| Resistances to powder mildew (Uncinula necator) and to downy mildew (Plasmopara viticold) in 67 accessions of 13 Chinese wild Vitis species and in 11 European cultivars (V. viniferd) were evaluated comprehensively under natural epiphytotic conditions The key mechanisms of disease resistance in grapevines were speculated according to development of symptoms in the fields. With identification under the natural epiphytotic conditions, 2 crosses of 88-110 (83-4-96 (V. qinquangularis) x 'Pink Rose' (V. viniferd) and of 86-2 ('May Purple' (V. viniferd) 'Guangxi-2' (V. pseudoreticulatd) were used to determine how resistances to powder mildew and to downy mildew were inherited in grapes. Using Bulk Segregant Analysis and a double pseudotest-cross strategy, genetic maps have been constructed respectively with markers linked to genes resistant to powder mildew, to downy mildew , to ripe rot and to white rot. From a single hybrid grape FI population of 88-110 ('83-4-96' 'Pink Rose'), genetic linkage maps of Vitis have also been constructed.Among 13 species of Chinese wild Vitis, 8 species (61.54%) and 5 species (38.46%) were respectively rated as powder mildew resistant and downy mildew resistant, 4 species that were rated as both powder mildew resistant and downy mildew resistant were V. romamtii, V. piazezkii, V. liubanensis, and V. davidii var. cyanocarpa. As a whole, Chinese wild Vitis had resistance to powder mildew and showed susceptibility to downy mildew; but with comparison with European grapes, Chinese wild Vitis had more resistances to two diseases above. Among species and among accessions in the same species, there existed resistances to two diseases in Chinese wild Vitis, and resistances to downy mildew among accessions showed more diversity than those to powder mildew.Under field epidemic conditions, wild grapes started to show symptoms of powder mildew 10-15 days later than European grapes, and symptoms were lighter on the former grapevines. The symptoms of downy mildew on the grapevines have been classified into 4 groups, one of which most wild grape species showed were: the grapevines had light symptoms in the beginning, then became more and more serious graduately; all kinds of leaves were infected by fungi, but young leaves were infected more seriously; the infected spots showed necrosis with sporulation on the edge; caused by the disease, the grapevines showed light leaf-drop at first, then became more serious at last. The key mechanisms of disease resistance to downy mildew were grouped into classes, one of which most wild grapes had was: the grapevines had resistance to stop fungi from invading into the body of the grapevines and had less resistance to stop fungi from spreading between the cells in the leaves after the fungi invaded into the leaves.About resistance to powder mildew, resistant hybrids and susceptible hybrids in cross"resistant susceptible" (88-110) showed 1:1 segregation according to X2 analysis; in cross "susceptible susceptible" (86-2), most hybrids were susceptible and there existed 11.27% resistant hybrids. About resistance to downy mildew, 2 crosses above belonged to "resistant susceptible" combination and resistant hybrids and susceptible hybrids both showed 1:1 segregation by X2 analysis. There existed some hybrids having more resistances than those of the resistant parent and a few hybrids showing more susceptibility than those of the susceptible parent, which indicated traits of quantitative inheritance, and it concluded that the resistances to powder mildew and to downy mildew were both controlled by a major gene combined with some mini-genes. The resistances to two fungus diseases in wild grapes had more inheritance than those in European grapes.Of 444 10bp arbitrary primers, 341 primers amplified RAPD polymorphic bands when selected parental DNA as templates. 341 primers were used to conduct RAPD reaction on the basis of surveys of the pool DNA mixed by resistant hybrids that showed polymorphic bands. 1:1 segregating polymorphic bands on the basis of X2...
|
PDF Full Text Request