Kirdat, K. and Thorat, V. and Ghole, T. and Takawale, P. and Yadav, A. (2019) First report of an association of multi-species phytoplasmas with Mango Phyllody and Little Leaf disease from western India. Plant Dis. .

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Abstract

Mango (Mangifera indica L., family Anacardiaceae) trees with malformed vegetative tissues at branch nodes and phyllody in panicles with thicker and stunted peduncle were observed in Pune region, Western India, in February and March 2018. Although the etiology of mango malformation disease is established by performing Koch’s postulate, confirming species of Fusarium are the causative agents (Chakrabarti 2011; Crespo et al. 2014), the observed symptoms, namely, excessive vegetative growth resulting in “bunchy top” appearance with shootlets bearing small, scaly leaves and leafy girdles, however, were also suggestive of phytoplasma infection. The growing symptomatic tissues were collected from one seedling, two panicles, and four branch nodal tissues from separate plants. Eight other asymptomatic samples were also collected. To confirm the presence of phytoplasmas, 2 g of malformed tissue from symptomatic plants was used for total DNA extraction using the CTAB method. The DNA was also extracted from asymptomatic plants. The phytoplasma 16S rRNA gene was amplified from 50 ng of DNA using primers P1/P7 followed by nested primers R16F2n/R16R2. The 16S rRNA gene of phytoplasma was detected in a symptomatic seedling, one nodal tissue, and one panicle sample, except in one symptomatic nodal tissue and a panicle. This may be owing to unevenly spread low phytoplasma titer, as known from previous studies (Abeysinghe et al. 2016; Caicedo et al. 2015). No amplification was observed in asymptomatic samples. All symptomatic samples were also tested for the presence of Fusarium DNA using universal PCR primers ITS1/ITS4; however, none of the samples tested positive, nor was fungal mycelium observed when sections of symptomatic tissue stained with cotton blue were observed under the microscope. The obtained 16S rRNA gene sequences from a symptomatic panicle (MH744151), nodal tissue (MH744152), and seedling (MH744153) samples showed 99.30% sequence similarity with ‘Candidatus Phytoplasma asteris’ AYWB (CP000061), 16SrI group (aster yellows); 99.53% with ‘Ca. P. balanitae’ Balanites triflora (AB689678), 16SrV group (elm yellows); and 98.57% with ‘Ca. P. aurantifolia’ WBDL (U15442), 16SrII group (peanut witches’ broom), respectively, when analyzed using EzTaxon database and iPhyClassifier. So far, unknown phytoplasma associated with malformed mango inflorescence was reported from Egypt using electron microscopy (El-Banna et al. 2007), and ‘Ca. P. asteris’ (group 16SrI) was PCR detected from Pakistan (Fahmeed et al. 2009). These results suggest that polyphagous sap-sucking insect vectors must be involved in phytoplasma transmission from other alternate plant hosts to mango, and further studies are required. India produced over 19 million tons of mangoes, which is over 40% of the world’s production, and exported over U.S.$60 million worth of mangos in 2016 to 2017. To our knowledge, this is the first formal evidence of the association of multispecies phytoplasma strains with a mango malformation disease in India. The malformation is a severe disease of mango that causes serious damage to the seedlings and flowering tissue, resulting in severe economic losses. It is therefore essential to understand the etiology of mango malformation disease associated with phytoplasmas beyond the existing knowledge by collecting additional samples from different agro-climatic regions of India, ultimately for the better management of the disease.

Item Type:	Article
Depositing User:	Mr. Rameshwar Nema
Date Deposited:	21 Feb 2020 08:57
Last Modified:	10 Feb 2021 08:07
URI:	http://nccs.sciencecentral.in/id/eprint/742

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