Advances in the research on peach yellows disease, in the productive areas of Jujuy, Argentina
In Jujuy, there are 850 hectares of peach trees (Prunus persica L.), 800 hectares are found in the temperate valleys, where plants with symptoms of yellowing, redness, leaf curl and necrosis, premature defoliation and shortening of internodes, even plant death, began to be observed a few years ago. The causal agent is Argentinean Peach Yellows phytoplasma (arpy), from the subgroup: 16Sr III-B, X-disease. The disease is called “peach yellows”, and it is an expanding pathology without records in the country. Hence, the objective of this study was to know its epidemiology: presence and dispersion in introduced and naturalized cultivars, characterization of the symptoms and their seasonal variation. Through visual surveys, the prevalence/incidence of the pathology in arid and temperate valleys was estimated during the past crop cycle. In arid and high temperate valleys, symptomatic plants were no recorded; however, diseased plants were visualized in the low temperate valleys and the diagnosis was confirmed in the laboratory. Seasonal variation of the symptoms was observed, in spring, the plants were partially or totally affected, with shortening of internodes, witches' broom on leaves, yellowing, reddening and stiffening of basal leaves; in summer, symptomatic branches of the previous spring were dead or about to die but without new symptoms; in autumn, there was death of symptomatic twigs and early defoliation. Out of 25 productive lots surveyed, in Flordaking, Opedepe and Rojo Dos cultivars, a prevalence of 100 % was determined. The incidence in plants was highest in Flordaking. The severity of the disease, using a 6-degree scale, reflected that of a total of 8,871 surveyed plants, the highest degrees of severity were observed in Flordaking plants, followed by Opedepe and, finally, Rojo Dos.
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