Combining Ability for Resistance to Maize Lethal Necrosis Disease in Kenya

Abstract

Maize is a natural host to more than 50 viruses including members of the Potyviridae group which in combination with Maize Chlorotic mottle virus (MCMV) cause maize lethal necrosis leading to high yield losses. A study involving an assortment of maize germplasm was used to estimate the genetic effects attributable to the resistance to maize lethal necrosis resistance. The maize genotypes were crossed in a North Carolina design II to generate 25 crosses. The parents and their derivative crosses were screened for their combining ability for MLN and associated disease parameters. Among the parents involved in the study, only one parent UON-2015-119 showed desirable GCA for all the traits implying diversity of the rest of the material involved. Thus, the good combiners for the different traits could be used to produce desirable transgressive segregants to maximize the disease resistance. For the SCA effects, UON-2015- 50/ UON-2015-109, UON-2015-50 /UON-2015-112 and UON-2015-50 / UON-2015- 113 showed good values for all the disease parameters. These elite crosses had the parent UON-2015- 50. The parent UON-2015- 50 showed poor GCA effects for all the disease parameters. Also, the parent UON-2015-119 showed poor SCA effects despite the desirable GCA effect for all the disease parameters. This implies that any breeding method chosen should first accumulate favourable genes in homozygous state while breaking the linkage blocks. Also, non additive gene action attributable to both additive x epistatic and dominance x dominance gene interaction could be responsible for the resistance to the MLN. The non additive gene action is also non allelic and produces over-dominance which is non fixable. These superior parents and crosses could be used to develop maize varieties to improve maize production in Kenya.