Seminars

Rice possesses a fibrous root system comprising the primary root, crown roots that arise in large numbers from the basal stem nodes, and lateral roots that originate from both the primary and crown roots. Two distinct lateral root types are recognized in rice: large L-type lateral roots and small S-type lateral roots. Substantial genotypic variation exists in the densities of both LLR and SLR. We have identified a major quantitative trait locus regulating large L-type lateral root density on crown roots, which explains 46% of the phenotypic variance and confers a 33.8% difference in L-type lateral root density between lines carrying the positive versus negative allele. Additional QTL were detected on chromosome 9 for crown root number, qRNO9, which is distinct from a QTL associated with crown root number qNRN9 expressed during the post-drought period. The objectives of our research are: (1) to elucidate the genetic determinants underlying natural variation in lateral root density, and (2) to determine the functional contributions of different root classes to resource acquisition under nutrient- and water-limited conditions, as well as during post-drought recovery.