Examinando por Materia "Pathogenicity"

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Fusarium ear rot and how to screen for resistance in open pollinated maize in the Andean regions
(Springer Nature, 2006-10-13) Silva, E.; Mora, E.A.; Medina Hoyos, Alicia Elizabeth; Vasquez, J.; Valdez, D.; Danial, D. L.; Parlevliet, J. E.
Ears infected with ear rot were collected from five provinces in Ecuador. Of the 44 samples analysed 26 carried Fusarium verticillioides, 11 F. subglutinans, two F. graminearum and five carried fungi different from Fusarium. The pathogenicity of ten isolates, seven of F. verticillioides and three of F. subglutinans, were tested. Per isolate 30 ears of the susceptible cultivar Mishca were inoculated by pricking a steel pin, dipped into a spore suspension, through the husks in the central part of the ear 14 days after mid-silk. Ears inoculated with sterile water and ears without any treatment, natural infection, served as controls. The disease severity (DS) of the ears ranged from 14 to 58% ear rot, the range being similar for both species. The DS of the water control, 19%, was much higher than that of the natural control of 2%. Five strains gave a DS of over 40%, significantly higher than the water control. The DS of the others were similar to the water control. In a series of experiments the effect of various methods of applying Fusarium spores through the husks into young ears were compared. All tested methods resulted in DSs significantly higher than those of the two controls. Inoculation with tooth picks and steel pins dipped in a spore suspension gave similar ear rot percentages. Inoculations at 7 to 14 days after mid-silk produced the highest DS’s. There was no significant effect of spore concentration on the DS. Cultivars differed considerably, the range being from around 20% to over 50%. Surprisingly, only wounding the husks, the sterile water control, resulted in a fairly high DS, much higher than that of the natural control. As the ranking order of the cultivars after wounding only and after inoculation did not seem to be different from the ranking order of the natural control it is suggested to use in areas with high inoculum pressures like the Andes only wounding by means of a steel pin for screening for resistance to maize ear rot.
Morphological and genome characterization of Alternaria alternata causing blueberry (Vaccinium corymbosum L.) leaf spot in Peru
(SCIEPublish, 2026-05-20) Velasquez Ochoa, Edwin Ricardo; Osorio, Valentina; Leiva, Ana María; Pardo, Juan Manuel; Gil Ordoñez, Alejandra; Bartolini, Ida; Cuellar, Wilmer J
Blueberries (Vaccinium corymbosum L.), valued for their nutritional benefits and economic significance, have become Peru's leading agro-export crop. However, intensive cultivation can lead to phytosanitary problems if not addressed promptly, posing a serious threat to blueberry production. This study aimed to isolate and identify the causal agent of leaf spot symptoms initially observed in blueberries cultivated in Peru, marking the first formal documentation of its presence in the country. In 2022, leaf spot symptoms were recorded on V. corymbosum cv. Biloxi, in the north of Lima, Peru. Field observations revealed necrotic, sunken spots on leaves and fruits, with 4.84% of leaves diseased and 1.28% of fruits affected. Pathogen isolation and microscopic studies identified Alternaria alternata as the primary causal agent, which was confirmed by genome sequencing using Oxford Nanopore Technology. Pathogenicity tests demonstrated the fungus' ability to reproduce symptoms identical to those observed in the field, fulfilling Koch's postulates. Under experimental conditions, disease severity increased over time, with the affected leaf area ranging from 9.35% to 25.61% between 7 and 14 days post-inoculation. This study establishes A. alternata as a pathogen of blueberries in Peru and provides essential insights for future research and strategies to mitigate its impact on the industry.