Quantitative trait locus mapping associated with earliness and fruit weight in tomato

ABSTRACT The flowering time is regarded as an important factor that affects yield in various crops. In order to understand how the molecular basis controlling main components of earliness in tomato (Solanum lycopersicum L.), and to deduce whether the correlation between fruit weight, days to flowering and seed weight, is caused by pleiotropic effects or genetic linkage, a QTLs analysis was carried out using an F2 interspecific population derived from the cross of S. lycopersicum and S. pimpinellifolium. The analysis revealed that most of the components related to earliness were independent due to the absence of phenotypic correlation and lack of co-localization of their QTLs. QTLs affecting the flowering time showed considerable variation over time in values of explained phenotypic variation and average effects, which suggested dominance becomes more evident over time. The path analysis showed that traits such as days to flowering, seed weight, and length of the first leaf had a significant effect on the expression of fruit weight, confirming that their correlations were due to linkage. This result was also confirmed in two genomic regions located on chromosomes 1 and 4, where despite showing high co-localization of QTLs associated to days to flowering, seed weight and fruit weight, the presence and absence of epistasis in dfft1.1 × dftt4.1 and fw1.1 × fw4.1, suggested that the linkage was the main cause of the co-localization.

摘要 开花期被视为影响多种作物产量的重要因素。为解析调控番茄（Solanum lycopersicum L.）早熟核心性状的分子基础，并明确果实重量、开花天数与种子重量间的相关性是由多效性效应还是遗传连锁所导致，本研究以栽培番茄（S. lycopersicum）与醋栗番茄（S. pimpinellifolium）杂交得到的种间F2群体为材料，开展了数量性状位点（Quantitative Trait Loci, QTLs）分析。分析结果表明，与早熟相关的多数性状彼此独立，这是因为它们未表现出表型相关性，且其QTLs未发生共定位。调控开花期的QTLs在表型变异解释率和平均效应随时间推移存在显著变化，表明显性效应随时间推移愈发显著。通径分析结果显示，开花天数、种子重量以及第一叶长等性状对果实重量的表达具有显著影响，证实了三者间的相关性源于遗传连锁。这一结果在位于1号和4号染色体上的两个基因组区域中得到了验证：尽管与开花天数、种子重量与果实重量相关的QTLs呈现高度共定位，但dfft1.1 × dftt4.1以及fw1.1 × fw4.1这两组位点的上位性存在与否表明，遗传连锁是共定位现象的主要成因。