As nutrient allocation trade-offs occur between reproductive and vegetative development in crops, optimizing their partitioning holds promise for improving agricultural productivity and quality. Herein, we characterize the phenotypic diversity of the fruitfulness trait and identify associated genes in tea plants (Camellia sinensis). Over three consecutive years, we monitored the fruitfulness of an F₁ hybrid population (n = 206) derived from crosses of ‘Emei Wenchun’ and ‘Chuanmu 217’. A marked variation was observed in the yield of individual plants, ranging from complete sterility (zero fruits) to exceptionally high fertility (1612 fruits). Using the high-resolution genetic linkage map and the fruitfulness data, we identified a stable major QTL designated as qFN5. To fine-map the underlying gene(s), artificial pollination experiments were conducted with extreme phenotype individuals (with the highest vs. lowest fruit numbers). Bulked segregant RNA sequencing (BSR-Seq) with ovules collected at two and seven days post-pollination (DPP) identified the genomic intervals that exhibit a high degree of overlap with qFN5. Analysis of expression dynamics combined with functional genomics data revealed a prominent candidate gene, CsETR2 (TGY048509), which encodes an ethylene receptor protein. When CsETR2 was overexpressed in Arabidopsis thaliana, the transgenic lines exhibited significantly decreased reproductive performance relative to the wild-type plants. Relative to the wild type, the transgenic lines exhibited a significant decline in several key traits: the number of effective panicles decreased by 72.5%, the seed setting rate dropped by 67.7%, and the silique length shortened by 38%. These findings demonstrate its role in regulating plant fruitfulness. Furthermore, yeast one-hybrid and dual-luciferase assays verified that CsMYB15 (TGY110225) directly binds to the CsETR2 promoter, thus repressing its transcription. In summary, our findings expand the understanding of genetic regulation underlying fruitfulness in tea plants and provide candidate target loci for breeding.

Tea plantations in Sichuan Province face significant soil degradation due to long-term over-fertilization, leading to severe acidification and nutrient depletion. This study investigated the potential of biochar as a soil amendment to mitigate these issues and promote sustainable tea production. Three types of biochar (corn stover, reed, and coconut shell) were applied at varying concentrations (0%, 0.5% and 1.0%) to tea plantation soils, and their effects on soil pH, enzyme activities, nutrient content, and microbial communities were evaluated over a 45-day incubation period. Results indicated that coconut shell biochar significantly increased soil pH and enhanced catalase and urease activities, particularly at higher application rates. Additionally, biochar application improved soil organic matter and available phosphorus content, with coconut shell biochar showing the most pronounced effects. Microbial community analysis revealed that biochar increased bacterial diversity and altered fungal community composition, favoring beneficial taxa such as Ascomycota and Mortierellomycota. These findings suggest that biochar, especially coconut shell-derived, can effectively ameliorate soil acidity, enhance nutrient availability, and improve microbial diversity in tea plantations. This research could contribute to integrating biochar into sustainable tea cultivation, presenting a promising strategy for soil remediation and long-term agricultural productivity.