Assessing the genetic value of exotic maize inbred lines and agronomic performance of their corresponding maize single-cross hybrids with the elite CIMMYT lines.

Abstract

Exotic germplasm is known to improve productivity and variability of the locally adapted populations, however little has been done to assess gains that could be attained after genetic integrations in the CIMMYT-Zimbabwe maize breeding program. The objectives of the experiment were to: (i) identify high yielding and stable single cross hybrids of the local (i.e., CIMMYT-Zimbabwe lines) and the exotic lines; and, (ii) to estimate the combining abilities of the local and the exotic inbred lines. In this study, exotic inbred lines sourced from the CIMMYT’s temperate (T), tropical (E) and sub-tropical (S) breeding programs were crossed with the CIMMYT-Zimbabwe (L) elite lines, using the partial diallel mating design. The 91 singe-cross hybrids (F1s) generated were evaluated together with nine (9) commercial check hybrids in multi-environmental trials (METs) at eight locations, representing the diverse maize growing conditions in Zimbabwe. MET data showed differences in grain yield (GY) performance of the singe-cross hybrids in some of the sites. Significant effects of the environment in hybrid performance was also detected (GEI; p < 0.05). Crosses between the local and temperate inbred lines (LXT) showed the highest GY potential (e.g., G55; GY = 10.2924 t/ha) compared to the other crosses. Apart from showing high GY potential, hybrids from this combination also demonstrated to; be stable in diverse environments, to mature earlier than the best commercial check hybrids. In conclusion, incorporation of exotic genes, especially those with a temperate background, may improve the yielding ability and stability, and can introduce earliness in maturity in the local maize populations (i.e., sub-tropical maize populations).