Studies On The Morphological Characteristics And Fruit Quality Of The Tetraploid Muskmelon

Four kinds of concentration of colchicines, 0.1%,0.3%,0.5% and 0.7%,were used to treat the growing point of muskmelon inbred line M01-3 through the smear method. Chromosome numbers of the tendril cells and cytology analysis were used to determine ploidy level. The physiological and biochemical characteristics of the teraploid plants and fruit qualities were measured. The main results were as follows:1. Tetraploid muskmelon plants were induced successfully from diploid cucumis melo inbred M01-3 (2n=24) by colchicines, Chromosome num -bers of the tendril cells and cytology analysis were used to determine ploidy level.2. Morphological characteristics has been changed by chromosome doubling.The results showed that the plant height of the tetraploid plants was higher, the stem diameter was thicker, the leaf area was much bigger than those of the diploid plants throughout plant development and the fully expanded mature leaf area was approximately 30% bigger than that of the diploid plant. Moreover, the net photosynthetic rate of the tetraploid plants was similar to the diploid plants'at early stages of plant development, but slightly higher than that of the diploid plants at later stages.We analyzed the leaf cellular and subcellular structures of the tetraploid and the diploid plants. Microscope observation showed that there were no differences in the epidermal cells and the spongy cells of the tetraploid and the thediploid leaves, but palisade cells of the tetraploid leafwere longer than those of the diploid leaf and the tetraploid leaf(7.06 mm)was thicker than the diploid leaf (6.70 mm). The electronic microscope analysis revealed that the numbers of chloroplast, granule and grana, chloroplast length and granule length of the teraploid leaves were significantly more or bigger than those of the diploid leaves. However, no significant difference was observed in the widths of chloroplast and granule between the tetraploid and diploid leaves. The electronic microscope analysis revealed that the numbers of chloroplast, granule and grana, chloroplast length and granule length of the teraploid leaves were significantly more or bigger than those of the diploid leaves. However, no significant difference was observed in the widths of chloroplast and granule between the tetraploid and diploid leaves.3. Tetraploid fruit was bigger and fruit quality was superior to diploid fruit. The result indicated that tetraploid fruit was distinctly bigger and heavier than that of diploid fruit. And the tetraploid fruit mesocarp was approximately 0.9 cm thicker than that of diploid fruit. But, there was no difference in fruit shape index between tetraploid and diploid fruits. Interestingly, fruit quality of tetraploid muskmelon improved apparently comparing to diploid fruit, the contents of soluble solid, soluble sugar and vitamin C in tetraploid fruit were approximately 20%, 30% and 5 times higher, respectively than those in diploid fruit. In addition, the skin color of the tetraploid fruit wasdeeper than that of diploid fruit.4. Tetraploid fruits produced fewer plump seeds (average 179 plump seeds per single fruit) than the diploid fruit (average 315 plump seeds per single fruit) and the seeds from tetraploid fruit were broader and thicker than those from the diploid fruit.