Preliminary Mapping Of A Major-effect QTL QFW9.1 For Tomato Fruit Weight

Tomato?Solanum lycopersicum?is an important vegetable crop worldwide.High yield is one of the most important tomato breeding objectives,and fruit weight is the component of individual plant yield.Fruit weight is a quantitative trait controlled by multiple loci?QTL,quantitative trait locus?.The dominant and recessive inheritance and the contribution rates of the QTLs of fruit weight are different.Major-effect QTLs can contribute to larger fruit weight variability,and dominant QTLs can also make fruits larger in heterozygotes compared to recessive QTLs.Therefore,the identification of dominant major-effect QTLs of fruit weight is very important for heterosis breeding.In addition,tomato is a model plant for berry-like fruit development and ripening.Therefore,the research results on QTLs for tomato fruit weight has important reference value for other crops.In this study,QTL-seq and single-marker analysis were performed using an F₂ population derived from the cross between inbred tomato cultivar'Heinz1706'and cherry tomato varieties'VFNT Cherry'and detected 10 QTLs for fruit weight.Among those loci,the locus displayed the highest percent variance explained?PVE?was further narrowed down by recombinant progeny testing.The main research results of this study are as follows:1.In this experiment,'Heinz1706'has a larger fruit weight with an average fruit weight of 43.6 g,and'VFNT Cherry'has a smaller fruit weight with an average fruit weight of 19.5 g.The average fruit mass of F₁ was 45.2 g,which displayed obvious heterosis.The fruit weight of the plants in the F₂population showed a continuous variation and approximated normal distribution.2.According to the fruit weight of the plants in the F₂ population,two QTL-seq bulks were constructed:largest fruit bulk and smallest fruit bulk.QTL-seq was performed using the above two bulks and single-marker analysis was performed using all plants in the F₂ population.Finally,10 QTLs controlling fruit weight were identified:qtl for fruit weight 1.1?qFW1.1?,qFW2.1,qFW3.1,qFW5.1,qFW5.2,qFW6.1,qFW7.1,qFW8.1,qFW9.1,qFW10.1.The PVE of the above 10 QTLs were between2.55%and 12.19%,among which the PVE of qFW5.1 was the lowest and qFW9.1 was the highest.The large-fruit alleles for qFW2.1,qFW5.1,qFW7.1,qFW8.1,qFW9.1 were from'Heinz1706',and for qFW1.1,qFW3.1,qFW5.2,qFW6.1 and qFW10.1 were from'VFNT Cherry'.The large-fruit alleles for these QTLs were hyperdominant or partially dominant or partially recessive to small fruit alleles.The d/a values indicated that the large-fruit alleles for qFW1.1,qFW5.1 and qFW6.1 were superdominant,and for qFW2.1,qFW5.1,qFW7.1,qFW8.1,qFW9.1 were partially dominant,and for qFW3.1 and qFW10.1 were partially recessive.3.Based on the results of QTL-seq and single-marker analysis,the interval of the qFW9.1 locus was narrowed down to a region of 4.5 Mb by recombinant progeny testing.Based on that results,a total of 10 QTLs for fruit weight were detected in the F₂ population derived from the cross between'Heinz1706'and'VFNT Cherry'.Most of their large-fruit alleles are hyperdominant and partially dominant,and the sources of their large-fruit alleles are different.Therefore,the F₁ plants aggregate the large-fruit allelles of hyperdominant and partially dominant QTLs from both parents,so that the fruit weight appeared super parental.At the same time,the interval of the qFW9.1 locus with the highest PVE was narrowed down to a region of 4.5 Mb,which laid a foundation for its further fine mapping and cloning.