Root growth of soybean cultivars under different water availability conditions

Vigorous growth of soybean root system is a desired trait in breeding programs. However, few studies have evaluated this feature under field conditions. The aim of this research was to evaluate root growth of eight soybean cultivars under different water availability conditions. The experiment was carried out in Londrina, Paraná state, Brazil, during two growing seasons - with and without water deficit during the vegetative period. Soybean roots were sampled at flowering and assessed for dry matter yield, area and length at 0-0.25; 0.25-0.50; 0.50-0.75 and 0.75-1.00 m depth ranges. On average, root length and area of the cultivars Embrapa 48 and BRS 284 under water deficit were 66% and 40% larger than the others at 0.25-0.50 and 0.50-0.75 m layers, respectively. Under suitable water supply, BRS 282 showed the highest root length and area. Apart from the cultivars Embrapa 48, BRS 284, and BRS 255RR, soybean root growth was mostly lower under water deficit throughout the vegetative stage, which might been due to a higher soil resistance to root penetration, resulting from low soil water content. Drought increased the proportion of soybean roots at subsoil layers, mainly for Embrapa 48 and BRS 284. The cultivars Embrapa 48 and BRS 284 are promising to be used in breeding programs targeting superior root growth in subsoil layers.