Variance components and heritability of traits related to root: shoot biomass allocation and drought tolerance in wheat

Enhanced root growth in plants is fundamental to improve soil water exploration and drought tolerance. Understanding of the variance components and heritability of root biomass allocation is key to design suitable breeding strategies and to enhance the response to selection. This study aimed to determine variance components and heritability of biomass allocation and related traits in 99 genotypes of wheat (Triticum aestivum L.) and one triticale (X. Triticosecale Wittmack) under drought-stressed and non-stressed conditions in the field and greenhouse using a 10x10 alpha lattice design. Days to heading (DTH), days to maturity (DTM), number of tillers (NPT), plant height (PH), spike length (SL),shoot and root biomass (SB, RB), root to shoot ratio (RS), thousand kernel weight (TKW) and yield (GY) were recorded. Analyses of variance, variance components, heritability and genetic correlations were computed. Significant (p<0.05) genetic and environmental variation were observed forall the traits except for spike length. Drought stress decreasedheritability of RS from 47 to28% and GY from 55to 17%. The correlations between RS with PH, NPT, SL, SB and GY were weaker under drought-stress (r-0.50; p<0.05) compared to non-stressed conditions, suggesting that lower root biomass allocation under drought stress compromises wheat productivity. The negative association between GY and RS (r=-0.41 and -0.33; p<0.05), low heritability (<42%) and high environmental variance (>70%) for RS observed in this population constitute several bottlenecks for improving yield and root mass simultaneously. However, indirect selection for DTH, PH, RB, and TKW, could help optimize RS and simultaneously improve drought tolerance and yield under drought-stressed conditions.