Evaluation of Malawi pigeon pea (cajanus cajan l) accessions for tolerance to moisture stress and superior agronomic traits in Uganda.
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Narrow genetic diversity among Ugandan local germplasm has greatly slowed down pigeon pea breeding progress in Uganda. Low yielding and drought susceptible cultivars are under cultivation by farmers due to unavailability of improved varieties with farmers’ preferred traits. This has contributed to the decline in area under pigeon pea cultivation with farmers’ shifting interest to other competitive crops. However, the crop is still popular with farmers as is evidenced by its backyard cultivation. It is therefore believed that, the crop can regain its productivity after improvement on drought and other traits of economic importance. In this study, 52 pigeon pea accessions from Malawi, two local check varieties (20L and 22L) from Uganda were evaluated under field conditions for agronomic traits of economical importance at Makerere University Agricultural Research Institute-Kabanyolo (MUARIK) in Wakiso district for two rain seasons (2010a and 2011b) and at Ngetta Zonal Agricultural Research and Development Institute (NgeZARDI) in Lira district in Uganda for (2010a) season . The experiment was set up in a partially balanced lattice and replicated twice. Data on days to 50 % flowering and days to 75 % maturity, plant height, yield and yield components were recorded. Pest damage levels due to pod suckers Clavigralla tomentosicollis Stal., pod borers Helicoverpa armigera Hubner and pod fly Melanagromyza chalcosoma Spencer were recorded on the accessions at flowering, podding and pod maturity. Results showed no significant differences (P > 0.05) for all tested lines in their response to pest damage across locations. However, significant differences (P ≤.0.01) to pest damage were expressed across seasons at MUARIK. Across locations results showed that 90% of the lines were highly resistant at flowering, 19% during podding and 21% at pod maturity while 78% were highly resistant to pest damage at all stages. Significant differences at (P ≤ 0.05) were observed for days to 50 % flowering and 75 % maturity, plant height, yield and yield components among genotypes. About 22 % expressed short maturity duration, 77% were xii medium duration while only 1% exhibited long duration maturity period. Sixty nine percent of the accessions were medium seeded and about 22% of these accessions including local check 20L gave yield of > 500kg/ha for both across locations and seasons. Accessions in this include; KB05-2, KB06, KB14, AP02, AP04, AP29, 2246, 2256, 2306, 2321 and 2328. Grain yield showed high and positive association with 100 seed weight (r=0.603**) and number of pods per plant (r=0.888***). Based on the above traits, 14 lines; 2311, 2302, 2047, 2300, 2263, KB05-2, KB03, KB06, KB08, AP10, AP10 (2), AP10 (3), AP01 and 20L were selected and screened for post flowering drought tolerance alongside checks KAT 60/8 and ICEAP00068 using a two factorial (watering regimes and genotype) split plot experimental design. The experiment involved the accessions being subjected to four watering regimes; i) 1000mm, ii) 500mm, ii) 250mm and iv) 0 mm applied every seven days starting at 50% flowering (approximately 97 days after planting) until harvest and the experiment was repeated twice. Data was collected on relative leaf water content, chlorophyll content, leaf defoliation and flower fall, leaf wilting, root biomass and grain yield. Results showed that post flowering drought significantly (P < 0.05) reduced grain yield by 50%. Accessions KB06, KB08 and KB05-2 recorded higher significant (P < 0.001) drought tolerance efficiency (DTE ≥ 80%), lower drought susceptibility index (≤ 1) and high grain yield compared to KAT 60/8, ICEAP00068 and 20L. Accession AP10 gave zero yield under 500mm, 250mm and 0mm water treatment and was therefore regarded the most susceptible to post flowering drought. These results demonstrate that Malawian pigeon pea accessions have exploitable amount of genetic diversity useful to improve yield and drought tolerance traits in current Uganda local germplasm. However, multi-location evaluation, inclusion of farmers’ preferences and understanding the physiological relationship of drought parameters and yield should be considered in follow up studies