Soya bean (Glycine max L. Merr.) genotype response to early-season flooding:: II.: Aboveground growth and biomass

Soya bean is often grown in regions prone to periodic flooding, thus selecting cultivars that maintain production under waterlogged conditions is desirable. An experiment involving flooded soya beans was planted in southern Florida to examine (1) stem and leaf growth; (2) morphological adaptations; and (3) the relationship between early-season and late-season flood tolerance in flooded soya beans. Eleven soya bean genotypes previously defined as tolerant or sensitive to flooding were subjected to three treatments at 21 days after sowing (DAS): (1) no flood, (2) 2-week flood and (3) 4-week flood. All plants were harvested 49 DAS. Flooded plants exhibited lower stem dry weights but greater partitioning to the stem. Non-flood treatments had greater leaf dry weight, leaf area and partitioning to leaves than flooded plants. There were positive correlations of genotype stem dry weight and leaf dry weight to early-season flood tolerance but stem partitioning was negatively correlated with early-season flood tolerance. Genotypic rankings of early-season flood tolerance in this study were not correlated with earlier studies basing flood tolerance on seed yield. Our study highlights the range of soya bean morphological adaptations in response to flood. However, our results indicate that early-season screening may not be an accurate predictor of soya bean genotypic response to late-season flood.