Evaluación de la resistencia de variedades de manzano autóctonas de España a fuego bacteriano (Erwinia amylovora) y moteado (Venturia inaequalis)
- Autores: Alejandro Martínez Bilbao
- Directores de la Tesis: Jesús Murillo Martínez (dir. tes.)
- Lectura: En la Universidad Pública de Navarra ( España ) en 2006
- Idioma: español
- Tribunal Calificador de la Tesis: Fernando García Arenal (presid.), Antonio Trapero Casas (secret.), Enrique Dapena de la Fuente (voc.), Emilio Montesinos Seguí (voc.), María Milagros López González (voc.)
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- Resumen
Erwinia amylovora and Venturia inaequalis are the causative agents of fire blight and apple scab, respectively, which are among the three most important diseases of apple. The utilization of cultivars that show a limited susceptibility, or resistance, to these diseases is one of the main methods for their integrated management, which contributes to ralentize the dissemination of the pathogen and to reduce production costs. In Navarra, the Instituto Técnico de Gestión Agrícola (ITGA) maintains a collection of 253 local apple cultivars, which represent an inportant germplasm source for their agronomic use or to include themm in breeding programs. In this work we have undertaken the evaluation of the susceptibility of these cultivars to fire blight and apple scab, as well as the identification of the races of V. inaequalis present in Northern Spain. The susceptibility assays require the inoculation fo several plants per cultivar, making impractical the evaluation of a large of number of cultivars, as it occurs with the ITGA collection. With the aim to reduce the number of cultivars to evaluate, we first implemented a rapid test using detached leaves for inoculation. The results of these assays allowed us to concentrate our efforts on 103 cultivars, that were selected due to their low susceptibility to fire blight or because their characteristics. We then proceeded to assay yong shoots, which results in a more realistic evaluation of varietal susceptibility to fire blight. The results of the inoculations of detached leaves and shoots showed a significant correlation (r=0,56; ###=0,01). Although the essay in leaves could not be useful for the reliabel identification of varieties showing low susceptibility to E. amylovora. However, this distribution showed that the detached leaves assy could be used for the exclusion of higly susceptible cultivars from evaluation programmes. From the shoot assay, we were able to classify the cultivars in three susceptibility groups and to identify 48 cultivars (46,6%) that showed a low susceptibility to the pathogen. As well, we evaluated the susceptibility to apple scab of a total of 92 cultivars, that included all those that showed low susceptibility to fire blight using a mixed inoculum (UPNA 99) that was obtained from lesions collecte in Northern Spain. Thirty eight cultivars showed low susceptibility to scab, from which twelve also showed a low susceptibility to fire blight and total resistance to aplle scab. These twelve cultivars showed different levels of resistance to races 1, 6 and 7 of V. inaequaleis, although all the cultivars were resistant to at least one of the races. The inoculation of differential apple cultivars with different natural inocula allowed us to identify the presence in the nort-east of Spain of races 1, 2, 3, 5, 6 and 7 of V. inaequalis, which should be taken into account in integrated control programs that make use of plant resistance.
