Analysis Of Morphological Characters And Eveluation Of Disease Resistance For Rootstock-used Pumpkin Germplasms

Pumpkin is one of commonly grafted rootstock species for cucumber, bitter gourd and other cucurbits. Cucurbita moschata、Cucurbita、 maxima、Cucurbita、pepo、Cucurbita. Mixta and Cucurbita. ficifolia are common cultispecies around the world. However, there are few reports about the research on genetic breeding、diversity and disease resistance for rootstock-used pumpkin germplasms. Correspondingly, there is less study on the breeding of disease-resistant rootstock, especially the resistance to root-knot nematode and Fusarium oxysporum f. Sp. momordicae.35 rootstock-used pumpkin inbred lines collecting at home and abroad use for test materials.The genetic diversity and morphological traits were assessed using the means of quantitative genetics; the resistance to the root-knot nematode (Meloidogyn incognita) and fusarium wilt (Fusarium oxysporum f. Sp. momordicae) of these inbred lines were identified at the seedling period through inoculating; 9 inbred lines showing suitable characteristics were chosen preliminarily, and study the effects of grafting different rootstocks on bitter melon. The results can clear and definite the genetic diversity and disease resistance of these rootstock-used pumpkin germplasms, but also directly provide materials to breed superior rootstocks for bitter or other cucurbit corps. The main results are as follows:1.48 morphological traits of 32 rootstock-used pumpkin germplasms were analyzed. The results showed that coefficient variation(CV) of the time of male flowering(7.79%、seed shape index(7.74%)、Fruit shape index (7.74%) was smaller among the characters.The maximum of coefficient variation was the weight of single fruit (129.12%).The average coefficient variation of qualitative characters was36.12%, the melon shape and flesh color had more variation. However, the maximum of coefficient variation was the leaf blade white spot content.2.The cluster was generated by using 48 morphological characters. 32 inbred lines were divided into six main clusters. Yet 23 inbred lines of C. Moschata contained five main clusters, as well as each group had its own characteristics. It stated clearly that the inbred lines of C. Moschata had different genetic background. The principle component analysis(PCA) indicated that the first five PCs of the morphological variation making a total of 64.82%. When using the morphological characters study the pumpkin, the leaf size and seed traits are considered firstly; the next is calyx characteristics and the time of initial blooming; the last is the fruit shape.3.The resistance to fusarium wilt (Fusarium oxysporum f. Sp. momordicae) of these inbred lines were identified at the seedling period through inoculating. Compared to the control, the pathogen could affect the normal growth for most of inbred lines, yet did not make the plant dead. Except the N07 and N09 had higher disease index (31.25 and 42.83), the other material presented a low disease index. The resisitant levels to bitter melon Fusarium wilt of all the germplasm materials were evaluated as 25 above high resistance (HR),4 resistance (R),4 moderate resistance (MR),2 susceptibllity (S).The pathogenic bacterium was easily separate from disease plant of bitter plant, but it got seldom pathogenic bacterium from vascular bundle in the disease pumpkin. It showed that pumpkin root had defense capability to Fusarium wilt in some ways.4.The resistance to the root-knot nematode (Meloidogyn incognita) of these inbred lines were identified using the root distortion (root knot or root nodes) percentage statistics.The results showed that inbred lines of N10 and NX02 were general resistant, disease index was 16 and 20 respectively; inbred line of NCI 0 and N01 were moderately resistant, disease index was 40 and 44 respectively; there are 16 and 15 inbred lines presenting susceptibIlity(S) and high susceptibIlity(HS) respectively, accounting for 88.57%.5. Nine inbred lines showing suitable characteristics were chosen preliminarily, and study the effects of grafting different rootstocks on bitter gourd. Except the inbred lines of NC02 and NC04, the other material grafting bitter gourd had higher survival rate (above 90%); The grafted bitter gourd presented better disease resistance and incidence of grafted plant were less than 30%; The control effect were more than 80%. For all of these reasons, the inbred lines of N03、NC02、NC06 and N10 had excellent performance grafting bitter gourd and can be used as breeding parents for bitter gourd.