Aspectos genéticos, bioquímicos e fisiológicos do feijão-caupi infectado por Fusarium oxysporum f. sp. tracheiphilum e uso de nanopartículas de prata e cobre no manejo da murcha de Fusarium

Abstract

Cowpea (Vigna unguiculata (L.) Walp.) is a legume cultivated and consumed worldwide, but predominantly in tropical regions. Among the various biotic factors that can impair its production, the wilt caused by the fungus Fusarium oxysporum f. sp. tracheiphilum (Fot) and considered of great importance. This soil fungus penetrates the roots causing various plant symptoms such as reduced height, chlorosis, vascular discoloration, wilting and premature leaf drop. Thus, this study aimed to evaluate the physiological performance (chlorophyll (Chl) a fluorescence, vegetative vigor, water potential and the concentration of photosynthetic pigments), the activities of antioxidant enzymes (ascorbate peroxidase (APX), catalase (CAT), peroxidase (POX), superoxide dismutase (SOD),) and phenylalanine ammonia lyase (PAL) activity in roots and leaves of susceptible plants (BR 17 Gurguéia) and resistant plants (Miranda IPA 207 and MNCO1-649F-2-1).The effect of preventive application of Copper and Silver Nanoparticles (NPs) on cowpea fusarium wilt and to determine the inheritance of cowpea resistance (named by the genotype Miranda IPA 207) to fusarium wilt. Wilt severity was significantly lower for resistant plants compared to susceptible plants. This result showed higher concentrations of chlorophyll (Chl) a, Chl b and carotenoids, in addition to a greater water potential in these plants. Additionally, due to its lower severity, the functionality of the photosynthetic apparatus was preserved in the leaves. SOD, CAT, POX and APX activities increased in the leaves and roots of infected plants compared to uninoculated pairs, with the magnitude of increase higher in resistant plants. For the roots of resistant plants, PAL activity was significantly higher compared to the BR 17 Gurguéia roots. To examine the sensitivity of Fot to increasing doses of AgNPs and CuNPs, in vitro tests were performed to verify the growth of Fot in Petri dishes with increasing doses of both NPs. Subsequently, one in experiment was carried greenhouse conditions in a completely randomized design in experiment with five replications, being used cultivars BR17 Gurguéia plants. The treatments were: control treatment inoculated, Acibenzolar-S-Methyl (ASM), SiNPs (5 μL L-1) and CoNPs (5 μL L-1). These treatments were applied or by soil flooding in the region close to the plant or by spraying the leaves. Inoculation with Fot was performed 24 hours after application of treatments using a concentration of 1 x 106 conidia mL-1. The mycelial growth index and mycelial diameter were lower with increasing doses of both NPs. Compared to control, the wilt disease was significantly reduced by 65% in plants treated by the soil flooding method with CoNPs. For the spray method, there were a significant reduction for the severity of 30, 28 and 72% for the treatments CoNPs, ASM and SiNPs, respectively. To study inheritance, two parental genotypes Miranda IPA 207 (resistant) and the cultivar BR-17 Gurguéia (susceptible) were crossed, obtaining populations F1 and F2. Subsequently, the generations and parents were inoculated with a conidia suspension of Fot (106 conidia/mL) by the method of immersion in conidia roots. The evaluation of the intensity of fusarium wilt was performed 21 days after inoculation, with the aid of a descriptive scale. As visualized in the chi-square test in the F2 generation accepted the 9:7 ratio (resistant: susceptible), considering the hypothesis that inheritance Fot resistance genetics is controlled by two complementary dominant genes.