DEVELOPMENT AND YIELD STABILITY OF YELLOW MAIZE (Zea mays L.) HYBRIDS RESISTANT TO Striga hermonthica IN MALI
ABSTRACT
Maize (Zea mays L.) production is constrained by Striga hermonthica in Mali leading to high yield losses. To minimize the negative impact of the parasite, breeding hybrid maize resistant to S. hermonthica is a promising alternative. Some resistant varieties are available but efforts to breed hybrid resistant to S. hermonthica however, are yet to take off. The general objective of this study was to improve maize yield through the development of high yielding and adapted hybrids resistant to S. hermonthica. The specific objectives were (i) to identify farmers’ major maize production constraints and preferred varieties, (ii) to identify inbred lines with resistance to Striga hermonthica, (iii) to estimate heterosis and stability of hybrids under Striga-infested and Striga-free conditions, and (iv) to determine the combining ability of parents and their hybrids under Striga-infested and Striga-free conditions. Data were collected from farmers through focus group discussions followed by interview of individual farmers in Striga endemic communities in Bancoumana and Kolokani where maize is used for consumption and sale. The results indicate that Malian farmers grew local maize varieties and had low adoption of improved varieties. Farmers identified three major constraints to maize production namely low soil fertility, fertilizer cost and infestation by S. hermonthica. Farmers’ coping strategies for S. hermonthica control in the two communities were use of landraces and OPVs, use early and intermediate and homestead. Beside the differents control methods farmers used strategies. The top three preferred traits were high yielding, early maturity and Striga resistance. Line by tester crosses involving fifteen (15) lines and three (3) testers were used to determine genetic parameters, heritability, combining ability and heterosis for yield, Striga traits and related agronomic traits. Evaluation of parents, crosses and checks was carried out under artificial Striga-infested and Striga-free conditions in Sotuba and Sanankoroba for two years. Grain yield, days to 50% anthesis and silking, plant height, ear height, Striga related traits, plant aspect, and ear aspect had high heritability values under Striga-infested conditions. Ten inbreds, TZISTR1028, TZISTR1223, TZISTR1218, TZISTR1214, TZISTR1235, TZISTR110, TZISTR106, TZISTR112, TZISTR1211 and TZISTR1222 were Striga resistant. Specific combining ability (SCA) effects had greater proportion of variance than general combining ability (GCA) effects, suggesting that non-additive gene effects control the inheritance of yield and Striga resistance. Good combiners for yield and Striga damage ratings under Striga-infestation were TZISTR1214 and TZISTR1223. However, TZISTR1223 had good GCA for grain yield under both Striga-infested and Striga-free conditions. Two hybrids TZISTR1207/TZISTR1214 and TZISTR106/TZISTR1218 as high yielding and stable under Striga-infested conditions and TZISTR106/TZISTR1028 as high yielding but not stable under Striga-free conditions.The hybrids TZISTR1207/TZISTR1214 and TZISTR1033/TZISTR1223 were stable and high yielding across environments.