Compound And Evaluation Of New Hybrid Combinations Of Rootstock-used Pumpkin Suitable For Grafting Of Small-fruit Watermelon

Small-fruit watermelon has become more and more popular among consumers in recent years because of its small and beautiful appearance,thin peel and good fruit quality.Facility cultivation is often used in the production of small-fruit watermelon,in order to avoid the influence of soil continuous cropping obstacle,grafting cultivation is mainly used,and pumpkin is mainly used as rootstock,but there is still a lack of special rootstock suitable for grafting of small-fruit watermelon,the rootstock suitable for medium-fruit and largefruit watermelon grafting is still used in production of small-fruit watermelon,which is easy to cause some problems,such as weakening of compatibility,fruit taste and quality and easy to split fruit.Based on the previous research results of our research group,we screened high-quality rootstock-used pumpkin inbred lines,used them to compound rootstock-used pumpkin hybrid combinations by heterosis cross breeding,and we take good compatibility,strong stress resistance,no premature aging,no acute wilting,and no reduction in fruit taste and quality as the breeding goals,in order to select some excellent pumpkin hybrid combinations suitable for small fruit watermelon grafting.The main results of this experiment are as follows:1.Using 11 high-generation inbred lines of high-quality rootstock-used pumpkin in the research group,we compounded 41 hybrid combinations of rootstock-used pumpkin through heterosis cross breeding,which include 10 interspecific hybrid combinations of C.maxima×C.moschata,28 intraspecific hybrid combinations of C.moschata×C.moschata,3 intraspecific hybrid combinations of C.maxima×C.maxima,plus 8 parents of C.moschata,3 parents of C.maxima,and used commercial rootstock-used pumpkin ‘Fenglejinjia’(C.maxima×C.moschata),‘Weizhen No.1’(C.moschata×C.moschata)and watermelon‘Zaojia 84-24’(Citrullus lanatus),‘Wunong No.8 ’(Citrullus lanatus)as control,a total of56 materials.The plant from one-leaf and one-heart stage to two-leaves and one-heart stage was inoculated with watermelon Fusarium wilt by the method of soaking the injured root with spore suspension.After 30 days(when its condition was stable),we calculated the disease classification statistics and disease index,according to the disease index classification,we screened out 5 highly resistant watermelon Fusarium wilt materials,40 resistant watermelon Fusarium wilt materials,6 moderately resistant watermelon Fusarium wilt materials,and 1 susceptible watermelon Fusarium wilt materials.2.Using the above-mentioned 56 materials,the plant of one-leaf and one-heart stage to two-leaves and one-heart stage was inoculated with the watermelon root rot pathogen by the method of irrigating root with spore suspension.30 days later(when the disease was stable),we calculated the disease classification statistics and disease index,according to the disease index,we screened out 40 highly resistant watermelon root rot materials,10 resistant watermelon root rot materials and 1 susceptible watermelon root rot material.3.Using the above-mentioned 54 pumpkin materials,the pumpkin plants were placed in a plastic greenhouse for natural low temperature treatment at the stage of 3-leaves and 1-heart.The ambient temperature was recorded with a temperature and humidity recorder.The average day and night temperature was 7.8°C/4.5°C.We counted and calculated the chilling injury index,taking 35% and 65% as cut-off points,and divided 54 materials into3 categories,including 3 materials with strong cold resistance,21 materials with medium cold resistance,and 30 materials with weak cold resistance.4.Using the above-mentioned 54 pumpkin materials,the plants were subjected to repeated 3 drought treatments at the stage of three-leaves and one-heart.After the treatment,we counted the drought damage level and plant height,and calculated the drought stress index and plant height stress.we used the pheatmap function of Rstudio 4.03 to draw a heat map,and performed cluster analysis on the results,we found the analysis results divided the materials into 3 categories,namely 12 drought-resistant materials,40 relatively drought-resistant materials and 2 drought-intolerant materials.5.The 41 rootstock-used pumpkin hybrid combinations were further screened and 17rootstock-used pumpkin hybrid combinations were obtained.The applicability of grafting was evaluated with the 17 rootstock-used pumpkin hybrid combinations for rootstock and the small-fruit watermelon ‘Wunong No.8’ as scion,which the commercial pumpkin varieties ‘Fengle Jinjia’,‘Weizhen No.1’ and watermelon ‘Wunong No.8’ were used as the control.The graft survival rate at seedling stage,cotyledon length,cotyledon width,hypocotyl length,hypocotyl thickness and other indexes were measured to evaluate the graft compatibility and operability,the colonization survival rate,plant height,stem diameter and leaf SPAD value of watermelon grafted seedlings at field growth stage were measured to evaluate their symbiotic compatibility,growth potential and anti premature aging ability,the fruit shape index,single fruit weight,Rind thickness,Rind hardness,flesh hardness,soluble solids titratable acid,soluble sugar(fructose,sucrose,glucose)and sensory evaluation were used to evaluate the appearance and internal quality.Finally,the comprehensive satisfaction method was used to comprehensively evaluate these indexes,combined with the identification results of cold resistance,watermelon Fusarium wilt and watermelon root rot,we screened out 3 excellent rootstock-used pumpkin hybrid combinations: Z5(R217×R208)、Z11(R216×R214)、Z20(R213×R216).