Shaohong Zhang, Xiuying He, Junliang Zhao, Yongsheng
Cheng, Zhimei Xie, Yuehan Chen,Tifeng Yang, Jingfang Dong, Xiaofei Wang, Qing
Liu, Wei Liu, Xingxue Mao, Hua Fu, Zhaoming Chen, Yaoping Liao and Bin Liu*

Rice 

    DOI 10.1186/s12284-017-0183-0

Abstract

    Background: Harvest index (HI) in rice is defined
as the ratio of grain yield (GY) to biomass (BM). Although it has been
demonstrated that HI is significantly related to yield and is considered as one
of the most important traits in high-yielding rice breeding, HI-based
high-yielding rice breeding is difficult due to its polygenic nature and insufficient
knowledge on the genetic basis of HI. Therefore, searching for rice varieties
with high HI and mapping genes associated with high HI can facilitate
marker-assisted breeding for high HI in rice.

Results: Yuexiangzhan, a popular indica cultivar
with good reputation of high HI was crossed with Shengbasimiao, an indica
cultivar with lower HI to develop a recombinant inbred line population, and QTL
mapping for HI and its component traits was conducted. In total, five QTLs for
HI, three QTLs for GY, and six QTLs for BM were detected in two-year
experiments. Among the three GY QTLs, one co-located with the HI QTL on
chromosome 8, while the other two co-located with the two tightly-linked BM
QTLs on chromosome 3. The co-located QTLs in each of the chromosomal regions
produced additive effects in the same direction. Particularly, the HI QTL on
chromosome 8, qHI-8, could be detected across two years and explained 42.8% and
44.5% of the phenotypic variation, respectively. The existence of qHI-8 was
confirmed by the evaluation of the near isogenic lines derived from a residual heterozygous
line, and this QTL was delimitated to a 1070 kb interval by substitution
mapping.

Conclusion: In the present study, the detected GY
QTLs overlapped with both HI QTL and BM QTL, suggesting a positive relationship
between GY and HI or BM, respectively. With an understanding of the genetic
basis for grain yield, harvest index and biomass, it is possible to achieve
higher yield through enhancing HI and BM by pyramiding the favorable alleles
for the two traits via marker-assisted selection (MAS). As qHI-8 has a large
phenotypic effect on HI and expresses stably in different environments, it
provides a promising target for further genetic characterization of HI and MAS
of high HI in rice breeding.

附件：Identification and validation of a novel major QTL for harvest index in rice