QTL Mapping Of Fruit Size In Tomato

Fruit weight(fruit size) is an important agronomic trait which influences the appearance of tomato fruit and yield, and is also an important breeding objective for modern tomato breeding. Currently through molecular genetic studies have identified 28 QTLs regulating tomato fruit weight, but only three genes have been cloned and identified. They are FW2.2 encoding a member of the Cell Number Regulator family,FW3.2 encoding a P450 enzyme, and FW11.3 the ortholog of KLUH and Cell size regulators. It is important to resolve the other QTLs, discover the key genes regulating tomato fruit weight, and characterize its biological function and elucidate its mechanism in the regulation of fruit development for resolving the developmental mechanisms of tomato fruits and tomato’s molecular breeding.In this study, using modern cultivated tomato line 11g32 of large fruit crossed with wild tomato TS-19(LA1589) of small fruit and continuous backcross two generations and then selfed to built BC2F4 and BC2F5 populations for phenotypic investigation and genetic analysis. Use QTL analysis software to obtain QTL regulating tomato fruit size and related genes. The main findings are as follows:(1). We have designed 340 pairs of makers and obtained 179 pairs of polymorphic markers(172 pairs of Indel marker, 7 pairs of caps marker) by polymorphism screening.The average filter efficiency is 53%. For each chromosome, the screening efficiency is higher than 50% and the polymorphic markers can reach 10 pairs above, in which the co-dominant markers’ s proportion is higher than 50%. Using 179 pairs of polymorphic genetic markers, we have constructed linkage map of molecular makers for the two parent materials, covering 12 chromosomes of tomato, and the marker density on each chromosome can reach 6M or less.(2). Using 11g32 crossed with wild tomato TS-19(LA1589) to obtain F1, and F1 was backcrossed to TS-19 two times.Then selfing to obtain BC2F3 population.According the fruit size separation in population, using known information to develop molecular markers to exclude the published genes’(fw2.2 and fw3.2) role and finally screening four lines ABBB-5-1, ABBB- 8-5, ABBB-9-1, ABBB-41-1 to construct BC2F4 population.(3). Identifying the phenotyping of plants in BC2F4 populations, using molecular markers for genotyping analysis and using software for genetic linkage analysis and QTL analysis. The results show that in ABBB-5-1 population two fruit weight QTLs located on chromosome 10 and chromosome 11 respectively were detected, and explain 15.43% and68.15% of the phenotypic variation; in ABBB-9-1 population, the main effect QTL was detected on chrosome 10 and explain 11.65% of the phenotypic variation.(4). Screening plants to construct BC2F5 populations ABBB-5-1, ABBB-9-1according to the fruit weight QTLs detection results. QTL detection results show that in ABBB-5-1 population the detected major QTLs of BC2F5 population are not completely consistent with the results of BC2F4 population,but the QTL in 3ch11-8 ~ ch11-12 interval was detected in both populations and explain 13.3% of the phenotypic variation;in ABBB-9-1 population the detection results of BC2F5 population are not consistent with the detected major QTLs of BC2F4 population,but the genotype of plants used to construct the BC2F5 populations is consistent with the segregation in BC2F5 populations,which can prove the existence of QTL controlling fruit size on chrosome 10.