Etiology and immuno-molecular detection of snake gourd (Trichosanthes anguina L.) mosaic disease in Kerala, India

Abstract

In August 2022, snake gourd plants (cv. Kaumudi; n = 90) were observed with mosaic, mottling, blistering, vein banding and deformed fruits at Vellayani (N 8°25’59.6”, E 76°59’09.5”), Kakkamoola (N 8°25’26.0”, E 77°00’21.9”) and Manamboor villages (N 8°42’58.0”, E 76°46’36.0”) of Thiruvananthapuram district of Kerala, India. Disease incidence ranged between 28.5 and 100%. The viruses were sap transmissible and maintained in snake gourd and in local lesion hosts viz., Chenopodium amaranticolor and Nicotiana tabacum var Samsun. The viruses were mechanically transmissible to cucurbitaceous crops and N. glutinosa. No symptoms were produced in tomato, chili, brinjal and papaya. The symptomatic snake gourd samples reacted positively with Papaya ringspot virus (PRSV) polyclonal antiserum (DSMZ, Germany) in double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) and Cucumber mosaic virus (CMV) polyclonal antiserum (ICAR-NRC, Tamil Nadu) in Direct antigen coating ELISA. Reverse transcriptase polymerase chain reaction gave amplicons of size 1200 and 400 bp with primers specific to the coat protein gene of PRSV and the 2a protein gene of CMV, respectively. Comparative nucleotide sequence alignment of isolates revealed 86.5 and 93.8% homology with PRSV and CMV isolates of snake gourd from Tamil Nadu. Phylogenetic analysis identified PRSV isolates as type W. The results of the current study revealed for the first time the etiology of the snake gourd mosaic disease complex in Kerala, which can pave the way for devising management strategies.