This study is to investigate the role of lipid transfer protein （LTP1） gene of potato （Solanum tuberosum） in bacterial wilt （Ralstonia solanacearum） resistance. A novel cDNA clone encoding nsLTP was isolated from cultivated potato （Solanum tuberosum） infected with R. solanacearum by 5＇-rapid amplification of cDNA ends （RACE）. The temporal and spatial expression of StLTPbl was studied during the early stages of potato-R, solanacearum interaction by reverse transcriptase PCR （RT-PCR） and Northern blotting. The sequence analysis of the cloned cDNA, named StLTPbl, showed 691 bp which encoded a type 1 nsLTP of 91 amino acids. Construction of a phylogenic tree showed that StLTPbl is well conserved in the coding region with high identity at the amino acid level with other Solanaceae nsLTPs. The temporal and spatial expression of StLTPbl was studied during the early stages of potato-R, solanacearum interaction. StLTPbl transcription is induced faster and transcripts accumulate to higher concentrations in resistant compared with susceptible genotypes by the pathogen. Dominant differences in the pathogen-induced gene expression pattern between the upper and lower leaves and stems were observed within the same genotypes. In situ hybridization results showed that the StLTPbl mRNA was localized in phloem cells of vascular tissues in potato leaf and stem tissues after pathogen infection. Salicylic acid, methyl jasmonate and abscisic acid could induce StLTPbl gene expression without significant difference between the upper and lower tissues. These abiotic elicitors could produce a long-lastingeffect on the StLTPbl during early stages of potato-R, solanacearum interaction. Differential expression of StLTPbl gene between resistance and susceptible potato genotypes in response to R. solanacearum suggests that this gene plays a key role in plant defense mechanisms.
Cultivated potato with high level of horizontal resistance against late blight is one of the most important goals of potato breeding.The recurrent selection has been adopted to increase the level of potato horizontal resistance and a B3C1 population without R1-R11 dominant genes has been released by the International Potato Center at the short-day condition of Peru.The present research was carried out to further improve the resistance and the agronomic traits of B3C1 population under long-day condition of Hubei,China,with maximized retention of its genetic diversity.Twenty-seven individual clones of B3C1 were used to generate population B3C2 by in-population crossing with the bulk pollens aiming to elevate the frequency of late blight resistance genotypes and to improve the adaptation to local long-day conditions.The late blight resistance and the main agronomic traits including the maturity,the plant characters and the tuber traits were evaluated for the foreground selection in three years,by which 130 pedigrees were maintained as the basic population of B3C2 for further selection.A total of 312 polymorphic loci detected by 9 AFLP marker combinations were used to monitor the genetic diversity of the populations for the background selection.The B3C2 population of 51 clones was finally selected,of which the frequency of resistant genotypes increased by 23.8% points and the genetic diversity was maintained by about 96% as referred to B3C1.Our results strongly suggested that combination of the foreground selection for target traits and the background selection for the genetic diversity is an efficient strategy in the recurrent selection of tetraploid potato to improve quantitative traits.
YAO Chun-guangSONG Bo-taoLIU JunWU Cheng-jinCHENG QunLI Da-chunXIE Cong-hua
