Indução de resistência a Xanthomonas axonopodis pv. phaseoli mediada por diferentes espécies de Trichoderma na cultura do feijão

Abstract

The ease of using agrochemicals and the increasing demand for high productivity make the management of plant diseases to happen mainly through the use of chemicals. On the other hand, there is a growing search for new technologies that enable a production model compatible with sustainability. In this sense, research has been proving the efficiency in reducing the intensity of various diseases through induction of resistance. Therefore, this work aimed to investigate the potential of Trichoderma spp. isolates in the biological management of Xanthomonas axonopodis pv. phaseoli, which causes common bacterial blight, in the bean crop, by its direct action and/or through the induction of resistance through the activation of enzymatic defense mechanisms. Fifteen isolates of Trichoderma spp. (TI2, TI4, TLB2, TLB3, TLB4, TLB12 and TOD3 (Trichoderma harzianum); TM1, TM2, TM4, TLB9 and TLB15 (Trichoderma virens); TLB6 (Trichoderma asperellum); TLB17 (Trichoderma koningiopsis) and TOD2B (Trichoderma longibrachiatum)) were used in three in vitro tests: direct comparison with the pathogen and production of volatile and non-volatile compounds, and two in vivo tests: evaluation of the severity of common bacterial blight in bean plants and evaluation of induction of resistance through defense enzymes analysis; peroxidase (POX), polyphenol oxidase (PFO), phenylalanine ammonia lyase (FAL) and β1,3-glucanase (β-GASE). The isolates tested together with the factor soil, autoclaved and nonautoclaved, presented very discrepant results in relation to the severity, in vitro results, protein concentration and activities of the four enzymes related to induction of resistance evaluated at work. The isolates TM4, TLB6, TLB4, and TI4 were able to limit the development of Xanthomonas axonopodis pv. phaseoli in the three in vitro tests performed, direct comparison and volatile and non-volatile compounds. Isolates TLB15, TM4, TLB9, TLB6, TLB2, TLB12, TOD3 and TLB17 reduced the severity of common bacterial blight. TLB3, TI4, TLB12 and TLB15 isolates promoted increased activity of POX, PFO, and β-GASE enzymes. Isolates TLB15, TLB12, TI4, and TLB3 were the only ones that provided increased expression in the total protein content and in three of the four enzymes tested: POX, PFO, and β-GASE. The TLB2 isolate was the one that provided the greatest reduction in disease severity (80.58%) but showed little efficiency in the in vitro tests and little action in the expression of enzymatic activities. On the other hand, the TLB15 isolate, which reduced the severity at a 69.86% rate, showed in vitro action of both compounds (volatile and nonvolatile) and induced higher total protein content and POX, PFO and β-GASE expression. The TLB15 isolate was the isolate that provided most frequently when compared to control, increasing of the expression of the activity of the enzymes evaluated. In general, Trichoderma sp. may be considered promising in the management of common bacterial blight in bean crop.