Abstract
Wet root rot caused by Rhizoctonia solani is one of the important diseases in chickpea worldwide. In the present study, 10 random amplified polymorphic DNA (RAPD) primers were used to assess the molecular diversity of 50 chickpea isolates of R. solani. There was a great diversity among the isolates studied and was in the range of 52 to 93%. The isolates were highly variable in aggressiveness and caused up to 100% wet root rot incidence in chickpea. Accurate detection and identification of plant pathogens are fundamental to plant pathogen diagnostics and management. Therefore, a polymerase chain reaction (PCR) assay was developed for accurate and sensitive detection of R. solani from mycelial DNA and infected chickpea plants. RAPD primer OPA 11 consistently amplified ≈1700 base pairs (bp) product in PCR only from the DNA of R. solani isolated from chickpea. The common DNA fragment was sequenced and used to design a pair of oligonucleotide primers amplifying 285 bp sequence characterized amplified region (SCAR). The specificity of the SCAR primers was evaluated. The detection sensitivity of R. solani was 0.5 ng for the genomic DNA and 5 ng for the DNA extracted from infected chickpea root samples. Also, SCAR primer was validated with Q-PCR to detect and quantify R. solani upto 1 pg from infected chickpea root samples. These new SCAR marker are useful for early detection and quantification of wet root rot pathogen in chickpea. Key words: Anastomosis grouping, chickpea, wet root rot, quantitative-PCR (Q-PCR), random amplified polymorphic DNA (RAPD), sequences characterized amplified region (SCAR).
Highlights
Chickpea (Cicer arietinum L.) is a leading winter legume crop in India
The study clearly indicates that there was considerable variability among R. solani isolates collected from different chickpea growing areas of India
The isolates of R. solani included in the present study showed high genetic variation from 52 to 93%
Summary
Chickpea (Cicer arietinum L.) is a leading winter legume crop in India. It is cultivated in an about 8.21 million hectares, with an average annual production of 7.48 million tonnes along with a productivity of 911 kg ha-1 (Anonymous, 2010). Kabuli type chickpea is grown in temperate regions while the desi type is grown in semi arid tropics Both types of chickpea are commonly grown in India, but the cultivation of desi type is predominated. Wet root rot (WRR) caused by R. solani Kühn, is important production constraints in chickpea cultivation especially in rice-chickpea cropping system or in wet areas (Haware, 1998). WRR is an important disease affecting seedling establishment of chickpea which leads to the reduction of chickpea yields in Canada (Hwang et al, 2003) This disease is most commonly observed at early in the season when soil moisture content is often high; it can be observed any time during the season
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