Survey and molecular detection of Sri Lankan cassava mosaic virus in Thailand

Abstract

Cassava plantations in an area of 458 hectares spanning five provinces along the Thailand–Cambodia border were surveyed from October 2018 to July 2019 to determine the prevalence of cassava mosaic disease (CMD) caused by Sri Lankan cassava mosaic virus (SLCMV) in the region. CMD prevalence was 40% in the whole area and 80% in Prachinburi, 43% in Sakaeo, 37% in Burium, 25% in Surin, and 19% in Sisaket provinces. Disease incidence of CMD was highest 43.08% in Sakaeo, followed by 26.78% in Prachinburi, 7% in Burium, 2.58% in Surin, and 1.25% in Sisaket provinces. Disease severity of CMD symptoms was mild chlorosis to moderate mosaic (2–3). The greatest disease severity was recorded in Prachinburi and Sakaeo provinces. Asymptomatic plants were identified in Surin (12%), Prachinburi (5%), Sakaeo (0.2%), and Buriram (0.1%) by PCR analysis. Cassava cultivars CMR-89 and Huai Bong 80 were susceptible to CMD. In 95% of cases, the infection was transmitted by whiteflies (Bemisia tabaci), which were abundant in Sakaeo, Buriram, and Prachinburi but were sparse in Surin; their densities were highest in May and June 2019. Nucleotide sequencing of the mitochondrial cytochrome oxidase 1 (mtCO1) gene of whiteflies in Thailand revealed that it was similar to the mtCO1 gene of Asia II 1 whitefly. Furthermore, the AV1 gene of SLCMV—which encodes the capsid protein—showed 90% nucleotide identity with SLCMV. Phylogenetic analysis of completed nucleotide sequences of DNA-A and DNA-B components of the SLCMV genome determined by rolling circle amplification (RCA) indicated that they were similar to the nucleotide sequence of SLCMV isolates from Thailand, Vietnam, and Cambodia. These results provide important insights into the distribution, impact, and spread of CMD and SLCMV in Thailand.

Cassava molecular genetics and genomics for enhanced resistance to diseases and pests

“…Surveillance has also identified co‐infections and pest resurgence within cassava farms in Congo (Bisimwa et al., 2019 ). SLCMV surveys have also been conducted in Thailand, with observations revealing a relatively high level of similarity to SLCMV (Saokham et al., 2021 ). A combination of surveillance and evolutionary analyses was able to identify a new cassava mosaic virus named African cassava mosaic Burkina Faso virus (ACMBFV), a recombinant between tomato leaf curl Cameroon virus and cotton leaf curl Gezira virus (Tiendrébéogo et al., 2012 ).…”

Metabolic profiles of Sri Lankan cassava mosaic virus-infected and healthy cassava (Manihot esculenta Crantz) cultivars with tolerance and susceptibility phenotypes

“…Forward (5ʹ-GTT GAA GGT ACT TAT TCC C-3ʹ) and reverse (5ʹ-TAT TAA TAC GGT TGT AAA CGC-3ʹ) primers were used to amplify the partial AV1 gene fragment referred to in a protocol described by Saokham et al . (2021) [ 69 ]. The 25-µL reaction contained 1 × PCR buffer (PCR Biosystems, London, UK), 0.2 µM each of forward and reverse primers, and 50 ng genomic DNA.…”

Analysis of proteomic changes in cassava cv. Kasetsart 50 caused by Sri Lankan cassava mosaic virus infection

“…To identify infected plants, the AV1 gene of SLCMV was amplified using gene specific primers (forward: 5’-GTT GAA GGT ACT TAT TCC C-3’ and reverse: 5’-TAT TAA TAC GGT TGT AAA CGC-3’) [ 27 ]. Amplification was performed in a 25-μL reaction volume containing 1 × PCR buffer (PCR Biosystems, London, UK), 0.2 μM each of forward and reverse primers, and 50 ng of the genomic DNA.…”