Evaluation Of Resistance And Associated Molecular Markers Of Bacterial Wilt Of Potato Somatic Hybrids Offspring

Bacterial wilt is a disease caused by Ralstonia solanacearum and epidemics in tropic, subtropic and part temperate zones, even occurs in cool regions. Bacterial wilt often results in a significant loss of potato yield in central and southwest China. However, there are have no efficient means to control this disease and, hence, breeding for resistant varieties has been attached with great importance. Since the resistance against bacterial wilt has only been identified in some wild potato species and relatives, somatic hybridization has been adopted to get rid of the interspecies sexual incompatibility and to introduce the resistance to cultivated potatoes. Based on previously obtained100backcrossing pedigrees of resistant somatic hybrids3c28-1、3c35-3and8c6-2, the present research evaluated their resistance level to bacterial wilt and screened the molecular markers suggested to be related to the resistance. The mains results are as bellow.1. Evaluation of disease resistance. The in vitro grown plantlets and green housed grown plants of100pedigrees of eight backcrosses were subjected to the inoculation of Ralstonia solanacearum. The in vitro inoculation showed that six clones exhibited higher resistance level to the pathogen, of which07SF.3-79and07SF.6-8were resistant and07SF.6-5,07SF.13-29,07SF.13-40and07SF.3-75were mid-resistant, whereas the other94clones were susceptible. Apparently, eight clones performed a relative higher resistance clarified by the inoculation with greenhouse grown plants, among them07SF.3-79,07SF.6-8,07SF.6-5,07SF.3-76and07SF.3-9were assigned resistant and07SF.1-55,07SF.2-47and07SF.6-6were scored mid-resistant. The rest92showed susceptible to the infection. Noticeably, three resistant clones (07SF.3-79,07SF.6-8and07SF.6-5) were almost consistent in resistance level between the two tests, except for07SF.6-5that showed mid-resistant in in vitro test but resistant in greenhouse test, suggesting a reliable consistency of the two inoculation methods and implying more rigorous of the in vitro than the greenhouse test.2. Selection of the molecular markers. Seven SSRs previously identified related to bacterial wilt resistance were screened first for polymorphism between the resistant (S. chacheonse) and susceptible (3#and8#) parents of the somatic hybrids. The two resistant somatic hybrids3C28-1and3C35-3were also employed in this screening. The results conformed seven polymorphic bands derived from four SSRs STI0051, STI0054, STI0056and STI0057s, which were used to test all100clones mentioned above. The results demonstrated that the three clones considered resistant in the two inoculations amplified the same bands as resistant control while they were absent in susceptible control. This is in accordance with the disease phenotyping and suggests an application potential of these SSRs in marker-assistant selection of bacterial wilt resistance introgressed from S. chacoense.