SCREENING OF SELECTED COMMON BEAN VARIETIES FOR RESISTANCE TO BEAN BRUCHIDS(Acanthoscelides obtectus say) JOSEPH MUGO WAMBUGU A22/35452/2010 DR.DORA KILALO
INTRODUCTION The common dry bean is the most important food legume directly consumed in the world. In Africa, beans are grown for subsistence even having been proved that beans are a major source of dietary protein, which is approved that for good body health a person needs at least 70grams protein per day(lowry, 1976). Its quality in terms of colour, taste, nutritional and physical characteristics is of great significance to the ultimate consumer.
Problem statement There has been a drastic yield loss to storage pests due to poor post harvest handling and storage structures, ultimately leads to food insecurity, hunger and low farm income. Justification Chemicals have been used in control of A. obtectus by malathion and lindane but their use has been reported to fail due to strains emergence that are resistant to insecticide (Champ and Dyte, 1977). Nevertheless, use of insecticide in storage could be hazardous than field use due to low or no degradation
Objective To determine the bean variety that is resistant to bean weevils. Specific objective 1.To determine the percentage weight loss among various bean varieties to bean bruchids. HYPOTHESIS There is no difference in damage/losses among various bean varieties due to bean weevil(a. obtectus)
Method and Materials Six varieties (treatments) were used for the study namely;katb 1, GLP 585( Red Haricot bean), SAITOTI, GLP 2 (Rose coco), NYAYO and GLP24(Canadian wonder).they were obtained from the local market. Bean seeds were preconditioned to the experimental conditions for one week before use. Their moisture content was determined for proper experimental conditions For average growth and development, most of bean weevils prefer seeds with about 7-12% moisture content(munro, 1966).
Cont.. Moisture content was determined using moisture meter and ranged between 9.25% and 11.24%. The colony of A.obtectus used was reared at entomology unit laboratory of the University of Nairobi. The plastic containers used were obtained from suppliers at a cost and small holes made on the lid of the container to allow for free circulation of air. This experiment was set up to test whether there is a difference in susceptibility of different varieties of beans when artificially infested with A. obtectus
Cont For each variety,400g of bean seeds were mixed 60 bruchids in equal proportions of male to females into 250ml 2 plastic containers each having 200g. Each variety was replicated four times and the experiment was subjected to a complete randomized design (CRD). The containers were kept in an experimental room at the field station and after 10days the parents were removed and discarded having oviposited. 100 seed weight was collected every two weeks for 3 months using an electronic weighing balance to measure the weight loss of seeds in storage.
means(gm) RESULTS 4 3.5 3 2.5 2 1.5 Series1 1 0.5 0 NYAYO GLP24(canadian wonder) GLP585(Red haricot) varieties comparison of means SAITOTI GLP2(rosecoco) KATB1
% CUMULATIVE WEIGHT LOSS 6 5 4 3 2 NYAYO CANADIAN WAIRIMU SAITOTI ROSECOCO KATB1 1 0 0 1 2 3 4 5 6 SAMPLING PERIOD (week) % CUMMULATIVE WEIGHT LOSS AGAINST TIME
DISCUSSION The results indicated that Nyayo had the least percentage weight loss. Canadian wonder and Saitoti being comparable had the highest weight loss over a period of 3 months. Red haricot(wairimu) and rose coco weight loss attributed to damage coursed by bruchid were not significantly different. KATB1 was significantly different from all the others other than Nyayo variety. The differences in preference of various bean varieties by the bean bruchid could be attributed to seed size, physical characteristic of the bean variety such as colour, shape and seed cot hardness.
Cont KATB1,having been synergized with other cultural pest management can produce a desirable result and aid the effort to enhance food security and alleviate poverty in developing countries.
GLP24-Canadian wonder KATB1 Nyayo
GLP585-red haricot Saitoti GLP2-Rosecoco