Abstract:
Identification of R gene homologous from chilli (Capsicum annuum L.) will provide important
information for improving disease resistance in breeding programs. A Nucleotide-Binding Site
(NBS) domain in R gene family accounts for the largest number of disease resistant genes in
plants. In this study it was aimed at detecting the presence of putative disease resistant genes
in commercially growing chilli varieties; MI Hot, MI 02, MICHHY1, MICH3, KA 02, Arunalu,
Hen miris using a specifically designed primer pair in a PCR-based approach. The PCR
amplified gene products were sequenced and homologies were explored in BLASTn. A
sequence identity matrix was constructed using these nucleotide sequences of the chilli
varieties along with 5 similar homologous sequences obtained from in Cluster W programme
of Bio-Edit (version 8.0). Phylogenetic analysis was performed in MEGA X. The similarity
between the tested nucleotide sequences of 07 chilli varieties showed more than 90% similarity
with each other except the accession, MICH3. Sequence analysis indicated that the identified
partial Resistance Gene Analogous (RGA) belong to the NBS–LRR type, which they gave
more similar matching with the RGAs identified in other plant species reported from previous
studies; more than 85% with C. annuum (XM 016690560), 70% with Solanum pennellii;
(XM015201323,) Solanum lycopersicum (XM026028184), Camellia sinensis;
(XM028216350) and Sesamum indicum; (XM011072521) available in the GenBank®,
suggesting the existence of common ancestors. The study reveals that the candidate R gene
nucleotide sequences of tested chilli accessions have a close relation to RGAs found in
Solanum peennellii and Solanum lycopersium. However, gradual alteration found in the
generated nucleotide sequences may lead to loss of resistance in target gene action for diseases
in chilli. Identified partial RGA nucleotide sequences found in this study are supposed to be
located on 11th chromosome due to the location of similar RGAs. The information generated
in this study is useful for making combinations of possible crosses for generating genetic
resistance in chilli for biotic stresses and these RGAs could be regarded as candidate sequences
of resistant genes for marker development. This is the first investigation report of NBS family
RGAs in Sri Lankan Capsicum germplasm.
