Development of virulence to Meloidogyne incognita on resistant pepper rootstocks

Abstract

The root-knot nematode (RKN) Meloidogyne incognita is a major soil parasite of pepper crops in greenhouses in Southeast Spain. Due to the limitations of the use of soil fumigants, grafting plants on resistant rootstocks (R-rootstocks) has become an important alternative to chemical nematicides. The repeated use of R-rootstocks can bring about the selection of virulent populations capable of overcoming resistance. We carried out a six-year investigation on resistant rootstocks in a naturally M. incognita infested greenhouse, and found that two successive years of growing plants grafted on R-rootstocks Atlante (ATL) were sufficient to overcome resistance (galling index 1.5 and 5.6 in the first and second years respectively). A large variability was observed between several R-rootstocks. Two R-rootstocks (C19 and Snooker) behaved like ATL while two others (Terrano and DRO 8801) were not infected by RKN. Laboratory studies with the same R-rootstocks, inoculated with two nematode isolates (avirulent and virulent against ATL) confirmed the greenhouse results, indicating that some rootstocks may be infested by virulent populations and others may not. It suggests that different R-genes, which are differentially overcome by RKN, have been introgressed into the rootstocks. This may have consequences for the management of resistant rootstocks in the field.

Effectiveness of quantitative resistance conferred by the genetic background of pepper in the control of root‐knot nematodes and influence onto durability of Me1‐ and Me3‐resistant genes in greenhouse conditions

“…Me1 demonstrated a high and durable resistance, while the resistance of Me3 was less pronounced and shorter lived, regardless of the genetic background around these R‐genes. These observations coincide with those of previous studies carried out in laboratory (Castagnone‐Sereno, Bongiovanni, Palloix, & Dalmasso, ; Djian‐Caporalino et al., ), and with those obtained under field and greenhouse conditions (Djian‐Caporalino et al., ; Ros‐Ibáñez et al., ). In these works, the appearance of nematode populations virulent to Me3 but not Me1 was observed.…”

“…() observed an increase in nematode infections in three consecutive growing seasons of plants carrying Me1 . In the case of Me3 , previous studies have clearly demonstrated the development of virulence in avirulent populations of M. incognita when there is strong pressure of Me3 , both in laboratory conditions (Castagnone‐Sereno et al., ) and in greenhouse‐grown pepper (Ros‐Ibáñez et al., ).…”

“…In pepper ( Capsicum annuum ), resistance against Meloidogyne incognita is conferred by the R‐genes: Me1 , Me3 and N (Djian‐Caporalino et al., ; Hendy, Pochard, & Damalso, ; Thies & Fery, ). However, this nematode develops virulent populations against Me3 and N genes in plants carrying the same gene when cultivation is repeated in the same soil (Ros‐Ibáñez, Robertson, Martínez‐Lluch, Cano‐García, & Lacasa‐Plasencia, ; Thies, ). To date, only the Me1 gene has been shown to be a durable source of resistance (Barbary et al., ; Sánchez‐Solana, Ros, Guerrero et al., ).…”

Host genetic resistance to root-knot nematodes,Meloidogynespp., in Solanaceae: from genes to the field

“…For more than 70 years now, although some other R genes have been identified in the wild tomato S. peruvianum , Mi‐1.2 has been the only source of resistance in tomato production against RKNs. Clearly, the extensive use of the same R gene at a large scale may result in the emergence and spread of virulent nematode populations able to overcome it, and Mi‐1.2 ‐resistance‐breaking populations in tomato have been discovered, as have N ‐ and Me3 ‐resistance‐breaking populations in pepper . Such ability to overcome plant resistance may thus constitute a severe limitation for RKN control.…”

Fitness cost but no selection for virulence in Meloidogyne incognita after two consecutive crops of eggplant grafted onto Solanum torvum

“…Regarding pepper, the selection for virulence to the Me3 gene has been reported after two consecutive pepper crops grafted onto the rootstock cv. Atlante (Ros‐Ibáñez et al , ). In relation to the N gene, virulence has been reported in the USA but without any information on the selection process (Thies, ).…”