Most agronomical traits of crop species are complex traits controlled by multiple genes and affected by environmental factors. While considerable efforts have been made to fine-map and clone major quantitative trait loci (QTLs) for yield-related traits in rice, it is not until recently that the attention has been paid to minor QTLs. Following previous dissection of QTLs for grain weight and grain size in a 12-Mb interval on the long arm of chromosome 1 in rice, this study targeted at one putative QTL region for a more precise mapping and for analyzing the genotype-by-environment interaction of minor QTLs. Four BC2F10 plants of the indica rice cross ZS97///ZS97//ZS97/MY46 were selected. They carried overlapped heterozygous segments that jointly covered the entire putative region for qTGW1.1 detected previously. Four sets of near isogenic lines (NILs) were developed from selfing progenies of the four plants. Each NIL set consisted of 32 ZS97 homozygous lines and 32 MY46 homozygous lines that differed in the corresponding heterozygous region. They were grown in two locations having distinct ecological conditions and measured for 1000-grain weight, grain length and grain width. Two QTLs were separated in an 835.2-kb interval flanked by DNA markers Wn28447 and RM11569. They both showed consistent effects across the two environments. The qTGW1.1a located within the 120.4-kb interval Wn28447 − RM11543 significantly affect all the three traits with the enhancing allele derived from ZS97, showing a stronger influence on grain weight than on grain length and width. The qTGW1.1b located in the 521.8-kb interval RM11554 − RM11569 significantly affect grain weight and length with the enhancing allele derived from MY46, having a stronger influence on grain length than on grain weight. Consistent performance of the two QTLs was confirmed in a validation experiment using five NIL-F2 populations segregated for either qTGW1.1a or qTGW1.1b. Separation of closely-linked QTLs having small effects is achievable in the absence of major-QTL segregation. Minor QTLs for complex traits could act consistently in diverse environments, offering the potential of pyramiding beneficial alleles of multiple minor QTLs through marker-assisted selection.

Heat shock protein 70 (HSP70) regulates the stress tolerance and reproductive ability of insects. In this study, the SfHSP70-7 gene was cloned and identified from the rice pest Sogatella furcifera. SfHSP70-7 encodes a typical cytoplasmic HSP70 protein that has a conserved functional domain and is highly similar to the HSP70 homologous protein of Laodelphax striatellus. SfHSP70-7 was found to be widely expressed across all developmental stages, with the highest levels in nymphs and female adults. In terms of tissue distribution, it was particularly abundant in the gut and ovaries. Its expression was strongly induced by high/low temperatures and three insecticides (triflumezopyrim, sulfoxaflor, and imidacloprid), with the maximum induction under heat and triflumezopyrim stress. RNA interference (RNAi) efficiently silenced SfHSP70-7 and significantly increased the susceptibility of S. furcifera to triflumezopyrim and sulfoxaflor, but it had no effect on susceptibility to imidacloprid. RNAi knockdown of SfHSP70-7 markedly reduced survival by 45.5% (30 °C) and 38.9% (35 °C) under heat stress. In addition, gene knockdown can damage the reproductive performance of females by reducing oviposition and egg hatchability. These results indicate that SfHSP70-7 is involved in regulating the heat tolerance, insecticide adaptability, and reproductive regulation mechanism of S. furcifera, providing a potential target for pest control.

Heat shock protein 70 (HSP70) serves as a critical molecular chaperone governing environmental stress responses in insects. This study aimed to characterize the expression pattern of SfHSP70-8 and determine its functional role in thermotolerance and insecticide susceptibility in the white-backed planthopper, Sogatella furcifera. Here, we cloned and characterized SfHSP70-8, a cytosolic member of the HSP70 family from S. furcifera. The encoded protein contains characteristic conserved domains and shares close sequence identity with the HSP70 homolog of Laodelphax striatellus. Spatiotemporal expression profiling revealed ubiquitous transcription across all developmental stages, peaking in third-instar nymphs, and pronounced enrichment in the gut and fat body. Transcript levels were robustly elevated following exposure to both thermal extremes (10–40 °C) and LC₅₀ concentrations of triflumezopyrim, sulfoxaflor, and imidacloprid. RNAi-mediated silencing of SfHSP70-8 significantly compromised tolerance to triflumezopyrim and sulfoxaflor while leaving imidacloprid susceptibility unchanged, and markedly decreased survival rates under chronic heat stress at 30 °C and 35 °C. Collectively, these findings demonstrate that SfHSP70-8 functions as an essential regulator of thermotolerance and insecticide adaptation in S. furcifera, offering a potential molecular target for future development in sustainable pest management.