Studies On The Ployploid Induction And Determination Of Citrullus Lanatus (Thumb.) Matsum & Nakai

Studies on the polypliod induction of watermelon has not only theory significancebut economic value extremely. The methods with induced watermelon by colchicinewas discussed preliminarily in this paper. The methods of ploidy determination andcomparison of different polypliod were investigated. The results are as fellowing:1. Effects of the colchicine concentrations (0.1%, 0.2%, 0.3%, 0.4%) and the timeof soaking buds induced the ployploid watermelon were investigated. The resultshowed that germination rate and survival rate appeared dropping as colchicineconcentrations hoisted. The total number of variation of "0513","0517" and "0526"is 4, 14 and 6 respectively. With soaking buds 12 hours and the colchicines density of0.1%, The variation rate of "0513", "0517" and "0526" is 2.4%, 3.6% and 2.7%respectively.2. Effects of the above colchicine concentrations and the time of soaking seedsinduced ployploid watermelon were investigated. The result indicated that ascolchicine concentrations hoisted, germination rate increased at first but reduced then,plumule increased rate always depressed. With the time of soaking seeds increased,germination rate and survival rate also appeared reducing. The number of variationtotal of "0517" and "0525" is 20 and 5 respectively. With the time of soaking seeds24 hours and the colchicine concentrations of 0.1%, The variation rate of "0517" and"0525" is 4.0% and 2.0% respectively.3. Effects of the above colchicine concentrations dropped seedling induced theployploid watermelon were investigated. The result indicated that death rate graduallyincreased as colchicine concentrations hoisted. The total number of variation of"0526","0515" and "0513" is 12, 9 and 3 respectively. With the colchicineconcentrations of 0.3%, the variation rate of "0513", "0517" and "0526" is 5.1%,2.5% and 1.9% respectively.4. Direct (chromosome counting) and indirect (flow cytometry, stomatal size,chloroplast number of the guard cells and morphological observations) methods weretested in order to determine the ploidy levels of tetraploid and diploid watermelon. Theresults revealed that while counting chromosomes is cumbersome, but practical waseffective. Producing plants for morphological observations requires a long time andcannot take the only standard of ployploid determination. Although flow cytometry isexpensive, it can earlier determinated the ployploid of watermelon. On the other hand,measurement of stomata and chloroplast counting methods are simple to use are less labour intensive and hence can be considered a practical alternative to the others. Thedata for the stomata in the diploids were length, 22.6μm; and number of chloroplasts ofthe guard cells, 9.7 and in the tetraploids they were 30.8μm and 18.9, respectively.5. Tetraploid watermelon lines developed by colchicine treatments were comparedwith their diploid counterpart for plant, flower, fruit, seed and qualitative characteristics.Tetraploid genotypes attained statistically higher leaf area (350.1 cm~2) and chlorophyllcontent (48.7) while chlorophyll fluorescence was similar to their corresponding diploid.Staminate flower organs (the thick and length pedicel, anther, the length and width ofpetals) were larger in tetraploid plants. Fruit weight and solid solubility content in bothploidy fruits was similar. The weight of one thousand seeds in fruits varied significantlyand averaged 35.3 and 67.3 g in diploid and tetraploid fruits, respectively. Tetraploidgenotypes yielded lower number of seed was 28.4 per fruit.