Phytophthora nicotianae is the pathogen that causes root and crown rot disease in open field paprika pepper crops of Extremadura (central-western Spain). A field experiment was established during spring, a period compatible with the pepper crop cycle in this region, to evaluate the effects of biofumigation with pellets of Brassica carinata defatted seed meal, at the rate recommended by the manufacturer (3 tons ha−1), on the survival and infectivity of P. nicotianae chlamydospores inoculum. Furthermore, three biofumigant rates (3, 6, and 20 tons ha−1) were assayed in laboratory experiments with natural soil inoculated with chlamydospores. In the field trial, the incorporation of pellets at 3 tons ha−1 did not produce remarkable changes in soil enzyme activity or soil properties. In both the field and laboratory tests, survival and infectivity in the biofumigated treatment at 3 tons ha−1 did not differ from those in the untreated control. On the contrary, the same rate added to autoclaved soil completely suppressed the inoculum, suggesting that the soil microbiota degrades B. carinata pellets before being effective against P. nicotianae. Increasing the recommended rate to 6 tons ha−1 decreased inoculum survival in the laboratory test and 20 tons ha−1 completely inhibited the inoculum, although the economic value of such a high rate application is a factor to be assessed. In phytotoxicity tests on radish and white mustard seeds with several concentrations (100, 50, 25, 10, 5, and 0%) of B. carinata pellets solution, no phytotoxic effect was observed with the two lowest concentrations, and no symptoms of phytotoxicity were found in the bioassays of pepper plants.
Chestnut blight, caused by Cryphonectria parasitica, is a severe disease that may be biologically controlled by the use of hypovirulent strains, but the diversity of the pathogen population affects biocontrol feasibility. Villuercas–Ibores–Jara, the Jerte Valley and La Vera are the main chestnut production districts in Cáceres (central-western Spain). The purpose of this study is to determine the Vegetative Compatibility Groups (VCGs) and mating types in these districts and to identify hypovirulent isolates to be used in biological control. The VCGs were determined by the merging/barrage response; PCR tests were used for the mating type determination and CHV-1 hypovirus detection. In total, 40 sites were surveyed and 269 isolates were obtained, most of them (227) from the Villuercas–Ibores–Jara district, where EU11 was the predominant VCG (88.1%) with EU1 (6.6%) and EU12 (4.4%) being also present. In the Jerte Valley and La Vera, EU1 (61.9%), EU11 (11.9%) and EU12 (11.9%) were the predominant VCGs. Both mating types were detected (48% MAT-1; 50% MAT-2) and in general, only one mating type was found in each site. The presence of Cryphonectria hypovirus 1 (CHV-1), subtype I, was identified in only one isolate (VCG EU11) from Villuercas–Ibores–Jara. The characteristics of the C. parasitica population in this district and the occurrence of CHV-1 hypovirus support the potential of successful biological control in Villuercas–Ibores–Jara using hypovirulent strains, while in the Jerte Valley and La Vera only preventive measures are recommended.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.