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Masuka B.,Maize and Wheat Improvement Center | Magorokosho C.,Maize and Wheat Improvement Center | Olsen M.,CIMMYT | Atlin G.N.,Bill and Melinda Gates Foundation | And 15 more authors.
Crop Science | Year: 2017

Open-pollinated varieties (OP Vs) still represent a significant proportion of the maize (Zea mays L.) seed system in many countries of sub-Saharan Africa. The International Maize and Wheat Improvement Centre (CIMMYT) has been breeding improved maize varieties for the stress-prone environments experienced by most smallholder farmers in eastern and southern Africa for over 30 yr. Hybrid breeding is now the major focus of the CIMMYT breeding pipeline. However, OP Vs are generated within the hybrid pipeline. This is the first study to document genetic gain for maize grain yield under both optimal and stress (random and managed drought, low nitrogen [N], and maize streak virus [MSV]) conditions within the CIMMYT eastern and southern African OP V breeding pipeline. Genetic gain was estimated using the slope of the regression on the year of OP V release in regional trials over a 12-yr period (1999–2011). Open-pollinated varieties were separated into two maturity groups, early (<70 d to anthesis) and intermediate-late (>70 d to anthesis). Genetic gain in the early maturity group under optimal conditions, random drought, low N, and MSV was 109.9, 29.2, 84.8, and 192.9 kg ha−1 yr−1. In the intermediate-late maturity group, genetic gain under optimal conditions, random drought, low N, and MSV was 79.1, 42.3, 53.0 and 108.7 kg ha−1 yr−1. No significant yield gains were made under managed drought stress for both maturity groups. Our results show continued improvement in OP Vs for both yield potential and stress tolerance. © Crop Science Society of America.

Ornella L.,French Argentine International Center for Information and Systems science | Sukhwinder-Singh,Maize and Wheat Improvement Center | Perez P.,Colegio de Mexico | Burgueno J.,Maize and Wheat Improvement Center | And 7 more authors.
Plant Genome | Year: 2012

Durable resistance to the rust diseases of wheat (Triticum aestivum L.) can be achieved by developing lines that have racenonspecific adult plant resistance conferred by multiple minor slow-rusting genes. Genomic selection (GS) is a promising tool for accumulating favorable alleles of slow-rusting genes. In this study, five CIMMYT wheat populations evaluated for resistance were used to predict resistance to stem rust (Puccinia graminis) and yellow rust (Puccinia striiformis) using Bayesian least absolute shrinkage and selection operator (LASSO) (BL), ridge regression (RR), and s upport vector regression with linear or radial basis function kernel models. All parents and populations were genotyped using 1400 Diversity Arrays Technology markers and different prediction problems were assessed. Results show that prediction ability for yellow rust was lower than for stem rust, probably due to differences in the conditions of infection of both diseases. For within population and environment, the correlation between predicted and observed values (Pearson's correlation [ρ]) was greater than 0.50 in 90% of the evaluations whereas for yellow rust, ρ ranged from 0.0637 to 0.6253. The BL and RR models have similar prediction ability, with a slight superiority of the BL confirming reports about the additive nature of rust resistance. When making predictions between environments and/or between populations, including information from another environment or environments or another population or populations improved prediction. © Crop Science Society of America.

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