Mapping QTLs and candidate genes for rice root traits under different water-supply conditions and comparative analysis across three populations.

To investigate the genetic factors underlying constitutive and adaptive morphological traits of roots under different water-supply conditions, a recombinant inbred line (RIL) population derived from a cross between the lowland rice variety IR1552 and the upland rice variety Azucena with 249 molecular markers, was used in cylindrical-pot experiments. Eighteen QTLs were detected for seminal root length (SRL), adventitious root number (ARN), and lateral root length (LRL) and lateral root number (LRN) on the seminal root at a soil depth of from 3 to 6 cm under flooding and upland conditions. One identical QTL was detected under both flooding and upland conditions. The relative parameters under the two water-supply conditions were also used for QTL analysis. Five QTLs for upland induced variations in the traits were detected with the positive alleles from Azucena. A comparative analysis was performed for the QTLs detected in this study and those reported from two other populations with Azucena as a parent. Several identical QTLs for root elongation were found across the three populations with positive alleles from Azucena. Candidate genes were screened from ESTs and cDNA-AFLP clones for comparative mapping with the detected QTLs. Two genes for cell expansion, OsEXP2 and endo-1,4-beta-D-glucanase EGase, and four cDNA-AFLP clones from root tissues of Azucena, were mapped on the intervals carrying the QTLs for SRL and LRL under upland conditions, respectively.

[QTLs and epistasis underlying rice (Oryza sativa L.) panicle length in different genetic background and environments].

A double haploid (DH) population and a recombinant inbred (RI) population derived from a cross between a japonica male parent Azucena and indica female parents, IR64 and IR1552 respectively, were used in both field and pot experiments for detecting QTLs and epistasis for rice panicle length in different genetic background and different environments. Panicle length (PL) was measured at maturity. QTLs for PL were detected using single marker analysis and interval mapping. Epistasis effects on the trait were also analyzed. Nine QTLs were detected in DH population, including 5 QTLs detected from field experiment and 4 from pot experiment, among them 3 QTLs mapped on chromosomes 1 and 4 were identified in both field and pot experiments. No significant epistasis effect was detected for PL. Four QTLs were detected in RI population, among them 2 from field condition and 2 from pot experiment. 6 pairs of epistasis loci were detected in RI population. One QTL mapped on chromosome 4 and two pairs of epistatic loci were detected in both field and pot experiments. One QTL on chromosome four was identified in both populations, and one marker locus RG323 on chromosome one was involved in additive effect in DH population, but epistasis effects in RI population.