| Watermelon(Citrullus lanatus(Thunb.)Matsum.et Nakai.)is one of the important economic crops in China.Because it is native to tropical regions of Africa,it is temperatureloving and sensitive to low-temperature environments.In recent years,continuous cropping pattern in watermelon production has caused a wide range of cropping obstacles,which is also a reason for the spread of watermelon wilt disease.Fusarium wilt caused by low temperature in winter and spring and continuous cropping is the main factor affecting the development of the watermelon industry in the facility.Grafting is an effective means to alleviate lowtemperature stress and fusarium wilt of watermelon and has been widely used in production.However,watermelon rootstocks such as pumpkin and gourd are commonly used in production to alleviate the obstacles of continuous watermelon cropping and at the same time seriously affect the quality and taste of watermelon fruit.In this paper,the watermelon variety’ Nongkeda No.5(N5)’,the wild germplasm(ZTC,YL),the inbred line(M08),the hybrid combination(M08×YL),and the root-use white-seed pumpkin’ Qing The low temperature and fusarium wilt resistance of materials such as ’Yan No.1’,melon varieties ’Jingtian-1’ and’Jiashigua’ were evaluated,and the resistance of these materials to low temperature and fusarium wilt,growth and development of watermelon grafted as rootstocks was studied.The impact of yield and quality were also examined.The main research conclusions are as follows:1.Evaluation and identification of low temperature resistance of different rootstock materials.After 48 hours of low temperature(7/4 ℃,day/night)treatment on each rootstock material,physiological indicators such as photosynthetic performance,chlorophyll fluorescence characteristics,cell membrane damage,antioxidant enzyme activity and root vitality were measured,and their low temperature was measured by membership function The resistance was evaluated comprehensively,and it was found that ZTC>White Seed Pumpkin>Jingtian No.1>M08>M08×YL>Jiashigua>Nongkeda No.5.After performing principal component and regression analysis on the membership function values of each index,the low-temperature resistance model equation is obtained,which is expected to predict the low-temperature resistance of unknown rootstock materials.Then,we grafted the abovementioned materials as rootstocks to study their effects on the low temperature resistance of the watermelon scion.The results showed that under low temperature stress,the net photosynthetic rate Pn and Fv/Fm of rootstock grafted plants such as ZTC,Baizi Pumpkin,Jingtian 1,and M08 were significantly higher than those of other rootstock grafted seedlings and controls,while their relative conductivity and MDA The content was lower than other rootstock materials grafted seedlings and controls.These data indicate that the lowtemperature resistance of grafted seedlings is closely related to the low-temperature resistance of rootstocks.ZTC,White Seed Pumpkin,Jingtian No.1 and M08 are potential lowtemperature resistant watermelon rootstock materials.2.Evaluation of the resistance of different rootstock materials to fusarium wilt.The root of different rootstock materials was soaked in inoculation media of Fusarium wilt Physiological Race 1(FON1).After 21 days,the incidence and disease index were counted,and physiological indexes such as SPAD,root vigor,MDA content,REC and dry and fresh weight were measured.The results showed that the control watermelon variety N5 had an increase of incidence rate by 90%,which was a susceptible variety;the white seed pumpkin and two melon materials had a fusarium wilt incidence rate of less than 20%,and were highly resistant materials;ZTC,M08,YL,M08 The incidence of watermelon germplasm such as M08×YL is between 40%-60%,and it is a medium-resistant material.The strong resistance of white-seed pumpkin and melon cultivars is related to FON1 being a watermelon-specific type.In terms of root vitality and plant biomass,the above-mentioned rootstock materials were significantly better than the control varieties.Among them,white seed pumpkin and melon varieties performed best,followed by watermelon materials such as ZTC,M08,YL,and M08×YL.Comprehensive evaluation of low temperature resistance and fusarium wilt resistance,white seed pumpkin,ZTC,Jingtian No.1 and M08 were selected as watermelon rootstocks with both low temperature resistance and fusarium wilt resistance potential.3.The effect of different rootstock materials on watermelon wilt,growth and development,yield and fruit quality in continuous cropping fields were examined.The watermelon plants grafted with different rootstocks were planted in 11-year continuous cropping watermelon fields,and their field growth,the incidence of fusarium wilt,fruit yield and quality were analyzed.The white seed pumpkin grafted plants were significantly higher than other rootstock grafted plants in terms of field growth,fusarium wilt resistance,single melon weight and yield.The incidence of fusarium wilt in the grafted plants of ZTC,YL and Jingtian No.1 are all lower than 40%,which is significantly better than that of other grafted plants except the white seed pumpkin grafted plants,but they are comparable to Jiashigua,XY-99,M08 in terms of yield.M08×YL and other grafted plants have almost no obvious difference.However,in terms of quality determination and evaluation,the fruit of ZTC grafted plants ranked first in the comprehensive evaluation of the membership functions of each quality index,followed by M08 and XY-99,both of which were superior to N5 seedlings and their self-rooted grafted seedlings.The overall fruit quality of grafted plants such as White Seed Pumpkin,YL,Jiashigua,and Jingtian No.1 were not as good as the control.Among them,the fruit of the White Seed Pumpkin grafted plant ranked the lowest in the comprehensive quality evaluation.Therefore,in terms of comprehensive low temperature tolerance,resistance to fusarium wilt,yield and quality,the white seed pumpkin rootstock has obvious advantages in resistance to fusarium wilt and yield.It is suitable for watermelon cultivation in heavy continuous cropping(more than 10 years),which is of better quality.The large negative impact does not apply to the production of high-quality and high-end watermelon facilities.Wild watermelon germplasm ZTC has outstanding performance in low temperature resistance as a rootstock.Although its resistance to fusarium wilt is not as good as that of white-seed pumpkin,it has no adverse effect on watermelon quality.It can produce high-quality and high-end watermelon in medium continuous cropping areas(3-8 years).Larger application potential.In addition,ZTC can be further used to create excellent watermelon germplasm and breed excellent watermelon cultivars or rootstock varieties. |
