Examinando por Materia "Resistance"

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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.
Obtaining new potato cultivars with late blight resistance and adapted to climate change using participatory varietal selection
(David Publishing Company, 2020-02-28) Zúñiga López, Luz Noemí; Gastelo Benavides, Manuel Antonio; Bastos Zuñiga, Carolina; Reyes Espinoza, Jhercy Pepe; Alania, Edson; Ninalaya Cerrón, Evelin Natali
The potato crop in Peru is the main income and food source for the smallholder of the highland grower of the Peruvian Andes. For urban population, it represents one of the main components of the food basket and for commercial intermediaries. It is the main brokerage product considering its volume and value. To facilitate the adoption and diffusion of new potato cultivars after its release, adequate methodologies are necessary to apply during the process of evaluation and selection. One of these methodologies is called participatory varietal selection (PVS). The objective of this study was to identify new potato cultivars and/or genotypes with resistance or tolerance to adverse effects of climate change applying PVS, in order to obtain new varieties with acceptable economic yields. In this way potato growers of the Peruvian highland Andes should benefit through the improvement of their economic status, food security and overall life quality. During 2016-2017, three potato clones (CIP393079.4, CIP387096.2 and CIP396034.268) and two commercial varieties (Unica, Canchan) were evaluated at eight Peruvian locations in three regions (Huánuco, Junín and Huancavelica). Data were analyzed using a randomized complete block design, with three replications. Main criteria for selection were late blight resistance, abundant foliage, drought tolerance, yield and uniform and healthy tubers. In all three regions the three best clones selected were CIP396034.268, CIP393079.4 and CIP387096.2, ranking in first, second and third place, respectively. Men and women selected the same clones, but in a different order. Commercial cultivars ranked 4th and 5th. However, local growers selected Canchan, CIP387096.2 and CIP393079.4 based on appearance, texture and taste tests. The last two clones (CIP387096.2 and CIP393079.4) should be considered for a future release.