Evaluation of selected MRI seed maize (zea mays.l) inbred lines for tolerance to seedling drought stress.

Abstract

Zambia’s many seed companies are involved in maize cultivar development with the primary focus of breeding for yield and disease tolerance. Despite having high yielding potential, most available maize cultivars are greatly affected by drought and heat stress. The parental line stock used in the development of most cultivars have not been evaluated for resilience to drought and climate shocks. Therefore, the aim of this study was to evaluate 18 selected MRI-Seed maize (Zea mays L.) inbred lines for tolerance to drought stress imposed at seedling growth stage. The study was conducted at Chakana Farm where twenty seedlings for each of the 18 MRI seed maize inbred lines were raised in a Randomized Complete Block Design (RCBD) with three replicates. The plants were observed for 42 days for their phenotypic expression and growth performance under water stress conditions and data on vegetative seedling traits were recorded. Data collected was subjected to Analysis of Variance (ANOVA), Principal Component Analysis (PCA) and correlation analysis. Results of the study showed significant differences at p≤0.05 and p≤0.01 among the parental lines on moisture content of root, fresh shoot weight, total fresh biomass and seedling aspect, indicating that there was wide variability in the response of the genotypes for tolerance to drought at seedling stage. Principal Component Analysis also confirmed these traits as the primary ones contributing to diversity among the parental lines under induced drought stress at seedling growth stage, in that they were loaded under PC1 with Eigen values greater than 0.3 and contributing 27% of total effect observed while other traits collected were loaded in PC2 and PC3 with total effect contribution of 22% and 19% respectively. Correlation analysis showed differential association among traits of the parental lines, indicating that mechanism of tolerance to drought among the lines were different and that seedling aspect, moisture content of root , fresh shoot biomass, and total fresh biomass were important drought adaptive traits that could be considered for base indexing when selecting drought tolerant maize genotypes at seedling stage. The correlation coefficients of root moisture content to seedling aspect and total biomass was r =0.56* and r =0.99** (at p≤0.05 and p≤0.01) respectively. Overall, the study identified five MRI inbred lines, coded as 15ZMB990298, 15ZMB990309, 16ZM901059, 16ZM902623 and 16ZM920511 to be well tolerant to water stress at seedling growth stage. These inbred lines could be recommended for inclusion in crossing blocks to generate F1 drought tolerant hybrids at seedling stage depending on their General Combining Ability (GCA) and also Specific Combining Ability (SCA). Key words: Maize, principal component, biomass, seedling aspect, root moisture