Abstract
The type of gene action conferring combined resistance to maize streak virus (MSV) and maize stripe virus (MStV) was investigated in a Quality Protein Maize (QPM) population, ART/98/SW6-OB. Full-sib and half-sib progenies generated using North Carolina Design I mating scheme were evaluated in 2015 and 2016 in two locations endemic to the viral diseases in Nigeria. Serological study was also conducted on the progenies to validate the disease scores on the field. Significant mean square of genotypes was observed for MSV severity, MStV incidence and severity, plant height and days to flowering, while mean square of environment by females in males’ interaction was significant for grain yield and MSV incidence. Estimates of additive variances were larger than dominance variance for grain yield and MSV severity with moderate to high narrow-sense heritability estimates. This indicates that there is adequate genetic variability for improving grain yield and resistance to MSV in the maize population. The mean titre values of MSV and MStV for the progenies were significantly higher than the healthy control. MSV and MStV incidence were negatively correlated to days to 50% silking. Titre values were negatively correlated with grain yield but positively correlated with MSV and MStV incidence. Recurrent selection method that capitalizes on both additive and dominance variances would be effective in improving the population for grain yield and resistance to MSV and MStV diseases. Key words: Correlation, gene action, maize streak virus, maize stripe virus, resistance, North Carolina design.
Highlights
The development of quality protein maize (QPM) which contains twice the levels of tryptophan and lysine in most normal endosperm maize has brought a great hope for human and animal nutrition (Akande and Lamidi, 2006)
It is a flint-dent, intermediate maturing, and whitegrained maize population adapted to the forest zone. 200 noninbred (S0) plants were randomly selected from the maize population and used to produce both full- and half-sib progenies using the North Carolina Design I (NCD I) mating scheme of Comstock and Robinson (1952)
The moderate grain yield (1.84 ton/ha) despite the high Maize stripe virus (MStV) incidence suggested that the maize population has some level of tolerance for MStV infection
Summary
The development of quality protein maize (QPM) which contains twice the levels of tryptophan and lysine in most normal endosperm maize has brought a great hope for human and animal nutrition (Akande and Lamidi, 2006). Despite this good attribute, QPM varieties are threatened by downy mildew and Maize Streak Virus (MSV) diseases among other constraints (Mariote, 2007). Maize stripe virus (MStV) and MSV are two of the biotic factors responsible for reduced yield in maize in Africa (Shepherd et al, 2010). The symptoms are characterized by broken to almost continuous chlorotic stripes centered on tertiary leaf veins
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