Development of pigeonpea [Cajanus cajan (L.)] hybrids for the semi-arid Kenya.
Pigeonpea (Cajanus cajan (L.) Millsp.) is cultivated by many farmers in the semi-arid areas of Kenya as a source of food and cash. However, the yields have remained low, ranging between 500 to 800 kg haˉ¹. Apart from drought, fusarium wilt is reported to affect yield. Breeding pigeonpea hybrids, using cytoplasmic male sterile (CMS) lines, hybridized with the local improved germplasm, have the potential for increasing yield and improve income for smallholder farmers. The objectives of the study were to: 1) examine the various stakeholders of the pigeonpea value chain and their core functions and identify characteristics of the pigeonpea varieties preferred by the market to be considered in the hybrid breeding programme, 2) evaluate cytoplasmic male sterile lines of Indian origin for stability across several environments in Kenya, 3) screen pigeonpea genotypes for general resistance to Fusarim udum Butler and 4) evaluate pigeonpea hybrids for grain yield and earliness across sites and seasons in Kenya. The stakeholder analysis established that the main players in the pigeonpea value chain were farmers, traders/processors, International Crops Research Institute for the Semi-Arid Tropics, Kenya Agricultural Research Institute, Kenya Plant Health Inspectorate Services, and Ministry of Agriculture. White seed, large seed size and medium maturity were the preferred traits by farmers and processors/exporters for both domestic and export markets. The unavailability of quality seed in sufficient quantities of high yielding varieties was cited as the main factor negatively affecting pigeonpea production. The stakeholder analysis approach, used for the first time in a breeding programme, demonstrated that it can be an important tool that can be used to diagnose crop production constraints, and define opportunities available for setting up a breeding programme that is highly client-oriented. Two CMS lines, ICPA2043 and ICPA2039 were the most stable across sites with 100% and 99% pollen sterility respectively. Screening for the presence of physiologic races of F. udum based on morphological and cultural characteristics on PDA identified three distinct isolate groups named ISO-A, ISO-B, and ISO-C. Studies under controlled conditions using the three isolates identified seven pigeonpea genotypes (ICPB2043, ICP12012, ICP13092, ICPA2039xICP13092, ICPA2043xICP12012, ICPA2043xICP13092, ICPA2043xICP9135) resistant to the three F. udum isolates. In the field evaluation, seven genotypes (ICPA2039xICP13092, ICPA2039xAsha, ICPA2043x12012, ICPA2043xICP13092, ICPA2043xICEAP557, ICPB2043 and Maruti) were found to be moderately resistant. The variances due to GCA and SCA were significant, showing that both additive and non-additive gene actions were important. The resistant hybrid, ICPA2043xICP12012 had the highest negative SCA that was highly significant for all the isolates and in the field indicating general resistance. The CMS (A) line ICPA2043 was found stable across environments and highly resistant to the three F. udum isolates. Therefore, it can be evaluated further for commercial hybrid seed production in Kenya. Evaluation of the pigeonpea genotypes across environments indicated that the highest yielding environment was Kiboko, with average and maximum yield of 2,249 kg haˉ¹ and 4,234 kg haˉ¹ respectively. Most hybrids were in the medium duration maturity group with days to maturity ranging from 147 to 186. Overall, the highest yielding hybrids were A2043xTZ26 and ICPA2039xTZ24 with mean yields 2,803 kg haˉ¹ and 2,527 kg haˉ¹ respectively. Mean yields for the best performing parents were 2,036 kg haˉ¹ for ICP12012 and 1,629 kg haˉ¹ for Asha. For specific sites, the highest yielding hybrids in Kabete, Kiboko and Leldet were A2039xTZ24 (2,057 kg haˉ¹), A2043xTZ26 (2,803 kg haˉ¹), and A2043xUG8 (1,708 kg haˉ¹) respectively. Mean heterosis for yield varied from -35% (A2039xA2043) to 50% (A2043xUG8). In Kenya, the potential for production and commercialization of hybrid pigeonpea is feasible due to high hybrid vigour recorded, and the stability of the CMS lines. Hybrids also have greater uniformity in grain size a factor which is important for the market.
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