Identification of QTLs Conferring Rice Leaf Inclination Angle and Analysis of Candidate Genes

The leaf inclination angle is an important agronomic rice trait and an indicator of ideal plant architecture, yield and revenue. Based on 120 recombinant inbred lines (RILs) obtained from crossing of the F1 generation of the indica rice cultivar Huazhan as the male parent and the japonica rice cultivar Nekken2 as the female parent, followed by inbreeding for 12 generations, the leaf inclination angle of the first, second and third leaves from the top of the plants were analyzed. At the same time, quantitative trait locus (QTL) mapping of the leaf inclination angle was performed using encrypted genetic maps constructed for this population. A total of 33 QTLs were detected, including two related to the first leaf inclination angle (FLIA), nine related to the second leaf inclination angle (SLIA) (highest Lod value of 5.94), and 22 related to the third leaf inclination angle (TLIA) (highest Lod value of 8.53). At the same time, candidate genes analysis were conducted on the detected QTLs' intervals, and a total of 15 candidate genes were screened. The expression levels of candidate genes were detected by RT-qPCR, we found that LOC_Os03g46920, LOC_Os03g52630, LOC_Os04g24328, LOC_Os08g25380, LOC_Os09g23200, LOC_Os09g32080, LOC_Os09g35940, LOC_Os09g37330 and LOC_Os09g37495 displayed extremely significant differences in expression between the parents. The results showed that these genes may be the cause of the difference in leaf inclination. The present study provided substantial foundation for the further validation of the function of leaf inclination angle genes and molecular breeding practices.