Date Published: June 23, 2015
Publisher: Springer Berlin Heidelberg
Author(s): R. Kaunain Roohie, S. Umesha.
The suppression subtractive hybridization was employed to elucidate the resistance mechanism in Brassica oleracea var. capitata upon infection with Xanthomonas campestris pv. campestris. A cDNA library was constructed enriched in differentially expressed transcripts in the resistant cultivar Pusa mukta. A total of 150 unigenes were classified into five functional categories. The present study indicates that the defense-related unigenes accounted for the 35 % of the total unigenes studied. Confirmation of defense-specific representation genes through semiquantitative RT-PCR revealed their increased expression in the resistant cultivar which was validated by qPCR. The resistant cultivar elicited a strong hypersensitive response upon attack by black rot pathogen. The study is first of its kind where the resistant cultivar Pusa mukta in India has been assessed for its resistance to the bacterial pathogen.
Black rot, caused by Xanthomonas campestris pv. campestris (Pammel) Dowson is a major seed-borne biotic constraint for cabbage (Brassica oleracea var. capitata L.) production by all over the world which causes substantial crop loss especially during warm, humid seasons (Williams 1980). The pathogen enters the plant through the hydathodes and spreads in the vasculature of the leaf and stem. The typical symptom of black rot is the occurrence of V-shaped chlorotic lesions with vertices towards the mid rib of the leaves.
SSH which is a powerful technique used to enrich libraries with differentially expressed cDNAs and includes a normalization step that enables detection of low abundance differentially expressed transcripts such as those involved in signaling and signal transduction and might thus identify essential components in biological processes (Birch and Kamoun 2000). The transcriptional diversity in B. oleracea var. capitata–X. campestris pv. campestris interaction in resistant cultivar Pusa mukta was studied. 150 unigenes were obtained from the 500 randomly picked positive clones. Upon functional annotation of the 150 unigenes, the ESTs with known biological function accounted for 80 % of total genes. The main aim of the study was to focus on the genes involved in resistance mechanism against X. campestris pv. campestris in resistant cultivar Pusa mukta. Pusa mukta is a resistant cultivar obtained from a cross between EC 24855 × EC 10109 by pedigree selection. It is one of the popular resistant cultivar in northern part of India, but its performance depends on the geographic location and its performance in the southern part of India was assessed.