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Wheat is one of the most important cereal crops grown in the Western Himalayas of India but its production is challenged by the insect "cereal leaf beetle (CLB)". This study explores the impact of domestication and modern crop improvement on wheat's defense mechanisms against the CLB, a global threat to wheat cultivation. Sixteen diverse wheat genotypes having different ploidy levels were investigated, including wild wheat, landraces, mutants, advanced breeding lines, commercial varieties, and a Rye grass genotype. Genotypes with resistance genes, landraces, and wild wheat exhibited the lowest CLB infestation and oxidative damage. These genotypes displayed enhanced antioxidant enzyme activity, such as peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD), and polyphenol oxidase (PPO), reduced reactive oxygen species (ROS) production, and increased plant secondary metabolite (phenol and tannin) production upon CLB infestation. Resistant durum wheat demonstrated moderate responses and exhibited higher levels of flavonoid production. On the other hand, susceptible durum wheat genotypes, commercial variety Shalimar Wheat‐02 (SW‐2), showed high CLB infestation, ROS production, reduced antioxidant enzyme and secondary metabolite production. This may be because modern varieties like SW‐2 were not selected for insect resistance. These findings emphasize the significance of preserving genetic diversity from wild wheat and landraces to bolster wheat breeding programs against pests such as CLB. This study underscores the need to harness ancestral wheat lines to enhance insect pest resistance in modern wheat cultivars. [ABSTRACT FROM AUTHOR]

Summary: Heterosis refers to the better performance of cross progeny compared with inbred parents, and its utilization contributes greatly to agricultural production. Several hypotheses have been proposed to explain heterosis mainly including dominance, over‐dominance (or pseudo‐overdominance) and epistasis. However, systematic dissection and verification of these hypotheses are rarely documented. Here, comparison of heterosis level across different traits showed that the strong heterosis of composite traits (such as yield) could be attributed to the multiplicative effects of moderate heterosis of component traits, whether at the genome or locus level. Yield heterosis was regulated by a complex trait‐QTL network that was characterized by obvious centre‐periphery structure, hub QTL, complex up/downstream and positive/negative feedback relationships. More importantly, we showed that better‐parent heterosis on yield could be produced in a cross of two near‐isogenic lines by the pyramiding and complementation of two major heterotic QTL showing partial‐dominance on yield components. The causal gene (BnaA9.CYP78A9) of QC14 was identified, and its heterotic effect results from the heterozygous status of a CACTA‐like transposable element in its upstream regulatory region, which led to partial dominance at expression and auxin levels, thus resulting in non‐additive expression of downstream responsive genes involved in cell cycle and proliferation, eventually leading to the heterosis of cell number. Taken together, the results at the phenotypic, genetic and molecular levels were highly consistent, which demonstrated that the pyramiding effect of heterotic QTL and the multiplicative effect of individual component traits could well explain substantial parts of yield heterosis in oilseed rape. These results provide in‐depth insights into the genetic architecture and molecular mechanism of yield heterosis. [ABSTRACT FROM AUTHOR]

Summary: Silique number is the most important component of yield in rapeseed (Brassica napus L.). To dissect the mechanism underlying the natural variation of silique number in rapeseed germplasm, a series of studies were performed. A panel of 331 core lines was employed to genome‐wide association study (GWAS), and 27 loci (including 20 novel loci) were identified. The silique number difference between the more‐ and fewer‐silique lines can be attributed to the accumulative differences in flower number and silique setting rate. Each of them accounted for 75.2% and 24.8%, respectively. The silique number was highly associated with the total photosynthesis and biomass. Microscopic analysis showed that the difference between extremely more‐ and fewer‐silique lines normally occurred at the amount of flower bud but not morphology. Transcriptome analysis of shoot apical meristem (SAM) suggested that most of enriched groups were associated with the auxin biosynthesis/metabolism, vegetative growth and nutrition/energy accumulation. By integrating GWAS and RNA‐seq results, six promising candidate genes were identified, and some of them were related to biomass accumulation. In conclusion, the natural variation of silique number is largely affected by the biomass and nutrition accumulation, which essentially reflects the positive regulatory relationship between the source and sink. Our study provides a comprehensive and systematic explanation for natural variation of silique number in rapeseed, which provides a foundation for its improvement. [ABSTRACT FROM AUTHOR]