Effects Of Different Rootstocks On Several Important Characters In Citrullus Lanatus

Nowdays, grafting thechnique is commonly used in watermelon production. It can solve many problems that resulted from the continuous cropping obstacle on watermelons, but seldom researches were taken on the mechanism affecting fruit quality by grafting. The five different rootstocks were used as materials and the effects of different rootstocks on the plant growth, fruit sugar accumulation and activities of sucrose metabolism-related enzymes during fruit developing stage in watermelons (Citrullus Lanatus) by grafting were all studied in this research. Zaojia, the own-rooted seedling as the ck in this research, and wild watermelon 1 and wild watermelon 2, pumpkin(Tiemuzhen), calabash(Changzhanlishi F1)and loofah were used as five different rootstocks. The results were as follows:1. Firstly, the grafting affinity and survival ratio after planted of the different grafting rootstocks were very significantly different among these several treatments and which of them the grafting affinity of wild watermelon rootstocks were the strongest, pumpkin and calabash rootstocks followed behind, and loofah rootstock was the weakest. For the survival ratio after planted, the ck and wild watermelon/zaojia treatments were the highest and the results of other treatments that were similar to the grafting affinity. Secondly, the growth vigor was affected by the different grafting rootstocks and which of them the growth vigor of pumpkin/zaojia and wild watermelon 1/zaojia treatments was the strongest, and loofah/zaojia treatment was the weakest. At last, different grafting rootstocks caused fruit set node of the female flower all to be delayed and different treatments were very significantly different.2. The antiviral ability was all improved by the different grafting rootstocks. The field investigation results showed that the ck and loofah/zaojia had been infected severely, pumpkin/zaojia and calabash/zaojia followed behind and wild watermelon treatments were lightly susceptible in the field. The water culture of spore liquid method was used to investigate the antiviral ability indoor, which indicated that the resistance of pumpkin rootstock and calabash rootstock to wilt disease were stronger than other treatments.3. The commercial quality and sensory quality of fruits were affected by the different rootstocks.(1)The weight of single fruit, thickness, central sugar content and marginal sugar content were all extremely significantly different. Compared with ck, first, the weight of single fruit was increased extremely significant by grafting with the wild watermelon 2, calabash, pumpkin and wild watermelon 1. But the weight of single fruit was decreased extremely significant by grafting with loofah rootstock. Second, the thickness was extremely significantly different after grafting with the different rootstocks. Third, central sugar content was increased extremely significant by grafting with the wild watermelon 2, pumpkin, calabash and wild watermelon 1 and it was decreased extremely significant by grafting with loofah rootstock. (2) The sensory quality was affected by the different rootstocks during the developing watermelon fruits and the wild watermelon/zaojia fruits and ck fruits were the best taste.4. The change trend of the fructose content and glucose rootstock was similar during developing fruits in own-rooted and grafted watermelons. The contents of hexose sugar of wild watermelon 1/zaojia, pumpkin/zaojia and loofah/zaojia were higher during previous period of fruit development. The content of hexose sugar was reaching the peak after 22 days from anthesis and that had become the main components of soluble sugars. The hexose sugar content of calabash/zaojia was kept reducing after 22 days from anthesis, but during developing fruits of wild watermelon 2/zaojia which were kept increasing. The accumulations of fructose, glucose and sucrose were all very significantly different among different grafting treatments during developing fruits. From 10 days to 33 days after anthesis, the content of fructose of wild watermelon 2/zaojia was the highest excepting for 22 days from anthesis, the content of fructose of loofah/zaojia was the lowest. At the same time, the content of glucose of wild watermelon/zaojia grafting treatment was higher, and the content of glucose of loofah/zaojia grafting treatment was the lowest. Besides, the content of sucrose of wild watermelon 2/zaojia grafting treatment was higher, and the content of glucose of loofah/zaojia grafting treatment was the lowest.5. Invertase, sucrose phosphate synthase and sucrose synthase may together act on sugar accumulation during the whole fruit development, and sucrose metabolism-related enzymes were extremely significantly different among these treatments. With the sucrose accumulation increasing, the activity of invertase was reducing, and the activities of sucrose phosphate synthase, sucrose synthase and net of enzymes were all increasing. Then, change of the activities of sugar metabolism-related enzymes affected on sugar accumulation and composition. The sucrose accumulation was very slow during the fruit development. In the earlier stage of fruit development, the activities of acid invertase and neutral invertase decreased slowly and weak light was made by continuous rainy weather, which all made hexose sugar accumulation more than sucrose accumulation.