Analysis Of Resistance To Clavated Calabash Fusarium Wilt Genetic Of Bottle Gourd Rootstock And Graft Applacation

Bottle gourd is one of the important rootstocks for grafting cultivation of melon vegetables.It’s main function is to control soil-borne diseases and improve the yield and quality of melon.Few reports on identification and inheritance of resistance to clavated calabash F.wilt in bottle gourd rootstock at home and abroad.In this study,39 bottle gourd rootstock germplasms resources were used as materials to identify and screen germplasms resistant to F.wilt,and to study the correlation between disease resistance and physiological indexes of seedling growth.Study on quantitative inheritance of resistance by different genetic analysis methods and grafting application of watermelon as scion to provide theoretical basis for breeding high resistance hybrid rootstocks.The main research results include:1.Identification of resistance to clavated calabash F.wilt in 39 bottle gourd rootstock germplasms by root injury perfusion inoculation at seedling stage,and twelve germplasms showed resistant(R),accounting for 30.77%of the total amount,14 medium resistant(MR)germplasms,and the remaining 13 germplasms showed susceptible(S).By analyzing the correlation between disease index and seedling growth physiological index,the results showed that disease resistance was positively correlated with seedling height,MDA content in plant,and negatively correlated with seedling hypocotyl diameter,total root length,root surface area,total chlorophyll content and carotenoid content.2.Quantitative genetic analysis of resistance showed that the resistance to F.wilt of bottle gourd rootstock generation group was controlled by poly genes,and conformed to the additive-dominant model with the additive effect as the key factor and resistance being partially dominant.The genetic model of resistance to F.wilt in different families was additive-dominant-epistasis,and the dominant genes were more than recessive genes.The narrow heritability of resistance was 77.68%,which indicated that the resistance of bottle gourd rootstock to F.wilt could be transmitted to offspring steadily.3.The results of combining ability effect analysis showed that the negative general combining ability of H041 was the highest(-8.595),and the cross combinations had stronger disease resistance and better specific combining ability effect.What’s more,emphasis should be laid on utilization in cross breeding.7 ofthe 12 cross combinations showed disease resistance,and 10 cross combinations showed negative mid-parent heterosis.The combination H041 × H12 also showed negative mid-parent heterosis(-51.48%),super-high parent heterosis(-22.56%)and super-high parent heterosis(-22.56%)and the strongest heterosis.4.Hybrid rootstocks of bottle gourd were used to watermelon grafting.The stress experiment of clavated calabash F.wilt was carried out.The results showed that hybrid rootstocks of bottle gourd significantly improved the disease resistance of grafted watermelon seedlings,and the disease prevention effect was 47.03%-80.75%.The above-ground growth(rootstock stem,scion stem diameter and scion length)and underground growth(total root length,root surface area)of grafted seedlings were significantly better than those of watermelon self-rooted seedlings.With the prolongation of the infection time of F.wilt,there was no significant change in the content of photosynthetic pigments in the leaves of grafted seedlings,which maintained normal photosynthesis.The accumulation of MDA in plants was low,and the activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)in the antioxidant system remained strong,while the activities of polyphenol oxidase(PPO)increased first and then decreased.On the contrary,the content of photosynthetic pigments in the leaves of self-rooted grafted watermelon seedlings decreased continuously,and the accumulation of MDA in the plants was relatively high.The activities of SOD,CAT,POD and PPO increased in the early stage of inoculation and decreased in the middle and late stages,resulting in yellowing,wilting and even dead.5.The results of field experiment showed that the yield of grafted watermelon in hybridized combination(H041×H05,H05×H041,H041 ×XH10,H10×H041,H12×H041,H12×H10)was significantly higher than that of contrast(contrast rootstock,white-seeded pumpkin)and watermelon self-rooting grafting,and the fruit quality was significantly higher than that of white-seeded pumpkin There was no significant difference in soluble protein content between the grafted and control rootstocks.The solid-acid ratio of fruit was 36.35～75.96,and the highest was H041 ×H12.The highest content of free amino acid was H041 ×H05(0.631 mg/g).Except for H041 ×H12 and H10×H12,the content of free amino acid was lower than that of contrast rootstock gourd,there was no significant difference between other hybrid rootstocks and contrast rootstock gourd.There was no significant difference in lycopene content between hybridized rootstocks and those of contrast and self-rooted.Combining all the indexes,the hybrids H041 × H05 and H041 × H10 had strong disease resistance,and the grafted watermelon had significant effect on increasing yield and improving fruit quality.