Root Elongation Among Diverse Soybean Genotypes.

Soybean (Glycine max L.) is an important crop with a wide range of agricultural and industrial uses.  Environmental factors such as water availability can have a large negative impact on soybean yield and quality and many soybean growing regions are predicted to have decreased rainfall over the next 50 years.  Understanding root anatomy and growth patterns will help us better understand how soybeans access water at different rooting depths.  This study aims to elucidate root elongation in select soybean genotypes previously studied in 2-3 week greenhouse experiments.  A total of 30 soybean genotypes (5 replications each) were grown in clear plastic tubes placed at an angle in the greenhouse to record weekly growth rates and overall root complexity for 6 weeks.  The five genotypes identified to have the deepest roots had an average rooting depth of 95.70 cm compared to 64.50 cm in the five shallowest rooting genotypes.  The deep rooting genotypes also had significantly higher average overall complexity rating score with 3.42 compared to 2.37 for the shallow rooting genotypes. Examination of daily growth rates revealed that deep rooters had the highest daily growth rates during the second week after planting while shallow rooting genotypes tended to have the highest daily growth rates during the third week.  Among the examined lines, 8 were identified for follow-up physiological studies, to develop mapping populations for rooting depth, and complementary studies examining root growth in the field.