Eggplant is susceptible to numerous soil-borne diseases like fusarium wilt (Fusarium oxysporum Schlecht. f. sp. melongenae), bacterial wilt (Ralstonia solanacearum) and verticillium wilt (Verticillium dahliae) that cause serious losses in yield and quality of eggplant.
Especially, R. solanacearum is able to survive in the soil for long periods (1–10 years) without a host plant, moreover the control mechanisms against the soil-borne bacterialwilt (BW) disease are expensive or not easily applicable. Nowdays, the best way to control BW economically is to develop cultivars resistant to this soil-borne pathogen. Resistance gene (R-gene) cloning and sequencing to obtain resistance gene analogs (RGAs) is one of the most recent approaches for obtaining disease resistant cultivars.
Indian scientists have used BW resistant cultivated variety Solanum melongena (IIHR-7 accession no: IC 393715) and some wild species, including Solanum gilo, S. marcocarpon and S. viarum. Plant R-genes from different species have been isolated and grouped into distinct classes based on their protein structure. Three different types of degenerative PCR based primers were used for isolating RGAs from resistant cultivated/ wild species through amplification of the target region of nucleotide binding site-leucine rich repeat (NBS-LRR).
Genetic diversity was observed in the sequences isolated, and six sequences showing specific conserved motifs were shortlisted as Solanum melongena RGAs (Sm7RGA1, Sm7RGA2, Sm7RGA4, Sm7RGA8 and Sm7RGA10) and Solanum viarum RGA (SvRGA2). The RGAs isolated in this study belong to both toll interleukin-1 receptors (TIR)-NBS-LRR and non-TIRNBS-LRR type R-genes and show similarity with other plant resistance genes.
This study also confirmed the hypothesis that dicots have both TIR and non-TIR resistance genes. The present study on eggplant RGAs will help develop RGA based markers linked to bacterialwilt in eggplant and other plant species.
Scientists conclude as follows:
- they have identified some of the major motifs of RGA which could be conferred resistance against Ralstonia solanacearum;
- six eggplant RGAs developed in this study can be used for characterizing resistance genes in eggplant and other related plant species.
- by using the eggplant RGAs isolated, five marker sets have been designed for identification of bacterial wilt in cultivated varieties and further work is underway;
- this study is the first report of NBS-LRR class resistance genes/RGA in resistant eggplant and its wild relatives against BW.
http://link.springer.com/article/10.1007%2Fs10658-015-0693-9
Source: Anand C. Reddy, Sudarshini Venkat, T. H. Singh, C. Aswath, K. Madhavi Reddy, D. C. Lakshmana Reddy, ‘Isolation, characterization and evolution of NBS-LRR encoding disease-resistance gene analogs in eggplant against bacterial wilt’, 2015, European Journal of Plant Pathology, DOI 10.1007/s10658-015-0693-9.
Contacts:
D. C. L. Reddy
Division of Biotechnology, Indian Institute of Horticultural Research (IIHR)
Hessaraghatta Lake Post
Bangalore 560089 - India
Email: lreddy@iihr.ernet.in ; dclreddy@gmail.com