Improvement for Bacterial Wilt Resistance in Potato By Conventional and Biotechnological Approaches

Bacterial wilt (BW) of potato caused by the bacterium Ralstonia solanacearum (Rs) is considered a serious problem particularly in tropical, subtropical and warm temperate regions. Chemical-, cultural-and biological control of BW has limited success. Thus, the control of BW through resistance breeding and biotechnology is considered to be very important and necessary. Rs is considered a 'species complex' and has significant variation at physiological, serological and genetic levels. The bacterium has an unusually wide host range with over 400 hosts belonging to more than 50 botanical families. A large number of Solanum species have been screened for resistance to this bacterium, but so far no Solanum species has been found to have complete immunity. A high degree of resistance to Rs was found only in S. phureja, a diploid relative of cultivated tetraploid potatoes. The resistance has been transferred from S. phureja to cultivated potatoes through introgression breeding as well as somatic hybridization. Although moderate to highly resistant potato varieties have been released, high frequency of latent infection in tubers is still a major problem. Further, the resistant cultivars are not adapted to different agro-climatic zones and are not effective against all the strains of the pathogen. Biotechnological approaches involving the use of antimicrobial peptides, plant defence genes and plant resistance genes are being tried. This paper reviews the global situation with regard to screening of genetic resources and their utilization in resistance breeding for BW in potato and also the status and the opportunities that biotechnology offers to combat this disease.