Fitonematoides associados a cereais de inverno no Rio Grande do Sul: caracterização de espécies, aspectos bioclimáticos e reação de cultivares de trigo a Meloidogyne javanica e M. arenaria

Abstract

Winter cereals play a strategic role in agricultural production systems in the Rio Grande do Sul, holding significant regional importance and contributing to crop diversification. However, these crops are susceptible to attacks by pathogens, such as plant-parasitic nematodes (PPNs). In this context, the present study aimed to: (i) conduct a survey of PPNs occurring in winter cereal-producing areas in Rio Grande do Sul; (ii) analyse the relationship between the distribution of PPNs and bioclimatic variables; and (iii) evaluate the host status of wheat cultivars (‘Lenox’, ‘TBIO Sossego’, ‘TBIO Calibre’, ‘TBIO Ponteiro’, ‘TBIO Duque’, and ‘TBIO Motriz’) to Meloidogyne javanica and M. arenaria. In relation to survey, 76 samples were analysed from fields cultivated with wheat (94.8%), white oats (2.6%), barley (1.3%), and ryegrass (1.3%). A total of 12 PPNs were identified for us, as fallows: Helicotylenchus (100%), Pratylenchus (28%), Rotylenchulus (21%), Xiphinema (17%), Scutellonema (14%), Meloidogyne (13%), Mesocriconema (9%), Rotylenchus (7%), Paratrichodorus (5%), Psilenchus (3%), Heterodera (1%), and Hoplolaimus (1%). Ten species were characterized among these: Helicotylenchus dihystera (96.1%), H. pseudorobustus (3.9%), Pratylenchus brachyurus, P. zeae (8%), P. penetrans (3.9%), Pratylenchus crenatus (1.3%), Scutellonema brachyurus (14.5%), Rotylenchulus reniformis (19.7%), M. javanica (5.3%), and M. incognita (1.3%). Molecular analyses of the ribossomal DNA ITS region (ITS1-5.8S-ITS2) confirmed through the algorithm blastn the results obtained a priori. Bioclimatic variables related to annual temperature and precipitation, as well as temperature during the wettest and driest quarters and seasonality were significant (p<0,05) for PPN abundance, whereas incidence was only marginally affected by these variables. In relation to the host status of wheat cultivars obtained under greenhouse conditions to M. javanica, all cultivars were resistant, with values of reproductive factor (RF) ranging between 0.06 and 0.22. Regarding M. arenaria, the cultivars were susceptible, with RF values between 1.07 and 1.71. The results suggest that the evaluated wheat cultivars have potential for use in crop succession systems in areas infested with M. javanica, although they may to act as hosts for M. arenaria. Still, the results revealed a diversity of PPNs in the sampled areas and indicated that the selection of wheat cultivars may influence Meloidogyne dynamics in crop succession systems.