Browsing by Author "Olsen, Michael"

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    Grain yield performance and flowering synchrony of CIMMYT’s tropical maize (Zea mays L.) parental inbred lines and single crosses
    (Euphytica, 2016) Worku, Mosisa; Makumbi, Dan; Beyene, Yoseph; Das, Biswanath; Mugo, Stephen; Pixley, Kevin; Ba¨nziger, Marianne; Owino, Fidelis; Olsen, Michael; Asea, Godfrey; Prasanna, Boddupalli M.
    Maize production constraints in sub-Saharan Africa (SSA) are being addressed by CIMMYT and partners through an array of projects, focusing on developing and evaluating parental inbred lines and single-crosses as well as formulating, evaluating and releasing high-yielding and stress resilient hybrids adapted to different agro-ecologies. The objectives of the present study were to (1) evaluate the grain yield performance of parental elite inbred lines developed over the years, and single crosses; and (2) ascertain the flowering synchrony among inbred lines and singlecross hybrid parents. Parental inbred lines and singlecrosses were evaluated at seven locations in two countries in 2014. Combined analysis of variance revealed differences (P\0.01) among genotypes for grain yield (GY) and among different years/era of release of the inbred lines. The improvement in GY of inbred lines was estimated to be 1.4 %per year. Under irrigated conditions GY of some single-cross hybrids was over 16 t ha-1. Some single-cross and inbred line parents showed acceptable flowering synchrony, good producibility, and stable performance across testing environments, suggesting that these have high potential for seed production. Further research is needed to determine the physiological and morphological characteristics that contributed to the GY improvement in the parental inbred lines. Information generated from this study will enhance the use of CIMMYT’s tropical mid-altitude parental germplasm by breeders working in both private and public breeding programs for developing and deploying high-yielding maize hybrids for the benefit of small-scale farmers in SSA.
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    Performance and yield stability of maize hybrids in stress-prone environments in eastern Africa
    (The crop journal, 2020) Santos Rezende, Wender; Beyene, Yoseph; Mugo, Stephen; Ndou, Eric; Gowda, Manje; Sserumaga, Julius Pyton; Asea, Godfrey; Ngolinda, Ismail; Jumbo, McDonald; Oikeh, Sylvester O.; Olsen, Michael; Boréma, Aluízio; Damião Cruz, Cosme; Prasanna, Boddupalli M.
    Identification and deployment of high-yielding and stress-tolerant maize hybrids adapted to stress-prone agro-ecologies is important for improving the food security and livelihoods of smallholder farmers in eastern Africa. The objectives of this study were to (i) assess the performance of maize hybrids under well-watered and drought stress conditions; (ii) evaluate grain yield stability of 65 intermediate-maturing and 55 early-maturing hybrids in 24 well-watered locations and seven drought stress locations; and (iii) identify representative and/or discriminative testing locations for increasing genetic gains for the target traits. There were significant differences for grain yield among early- and intermediatematuring hybrids tested under well-watered and drought stress environments. Among the early-maturing hybrids, the top 10 hybrids produced 46.8%–73.9% and 31.2%–42.1% higher mean grain yields than the best commercial check under drought and well-watered conditions, respectively. Among the intermediate-maturing hybrids, the top 10 hybrids produced 25.2%–47.7% and 8.5%–13.5% higher grain yield than commercial checks under drought stress and well-watered conditions, respectively, suggesting improvement in the levels of drought tolerance in both early- and intermediate-maturing hybrids. GGE biplot analysis and a bi-segmented regression linear method identified specific early-maturing and intermediate-maturing hybrids that performed well under both well-watered and drought stress conditions. These hybrids could be recommended for commercial production in eastern Africa. Kakamega in Kenya was found to be the most representative and highly discriminating site among well-watered testing locations, while Kabuku in Tanzania was the least representative of test locations. For testing under drought stress conditions, Kiboko in Kenya was identified as the most representative location. This information could be useful for allocating resources and streamlining CIMMYT maize hybrid testing in eastern Africa.