Avocado sunblotch viroid: Pest risk and potential impact in México

Abstract

70 Mexican race avocado trees (Persea americana var. drymifolia) located at different points in the municipalities of Quimixtlán, Puebla (19.254654 LN and −97.133851 LW), Zumpahuacán (18.832133 LN and −99.580109 LW) and Tenancingo in the Estado de México (18.957769 LN and −99.588872 LW) and 35 avocado trees var. ‘Hass’ from Tingambato, Michoacán (19.496635 LN and −101.858034 LW) were sampled and analyzed to detect the Avocado sunblotch viroid (ASBVd) by RT-PCR and Dot-Blot hybridization. Additionally, statistics from 1999 to 2015 of land area planted with avocado in México were analyzed considering 32 Rural Development Districts (RDD) that amount to 90% of avocado planted area and finally, the species distribution model Maxent was applied using 102 sites in 38 avocado producing municipalities amounting to 88% (149,294 ha) of avocado cultivated in México. These considered as risk indicators to the dispersion and establishment of ASBVd. The results indicated that the 70 Mexican race avocado trees from the different States were free of the ASBVd, but 14% incidence of plants infected with ASBVd was detected by RT-PCR and 8% by Dot-Blot hybridization in ‘Hass’ avocado trees from Michoacán. The dynamics of the increase of the growing area in México during the period 2000 to 2015 was heterogeneous since the maximum values occurred in 7 RDD of the states of Michoacán, Jalisco and Nayarit, and 11 municipalities showed a steady increase in the area intended for avocado cultivation. Maxent model produces better results than random predictions, for the Kappa index was greater than 0.74 and the mean of the Area Under the Curve (AUC) presented values of 0.99; additionally, the model represents the actual distribution of avocado var. ‘Hass’ and ‘Hass-Mendez’ in Mexico and corresponds to the physiographic region with the greatest diversification of the Mexican race avocado (Persea americana var. drymifolia).