| Pumpkins including five cultivated species were important vegetables around the world,and China is the largest producer,with a total planting area of 387,704 ha(21.6 % of world planting area)and a total production of 7,155,250 tonnes(29.1% of global production)(FAO,2013).Cucurbita.maxima was one of the three most economically important cultivated species(including C.pepo,C.maxima,and C.moschata).Strong femaleness is a very valuable agronomic trait,which can improve the fruit setting,field production,the hybrid seed quality,and reduced the seed production costs by labor-saving.The investigation of the trait inheritance and gene fine mapping will be very helpful for pumpkin breeding by the molecular marker-assisted selection and for further molecular mechanism discovering of this trait.Here,a strong female mutant line in C.maxima was obtained,and the genetic inheritance of this trait was investigated,then the gene was further fine mapped,the candidate gene was analyzed.The main results obtained are as follows: 1.The strong female line contains only the female flowers after the internode 4-6 in C.maximaThe strong female line 161 was planted in the field in 2016,and the flower differentiation in each internode from 1 to 35 was recorded.The results show that the strong female line contains only the female flowers after the internode 4-6.2.Strong femaleness was controlled by one recessive gene in C.maximaWe further investigated the inheritance of the trait of strong femaleness in F1,F2 and BC1 populations.Three independent crosses(161×162,161×163,161×164)were conducted and the segregation of strong femaleness to normal fit a 1:3 ratio in all three F2 population.The backcross progeny plants were all normal plants when 162,163 or 164 was the recurrent parent,whereas segregation of strongly female plants to normal plants was in agreement with a 1:1 ratio when the strong female line 161 was the recurrent parent.The results suggest that the strong femaleness in 161 is conferred by a single recessive gene.3.The strong female gene was mapped on the chromosome 2 of C.maxima at an interval of 35.2 Kb,flanked by makers 02-31 and 02-39Three pairs parental lines was screened by 846 SSR markers,and 107,92,and 83 differential presentation markers were obtained for the parental lines of crosses 161×162,161×163,and 161×164.The linked marker 02-14 for the strong femaleness gene was obtained with the method of bulk segregant analysis(BSA),and then the gene was further mapped on the chromosome 2 of C.maxima at an interval of of 35.2 Kb,flanked by makers 02-31 and 02-39 at a genetic distance of 1.3 and 0.7 cM,respectively.SSR marker 02-33 was co-segregation with the strong female gene f in these populations.4.Pentatricopeptide repeat-containing family gene possible was the candidate gene for strong female characteristic in C.maximaIn this interval of 35.2 Kb,12 genes were predicted,and one gene which code Pentatricopeptide repeat-containing family protein possible was candidate gene for strong femaleness in C.maxima. |
