Seed size is an important agronomic trait in melons that directly affects seed germination and subsequent seedling growth.  However, the genetic mechanism underlying seed size in melon remains unclear.  In the present study, we employed Bulked-Segregant Analysis sequencing (BSA-seq) to identify a candidate region (~1.35 Mb) on chromosome 6 that corresponds to seed size.  This interval was confirmed by QTL mapping of three seed size-related traits from an F₂ population across three environments.  This mapping region represented nine QTLs that shared an overlapping region on chromosome 6, collectively referred to as qSS6.1.  New InDel markers were developed in the qSS6.1 region, narrowing it down to a 68.35 kb interval that contains eight annotated genes.  Sequence variation analysis of the eight genes identified a SNP with a C to T transition mutation in the promoter region of MELO3C014002, a leucine-rich repeat receptor-like kinase (LRR-RLK) gene.  This mutation affected the promoter activity of the MELO3C014002 gene and was successfully used to differentiate the large-seeded accessions (C-allele) from the small-seeded accessions (T-allele).  qRT-PCR revealed differential expression of MELO3C014002 between the two parental lines.  Its predicted protein has typical LRR-RLK family domains, and phylogenetic analyses reveled its similarity with the homologs in several plant species.  Altogether, these findings suggest MELO3C014002 as the most likely candidate gene involved in melon seed size regulation.  Our results will be helpful for better understanding the genetic mechanism regulating seed size in melons and for genetically improving this important trait through molecular breeding pathways. 

Accurately estimating wheat yield potential under climate changes is essential to assess food production capacity.  However, studies based on crop modeling and imperfect management experiment data frequently underestimate the wheat yield potential.  In this study, we evaluated wheat yield potential based on CERES-wheat model and a well-managed 10-year (2008-2017) field observation in the North China Plain (NCP), and further identified the critical climate and management yield-limiting factors for improving wheat yield potential and closing wheat yield gap.  Our results revealed that wheat yield potential averaged 10.8 t ha^-1 in the recent decade.  The low growing degree days (GDD) in the pre-winter growing season (592) and solar radiation in the whole growth season (3,036 MJ m^-2) are the most critical climatic limiting factors of wheat yield potential in the current production system.  Nonetheless, wheat yield potential in the NCP is projected to decline during 2040-2059 by 1.8 and 5.1% under RCP4.5 and RCP8.5 scenarios, respectively, without considering the elevated CO₂ concentration.  However, the positive influence of CO₂ fertilization is sufficient to offset these negative impacts from climatic warming and solar dimming, ultimately leading to an enhancement in wheat yield potential by 7.5 and 9.8% during 2040-2059 compared to the baseline under RCP4.5 and RCP8.5, respectively.  We recommend selecting an appropriate planting date (5 October) and planting density (400 plants m^-2) that align with light and temperature conditions during the wheat growing season, thereby improving wheat yield potential.  Additionally, optimizing the timing and rate of water application (three times, 270 mm) and fertilizer use (based on in-season root zone nitrogen management) is crucial for closing the wheat yield gap.  Our study underscores the importance of adopting multiple management practices that account for complex climate–crop–soil interconnections to enhance wheat yield based on a long-term field experiment under the changing climate.