Interação Trichoderma-feijoeiro em diferentes condições edafoclimáticas e seu efeito na severidade de crestamento bacteriano comum

Abstract

Brazil is one of the world largest common bean (Phaseolus vulgaris L.) producers, with a great socioeconomic importance. Obstacles to crop production are diseases and their control. Highlight to common bean are bacterial diseases, with lack of economically viable curative products. Aim this work was to investigate resistance-inducing effect of Trichoderma sp. isolates to reduce severity of common bacterial blight (Xanthomonas axonopodis pv. phaseoli) and increases of yield on common bean in three homogenized substrates. Therefore layers (0 to 20cm) of ARGISSOLO sandy texture (ATA), LATOSSOLO VERMELHO Eutroférrico (LVE) and ‘NEOSSOLO REGOLÍTICO Eutrófico’ (NRE), were inoculated with Trichoderma virens (TI1, TI3, TM1, TM2, TM3, TM4, TLB9, TLB15 and TNH2), Trichoderma harzianum (TI2, TI4, TLB2, TLB3, TLB4, TLB12, TOD1 and TOD3), Trichoderma asperellum (TLB6), Trichoderma koningiopsis (TLB14 and TLB17), Trichoderma longibrachiatum (TOD2A and TOD2B) and Trichoderma spirale (TNH1) and the standards Bordeauxbroth (1,5%) and water (control). The effect on common bacterial blight severity, soil active fungal biomass, shoot and root dry weight, was evaluated. Based on the lowest severity of disease, the isolates T. harzianum (TOD1) andT. virens (TM4) in ATA, T. koningiopsis (TLB17) andT. spirale (TNH1) in LVE, T. harzianum (TLB12) and T. koningiopsis (TLB14) in NRE, and two isolated in common to the three substrates, T. virens (TLB15) and T. asperellum (TLB6) were selected. Isolates were tested under field conditions at second harvest (2015/2016) and first harvest (2016/2017) in Mundo Novo – MS (ATA), Marechal CândidoRondon - PR (LVE) and Marquinho – PR (NRE). Agro Mos® and Nem Out® were used as commercial standards. Fungal biomass and organic matter concentration were evaluated at V2, R5 and R7 stages, as well disease severity and yield. Under greenhouse conditions, the fungal biomass increased in LVE and NRE, as well as root and shoot dry weight. In the field, changes in the fungal biomass were punctual as well as the concentration of organic matter, common bacterial blight severity was reduced with greater efficiency in ATA than in LVE and NRE. Yield parameters were changed in a punctual way. The concentrations of fungal biomass analyzed for the regions in the second harvest (2015/2016), demonstrated that the highest concentration of fungal biomass was obtained in NRE followed by LVE and with the lowest concentration in ATA, treatments within crop development stages showed standard Bordeaux broth was like TLB15 isolate and Nem Out® commercial standard, observing that common bean crop tends to decrease fungal biomass. In the first harvest (2016/2017) the biomass concentration was similar in LVE and NRE and higher than the concentration in ATA maintaining these behaviors at the crop stages V2 and R5, however highest concentration was obtained in NRE followed by LVE and with the lowest concentration in ATA, at stage R7. Findings suggest that Trichoderma isolates seems effective to reduce de severity of common bacterial blight as well as edaphoclimatic conditions affect directly fungal biomass.