Maping Of Founction-Unknown Genes Associated With Horizontal Resistance To Late Blight In Potato

Potato (Solanum tuberosum L.) is the fourth most important food crops after wheat, maize and rice. China is the largest country in potato production. Late blight, caused by Phytophthora infestans, is a devastating potato disease worldwide causing serious loss of the production. Current disease control in the field mainly depends on repeated application of large amounts of fungicides. However, this strategy is enviromentally concerned, time-consuming and costly. Therefore, resistance breeding has been considered most efficient way for late blight control. The vertical resistance controlled by R gene is nondurable since new races of the pathogen could occur and overcome this monogenic resistance. On the contrary, horizontal resistance governed by many interacting genes is race-non-specific, hence lasts longer and attracts more attention currently. Unfortunately, tetrasomic inheritance of potato and complex interactions among the host genes, the pathogen and environment make it very difficult to evaluate and select pedigrees with this durable resistance.In present research, we selected variuos founction-unknown genes from 348 ESTs identifyed associated with horizontal resistance to late blight in potato. By detecting polymorphism in two potato populations the genes were mapped on the chromosomes and their functions were implied as to provide a base for developing markers related to the disease resistance in potato. The main results are as follows:1. There were 35 function-unknown genes selected from previously identified 384 ESTs associated with potato horizontal resistance to P. infestans.2. The specific primers were designed according to the EST sequences. Polymorphism was detected in two potato backcross populations, BCT and PCC1, for mapping the selected genes. Total seven polymorphic markers were obtained, five in PCC1 and two in BCT.3. Sequencing of the polymorphic bands indicated that six were the target genes (DR751788, DR751719, DR751998, DR752001, DR752011 and DR751984) and one amplified undesignedly from the potato genome.4. Five genes were successfully mapped on potato chromosomes, DR752011 located on chromosome 8 of PCC1 population, and DR751719, DR751984, DR752001 and DR751998 mapped on chromosome 6, 12, 1 and 4 of BCT population, respectively. Comparison to the identified QTLs related to late blight resistance showed that the mapped genes were not in the QTL regions.