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

Abstract

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.

Ralstonia solanacearum causing potato bacterial wilt: host range and cultivars’ susceptibility in Rwanda

“…No resistance to R. solanacearum is available in the nine potato cultivars tested in this study, but the level of susceptibility varied significantly among cultivars. Because all the cultivars are susceptible, breeding programmes should look for sources of resistance in the wild Solanum species that show tolerance or resistance to the disease to achieve successful results (Patil et al , ). Meanwhile, the potato cultivars Cruza, Kinigi, and CIP‐58, with least susceptibility to the disease, should be considered when planting potatoes in fields with a history of bacterial wilt.…”

Desempenho de cultivares de batata sob diferentes espaçamentos em solo naturalmente infestado com Ralstonia solanacearum

“…Isso se deve ao fato de a genética da resistência no germoplasma já explorado ser complexa, devido ao nível de ploidia da batata (tetraplóide), e porque os níveis de resistência encontrados são baixos e pouco estáveis, no tempo e no espaço, em virtude da alta variabilidade do patógeno (Silveira et al, 2007;Muthoni et al, 2012). Essas dificuldades têm desestimulado as pesquisas neste tema, motivo pelo qual se frustraram as poucas investidas iniciadas da década de 1970, com mais recente indicativo de que avanços consideráveis só serão possíveis por meio de transgenia (Patil et al, 2012). Embora altos níveis de resistência não estejam disponíveis nas cultivares mais plantadas no Brasil, nota-se que níveis intermediários de resistência podem ser úteis dentro do conjunto de medidas para o controle integrado da doença (Montenegro-Coca et al, 2012 …”

Genome sequencing of four strains of Phylotype I, II and IV of Ralstonia solanacearum that cause potato bacterial wilt in India

“…These phylotypes are further classified into sequevars, containing isolates with similar virulence patterns or common geographic origin 3 . Despite their considerable diversity, R. solanacearum strains are unified by their common etiology resulting in disease 7 . Three of the four phylotypes of R .…”