Chapter - 1. Studies on Compatibility and Survival Rate

Transcription

1 Chapter - 1 Studies on Compatibility and Survival Rate

2 1.1 INTRODUCTION Breeding varieties for drought resistance in a perennial crop like coffee is a long term process and not much progress has been achieved either in India or elsewhere. Utilization of drought tolerant species as rootstocks with high water use efficiency and carbon exchange rates for commercially important arabica cultivars seems to be a better approach in dealing with the stress problems and to improve the productivity of coffee. Grafting scions of susceptible or commercially important and promising newer hybrids of arabica genotypes on to resistant/tolerant rootstocks with better root characteristics and agronomical traits could be one of the best possible measures in order to improve the vigour, agronomical traits, carbon exchange rates and impart tolerance/resistance to drought and ultimately to improve crop production of coffee. Perusal of the literature on grafting in coffee indicates that grafting was carried out extensively in Indonesia almost a century ago to especially to tackle the nematode problem (Cramer, 1934). Top working by cleft grafting on suckers became eventually the standard method of propagating clones of robusta and other coffee in Indonesia (Cramer, 1957), East Africa (Fielden and Garner, 1940), and in Kenya (Van der Vossen and op de Laak, 1976). From time to time, different grafting techniques like tip grafting (Anonymous, 1978); side grafting (Anonymous,1980); seedling grafting before full expansion of cotyledons (Gutierrez and Jimanez, 1970); sucker grafting (Reddy and Srinivasan, 1983); and grafts (Purushotham, 1982) have been tried in coffee. But cleft grafting of very young seedlings at 'button' stage is identified as most popular method of grafting, in which a success rate of above 85 per cent could be obtained during monsoon period (Anonymous, 1984; Raghuramulu, 1994). Incidentally this method has been widely recommended for grafting susceptible arabica varieties on to tolerant robusta stocks as a means of overcoming nematode problem (Schieber and Grullon, 1969; Rodrigues, 1980). The next popular method of grafting in coffee is top working of unproductive off-type plants with a desirable material (Reddy and Srinivasan, 1983; Ramachandran et al., 1993). Generally good compatibility was observed between arabica scions and robusta rootstocks (Raghuramulu and Purushotham, 1987). 5

3 Among the various methods of grafting employed in coffee, wedge-cleft grafting of very young seedlings at 'button' or 'topee stage' before unfurling of the cotyledonary leaves has gained much prominence because of its simplicity, economy and high success rates. Fernandez (1964) reported that wedge grafting of 'button' stage seedlings would result in a success rate of above 95 per cent with Bourbon or Typica scions (both belong to C. arabica) on robusta rootstock. By adopting wedge grafting of 'button' stage seedlings, Reyna (1966) prepared thousands of grafts using 23 varieties of C. arabica as scions on C. canephora rootstocks. A success rate of above 95 per cent has been reported in a propagator by providing a temperature of o C and a relative humidity of per cent. Raghuramulu and Purushotham (1987) obtained per cent takes, by adopting wedge grafting at 'button' stage. They have reported that survival of rootstock scion combinations varied between 12 to 90% when rootstocks of different species were used. Raghuramulu (1994) obtained around 80 per cent success when arabica scions (cvs.s.795 and Sln.12) grafted on tree coffee species like C.abeokutae, C. arnoldiana, C. excelsa and C. liberica rootstocks. The percent survival/mortality may vary due to genetic differences between root stocks and scion materials as well as environmental conditions. Raghuramulu and Purushotham (1987) reported maximum mortality of 87.04% when Sln.7.3 arabica scion grafted to Sln.10 arabica rootstock and minimum of 11.76% in S.274 robusta rootstock and Sln.7 scion material which they attributed to incompatibility between genetically different scions and root stocks used. Anilkumar and Srinivasan (2001) reported mortality to an extent of 6% when arabica scions were grafted to diploid tree coffee rootstocks. In case of other beverage like tea also variations in graft compatibility and mortality was reported which varied between 30 to 100% between different rootstock scion combinations (Sreedhar and Satyanarayana, 1996). In the present investigation per cent compatibility and survival/mortality was studied in different rootstock scion combinations and also self combinations. 6

4 1.2 REVIEW OF LITERATURE The need to regulate growth in tree crops is based on several factors. The significance is the relationship between growth and fruiting. A certain amount of growth is necessary to maintain vigour and a healthy fruiting mantle with an adequate growth, leaf surface, besides higher carbon fixation and better water use efficiency. Vegetative growth may be regulated genetically, environmentally or by various cultural techniques. Production of efficient root stock scion combinations with better growth is one of the important horticultural techniques by adopting grafting technique in various crops. The desire to regulate excessive vegetative growth and maintain a smaller or larger fruit tree is not new (Hugard, 1980; Walker, 1980). Early efforts to manipulate fruit tree size focused more on rootstocks than selecting the scion cultivars with reduced vigour (Trajkovski, 1986). However, in recent years plant breeders have shown interest in scion vigour and have selected trees with reduced shoot growth and a more compact growth habit (Janick and Moore, 1996; Trajkovski, 1986; Scorza, 1987). Commercially important coffee hybrids require vegetative propagation to maintain the desirable characteristics of the original selections and to establish uniform plantations. Rooting of soft wood cuttings of orthotropic suckers was found to be a relatively easy and efficient method of clonal propagation (Van der Vossen and Op de Laak, 1976; Purushotham, 1982). However grafting could be employed to convert unproductive plantations into productive ones by top working with desirable materials and also to cultivate commercially important cultivars on rootstocks which are capable of withstanding the drought and other unfavorable biotic and abiotic conditions. Indonesia seems to be the first country, where grafting was practiced extensively in coffee for overcoming the nematode problem and also for top working since 1890's (Cramer, 1957). In India also grafting in coffee was first attempted during late 1890's at Lalbagh, Bangalore using arabica (Coffea arabica L.) and liberica (C. liberica Bull ex. Hlern). Not much work seems to have been done till Later Coleman and his co-workers re-initiated work 7

5 on coffee grafting at Mysore Coffee Experimental Station, Balehonnur presently known as Central Coffee Research Institute. Their experiments revealed that wedge-cleft grafting done at the 'button stage' of coffee seedlings (45-50 days after sowing) during early monsoon season would result in a maximum of 80 per cent success in grafting as well as further field establishment (Anonymous, 1954). Since then various aspects of grafting in coffee were investigated by different workers allover the world. A detailed review of these investigations is being attempted in this chapter. Grafting techniques employed in coffee for compatibility Top working For the purpose of top working in coffee, Ferwarda (1935) suggests that a strongly sprouting sucker which is just becoming woody should be selected as scion material. Gillet (1935) stated that the graft should be made on old brown wood on the rootstock and that the cut should be made just above the internodes. Graaff (1941) studied the best kind of shoots for grafting. His results revealed that the grafts on old trees treated with sector pruning showed the quick growth and top worked grafts on stumped nursery plants remained backward. Top working by cleft grafting of single node scions with leaves intact, on to a six months old suckers gave 85 per cent 'takes' in Kenya during Oct.- Nov. (Van der Vossen and op de Laak, 1976). In India, top working of offtype plants in seed blocks of Coffea arabica cvs. Sln.5 and Sln.6, with superior scion material from respective cultivars was attempted by Reddy and Srinivasan (1983). They reported a success rate of 42.4 and 32.5 per cent in Sln.5 and Sln.6 respectively. Ramachandran and his co-workers (1993) tried top-working of old unproductive plants of San Raman (C. arabica) and robusta (C. canephora) and reported that Cauvery (an arabica cv.) as scion gave 70 per cent success with San Ramon stocks and 60 per cent 8

6 success with robusta rootstock. Congensis x Robusta hybrid scions gave an 88 per cent success with robusta rootstocks. Hypocotyledonary grafting Terminal portions of suckers of arabica coffee with leaves severed and cm length were grafted on one and half to two year s old rootstocks of robusta at the tip end by wedge-cleft method at Central Coffee Research Institute (CCRI) in India. A success rate of 60 per cent was obtained during the months of May and June (Anonymous, 1978). Among the various methods of grafting employed in coffee, wedge-cleft grafting of very young seedlings at 'button' or 'topee stage' before unfurling of the cotyledonary leaves has gained much prominence because of its simplicity, economy and high success rates. Stionic influences on compatibility There may be a number of factors limiting the compatibility and success of grafting. The main reason being incompatibility often found between stock and scion. There are various degrees of incompatibility between different species and varieties of coffee and between individual plants. In some cases union will be rejected because of complete incompatibility. In most cases a slight degree of incompatibility may exist but unnoticed in initial stages. However, this becomes apparent when the trees start bearing heavy crop. Other symptoms may be yellowing of leaves, die-back and exhaustion not accountable to any environmental influences. Besides this, there are influences of scion upon the stock and vice-versa. These influences may be beneficial or detrimental. In sound grafting practice, the degree of compatibility of stock and scion and the influence of one on the other are known. This is true with many fruit crops like apples, grapes, pears, peaches and citrus. A small beginning earlier has been made with coffee and the influences and compatibilities of some are now known (Haarer, 1962). 9

7 Compatibility and survival between scion and stock The growth of small number of grafts of arabica on liberica stock was not satisfactory and very poor compared to that of seedlings. He opined that liberica was not a suitable stock for arabica. Robusta cv. Bgn seedlings gave poor results as a stock even when grafted with robusta cv. Bgn indicating presence of incompatibility within a variety/cultivar. The compatibility and mortality of graft combinations depends on genetic set up of rootstocks and scion materials (Cramer, 1928; 1957). Romero (1930) reported that C. auillou as scion is compatible with C. excelsa but the reciprocal grafts were not compatible. He also suggested that C. liberica is more compatible with C. excelsa than on C. auillou. Lambers (1931) observed that C. excelsa is not good as stock for robusta scions because of incompatibility problems. On the contrary Schweizer and Jacob (1938) reported that robusta clones on robusta rootstocks grow better than on other stocks like C. excelsa and C. devewrei. Ferwerda (1935) grafted robusta scions on Bgn stocks and classified as slow, medium and quick growing plants and observed no differences among the various grafts with respect to success of grafting, field mortality and the rate of growth. He also reported that lowest percentage of losses in the field with grafts on C. excelsa stocks. Fielden and Garner (1940) made an extensive review on the topic of grafting in coffee. In Kenya, C. arabica is compatible with various varieties of arabica, while C. arabica on C. eugenioides produced a dwarf and sickly tree. They also reported that arabica on robusta stocks produced trees which are susceptible to drought. Henriquez Chacon and Basagoitia (1981) grafted five partially rust resistant arabica coffee cvs. (F- 840; K.P.228; Geisha and S.12 Kaffa) on seven C. canephora and C. congensis rootstocks and observed good compatibility in all combinations. They reported that growth and development of scions were similar on all the rootstocks but was poor when compared to those of their seedling counterparts. 10

8 The first report on incompatibility between C. arabica and C. canephora was made by Pierres (1988). He states that this can be overcome by inserting an interstock such as C. congensis or C. liberica which are compatible with both stock and scion. Raghuramulu (1994) reported an average of 99.3% compatibility between rootstocks of C. excelsa, C. abeokutae, C. arnoldiana, C. canephora and C. arabica scions of S.795 and Sln.12. Raghuramulu and Purushotham (1987) while studying compatibility in different arabica and robusta rootstock scion combinations observed lowest graft `take of 33.33% in Sln.7/S.795 (arabica/arabica) and maximum in S.274/Sln.11 (robusta/arabica) combination. The poor compatibility or differences in compatibility in different combinations could be due to incompatibility between stock and scion as observed in many fruit trees (Argles, 1937). Anilkumar and Srinivasan (2001) reported 98 to 100% compatibility when arabica scions grafted to robusta and tree coffee root stocks. Such variation in compatibility depends on incompatibility between genetically different rootstocks and scions (Hayes, 1945). Raghuramulu and Purushotham (1987) reported maximum mortality of 87.04% when Sln.7.3 arabica scion grafted to Sln.10 arabica rootstock and minimum of 11.76% in S.274 robusta rootstock and Sln.7 scion material which they attributed to incompatibility between genetically different scions and root stocks used. Anilkumar and Srinivasan (2001) reported mortality to an extent of 6% when arabica scions were grafted to robusta and tree coffee root stocks. 11

9 1.3 MATERIALS AND METHODS The present investigations were carried out during the years 2008 to 2012 at Central Coffee Research Institute, Coffee Research Station, Chikmagalur District, and Karnataka. In this chapter attention was given to study the stionic influences in selective commercially important scion and rootstocks of arabica and robusta coffee with respect to compatibility/survival rate. Also aimed to understand influence of rootstocks on physiological aspects and identify superior rootstock scion combinations for commercial use. Experimental site The Central Coffee Research Institute (CCRI) is situated at 13 22" North Latitude and 75 28" East Longitude at an elevation of meters above mean sea level. Annual rainfall varies from 2286mm to 4003mm received mainly from May to October with an average of about 2838mm. Seventy per cent of the total rainfall is received from the South-West monsoon which extends from June to first fortnight of September. North-East monsoon rains are received from the second fortnight of September and continue till about the end of November. Usually the months of December, January and February are dry. However the dry period sometimes crosses 120 days which limits the crop production. Experimental period Meteorological data during the experimental period for the seasons 2008 to 2010 is presented in (appendix I). The mean maximum temperature recorded during the experimental period ranged from 24.5 to 33.6.C and the mean minimum temperature was 15 to 20.8 C. The total sunshine hours varied between hrs/day. The rainfall ranged from to3492 mm and relative humidity ranged from 72-90%. 12

10 Soil characteristics The soil used for seed sowing and rising of nursery was sandy loam characteristic of Malnadu coffee growing areas. The water holding capacity of the soil at 100% F.C was 21%. The physical and chemical properties of the soil are presented in (appendix II). Characteristics of scions materials The characteristic features of three scions used for conducting the experiment are explained below and showed (Fig. 3). a. Arabica cv. S.795 (C.arabica L.) This variety is a cross between S.288 X 'Kents' which was released for commercial cultivation during 1946 by Central Coffee Research Institute. Widely cultivated and most popular variety represents almost 50% of total arabica cultivation. It is a tall, wide spreading to semi-drooping in nature (Fig.6). This variety was susceptible to drought with moderate carbon exchange rate (CER). This variety shows vigorous branching with good number of secondary branches and tertiary branches. Internodal length 4-6 cm. Leaves linear, oblong, thick, dark green, wavy margin with long acuminate tip. Young leaf tip color is dark bronze color. Fruits per node, medium to bold, oblong with small to broad navel. Ripening normal with dark red pericarp. Beans bluish green in color, bold and medium sized. Produces 'A' grade beans of about 65 per cent. Cup quality rating is good to Fair Average Quality (FAQ). Spaced at 6'X 6' or 6'X 7 for commercial cultivation. Shows rust reaction of 'H' type with resistance to 26 races of Hemelia vastatrix. Yields 600 to 700 Kg of clean coffee per ha. b. Arabica cv. Sln.10 (C. arabica L.) This variety is a cross between of Cattura hybrid x Cioccie x S.795 with semi dwarf nature. Plant found to be drought tolerant with high carbon exchange rate (CER). It starts bearing at early stage compared to tall varieties. This variety shows more primary branches and secondary branches. Plants exhibit short internodal length of about 3-4 cm with compact clusters of fruits which are round, bold and dark red while ripening. Leaves of this cultivar are broader, thick, dark green and with green leaf tips. This cultivar also 13

11 shows deep tap root system. Coffee beans are bluish green with 60% `A grade size. The cup quality found to be FAQ. The cultivar is not much popular at present but advocated for drought prone areas with a spacing of 5 x 5. Under intensive cultivation, this variety produces a crop yield up to 1000 Kg.Clean.Coffee per ha. c. Arabica cv. Sarchimore Variety. S.4202(C.arbica L.) This variety is a promising new variety with high yielding potential. At present evaluated at various agro climatic conditions. Also this variety gaining popularity among the growers for its compact semi dwarf nature with abundant secondary branches and very bold fruits. This cultivar is moderately tolerant to drought but have very high carbon exchange rates (CER).The leaves of this cultivar are bold, thick, dark green with green tip leaves. Starts bearing early like any other dwarf varieties of coffee. This cultivar produces highest `A grade beans of 70% and known for 10 to 15% production of extra bold beans called as Mysore nuggets which fetches higher premium on export. Under intensive cultivation this variety produces a crop yield up to 1200 to 1750 Kg.C.C per ha. Recently released as Chandragiri variety. Characteristics of rootstocks Five different rootstocks were used for grafting experiments. They are shown in Fig. 4 and explained below: a. Robusta cv. S.274 (C.canephora Pierre ex froehner) This variety is being cultivated commonly in the coffee growing zones of India. It is a selected cultivar known for large bush size with robust growth. The leaves are broad and oblong. It is a semi drooping type with large number of secondaries and tertiaries. The long internodes of 5 to 7 cm with large clusters if fruits vary from 25 to 50 per cropping nodes. This variety found to have high root biomass, good water use efficiency, vigorous growth and resistance to major pest and diseases. The cultivar possesses high carbon exchange rates. The fruits are bolder in size with around 70% `AB grades. The fruits are reddish to dark red in color. A crop yield of 1800 to 2000 per ha could be expected under well cultivation practices. 14

12 b. Congensis X Robusta cv. CxR (C. robusta) This variety is an interspecific hybrid of Coffea congensis x Coffea robusta with high vigour, fast growth and drooping type medium size plant and advocated at a closer spacing of 8`x 8 under irrigated condition. The cultivar has high root volume and deeper root system with high carbon exchange rate and water use efficiency. The cultivars also possess drought tolerance. Smaller internodes (4-5 cm) with more clusters of fruits is a speciality of this genotype. The fruits are bolder with 70 to 80%`AB grades. The leaves are thick green, narrow with wavy margins. The fruits have protruded navel portion. Resistant to major coffee pest and diseases. It yields up to 2000 to 2500 Kg.C.C ha under intensive cultivation. c. Sln.9 (C.arabica L.) This is a cross between the arabica genotypes such as Hybrido de Timor (HdeT) and Tafarikela and very popular among the growers. A tall arabica variety with drooping branches with long internodes. This cultivar shows high extension growth. The leaves are broader with bronze tip. This genotype is tolerant to drought and also shows high carbon exchange rates with maximum leaf retention through out the period. This genotype also possesses high water use efficiency and better drought adoptability mechanisms. The fruit clusters are tight, early ripening gives around 70% `A grade beans. A crop yield to an extent of 1000 Kg.C.C ha could be expected under well maintained estates. d. Sln.5B (C.arabica L.) This includes two separate families of line between Devamachy x wild arabica Rume Sudan (S.881) and Devamachy x S.333. Devamachy is a spontaneous robusta x arabica hybrid. The family of with thick, small, oblong and leathery leaves and exhibits field resistance to leaf rust. It is moderate yielder produces more (nearly 40%) B grade beans. Devamachy x S.333 line (S.2931) characterized by uniform, medium size, semi drooping plants. Rust and moderately tolerant to drought with high vigour.these plants also exhibit higher resistance to leaf rust. Fruits are bold and has the potential of 1500 kg per ha. 15

13 e. Sln.11 (C.arabica L.) This is interspecific hybrid derived from cross of Coffea liberica and Coffea eugenioides. Bushes resembles arabica with erect to semi erect branches and narrow smaller leaves. This cultivar is resistant to leaf rust and drought tolerant. It is a moderate yielder but produces B grade beans (30%-40%) and Cup quality similar to arabica. Bean size is small with low `A grade beans. Preparation of rootstock scion combinations Raising the plant material The root stock scion combinations were prepared at central coffee research institute at Balehonnur, Karnataka and maintained under controlled nursery conditions for eighteen months for the study. The necessary nursery soil mixture was prepared using standard recommended method (Anonymous, 2003). Eight tons of jungle soil was spread uniformly in the field condition for one month and subjected to solarization for one month and thoroughly sieved for use in the nursery. Selfed seeds collected during January 2008 were mixed with ash and preserved. These seeds of scions and five rootstock materials were sowed in the primary nursery bed during the month of March 2008 and 2009 in order to obtain button stage seedlings. Seeds of the scion materials and root stock materials were collected by selfing. The nursery soil mixture consisted of 6:2:1 proportions of dried sieved top layer jungle soil, farmyard manure (FYM) and sand of river respectively. The nursery plastic bags of dimension 22.5cmx 35cm were filled with equal quantity of this mixture and arranged with bamboo stakes in the nursery which resulted in secondary bed. The nursery site was covered with overhead shade net which provided 60% shade and 40% daylight. Watering was done regularly based on need. The seeds started germinating after 40 days after sowing (DAS) and the germinated seeds attained button stage by 50 to 55 days after sowing. 16

14 Creation of rootstock scion combinations To get required root stock scion combinations the grafting was carried out during the months of May by adopting the technique like wedge-cleft method using button stage Seedlings. The uprooted scion and rootstock seedlings at button stage without damaging to the root system. The root portion was dipped in 0.01 per cent Carbendazem solution to avoid fungal attack in future. The top half of the rootstock seedlings and bottom half of the scion seedlings were severed using razor blade. A wedge of approximately one centi meter was made at the cut end of scion seedling and a cleft of same depth was made on the cut end of rootstock seedlings. The wedge portion of the scion was inserted in the cleft of the rootstock and the union was secured firmly by using a polythene strip covering the union portion (Fig. 5). A total of fifteen combinations were created using different rootstock and scions (Table.1) Transplanting The grafted seedlings were transplanted to secondary nursery. The nursery polybags were provided with holes to allow proper drainage of excess water. The nursery bags were arranged in the nursery in batches of 200 (20 rows x 10 each) by providing 60% shade with overhead shade net. Simultaneously 100 seedlings each of the scion were also raised. Though the pure line seedlings and respective grafts have the same age there will be difference in growth because grafts take more time to start actual growth due to fresh union of stocks and scions. Hence grafts of self rootstock and scions also raised parallely as control to take up comparative study and maintained in secondary nursery (Fig. 6). Plant protection and manuring A pinch of Thimet was added to each poly bag as a prophylactic measure against nematodes before transplanting of grafted plants. The rootstock scion combinations and 17

15 seedlings were watered regularly based on need. Alternate plant protection sprays with Bavistin (0.1 per cent) and Ekalux (1.25 ml L) were given at an interval of 20 days initially against collar rot and Cercospora disease and nursery pests respectively. Manuring of the young plants was done as per the standard nursery recommendations (Anonymous, 2003). Studies were carried out to find out the per cent compatibility and abnormalities between the arabica scions and desirable rootstocks of arabica and robusta coffee and calculated as per the following formulae. Per cent compatibility The per cent compatibility was recorded three month after the grafting and percentage compatibility was calculated using the formula, No. of combinations successfully got union (%) = No. of combinations made. Per cent mortality of combinations The per cent dead rootstock scion combinations were calculated six months after the union using the formula No. of total combinations Dead combinations Per cent mortality = x 100 Total No. of combinations Statistical analysis At the age of three months after the union, observations were recorded on compatibility using hundred seedlings per treatments. The percent survival was recorded six months after the graft union in the same combinations. Angular transformation of data was adopted wherever necessary by following the tables of Fisher and Yates (1974). The data were analyzed using Factorial RBD analysis, as described by Sundararaj et al. (1972). The values of Critical Differences (C.D) are mentioned at a probability level of 0.01 and

16 1.4 RESULTS The studies were carried out to identify the influence of the selective rootstock scion combinations on physiology and rootstock scion interactions of commercially important arabica and robusta coffee cultivars. The experimental results and findings on compatibility and survival rate/mortality are presented in this chapter. The compatibility between five rootstocks such as C x R, S.274, Sln.9, Sln.5B and Sln.11 and scions of commercially important arabica coffee such as S.795, Sln.10 and S.4202 were selected based on specific desirable traits were studied by assessing percent success in union of stocks and scions and percent survival of combinations on account of rootstock scion interactions and the results were presented. Compatibility Rate The different rootstock scion combinations involving arabica and robusta rootstocks with three important arabica scions were studied for compatibility in combinations with self-combinations. Though wedge cleft grafting technique was reported as most suitable grafting technique, significant (p<0.01) variations in compatibility was noticed in the present investigation among the different rootstock scion combinations compared to self combinations (Table.2). In general the graft compatibility varied between 80 to 100 percent. The percent compatibility indicated that among the different rootstock scion combinations the rootstocks of robusta coffee such as CxR (Congensis x Robusta) and S.274 induced significantly (p<0.05) poor compatibility (90 to 92%) respectively compared to rest of the rootstocks. Among the arabica rootstocks, the rootstock of Sln.11 indicated lower compatibility of 96.1% compared to other arabica rootstocks like Sln.9 and Sln.5B (100%). Among the scions S.4202 recorded poor compatibility of 90.4% followed by S.795 which was 96%. The observations on interactions between stocks and scions indicated that the CxR stock with S.795 and S.4202 scion and also S.274 stock with Sln.10 and S.4202 showed significantly (p<0.01) low compatibility. Among the arabica stocks the Sln.11 has significantly (p<0.01) poor compatibility with S.4202 scion. However 100% compatibility was noticed in all the 19

17 stocks with scions with self stocks and rootstocks with self scions. Among the scions S.795 showed 80% compatibility with CxR robusta stock whereas it has shown 100% compatibility with all other stocks. Similarly Sln.10 scion had 100% success with CxR robusta stock but only 90% with S.274 robusta stock and 100% compatibility with all the three arabica stocks. The scion of S.4202 had 80% compatibility with both the robusta stocks and 100% compatibility with Sln.9 and Sln.5B stocks but only 92% with Sln.11 stock. Among the stocks Sln.9 and Sln.5B have shown 100% compatibility with all the three scions whereas CxR, S.274 and Sln.11 significantly (p<0.05) low compatibility. Results indicated that in general, the compatibility between robusta stocks and arabica scions was poor compared to arabica stocks with arabica scions. The arabica Sln.11 stock have shown poor compatibility with S.4202 arabica scion. The robusta being diploid (2n=22) might have not completely successful in compatibility with arabica which is tetraploid (2n=44). Though the Sln.11 is arabica which is being an interspecific hybrid between Coffea liberica and Coffea eugenoides might have failed to show 100% compatibility with S Mortality Rate of grafted seedlings Though there is successful graft compatibility due to genotypic differences of stock and scion materials there are chances of mortality of the seedlings in rootstock scion combinations of the plants at later stages. Production of abnormal seedlings and mortality of graft combinations was assessed at the age of 6 months from grafting in comparison with self combinations of rootstocks and scion materials in the present investigation. Significant (p<0.01) differences in seedling mortality were observed between different rootstock scion combinations and also self combinations (Table.3). In general, high number of mortality was observed in the scion materials grafted with S.274 robusta rootstocks (28.3% and in the scions grafted to Sln.9 arabica rootstock (28.3%) followed by Sln.11 rootstock (20.8%). Among the different rootstock scion combinations CxR robusta stock indicated lowest (9.5%) mortality followed by Sln.5B arabica root stock (12.3%). 20

18 1.4 DISCUSSION Coffee is a perennial plant and its growth and development are governed by external and internal factors (Maestri and Barrows, 1977). The external factors include climatic and edaphic factors such as rainfall, light, temperature, soil nutrient status, soil moisture and soil temperature (Sylvain, 1954), while the internal factors include genetic make up, metabolic changes, biochemical composition, enzyme activities and nutrient uptake. Coffee is a seed propagated horticultural crop. Conventional breeding is commonly adopted to produce new hybrids and ediotypes with desirable characters. However breeding is a long term process in perennial crop like coffee. Grafting in fruit crops to produce better rootstock scion combinations has been described as a valuable technique for the improvement of plants having inferior characteristics such as poor growth, low productivity, inferior quality, disease susceptibility etc., (Tubbs,1973). Application of several methods of grafting in various crops has revealed the suitability of grafting method based on high level of compatibility (Hartmann and Kester, 1965). In coffee, various techniques have been tried in India as well as other coffee growing countries (Reddy and Srinivasan, 1983; Raghuramulu and Purushotham, 1987; Wamattu and King oro, 1993). The wedge cleft technique was found highly successful in coffee under Indian condition (D Souza et al., 1969; Anilkumar and Srinivasan, 1999). For grafting to be successful, the compatibility between rootstock and scion is very important besides higher degree of survival rate. The work done on rootstock scion combinations earlier in coffee simply confined to induce tolerance to root lesion nematodes and to improve vigour of scion materials by using diploid (2n=22) tree coffee species such as Coffea excelsa, C. liberica, C. abeokutae and C. canephora (Raghuramulu, 1994) which are tolerant to nematode problem. However information on influence of diploid robusta (2n=22) rootstocks on commercially important tetraploid scion materials is scarce. High success in terms of growth, development, drought tolerance, canopy size manipulation and yield was achieved in other horticultural crops like mango, cashew, apples, pears grapes etc., by identifying suitable rootstocks. Hence with these information and point of view, studies were carried out using three commercially important arabica scion materials and three 21

19 tetraploid and two diploid rootstocks with certain desirable characters to find out their influence on compatibility and survival rate/mortality, Compatibility In the present investigation significant variations in compatibility was observed between rootstock scion combinations. The graft compatibility varied between 80 to 100%. Among the rootstocks the diploid root stocks such as CxR (Coffea Congensis x Coffea canephora) and S.274 (Coffea canephora) induced significantly lower compatibility. The first report on incompatibility between C. arabica and C. canephora was made by Pierres (1988). However the tetraploid (arabica) rootstocks have shown better compatibility. These results are in conformity with the reports of Fernandez (1964), Reyna (1966), Raghuramulu and Purushotham (1987), Raghuramulu (1994) and Anilkumar et al., (2003). Among the arabica rootstocks, the rootstock of Sln.11 indicated lower compatibility of 96% compared to other arabica rootstocks like Sln.9 and Sln.5B (100%). Among the scions S.4202 recorded poor compatibility of 90.4% followed by S.795 which was 96%. The observations on interactions between stocks and scions indicated that the CxR stock with S.795 and S.4202 scion and also S.274 stock with Sln.10 and S.4202 showed significantly low compatibility. Among the arabica stocks the Sln.11 has significantly poor compatibility with S.4202 scion. However 100% compatibility was noticed in all the stocks with self scions and scions with self stocks. Among the scions S.795 showed 80% compatibility with CxR robusta stock whereas it has shown 100% compatibility with all other stocks. Similarly Sln.10 scion had 100% success with CxR robusta stock but only 90% with S.274 robusta stock and 100% compatibility with all the three arabica stocks. The scion of S.4202 had 80% compatibility with both the robusta stocks and 100% compatibility with Sln.9 and Sln.5B stocks but only 92% with Sln.11 stock. Among the stocks Sln.9 and Sln.5B have shown 100% compatibility with all the three scions whereas CxR, S.274 and Sln.11 significantly low compatibility. Results 22

20 indicated that in general the compatibility between robusta stocks and arabica scions was poor compared to arabica stocks with arabica scions. The arabica Sln.11 stock have shown poor compatibility with S.4202 arabica scion. The variations in compatibility observed in the present study between different rootstock scion combinations could be due to genetic differences of scion and rootstock materials (Hartmann and Kestar, 1965; Raghuramulu, 1994; Anilkumar et al., 2003). The study confirm that wedge cleft grafting during the month of May (Raghuramulu,1994) has advantage due to high compatibility of 80 to 100% on account of conducive environmental factors. Per cent survival/ mortality Though there is successful graft compatibility, due to genotypic differences of stock and scion materials there are chances of mortality of the seedlings in rootstock scion combinations of the plants. Production of abnormal seedlings and mortality of graft combinations was assessed at the age of 6 months from grafting in comparison with self combinations of root stocks and scion materials used in the present investigation. Significant mortality that ranged from of 0.1% to 46% was observed between rootstock scion combinations. In general, high number of mortality was observed in the scion materials grafted with S.274 robusta rootstocks (28.3%) and in the scions grafted to Sln.9 arabica rootstock (28.3%) followed by Sln.11 rootstock (20.8%). Among the different rootstock scion combinations CxR robusta stock indicated lowest (9.5%) mortality followed by Sln.5B arabica rootstock (12.3%). It is also interesting to note that the self combinations of all the five root stocks and three scion materials also shown mortality to an extent of 8-28%. The per cent mortality ranged between 9-28 % in self combinations of rootstocks and 8-15% in self combinations of scion materials. The self combinations of S.274 robusta have shown significantly high mortality of 28% and self combination of scion material such as S

21 lowest mortality of 8%. The mortality in self combinations could be due to self incompatibility as certain coffee species or genotypes with in the species found to posses incompatibility (Raghuramulu, 1994; Raghuramulu and Purushotham, 1987). The observations on interactions revealed lowest mortality of 0.1% in CxR/S.795 combination whereas the Sln.9/Sln.10 combination showed highest (46%) mortality of the graft seedlings followed by S.274/S.4202 combination (44%). The Sln.5B rootstock with Sln.10 scion also showed significantly lowest mortality to an extent of only 0.1%. However it could be decided that the mortality level of 0.1% observed in CxR/S.795 and Sln.5B/Sln.10 combinations as negligible. The dead rootstock scion showed abnormalities such as poor stunted growth, small leaves with very short internodal length before death. The mortality could be due to genetic differences in rootstock and scions resulted in poor development of union tissue at union portion hindering the translocation processes. Generally closely related species are known to be more compatible but differences do occur with in a species (Hartmann and Kester, 1965). The variations in compatibility and per cent mortality with in the grafts of own species and self combinations observed in this study confirms the assumption that varietal difference do occur with in a given species of coffee and such a low survival of arabica scions on arabica rootstocks was early reported by Raghuramulu and Purushotham (1987). Anilkumar and Srinivasan (2001) reported mortality to an extent of 6% when arabica scions grafted to robusta and tree coffee rootstocks. In tea also variations in graft mortality was reported which varied between 30 to 100% between different rootstock scion combinations (Sreedhar and Satyanarayana, 1996). Hence certain degree of mortality observed between different rootstock scion combinations in the present study could be due to genetic differences among the rootstocks and scion materials. 24

22 Table 1. Different Rootstock Scion Combination Raised using five Different Root Stocks Raising of Rootstock Scion Materials Rootstock Materials Scion Materials Sln.9 S.795 Sln.10 S.4202 Sln.5B S.795 Sln.10 S.4202 Sln.11 S.795 Sln.10 S.4202 S.274 S.795 Sln.10 S.4202 C X R S.795 Sln.10 S.4202 A total of fifteen combination were raised for the purpose of study and compared with Self Combination and Pure line Scion Seedlings.

23 Table 2. Grafting compatibility of stock and scion materials Stock CxR S.274 Sln.9 Sln.5B Sln.11 Scion Self S.795 Sln.10 S.4202 Mean * Self Mean (80) (96) CD at 5% 1% Stock Scion Stock x Scion (90) (98) (80) (80) (92) (90.4) (90) (92) (98) (96.1) * Angular transformed figures; Figures in the parenthesis indicate the actual percentage values Differences in grafting compatibility between different rootstocks and scions compared to selfcombinations. Maximum mortality was seen in the scions grafted to S.274 and selection rootstock and minimum in CxR and Sln.5B rootstocks.

24 Table 3. Mortality of rootstock scion combinations at six months Stock Scion Self S.795 Sln.10 S.4202 Mean CxR 17.51*(09) 2.06(0.1) 25.23(18) 19.46(11) 16.06(9.5) S (28) 33.37(30) 19.25(11) 41.32(44) 31.53(28.3) Sln (10) 36.61(36) 42.75(46) 27.37(21) 31.34(28.3) Sln.5B 22.90(15) 24.57(17) 1.87(0.1) 24.57(17) 18.48(12.3) Sln (18) 26.23(20) 24.57(17) 32.13(28) 26.96(20.8) Self (08) 21.47(13) 23.60(15) 20.41(12.0) Mean 23.22(16.0) 23.17(18.5) 22.52(17.2) 28.08(22.7) 24.29(18.6) CD at 5% 1% Stock Scion Stock x Scion * Angular transformed figures: Figures in the parenthesis indicate the actual percentage values Differences in grafting mortality between different rootstocks and scions compared to selfcombinations. Maximum compatibility was seen in the scion grafted to Sln.9, 5B and Self Rootstocks. The least Compatibility was with diploid rootstocks of CxR and S.274.