Plant parasitic nematode communities associated to apple orchards in the Southern Brazil

In recent years, apple (Malus domestica Borkh) has been one the most important fruit crops in the southern part of Brazil. Despite this, research about the attack by plant-parasitic nematodes (PPNs) and/or its involvement with apple replant disease (ARD) is poorly known up to now. Our study aimed to (i) identify and quantify the major PPNs (morphological groups) infesting apple growing areas in southern of Brazil; (ii) to evaluate the relationship between altitude, bioclimatic variables, types of soil and the occurrence and abundance of PPNs; and (iii) to characterize (morphologically and morphometrically) the Pratylenchus species obtained from the apple orchards. During 2020/2021 crop season, we identified five genera of PPNs with variable abundance Pratylenchus (95%; 50 to 425 specimens/250 cm(3) soil), Helicotylenchus (95%; 25 to 875 specimens/250 cm(3) soil), Tylenchus (90%; 25 to 325 specimens/250 cm(3) soil), Xiphinema (90%; 25 to 550 specimens/250 cm(3) soil) and Mesocriconema (21%; 25 to 250 specimens/250 cm(3) soil). The ecological indices were reasonably high, with values varying from 0.78 to 1.35 for H ' and 0.63 to 0.98 for J. The annual mean temperature (BIO1) and annual precipitation (BIO12) strongly influenced the abundance values, albeit in different ways (p < 0.01). Nevertheless, there was no influence of bioclimatic variables in the distribution of PPNs. Pratylenchus zeae and P. penetrans, which had not been reported in the apple plants in Brazil, were identified associated with the crop. Our findings open new perspectives about the research towards management measures of PPNs in infested apple orchards (nematicide development and selection of resistant rootstocks), especially where the ARD is already present. Naturally, epidemiological issues, such as delimitation of risk areas, should be taken into account as well.