Exploring natural variation of root architectural traits in seedlings of maize hybrid and inbred lines from Thailand

Root architectural traits refer to a spatial configuration of the root system providing a critical role in soil resource acquisition. In past decades, several lines of evidence have shown that maize possesses large phenotypic variations, including root architecture closely relating to physiological utility. Thailand has developed a unique maize germplasm over the years; however, root traits have often been neglected and have yet to be explored. In this present study, we examined natural variation of root architectural traits of twenty-eight inbred and hybrid lines at the seedling stage using a well-established roll-up culture system. We found that variation in root traits ranged from 4.22-fold in primary roots to 13.14-fold in seminal root length, while shoot mass presented the highest phenotypic variation among traits (23.42-fold). Most root architectural traits of maize hybrid lines were significantly higher than the inbred lines, particularly, seminal root length, which was 34.30% greater than that of inbred lines. In addition, we found that root traits, like other agronomic traits, express heterosis. Our findings suggest ample opportunity for incorporating root traits in maize breeding program in Thailand.