Yadav, V. and Thorat, V. and Mahadevakumar, S. and Janardhana, G.R. and Yadav, A. (2016) First Report of the Association of the 16SrII-D Phytoplasma Subgroup with Little Leaf Disease of Crotalaria in Karnataka, India. Plant Disease, 100 (12). p. 2523.

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Abstract

Smooth rattle pods plants (Crotalaria pallida Aiton. [Fabaceae]) are commonly grown as fodder and green manure in tropical and subtropical regions. In India, they are commonly used as nitrogen fixer in various agro-systems and as a source of various organic residues for soil nutrition enrichment. C. pallida is also used in folk medicine to treat urinary infections and as an anti-inflammatory agent. The extracted oil from the leaves of C. pallida is known for its antimicrobial properties. In January 2016, C. pallida grown in Mysuru area, Karnataka (India) was found associated with a characteristic little leaf disease, which was suggestive of phytoplasma infection. Symptoms also included small, yellow leaves with reduced lamina, stunting, and phyllody. The disease was noticed in the wild as well as in field-grown green manure crop. Approximately 30 to 50 plants from seven fields; that is, 10 to 15 plants randomly selected in 3 to 5 rows, were visually recorded for disease symptoms. Thirty-two out of 282 plants in different fields were estimated with phyllody symptoms, resulting in disease incidence of 11%. Leaf samples from five symptom-bearing plants along with two healthy leaf samples were collected and the DNA was manually extracted using a GenElute Plant Genomic DNA Miniprep Kit (Sigma-Aldrich, USA). PCR was performed to amplify the phytoplasma 16S rRNA gene using P1/P7 primers (Smart et al. 1996). The expected 1.8-kb amplicons were detected from symptomatic Crotalaria samples and none from the asymptomatic ones. The PCR products were purified, sequenced, and the consensus sequence was deposited in GenBank with accession number KX013260 (1,566 bp). It showed a 99% sequence identity with phytoplasma members of the group 16SrII ‘Candidatus Phytoplasma aurantifolia.’ The iPhyClassifier analysis (http://plantpathology.ba.ars.usda.gov/cgi-bin/resource/iphyclassifier.cgi) revealed that the C. pallida phytoplasma (KX013260) had a coefficient of similarity of 1.0 and shared identical RFLP profiles to those of Ca. P. australasia (Y10097), which belongs to the subgroup 16SrII-D. Phytoplasmas of group 16SrII-D have been found affecting various vegetables, crops, and weeds in India, including tomato, brinjal, sesame, and parthenium. Crotalaria species are the reported hosts of several groups of phytoplasma which include 16SrVII-D (C. juncea: shoot proliferation) from Brazil (Flôres et al. 2013); 16SrII-A (C. szemaoensis, C. zanzibarica, C. juncea: witches’-broom) from China (Wang et al. 2007), and 16SrI-B (C. spectabilis, C. tetragona: ‘fasciation’ and witches’-broom) from India (Kumar et al. 2010). To our knowledge, this is the first report of the association of the phytoplasma subgroup 16SrII-D with a disease on C. pallida in India. Recent disease reports and nucleotide sequence submissions revealed that the 16SrII phytoplasmas possess a wide plant host range; particularly economically important Fabaceae pulse crops (Thorat et al. 2016). Understanding the etiology and management of little leaf disease of C. pallida is critical as this may be a potential reservoir for 16SrII phytoplasmas.

Item Type:	Article
Subjects:	Insect Molecular Biology
Depositing User:	Mr. Rameshwar Nema
Date Deposited:	06 Dec 2017 06:55
Last Modified:	06 Dec 2017 06:55
URI:	http://nccs.sciencecentral.in/id/eprint/494

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