Enhanced Dissipation of Triazole and Multiclass Pesticide Residues on Grapes after Foliar Application of Grapevine-Associated Bacillus Species

Disease management in vineyards with fungicides sometimes results in undesirable residue accumulations in grapes at harvest. Bioaugmentation of the grape fructosphere can be a useful approach for enhancing the degradation rate and reducing the residues to safe levels. This paper reports the in vitro and in vivo biodegradation of three triazole fungicides commonly used in Indian vineyards, by Bacillus strains, namely, DR-39, CS-126, TL-171, and TS-204, which were earlier found to enhance the dissipation rate of profenophos and carbendazim. The strains utilized the triazoles as carbon source and enhanced their in vitro rate of degradation. Myclobutanil, tetraconazole, and flusilazole were applied in separate vineyard plots at field doses of 0.40 g L(-1), 0.75 mL L(-1), and 0.125 mL L(-1), respectively. Residue analysis of field samples from the treated fields reflected 87.38 and >99% degradations of myclobutanil and tetraconazole, respectively, by the strain DR-39, and 90.82% degradation of flusilazole by the strain CS-126 after 15-20 days of treatment. In the respective controls, the corresponding percent degradations were 72.07, 58.88, and 54.28, respectively. These Bacillus strains could also simultaneously degrade the residues of profenofos, carbendazim, and tetraconazole on the grape berries and can be useful in multiclass pesticide residue biodegradation.

Kinetics of degradation of carbendazim by B. subtilis strains: possibility of in situ detoxification

Food safety is a global concern due to the increased use of pesticides in agriculture. In grapes, carbendazim is one of the frequently detected fungicides. However, it is amenable to biodegradation. In this study, we aimed to assess the degradation of carbendazim by four Bacillus subtilis strains, which had earlier shown potential for biocontrol of grape diseases. In liquid medium, each of the four strains, namely, DR-39, CS-126, TL-171, and TS-204, could utilize carbendazim as the sole carbon source. The half-life was minimized from 8.4 days in the uninoculated spiked control to 4.0-6.2 days by the four strains. In Thompson Seedless sprayed with carbendazim at 1.0 g L(-1), the residue on grape berries in control was 0.44 mg kg(-1) after 25 days of application, whereas in grapes treated with the four B. subtilis strains, the residues had decreased to 0.02 mg kg(-1). The degradation kinetics showed low half-lives of 3.1 to 5.2 days in treated grapes as compared to 8.8 days in control. In inoculated soils, the half-lives were 5.9 to 7.6 days in autoclaved and 6.5 to 7.2 days in nonautoclaved soils as compared to 8.2 and 8.0 days in respective controls. The growth dynamics of these strains in all the three matrices was not affected by presence of carbendazim. Bacillus strains TS-204 and TL-171 showed higher degradation rate than the other two strains in all the three matrices and show promise for in situ biodegradation of carbendazim.

Biodegradation of profenofos by Bacillus subtilis isolated from grapevines (Vitis vinifera)

The biodegradation of profenofos, an organophosphorus insecticide, by four Bacillus subtilis strains, namely, DR-39, CS-126, TL-171, and TS-204, isolated from grapevines or grape rhizosphere was studied in liquid culture, on grape berries, and in vineyard soil. Each of the four B. subtilis strains enhanced the degradation of profenofos in all three matrices. Degradation rate constants were best obtained by first + first-order kinetics module. In nutrient broth spiked with 5 μg/mL profenofos, inoculation with B. subtilis strains DR-39, CS-126, TL-171, and TS-204 reduced the half-life (DT50) of profenofos to 4.03, 3.57, 2.87, and 2.53 days, respectively, from the DT50 = 12.90 days observed in the uninoculated control. In Thompson Seedless grapes sprayed with profenofos at a field dose of 1250 mL ai/ha, the DT50 values were 1.07, 1.00, 2.13, and 2.20 days in grapes inoculated with B. subtilis strains DR-39, CS-126, TL-171, and TS-204, respectively, as compared to 2.20 days in uninoculated grapes. These four B. subtilis strains also enhanced the degradation of profenofos in autoclaved soil (DT50 = 5.93, 7.47, 6.00, and 4.37 days) and in nonautoclaved soil (DT50 = 0.87, 2.00, 2.07, and 2.43 days) amended with 5 μg/g profenofos from the half-lives of 17.37 and 14.37 days in respective uninoculated soils. Growth dynamic studies indicated that all four B. subtilis strains were able to establish and proliferate on berries and soil equally well in the presence or absence of profenofos. Degradation product 4-bromo-2-chlorophenol was identified by GC-MS. Strain DR-39 was most effective in the natural environments of grape and soil.

First Report of Grapevine leafroll-associated virus 1 Infecting Grapevines in India

Viticulture, one of the most remunerative farming enterprises of India, is seriously affected by leafroll disease, which accounts for 62% of the losses in grape production worldwide due to viral diseases (4). Grapevine leafroll-associated virus 3 and 1 (GLRaV-3 and GLRaV-1) of the family Closteroviridae are the two most common viruses associated with the leafroll disease of grapevine (1). GLRaV-3 was previously confirmed in India through RT-PCR, cloning, and sequencing (2). A survey was conducted during 2010 and 2011 in the Nashik and Pune regions of western India and reddening of interveinal areas and downward rolling, typical symptoms of leafroll disease in dark fruited cultivars, were observed, first in 2010 and subsequently in 2011. Fourteen leafroll symptomatic samples from seven cultivars of seven vineyards were collected during 2011. Samples were subjected to double antibody sandwich (DAS)-ELISA using commercially available antibodies against GLRaV-3 and GLRaV-1 (Bioreba, Reinach, Switzerland) (2). An asymptomatic sample from another cultivar of a different vineyard and samples from two plantlets of two different cultivars produced in tissue culture were used as negative controls. GLRaV-1 was detected in two cultivars, Shiraj (Nashik region) and Pinot Noir (Pune region) using DAS-ELISA. GLRaV-1 was detected either alone in cultivar Pinot Noir or as mixed infection with GLRaV-3 in cultivar Shiraj. To further confirm the presence of GLRaV-1 in these two cultivars, crude extract from petioles of these two cultivars were subjected to one step reverse transcription (RT)-PCR using GLRaV-1 specific primers pORF9F and pORF9R (GGCTCGAGATGGCGTCACTTATACCTA and CCTCTAGACACCAAATTGCTAGCGA, respectively) (3). The ˜650 bp amplicons were cloned in pGEM-T easy vector and three independent clones of each amplicon were sequenced in both directions. The cloned amplified product was 646 bp, including 630 bp of p24 protein (ORF9) of GLRaV-1. Comparative sequence analysis, using the BioEdit 7.0.3 program ( http://www.mbio.ncsu.edu/BioEdit/BioEdit.html ), of ORF9 of the virus under study from the cultivars Pinot Noir and Shiraj shared maximum sequence identity of 95.8 and 96.1%, respectively, at the nucleotide level with the Clatervine isolate from the United States (GenBank Accession No. HQ833477). The corresponding values of maximum identities at the amino acid level were 96.6 and 96.1%, respectively, with the same Clatervine isolate. The maximum identity between these two isolates of GLRaV-1 was 96.1% at nucleotide level and 95.7% at amino acid level. To the best of our knowledge, this study represents the first report of GLRaV-1 from India. Grape production in India could be impacted by this virus; thus, identification of the virus is important. References: (1) B. Akbas et al. Hort. Sc. (Prague). 36: 97, 2009. (2) S. Kumar et al. Virus Genes. 45:195, 2012. (3) A. Little and M. A. Rezaian. Arch. Virol. 151:753, 2006. (4) A. Little et al. Virus Res. 80:109, 2001.