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Response to two cycles of S1 recurrent selection for turcicum leave blight in an open pollinated maize variety population (Longe 5)

J. Ayiga-Aluba, R. Edema, G. Tusiime, G. Asea and P. Gibson

Farmers have shown preference for the maize variety Longe 5 because of its quality protein nature, easy access to seed and high adaptability. However production of Longe 5 is constrained by endemic foliar diseases including turcicum leaf blight. The current study determined the effectiveness of two cycles of S1 recurrent selection towards improvement of resistance to turcicum leaf blight as well as improvement of yield and the associated traits. Selections were made by identifying and self pollinating foliar diseases-free plants from the base population of Longe 5 (the original cycle i.e. C0) grown at the National Crops Resources Research Institute (NaCRRI), Namulonge in Uganda. Over 400 selfed ears were obtained and evaluated under artificial inoculation for turcicum leafblight. Remnant seeds of 80 selected S1 lines were grown in isolation to reconstitute a new population of Longe 5 (C1). Individuals in subsequent cycles were not selfed, instead in 2012A, 200 families of C1 were grown in isolation to generate C2. The cycles were evaluated in 2012B following a randomized complete design with split plot arrangement replicated 10 times. Highly significant variations were observed among the S1 lines for turcicum leaf blight (TLB), grain yield (GY), plant height (PH), ear height (EH), ear aspect (EA), days to an thesis (DTA) and days to silking (DTS). Selection differential was positive for GY (0.12), PH (3.89) and EH (1.69) while it was negative for AUDPC (-2.98), EA (-0.085) and DTS (-0.83) as desired. The gain per cycle from C0 to C2 was -3.75% for DTA,-4.88% for DTS, -20.16% for EA, and -26.43% for AUDPC reflecting a significant reduction in the disease severity and significant improvement in the other traits. Positive significant gain was realised for grain yield (8.35%), 12.61% for EH and 0.21% for PH. There was a higher % gain cycle-1 realised for AUDPC in C1 (-18.21%) than in C2 (-10.07). Similar positive trends were realised for GY, DTA and DTS. The results indicate that the S1 recurrent selection method employed was effective in improving Longe 5 for TLB, grain yield and the associated traits