Screening of the hatching control of root-knot nematodes using extract concentrations from oat genotypes

Even though oats (Avena spp.) have the capacity to produce numerous compounds with the potential to act antagonistically against plant pathogens, studies on the genotypic effect of this crop focusing on their nematicidal activity are limited. The objective of this study was to verify the effect of the aqueous extracts prepared with the biomass of oat genotypes, on the hatching of second-stage juveniles of root-knot nematodes (Meloidogyne javanica and Meloidogyne incognita). The bioassays were carried out in a completely randomized design with four replications. Eighteen extracts were evaluated, consisting of a combination of six oat genotypes Agro Quaraí, Agro Esteio, Embrapa 139, AF 12202, UPFPS Farroupilha, and AF 1345 Ucraniana, and three extract concentrations (5 %, 10 %, and 20 % w/v). Three additional treatments were added to the study (distilled water, chemical nematicides abamectin, and imidacloprid + thiodicarb). The treatments and the suspension containing nematode eggs were placed in Petri dishes and incubated in a growth chamber for ten days. At the 5 % and 10 % w/v concentration levels, a genotype effect was observed in the hatching of juveniles for both nematode species. For the control of M. javanica the extracts of Embrapa 139 had a better performance, while the extracts of Agro Quaraí and AF1345 Ucraniana performed better when under the control of M. incognita. Thus, oat biomass formation might have the ability to suppress the nematode population in the soil, and could therefore, be used for the management of root-knot nematodes.

Physiological Response of Cape Gooseberry Seedlings to Three Biological Control Agents Under Fusarium oxysporum f. sp. physali Infection.

Cape gooseberry (Physalis peruviana) fruit has gained recognition owing to its nutritional value and versatility to be consumed processed or as a fresh product. These characteristics have made it an important product in both national and international markets. One of the main limitations for this crop is Fusarium wilt caused by the fungus Fusarium oxysporum f. sp. physalis, for which biological control is emerging as an alternative to conventional management with chemical synthesis products. However, information on the effect that biological control agents have on the growth and development of plants is scarce. In this research, the physiological response of cape gooseberry plants (stomatal conductance, leaf water potential, growth parameters, total chlorophyll, carotenoid, and proline and malondialdehyde contents) to the treatment with three potential biocontrol agents (BCAs) Trichoderma koningiopsis, Trichoderma virens, and Bacillus velezensis was determined. The study was conducted under greenhouse conditions; F. oxysporum was inoculated in the soil, and BCAs were soil drenched in the germination and transplanting stages. Plants inoculated with the pathogen and plants without inoculation were used as controls. It was found that the plants inoculated and treated with T. virens showed the lowest disease levels (area under the disease progress curve of 48.5 and disease severity index of 2.1). Additionally, they showed a lower water potential (-0.317 Mpa), a greater leaf area (694.7 cm2), and a higher stomatal conductance (110.3 mmol m-2 s-1) compared with the control. Consequently, it can be concluded that T. virens can be a good candidate for the management of Fusarium wilt in the cape gooseberry crop.