Identification and application of biocontrol agents against Cotton leaf curl virus disease in Gossypium hirsutum under greenhouse conditions
2016
Ramzan, Memoona | Tabassum, Bushra | Nasir, Idrees Ahmad | Khan, Anwar | T̤āriq, Muḥammad | Awan, Mudassar Fareed | Shahid, Naila | Rao, Abdul Qayyum | Bhatti, Muhammad Umar | Toufiq, Nida | Husnain, Tayyab
Biological control is a novel approach in crop protection. Bacteria, such as Bacillus spp. and Pseudomonas spp., are reported for this purpose and some of their products are already commercially available. In this study, the rhizosphere and phyllosphere of healthy cotton plants were used as a source of bacterial isolates with properties of potential biocontrol agents. The isolates were screened for phosphate solubilization activity, indole acetic acid (IAA) production and antifungal activity. Two isolates, S₁HL₃ and S₁HL₄, showed phosphate solubilization and IAA production simultaneously, while another two, JS₂HR₄ and JS₃HR₂, demonstrated potential to inhibit fungal pathogens. These bacteria were identified as Pseudomonas aeruginosa (S₁HL₃), Burkholderia sp. (S₁HL₄) and Bacillus sp. (JS₂HR₄ and JS₃HR₂) based on biochemical and molecular characteristics. The isolates were tested against Cotton leaf curl virus (CLCuV) in greenhouse conditions, both as individual bacterial isolates and consortia. Treated plants were healthy as compared to control plants, where up to 74% of the plants were symptomatic for CLCuV infection. Maximum inhibition of CLCuV was observed in the plants treated with a mixture of bacterial isolates: the viral load in the treated plants was only 0.4% vs. up to 74% in controls. This treatment consortium included P. aeruginosa S₁HL₃, Burkholderia sp. S₁HL₄ and Bacillus spp. isolates, JS₂HR₄ and JS₃HR₂. The principal-component biplot showed a highly significant correlation between the viral load percentage and the disease incidence.
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