Breeding Of New Combinations Of Rootstock-used Pumpkin And Evaluation Of Drought Tolerance And Salt Tolerance Of Pumpkin Germplasm

Watermelon(Citrullus lanatus)is one of the important fruit vegetbale crops of China,but with the expansion of cultivated area,continuous cropping is becoming an important problem of watermelon industry.Grafting is an important means to overcome this obstacle.In the production of grafted watemlon transplants,pumpkin is the common rootstock,Cucurbita moschata,Cucurbita maxima species,and their intraspecific hybrids are the main rootstocks that are being utilized.China's pumpkin germplasm is rich in resources,but the breeding of the rootstock varieties is relatively less focused.Grafting incompatibility,the negative impact of rootstock on quality of watermelon and adaptation to the narrow range of cultivation and other issues are the problems of watermelon industry.Therefore,this paper makes full use pumpkin germplasm and evaluated the adaptability of grafted watermelon inbred lines.The hybrid combinations were also used to evaluate the grafting suitability.We assessed the grafting compatibility,plant growth,and watermelon fruit quality of high quality pumpkin rootstock hybrid combinations for the new varieties of watermelon,so that rootstocks may be utilized in breeding programmes.At the same time,germplasm resources of the research group were utilized to screen out the highly salt and drought resistant rootstocks for further use.The main results of this subject are as follows:1.A total of 16 pumpkin inbred lines,including 9 Cucurbita moschata,7 Cucurbita maxima and 3 hybrids,included two hybrids of C.moschata × C.moschata,one of C.maxima × C.moschata were selected and watermelon 'Zaojia 8424' was grafted onto those rootstocks;The commercial rootstock 'Qinyan1' and 'Jingxinzhen4' were utilized as a control rootstock for ‘Zaojia 8424'.The effects of grafting survival rate,field survival rate,plant growth potential,relative chlorophyll content,fruit type,peel,soluble solid content,and taste of watermelon fruit were studied.L13,L9,L24,L25,L28,L29,Y20,and Y26 were selected to evaluate the adaptability of inbred lines and watermelon grafts.The nine inbred lines were selected as hybridization combination of parents.2.A total of 47 hybrids were selected from the 9 lines,which consisted of 36 C.moschata × C.moschata and 11 C.maxima × C.moschata interspecific combinations.A total of 47 hybrids and 5 inbred lines were used as the rootstock for watermelon 'Zaojia8424',the commercial stock ' Qinyan1' and ' Jingxinzhen4' was utilized as the control rootstock.The effects of seedling traits,grafting compatiability,and their effects on the growth,fruit quality and yield of watermelon were evaluated comprehensively.The following grafting combinations Y20 × L25,L23 × L6,L24 × Y13,and L24 × L25 4 perofmed better.3.A total of 94 pumpkin germplasm,including 11 C.moschata inbred lines,56 C.maxima inbred lines and 27 C.moschata × C.moschata hybrids were used as experimental materials,commercial commercials ' Qinyan1' and' Jingxinzhen4' as a reference.Under the treatment of 200 mM NaCl,the plant growth was observed.According to the classification table of salt damage,the degree of salt damage was divided into five grades,and the salt index was calculated.Fifty four salt resistant materials,such as Y3,Y16-9,L1 × L3,Y4,Y7-1 and L1 × L17 were divided into salt tolerant salt 35% and 65% Materials,Y15-1,Y20-1,L17 × L6 and other 20 kinds of salt resistant materials.4.74 lines of pumpkin germplasm,which were preliminarily expanded in the pre-project group,were used as experimental materials.Commercial pumpkin rootstock 'Qinyan1' and 'Jingxinzhen 4' was used as control.The drought stress index was calculated according to the drought hazard grading table when the plants show wilting and then re-watering treatment and drought treatment were applied.The plant height,stem diameter,dry weight and fresh weight were measured in the treatment group and the control group.Ten of these materials did not get enough data and found that the drought affected the indicators of the pumpkin material,in L23,L23 × L17 and 11 other lines,plant drought symptoms were not obvious;in L1 × L29,Y20 × L29 and other seven lines plant height was very small;in L1 × L29,Y20 × L28 plants plant stem diameter,Y8,Y20 × L29,Y20 × L29,Y20 × Y8 and so on.The fresh weight of plant material was not significantly affected.The results are as follows: Y20 × L29,L22 × L25,L29 × L9,Y20,Y49 and 5 other is the drought-resistant materials.The second category was highly drought-resistant materials that include Y8 × Y13,L24 × L25 and 19 other lines;the third category is the drought-resistant materials that include L24 × Y8,L22 × Y13 and 48 other lines.