ABSTRACT
Sugarcane leaf fleck incited by Sugarcane bacilliform virus is emerging as a major disease and affecting exchange of sugarcane germplasm and cultivation worldwide. Roving surveys conducted in 162 fields belonging to 81 villages spread over 14 sugarcane growing districts of Andhra Pradesh during 2021-2022 revealed 8 to 44% incidence of the disease. Mean maximum fleck disease incidence was reported in Anakapalli district (33.00%) followed by Srikakulam district (22.66%), whereas least incidence was observed in Alluri Sitharamaraju district (9.33%). The early and sensitive detection of pathogens is vital and necessary to reduce the danger of introducing new diseases or pathogen strains into sugarcane growing regions. Both serological and molecular methods were used in proposed investigation to identify the virus at the protein and nucleic acid levels. DAS-ELISA results were positive for 50 suspected SCBV infected sugarcane leaf samples out of 81, with mean absorbance (A405) values ranging from 0.50 to 2.20. Further PCR assays were performed using SCBV-specific primers targeting RT/RNase H coding region which is frequently employed as a taxonomic marker for species delineation in Badnaviruses. Out of 81 symptomatic samples collected, 61 samples gave positive results, and no amplification was observed in healthy control and negative control. Results made it evident that PCR was more sensitive than DAS-ELISA. Low virus concentration or variation in virus strains may be the reason for the low detection rate in DAS-ELISA in the current study. Extensive roving surveys conducted for the incidence of leaf fleck disease for the first time in the state of Andhra Pradesh revealed severe occurrence of leaf fleck disease under field conditions.
Subject(s)
Badnavirus , Saccharum , Badnavirus/genetics , Plants , Polymerase Chain ReactionABSTRACT
Mungbean yellow mosaic India virus (MYMIV) is one of the most serious commonly occurring yellow mosaic virus (YMV's) group in majority of the pulses especially black gram and green gram in southern India compared to previously reported mungbean yellow mosaic virus. In January 2020 Desmodium laxiflorum and Abelmoscus moschatus showing mosaic symptoms and vein yellowing were collected from Guntur and Prakasam districts respectively in Andhra Pradesh. PCR analysis using MYMIV and betasatellite specific primers gave desired expected amplification from the infected samples of A. moschatus (YMV-ABEL) whereas only MYMIV specific amplification was obtained in D. laxiflorum (YMV-DES). However, no PCR amplification was obtained in respective healthy leaf samples of both plants. Sequence analysis showed that the CP sequence of YMV-ABEL and YMV-DES showed a similarity of 99.19% with MYMIV (KP677496) and 99.75% with MYMIV (JN181003) respectively. The full-length betasatellite (1356 bp) showed highest identity of 90% with bhendi yellow vein mosaic betasatellite (BYVMB) (GU111977). Phylogenetic analysis clustered the test isolates with south Indian isolates of MYMIV whereas the betasatellite sequence clustered with various isolates of BYVMB, tomato leaf curl New Delhi virus betasatellite and okra leaf curl betasatellite reported from India and Pakistan. To the best of our knowledge, this is the first report of a MYMIV in D. laxiflorum and A. moschatus and MYMIV betasatellite complex in A. moschatus.
ABSTRACT
Variability among isolates of Alternaria solani, the causal agent of early blight of tomato, from Northern and Southern parts of India was determined based on conidial morphology, pathogenicity tests and random amplified polymorphic DNA (RAPD) techniques. The isolates varied with respect to size of conidia and number of septa. The average size of conidia varied from 150-224.9 microm x 12.4-17.2 microm. The number of horizontal (4-14), vertical (0-3) and beak (0-8) septa also varied among the isolates. The test isolates differed in the virulence pattern on ten tomato genotypes under screen house conditions. Based on disease severity, test isolates were categorized into three main groups. Isolates RAS (Rohtak) and HAS-I (Hisar) were more virulent than all other isolates. None of the genotypes were completely resistant to all the test isolates. The analysis of RAPD profiles showed that there was a high level of genetic variability among the isolates of A. solani. The cluster analysis based on similarity coefficients separated the ten A. solani isolates into two major clusters. There was no evidence for geographical clustering of isolates with high levels of genetic similarity, suggesting that isolates are widely spread across India.
