Genome Sequence and QTL Analyses Using Backcross Recombinant Inbred Lines (BILs) and BILF1 Lines Uncover Multiple Heterosis-related Loci

Abstract

Heterosis is an interesting topic for both breeders and biologists due to its practical importance and scientific significance. Cultivated rice (Oryza sativa L.) consists of two subspecies, indica and japonica, and hybrid rice is the predominant form of indica rice in China. However, the molecular mechanism underlying heterosis in japonica remains unclear. The present study determined the genome sequence and conducted quantitative trait locus (QTL) analysis using backcross recombinant inbred lines (BILs) and BILF 1 lines to uncover the heterosis-related loci for rice yield increase under a japonica genetic background. The BIL population was derived from an admixture variety Habataki and japonica variety Sasanishiki cross to improve the genetic diversity but maintain the genetic background close to japonica. The results showed that heterosis in F 1 mainly involved grain number per panicle. The BILF 1 s showed an increase in grain number per panicle but a decrease in plant height compared with the BILs. Genetic analysis then identified eight QTLs for heterosis in the BILF 1 s; four QTLs were detected exclusively in the BILF 1 population only, presenting a mode of dominance or super-dominance in the heterozygotes. An additional four loci overlapped with QTLs detected in the BIL population, and we found that Grains Height Date 7 (Ghd7) was correlated in days to heading in both BILs and BILF 1 s. The admixture genetic background of Habataki was also determined by subspecies-specific single nucleotide polymorphisms (SNPs). This investigation highlights the importance of high-throughput sequencing to elucidate the molecular mechanism of heterosis and provides useful germplasms for the application of heterosis in japonica rice production.

Exploiting heterosis and combining ability in two-line hybrid rice

“…Correlation coefficients are used to measure relationship between two variables as evident from positive correlation of yield components with GY except for FAR and highly significant for PE, PM, FP and AH traits, however, the negative correlation and significant was found with AH (Table 3). (Yu et al, 2020 found the correlation between the introgression rate of the Habataki pedigree and yield related traits, whereas the introgression rate was significantly negatively correlated to 1000-grain mass. Li et al (2019) found that correlations between agronomic traits and yield depend on the rice variety.…”

“…The three-line system is based on a cytoplasmic male sterile (CMS) line, a restorer line (to produce F 1 hybrid seeds) and a CMS maintainer line (to maintain the CMS line). The two-line hybrid system is based on environmentally sensitive genetic male sterility (Yu et al, 2020)" and it usually uses photoperiod-and thermo-sensitive genic male sterile (PTGMS) lines as maternal parents to produce hybrid seeds. PTGMS lines are sterile under restrictive conditions (high temperatures and long days) but become fertile under permissive conditions such as low temperatures and short days (Lan et al, 2019).…”

Global transcriptional profiling between inbred parents and hybrids provides comprehensive insights into ear-length heterosis of maize (Zea mays)

“…Heterosis is a phenomenon in which F 1 hybrid progenies exhibit superior performances compared with those of their parents [1][2][3]. It is used for hybrid crop breeding, which has greatly increased the productivity of many crops worldwide [4,5]. The successful exploitation of heterosis has also led researchers to determine its essential features.…”

Transcriptional regulation of maize (Zea mays) ear-length heterosis

“…Heterosis is a phenomenon in which F1 hybrid progeny exhibit superior performances compared with those of their parents [1][2][3]. It is used for hybrid crop breeding, which has greatly increased the productivity of many crops worldwide [4,5]. The successful exploitation of heterosis has also led researchers to determine its essential features.…”