Studies On Autotetraploid Watermelon Artifically Induced And The Heredity Of Main Quantitative Trait Of Seedless Watermelon

To gain tetraploid watermelon resource some diploid was treated with colchicine by means of soaking seeds before germination, dropping and daubing the terminal but of young plant. The inheritance of 19 quantitative traits and their correlations in triploid watermelon were analyzed by additive-dominant inheritance model based on thirty-six F₁ hybrids which were crossed by six inbred lines used as female parents from four ecotypes and six inbred lines used as male parents from same ecotype according to North Carolina II crossing design.The main results were concluded as follows:1. The result of induction methods studied shown that, three methods can all obtain mutant plant, and daubing the terminal bud of young plant with colchicines was simple and convenient method and also got the highest mutant frequency. So it was most suitable for watermelon induction.2. The morphologic appearance in field combined with chromosome count could obtain more exact results about the ploidy of mutant plant identified, and could mostly reduce the research load in laboratory.3. The analysis of trait heredity capacity and genetic correlation indicate that the heritability of the content of soluble solid substances in the watermelon center and edge, soluble sugars, lycopene, dry matter and organic acid were relatively high in a broad or narrow sense, so they could be improved directly. Because organic acid had positive negative correlation with solid substances in the watermelon center and edge, soluble sugars, lycopene and dry matter all of that could be improved by means of reducing the organic acid content in watermelon. Vitamin C had a relatively high broad heredity capacity too, but it's narrow heredity capacity was 0, which couldn't be improved directly, but could mended by selecting high dry matter and high free amino acid in hybrids to meliorate it indirectly. The broad and narrow heritability of free amino acid was relatively high, so it could be improved directly. It also could be increased by selecting combination with higher lycopene content indirectly. The broad heritability of seed number was more than 50%, and was controlled by additive effect and dominant effect equally according to the analysis of variant. It couldn't be meliorated directly, but could be improved by selecting combination with higher dry matter, lycopene and edge soluble sugars content indirectly.The heritability of the horizontal and vertical diameters of fruit, fruit peel thickness and the weight per fruit were all in the medium value, that could be improved directly, the weight per fruit also could be increased by selecting combination with higher lycopene content indirectly.The heritability of the node site where bearing the first female flower, the fruit setting and the length of vine were in relatively low value, that couldn't be meliorated directly, but could be improved by selecting combination with higher lycopene content indirectly.