the fertility status in arabica, Taschdjian used the mutant pupurascens as genetic indicator and recorded 39-93 percent cross pollination in the hybrid population and concluded that the Arabica coffee was allogamous despite its self-fertile behavior. In contrast to this, Krug and Carvalho (1949) achieved 7-9 percent cross-ability in arabica by using 21
cera mutant with yellow endosperm. As far as diploid species are concerned, all are selfsterile and pollinated mainly by wind and insects (Haarer, 1956). In a study on frequency of polyploids in Coffea arabica, Sreenivasan et al., (1981) examined 21,394 plants of cultivars S.795 and S.1934 and found the rarity of dihaploids and octoploids than hexaploids in S.1934 while, the occurrence of Bullata form in S.795 was a frequent phenomenon. Further, the fruit set in these plants was few or completely absent except one plant of hexaploid. Bullata type plants showed greater variability in the size of pollen grains. Leaves of these plants exhibited lesser number of stomata as compared to the normal tetraploid arabica. A cytological test of some plants of F 1 generation of S.1156 developed by back crossing of C. robusta x C. arabica indicated the presence of aneuploids that had normal flowering but no fruit set. These plants were nullisomic (2n=42), monosomic (2n=43) and trisomic (2n=45). Abnormal meiosis that exhibited presence of multivalent, univalents and irregular division of chromosomes during anaphase was supposed to produce anomalous pollen in the plants. A few counterparts of tetraploid plants were observed to have 22 chromosomes (dihaploids) resembles phenotypically normal arabica plants with little disparity in bush size, stem girth and leaf area. These aneuploid plants had higher intensity of stainable pollen but abortive to set fruit (Sreenivasan, 1981). Cruz (1975) described eight forms of monosomic plants in two cases of arabica var. Mundo Novo in which one was like normal type. Sreenivasan, (1981) studied the meiotic indices in eleven diploid species of Coffea and observed very uniform and gradual process of meiosis in majority of the cases under laboratory conditions except for erratic meiosis in one case. Under induced conditions, meiotic behavior was gradual and normal in most of species tested except in C. liberica in which a rapid completion of meiotic process was observed 22
under natural conditions. In C. stenophylla this process was almost similar under both conditions. 2.12. Coffee genetics Genetic analysis of thirty mutants of C. arabica indicated that majority of mutants developed spontaneously due to the involvement of one or more genetic factors. Krug (1937), identified three mutants in C. arabica called Bullata in two forms namely; hexaploid (2n=66) and octoploid (2n=88) but both had poor fruit set due to abnormal fertility behavior. Thick and broader leaves were observed to be the main morphological features of these plants. The other mutant Monosperma a diploid mutant in arabica (2n=22) is commonly apparent in both the varieties of arabica, Typica and Bourbon and poor yielder with single bean in a fruit. It produces narrow and thin leaves which vary from normal tetraploid arabica. Leaves of these arabica mutants showed inverse correlation between the chromosome number and stomatal counts per unit area (Franco, 1939). The study carried out by Mendes (1949) suggested that rarity of the occurrence of unreduced gametes could be the probable cause for the evolution of cultivar Bullata type of coffee while the emergence of diploid cultivar Monosperma might be because of occasional partheno-genetic development of a normal reduced egg-cell in the plant. A case of branch mutation has been noticed in Brazil where, tetraploid plant produced the branch of octoploid mutant and diploid plant had a branch of tetraploid mutant (Krug, 1951). The genetic relationship between the mutants derived from Arabian coffee and the varieties arabica (typica) along with bourbon were ascertained after studying the progenies generated by crossing the mutants with var. typica and bourbon. The crosses of var. arabica with murta and nana mutants revealed the genetic constitution of var. arabica. The F 1 generated by crossing nana with var. arabica was normal and F 2 developed by selfing F 1 plants exhibited different types of plants grouped as arabica, bourbon, nana and a new type 23
murta plants with broader leaves. Assuming the dominant genes AA carried by var. arabica besides NaNa genes and aa (nana) double recessive genes inherited by nana type plants, it was expected to get the plants with Aa Nana genotype in F 1 and in F 2 the plants with genotype AA nana (normal plants with larger leaves), Aa nana ( murta type with large leaves) and aa nana (dwarf types) in the ratio of 1:2:1. Based on the above findings, Krug and Carvalho (1951), differentiated the var. typica and bourbon and confirmed var. typica with dominant alleles AA and bourbon with double recessive aa. They also suggested the grouping of arabica species based on the presence of AA and aa genes carried by the plants and use of tt for bourbon and TT for typica varieties. They stated that the mutants such as Caturra, Semperflorence, Laurina and others as the mutated forms of variety bourbon while Maragogipe, cera, Goiba, Calycanthema and other mutants evolved from variety typica of C. arabica. Even, Arabian coffee Mocha or Mokha originated from C. arabica in the cultivated field in Yemen region of Southern Arabia. Mendes (1950) recorded more number of mutants in C. arabica than C. canephora perhaps due to self fertile nature of this species. In C.arabica the chances of emergence of mutants was higher due to theself fertile nature of the variety. There are several arabica mutants possessing different kinds of morphological traits namely; leaf shape and color, growth habit, flower, fruit and seed characters. Some more mutants reported (Carvalho, 1951; Sybenga, 1960 and Cramer, 1959) are mentioned as follows: Angutifolia (recessive gene, ag): A mutant of C.arabica it is characterized by narrow, elongated and thicker leaves with narrow angle at the base, less conspicuous veins, generally without domatia. Poor growth, open bush with few fruits is also some of the characters of this mutant. Bronze (incomplete dominant gene, Br): The presence of this gene causes bronze color leaf-tip at young stage and the leaves become normal green later. This is one of the 24
characteristics of C. arabica var. arabica (typica). This gene Br is dominant over the recessive gene br noticed in var. bourbon. Variety bourbon is characterized by green color of young leaf tip due to the presence of brbr genes (Krug and Carvalho, 1942). Caturra (dominant gene, Ct): The mutant from var. bourbon was reported in the State of Minas Gerais in Brazil (Krug and Carvalho, 1951) and characterized by dwarf bush having shorter internodes and comparatively larger and dark green foliage than the var. bourbon. It has complete dominance over tall type bush and governed by Ct gene. Caturra mutant is an early bearer and high yielder with greater commercial value. Due to its high yield potential and precocious bearing habit, the plants lead to the exhaustion and leaf rust attack. This mutant produces two types of plants one is Caturra Vermelho with red fruits and other Caturra Amarello with yellow fruit color at ripening. Caturra Amarello was crossed with Mundo Novo in Brazil to develop Catuai a popular cultivar being commercially cultivated. Catuai breeds two types of plants that are having red and yellow fruits. The red color of the fruits is governed by the dominant gene while, yellow color is exhibited by the recessive gene. Columnaris: The mutant grows taller with vigorous vegetative growth than normal arabica plants. Retention of lower branches and uniform bush spread from top to bottom are the main features of Columnaris mutant. It produces light green and broad foliage as compared to arabica. Shoots at the beginning of the internodes have broader leaves and gradually, leaf size reduces towards the growing tip of the shoot. The flowers and fruits are slightly larger than the other arabica cultivars. The bushes are more suitable for lower elevations. This was spotted in East Java during 1898 and studied for the genetic behaviour of the mutant. Erecta (dominant, Er): This mutant is characterized by the production of plagiotropic branches at a narrow angle of 25 from the main stem instead of 60 as generally noticed in 25
other arabica cultivars. The branches with crop also show tendency of being erect. Though the plants are low yielders but have higher resistance towards wind breakage. Laurina (recessive, lr): This is the mutant of bourbon origin and develops a small conical shape bush with light green small leaves that differs from other arabica varieties. Somewhat pointed seeds produced from pear-shaped fruits have ability of competence for excellent quality. It seems to be a drought tolerant material with a potential to yield a good crop under favorable conditions. Maragogipe (dominant, Mg): The important characters of this mutant were first noticed in a private plantation of Maragogipe province in Bahia State, Brazil during 1870. Extraordinarily larger size of beans, flowers, fruits and long internodes with broader leaves are the important genetic traits of the mutant. The plant with homozygous genotype MgMg alleles is a shy bearer but in heterozygous condition with Mgmg genotype, it bears reasonably better. The bluish green beans of Maragogipe mutant fetches better premium for its excellent quality and make the growers profitable even with its low yielding behavior. Mokka (recessive, mo): The mutant Mokka is a very old and popular variety that was into trade for long time. It is believed to be the native of Mokka but with some uncertainty about it origin. The morphological and yield characters vary significantly from those of arabica cultivars cultivated worldwide. Compact and conical shaped bush habit with smaller and elliptical leaves, short internodes, smallest fruits and seeds are the vital characters of this mutant. It is a low yielder. The mutant is controlled by two sets of mutagens, one is Laurina lr other one Mokka mo. Laurina is complete recessive while Mokka has incomplete dominance. True Mokka possesses the genetic constitution with lrlr momo genes and has a close affinity with Laurina mutant with lrlr MoMo genotype (Krug and Carvalho, 1951). Purpurascens (recessive, pr): This mutant is commonly available in most of the coffee growing countries with its dark purple new leaves which changes the color to deep green or 26
purple-green at maturity. Plant produces purple color flowers with reduced calyx, few fruits with green endosperm and branches with short internodes. San Ramon (dominant, Sr): Probably, it is a mutant of var. typica largely grown as a commercial cultivar in several coffee producing countries and known for its broader, thick and elliptical dark green foliage. Fruits are tightly clustered and situated on the short internodes. Variation in the ripening of the fruits in the same cluster is a distinct character of this variety. It has a conical shaped short stature bush even shorter than the Caturra mutant. Allele Sr is dominant over tall types and shows epistatic effect on Maragogipe mutant genes Mg. Due to its drought hardy nature and tolerance to calcium deficiency, it produces moderate crop in marginal areas. In India, three types of progeny viz. tall, medium and dwarf types are reported when propagated from open-pollinated seeds. The variation in plant height was due to genetic and environmental effect. (Srinivasan, 1981). Semperflorens (recessive, sf): Probably, it is a mutant form of var. bourbon with short internodes, short and erect lateral shoots besides a running blossom.. Xanthocarpa (incomplete recessive, xc): This mutant exhibits normal bush habit with yellow color fruits. It is originated from var. typica and was spotted during 1870 in Botucatu, Sao Paulo and cultivated as Amarelo de Botucatu. This mutant carries recessive genes xcxc. The red fruited Vermelho has XCXC genetic makeup with dominance over xcxc genes showing a monogenic control of the trait. Mutants of Coffea canephora: C. canephora is diploid and self-sterile, producing many different forms and varieties in the wild. The identification of cultivars is confused, but two main forms are recognized as 'Robusta' with upright forms, 'Nganda' of spreading type. There are several mutants identified in this species that are controlled by the recessive inheritable factors. Since, robusta is a fully cross pollinated crop, inheritance of the traits in further 27
generations of robusta lines is difficult.. Hence, improvement of robusta varieties through traditional breeding system is restricted. Sreenivasan et al., (1980) recorded a mutation for pericarp colour in Coffea canephora at Coffee Research Station that had color changing behavior right from the pepper stage of fruits to full maturity. Pericarp colour of the fruits underwent gradual change from red to yellow-red to yellow to yellowish to green-yellow to red. While in normal plant pericarp colour changed from green to red at ripening time. Sreenivasan(1980) noticed an unusual phenomenon in Coffea canephora character that had an additional chromosome (2n+1=23), the trisomic condition. This trisomic plant showed almost regular meiosis and produced 82 percent fertile pollen. A case of dwarf mutant with compact bush, short internodes, normal bearing habit and bean size was reported from India. The plants have ability to yield even 2000-3000kg clean coffee ha -1 by planting at closer spacing of 3x4 ft (Kumar et al, 1994). Sureshkumar et al.,(1999) identified a dwarf plant in CxR population in a private coffee plantation in Kerala with the characteristic features of short internodes, compact bush and large size beans compared to ordinary robusta. Fruit weight and germination percentage in dwarf plant was on par with the normal robusta variety. The open-pollinated progeny had exhibited tall, medium and dwarf type plant population. 2.13. Coffee breeding Coffee being a perennial crop, release of a new cultivar is a difficult task to the coffee breeders. It consumes about 20 years from first crossing until developing a new variety. The period of twenty years can be reduced to 10 years by making some alteration in breeding strategies and improvement methodology. An addition of new tools such as biotechnological protocols, informatics and biometrics would be of immense use (Sera, 2000). Selection of mother plants based on the yield potential and its stability, resistance to diseases and pest, 28
plant vigour, adaptability and quality of beans and beverage have been considered as the important criteria in coffee breeding through conventional and advance techniques (Wintgens, 2004). In most of the coffee growing countries, arabica breeding has been paid more attention than the robusta because of its susceptibility to many diseases and pests though superior in quality to robusta. Several varieties have been evolved in India as well as abroad. The arabica varieties like Caturra, Catuai, Tupi, in Brazil, SL.28 in Kenya, Kents and S.795 in India, Sarchimor in Costa Rica, Java in Cameroon and variety Columbia in Columbia, have been developed through pure line and pedigree selection. The F 1 hybrids such as Ruiru-11 and Ababuna were released from Kenya and Ethiopia. Similarly, the cultivars developed through inter-specific crosses of arabica and robusta are Icatu from Brazil and Sln.6 (S.2828) from India. Beside this, some robusta varieties such as, Apota, Nemaya and S.274 released from Brazil, Central America and India respectively (Van der Vossen, 2001). 2.14 Breeding in Coffea arabica L. C. arabica is a tetraploid (2n = 44 chromosomes) and is self-fertile. There are two distinct botanical varieties: arabica (typica) and bourbon. Historically, typica was cultivated in Latin America and Asia, whereas bourbon arrived in South America and later to East Africa via the French colony of Bourbon (Reunion). Because C. arabica is self-pollinating, these varieties tend to remain genetically stable. However, spontaneous mutations showing desirable characteristics have been cultivated in their own right, as well as being exploited for cross-breeding purposes. Some of these mutants and cultivars are described below. Coffee has been selectively bred to improve characteristics of growth and flowering, yield, bean size and shape, cup quality, caffeine content, disease resistance, drought resistance. Crosses between arabica and robusta aim to improve arabica by conferring disease resistance and vigour or to improve the cup quality of robusta. Hibrido de Timor is a natural 29
hybrid of arabica x robusta and resembles arabica coffee with 44 chromosomes. Catimor is a cross between Caturra and Hibrido de Timor and is resistant to coffee leaf rust (Hemileia vastatrix). A new dwarf hybrid called Ruiru 11, developed at the Coffee Research Station at Ruiru in Kenya, was launched in 1985. Ruiru 11 is resistant to coffee berry disease and to coffee leaf rust. It is also high yielding and suitable for planting at twice the normal density. Icatu hybrids are the result of repeated backcrossing of interspecific arabica x robusta hybrids to arabica cultivars Mundo Novo and Caturra. Arabusta hybrids are fertile interspecific F 1 hybrids from crosses between arabica and induced auto-tetraploid robusta coffee. The progenies developed through hybridization are multiplied by seeds and vegetative means viz; sucker cutting, grafting and to some extent by budding. Subsequently, new methods of propagation through tissue culture have also been found very promising in coffee breeding to regenerate the rare plants by means of leaves, embryos, anthers, pollen and root culture. A beginning in the field of tissue culture was made through in vitro culture micro-propagation of explants, vegetative buds and apical meristems and released the higher efficiency for production of limited quantity of unique genotypes (Fazuoli et al, 2000). In recent years the potential of genetic manipulation of Coffea using recombinant DNA technology and tissue culture techniques has been investigated. By introducing new genes for characteristics such as resistance to pests or to herbicides, or genes coding for desirable cup quality attributes, it may be possible to produce plants with any combination of features required (Sera, 2000). The primary objective of coffee breeding and selection program is to develop high yielding, excellent bean quality and disease resistant (especially rust) cultivars which are adapted to specific growing conditions. Four major goals have been set for to fulfill the major 30
objectives of coffee breeding. Firstly, breeding strategies needs to be developed secondly, techniques required to be evolved and implemented and thirdly, the procedures for vegetative propagation needs to be standardized and lastly, potentially elite individual plants needs to be selected from existing coffee plantations and propagated asexually (Van der Vossen, 2000). 2.15. Coffee breeding in India: Coffee Leaf Rust (CLR) is caused by the pathogen Hamellia vastratrix has been a disease of great economic significance in all coffee growing countries ever since it became an epidemic in the late 19th Century in Sri Lanka and India. CLR was reported first in 1861 from the wild Arabica coffee plants around Lake Victoria in Kenya. On cultivated coffee the disease was first noted in the year 1868 in Ceylon. The crop loss caused by the disease was so high that within a decade arabica coffee cultivation in that country was replaced by Robusta. The coffee cultivation in Indonesia also suffered a similar impact of Coffee leaf rust. The disease was widespread in the coffee growing countries of Asia and Africa by 1920. In the Latin American countries, the disease first appeared in the year 1970 and quickly spread to most of the South and Central American countries. At present, Hawaii is the only coffee producing country free of CLR. In India, the disease was first noticed on an epidemic scale in the year 1869 (Anonymous,1995). Enterprising coffee planters of India resorted to selection of tolerant types, introduction of hardy species and even hybridization of Arabica and the hardy species like Robusta and Liberica. The Folk Selection Era of coffee breeding has happened in our country and pioneer coffee growers like Stanley Jupp and L.P. Kent and others are remembered even today for their contributions. The variety of developed materials like Hamiltons, Jacksons, Netrakonda and Chandrapore hybrids are worthy of mention in the history of coffee breeding (Srinivasan et al., 2000). 31
2.16. Coffee Selection and Breeding Arabica coffee (Coffea arabica L.) is more prone to several diseases and pests. This species faces various biotic adversaries when cultivated on large scale. Among these, coffee leaf rust is of immense economic importance and is caused by the pathogen Hemileia vastatrix Berk and Broome. Mayne (1932) identified four physiological rust races occurring in Arabica coffee in India and confirmed the phenomenon of physiological specialization in rust and race-specific resistance in Coffea arabica. Genetic transmission of rust resistance in arabica varieties began with a systematic attempt at the Mysore Coffee Experiment Station presently, known as Central Coffee Research Institute (CCRI) during 1925 applying traditional breeding techniques (Narasimhaswamy, 1961). Different breeding protocols were adopted for arabica and robusta cultivars based on their dissimilarities in genetic behaviors. During 1925 to 1940, the indigenous collections made from different coffee estates in India were utilized to evolve rust resistant genotypes. Subsequently, in 1953 several coffee germplasm from various coffee growing countries as well as semi-wild and wild genotypes from Ethiopia the homeland of Arabica coffee were introduced. 2.17. Early Indian Selections: An indigenous arabica genotype, S.26 was awarded with a title of The Great Grand Mother of Indian released selections collected from Doobala Estate a private coffee estate in Karnataka. This plant had vigorous growth and high yielding behavior with an ability to produce 2250 kg clean coffee per ha combined with rust resistance to the races I and II of the rust pathogen widespread during that period. It exhibited 50 percent A grade beans with FAQ and above cup quality. Due to its outstanding nature it was used to produce its selfed progenies namely; S.288, S.952, S.953 and S.947. The self-pollination progeny (S.288) of this mother plant was released as Sln.1 to the industry for commercial cultivation 32
in 1937 (Anonymous, 1968). Accession S. 288 was found to be the carrier of S H 3 gene that conditioning resistance to these rust races, which was later, confirmed by the Centro Investigacao das Ferrugens do Cafeeiro (CIFC), Portugal. Thereafter, due to its higher percentage of defective beans (triages), an inherent character of this material, it was crossed with var. Kents to improve its bean quality. The progeny (S.795) was found to manifest good plant vigour, resistance to the prevalent races of rust as well as good cup quality and released as Selection.3 in 1946-47 (Narasimhaswamy, 1960). The studies on the segregating behavior of S.795 revealed that this genotype followed the Mendelian ratio of 3:1 (resistant: susceptible plants). Presence of S H 3 gene that was responsible for the resistance in S.795 material was thought to have been derived from tree coffee (Coffea liberica Bull ex Hiern). Introgression of S H 3 gene from liberica coffee has been well studied (Prakash et al., 2002, Prakash et al., 2004). The studies on DNA markers indicated the similarity in AFLP fragments of C. liberica and C. arabica cultivar S.288 and its descendants S.795 and S.1934. The available information suggested that the recombination of homologous chromosomes C. liberica with C. arabica along with intra-genic recombination could be the cause for transmission of S H 3 gene in Indian Selections (Santa Ram, 2006). 2.18. New Coffee Selections: In 1950s, a huge gene bank of over 400 cultivated varieties along with wild Arabica genotypes such as Agaro, Cioccie, Tafarikela, S 12 Kaffa and Geisha was established at CCRI. These, Ethiopian land races, were found to offer excellent quality as well as substantial resistance habituated by the genes S H 1, S H 2, S H 4 and S H 5 in diverse combinations. The above Ethiopian lines were included in Selection.4. It was understood that the cultivars with single resistance gene could give only short-lived relief and this paved way for breeding arabica with the high resistance originated in the diploid species (Mayne, 1932). 33
Central Coffee Research Institute under Coffee Board s Research Department has released 13 arabica and 3 robusta selections for commercial cultivation and recommended standard methods of propagation by seed as well as clones (Srinivasan and Kumar, 2000). 2.19. Type and Sources of Resistance Rodrigues, (1995) described the economical, biological, physical aspects of coffee leaf rust including hyperparasitism of rust. The presence of an antifungal substance was indicated in the diffusates of leaves inoculated with an incompatible virulent race. This substance was found capable of causing reduction in the spore germination and inhibition in germ tube length of the inoculated rust races by 40-50 percent, while, the diffusates of compatible combination did not exhibit significant influence on spore germination. Chiarappa and Pinto (1997) reported the role of presence of dew during dry period of May to July to accelerate the spread of coffee leaf rust in Brazil. Exposure of coffee urediospores to Ultra-violet rays for a short period was found to stimulate sporulation. In a study on viability of rust spores, it was observed that the urediospores maintained under dry environment was capable of causing more infection than the spores thrived under humid conditions. Beside this, a minimum of 15 C and maximum of 28 C was confirmed to be the ideal temperature for germination and penetration of rust spores. A dry period of 4-5 hrs followed by wet conditions inhibited the germination of rust spores. Monaco and Carvalho, 1997 described the horizontal resistance in coffee to be under the control of polygenes besides in some cases to be due to transmission of oligogenes. They suggested that horizontal resistance could be more durable as compared to vertical resistance and that emphasis must be given to incorporate this kind of resistance in the commercial cultivars through selection and breeding. Srinivasan and Vishveshwara, (1981) indicated the presence of horizontal resistance to leaf rust in Tafarikela, Rume Sudan and Barbak Sudan from Ethiopia. Simultaneously, the 34
highest vertical resistance was apparent in S.12 Kaffa and the lowest in Matari and interestingly, both happened to be from Ethiopia. Most of the morphological characters studied in the 246 world collections showed a large variability which signified the polymorphic nature of arabica species. Srinivasan et al., (1981) evaluated horizontal resistance to leaf rust in arabica in two varietal trials and scored the rust incidence and its intensity using a 5 point scale. The intensity was worked out in June, September and December 1980 following the fixed scale as 0= no infection, 0.25= few spot, 0.50= mild susceptibility, 0.75= high susceptibility, 1.00= high susceptibility with defoliation. The results indicated increasing pattern in rust incidence from initial data recorded to the successive period. According to Santaram, (2006), the concept of gene pyramiding is a noble approach in coffee breeding system to combat the problems of serious diseases and insect-pests. Through this method, it would be possible to integrate major dominant genetic factors of immense significance into a genotype from diverse sources. Prakash et al, (2010) screened two Indian cultivars Sln.5A and Sln.6 against CBD and CLR. Among both selections Sln.5A manifested high tolerance to CBD while Sln.6 showed relative tolerance. Kilambo et al., (2013) studied the response of compact coffee clones against coffee berry and coffee leaf rust diseases in Tanzania and found a significant effect of resistance of compact genotypes tested across the coffee growing areas. 2.20. Inter-specific hybridization in coffee Great potential was realized in breeding C. arabica with the diploid Coffea species such as C. canephora, C. congensis, C. recemosa and C. liberica var. dewevrei (Madina Filho et al., 1984). The release of Brazilian varieties Icatu Vermello, Icatu Amarello and 35