Rice is a major crop susceptible to chilling stress. The identification of quantitative trait loci and genes for cold tolerance is crucial for the rice breeding. Of 30 quantitative-trait loci affecting seedling cold tolerance identified in a genome-wide association study of 540 rice accessions, OsbZIP72 was assigned as the causative gene for one, qCTS9.1. A single-nucleotide polymorphism in its promoter accounted for variation in expression between indica and japonica subspecies. The favorable haplotype of OsbZIP72 originated in wild rice and contributed to the expansion of japonica rice to colder habitats. OsbZIP72 positively regulates genes coding reactive oxygen species (ROS)-scavenging proteins and maintains intracellular ROS homeostasis. These findings not only enhanced our understanding of environmental adaptation but also provide novel genetic resources and potential targets for molecular design breeding for cold tolerance in rice.

Rice panicle architecture affects grain number per panicle and thereby grain yield. Many genes involved in control of panicle architecture have been identified in the past decades. According to their effect on phenotype, these genes are divided into three categories: panicle branch and lateral spikelets, multifloret spikelets, and panicle type. We review these genes, describe their genetic regulatory network, and propose a strategy for using them in rice breeding. These findings on rice panicle architecture may facilitate related studies in other crops.

The yield of rice is mostly affected by three factors, namely, panicle number, grain number and grain weight. Variation in panicle and grain numbers is mainly caused by tiller and panicle branches generated from axillary meristems (AMs). MOC1 encodes a putative GRAS family nuclear protein that regulates AM formation. Although several alleles of MOC1 have been identified, its variation in germplasm resources remains unclear. In the present study we characterized a novel moc1 allele named gnp6 which has a thymine insertion in the coding sequence of the SAW motif in the GRAS domain. This mutation causes arrested branch formation. The SAW motif is necessary for nuclear localization of GNP6/MOC1 where it functions as a transcription factor or co-regulator. Haplotype analysis showed that the coding region of GNP6/MOC1 was conserved without any non-synonymous mutations in 240 rice accessions. However, variation in the promoter region might affect the expression of it and its downstream genes. Joint haplotype analysis of GNP6/MOC1 and MOC3 showed that haplotype combinations H9, H10 and H11, namely MOC1-Hap1 in combination with MOC3-Hap3, MOC3-Hap4 or MOC3-Hap5 could be bred to promote branch formation. These findings will enrich the genetic resources available for rice breeders.

To dissect the genetic mechanism of multi-seed pod in peanut, we explored the QTL/gene controlling multi-seed pod and analyzed the interaction effect of QTL and environment. Two hundred and forty eight recombinant inbred lines (RIL) from cross Silihong×Jinonghei 3 were used as experimental materials planted in 8 environments from 2012 to 2017. Three methods of analysis were performed. These included individual environment analysis, joint analysis in multiple environments, and epistatic interaction analysis for multi-seed pod QTL. Phenotypic data and best linear unbiased prediction (BLUP) value of the ratio of multi-seed pods per plant (RMSP) were used for QTL mapping. Seven QTL detected by the individual environmental mapping analysis and were distributed on linkage groups 1, 6, 9, 14, 19(2), and 21. Each QTL explained 4.42%–11.51% of the phenotypic variation in multi-seed pod, and synergistic alleles of 5 QTL were from the Silihong parent. One QTL, explaining 4.93% of the phenotypic variation was detected using BLUP data, and this QTL mapped in the same interval as qRMSP19.1 detected in the individual environment analysis. Seventeen additive QTL were identified by joint analysis across multiple environments. A total of 43 epistatic QTL were detected by ICIM-EPI mapping in the multiple environment trials (MET) module, and involved 57 loci. Two main-effect QTL related to multi-seed pod in peanut were filtered. We also found that RMSP had a highly significant positive correlation with pod yield per plant (PY), and epistatic effects were much more important than additive effects. These results provide theoretical guidance for the genetic improvement of germplasm resources and further fine mapping of related genes in peanut.