| Black wax gourd is one of the major vegetable cultivars in eastern and southern China;it also plays an important role in regulation off-season vegetables in summer and autumnal,and in assurance supplying vegetables in the full year,and in transporting the vegetables from south to north of China.Through my researched,I found that autotetraploid black wax gourd expressed some advantageous characteristics,such as the gourd flesh became thickening,the average gourd weight increased,and the storability enhanced,but it also expressed some disadvantageous characteristics,such as low fruit-setting rateand fewer seed numbers.In order to solve these problems,and enhance the utilization and exploitation of autotetaploid black wax gourd,we carried out the following research:(1)Taking inbred lines of diploid black wax gourd(6-2x)as materials,through using different concentrations of Colchicine and ORYZALIN in different time period to treat the growth point of seedlings to study the optimum condition of obtaining the autotetraploid black wax gourd in room temperature;(2)taking inbred lines of autotetraploid(0911-1012-6-4x)and diploid(6-2x)black wax gourd as materials,comparative researched the botanic characteristics,nutritional quality,storability and photosynthetic characteristics;through phytopalynology,embryology and endogenous hormones to study the low fertility mechanism of autotetraploid black wax gourd;(3)primary discussed the way to improve the fruit-setting rate and seed numbers at last.The main results were summarized as follows:1.There were some mutagenic effects in inducing autotetraploid black wax gourd of all the treatments,but the best treatment was using 0.2%concentration of Colchicine at 6:00am to 7:00am,and the induction rate was 32.18%.2.There were some significant differences in botanic characteristics between autotetraploid and diploid black wax gourd,but autotetraploid black wax gourd had obvious advantages.The branch of autotetraploid black wax gourd was less than diploid,the stem thickness,leaf width,leaf thickness,leaf area and petiole diameter of autotetraploid black wax gourd were significantly higher than those of diploid;The first male and female flower node of autotetraploid black wax gourd was lower than diploid,and the flowering time was earlier than diploid.The average number of female flowers of autotetraploid black wax gourd increased markedly compared with diploid,and the petal of male flower became bigger and the fruiting node was lower than diploid;The average gourd weight,gourd length,gourd diameter,gourd flesh,seed cavity length,flesh hardness and density of autotetraploid were significantly higher than diploid.The seed cavity diameter became smaller than diploid.The average seed yield significantly reduced,and the seed size was bigger than diploid.3.The nutritional quality and storability of autotetraploid black wax gourd were obvious better than diploid.Dry matter content,vitamin C content,total soluble sugar,soluble protein content,gourd flesh hardness and gourd flesh density of autotetraploid black wax gourd were significantly higher than diploid in picking time and after 30 days of room temperature storage,respectively increased by 17.190%and 10.939%,20.95%and 7.39%,5.13%and 30.13%,22.94%and 40.17%,11.92%and 25.45%,6.30%and 4.78%.Water content of autotetraploid black wax gourd was less than diploid in picking time and after 30 days of room temperature storage,respectively reduced by 0.666%and 0.457%.4.The most proper photosynthetic and light response model and C02 response model of autotetraploid black wax gourd was subsection function and modified rectangular hyperbola.The results of fitted photosynthetic and C02 parameters,the total chlorophyll content,the chlorophyll fluorescence parameters and leaf ultrastructure showed that,autotetraploid black wax gourd had more superior photosynthetic performance than diploid.5.There were four reasons of low fertility for autotetraploid black wax gourd:(1)the pollen size of autotetraploid black wax gourd was bigger than diploid,there were many abnormal structures of pollens,and the abnormal pollen rate was 42.43%of autotetraploid black wax gourd.The pollen germination rate of autotetraploid black wax gourd was 62.04%after three hours self-pollination on pistil,which was significantly lower than diploid.The growth of pollen tubes in styles was slow,which did not enter into ovary after 12hours ·self-pollination and during the germination and growth of pollens,there were some abnormal phenomenon,such as single pollen had two tubes,twisted or coiled pollen tube or the swelling as balls at the tip of pollen tubes.The reasons of above abnormal phenomenon were that the content of ZR and IPA in the female organs and pollens of autotetraploid black wax gourd was lower thandiploid,the content of ABA was higher than diploid,and the ratio of(IAA+GA3+ZR+IPA)/ABA was lower than diploid.(2)There were a lot of abnormal embryo-sacs at flowering day and after a long time of fertilization,such as disintegration,degeneration or abortion of embryo-sacs.(3)The fertilization process of autotetraploid black wax gourd was normal,but fertilization rate of embryo-sacs was lower,only 32.48%after 96 hours self-pollination.(4)The dormancy time of zygote of autotetraploid black wax gourd was longer than diploid,and the embryos of autotetraploid developed slower,later five days than diploid.During embryonic development,there were higer frequency of embryonic development lag,abnormal development of zygote,and a lot of endosperm cells with large nuclei,and a lot of free nuclei and cellular endosperm disintegrated at dormancy stage and globular stage.Because of the abnormal endosperm led to embryonic degeneration.6.Continuous four-generations orientated self-pollination of superior individual plant and three-generations hybrid crossover of sister lines of autotetraploid black wax gourd could not significantly improve the fruit-setting rate and seed numbers.(2)Sprayed "GAO LI DA" on flowering stage could significantly improve the fruit-setting rate of autotetraploid black wax gourd,but could not significantly increase seed numbers.Sprayed“Speedfol-B" on flowering stage could significantly reduce the fruit-setting rate and not receive plump seed. |
