Occurrence of Resistance-breaking Populations of Root-knot Nematodes on Tomato in Greece

Abstract

Nine populations of Meloidogyne spp. from Greece have been identified as M. javanica or M. incognita using either isozyme phenotypes or the sequence characterized amplified region-polymerase chain reaction (SCAR-PCR) technique. Virulence against the Mi resistance gene was assayed by pot experiments in controlled conditions and revealed the ability of five populations of M. javanica and one population of M. incognita to reproduce on tomato cultivars containing that gene. A resistance-breaking population of M. incognita is reported for the first time in the country; the M. javanica populations constitute new records for the Greek mainland.Resistance in commercially grown tomato hybrids to root knot nematodes (RKN, Meloidogyne spp.) is conferred by the Mi gene which is effective against M. javanica, M. incognita and M. arenaria at moderate soil temperature (Williamson, 1998). However, there are several reports of virulent populations of these Meloidogyne species on resistant tomato cultivars occurring either naturally (cited by Williamson, 1998) or after repeated exposure and selection on tomato cultivars with the Mi gene (Castagnone-Sereno et al., 1994). Such populations of M. javanica have been also found in Crete (Tzortzakakis et al., 1999) and the objective of this study was to characterize further populations from Greece.Populations were collected from vegetable crops from Preveza, Epirus (10 greenhouses) and Kyparissia, Peloponissos (one outdoor site) on mainland Greece and used to establish cultures on potted tomatoes. Egg masses from these cultures were used to inoculate (six egg masses per plant) seedlings of either the susceptible tomato cv. ACE or the nematode resistant cvs Nikita and Alpado grown in pots. The plants were grown in a controlled environment with a 16 h photoperiod and a soil temperature of 24-26°C. They were watered and fertilized as required and roots were examined after 7 weeks. If a large number of egg masses were produced on the resistant tomato cultivars, the egg masses were inoculated onto another plant and the process repeated. Four populations from Preveza (Mj P1, Mj P2, Mj P3 and Mj P4), which sustained high reproduction rates on resistant tomato cultivars for four successive tests were selected for further study. Two populations from Crete (Mj C1 and Mi C1) that had been sent to the laboratory

How Durable is Root Knot Nematode Resistance in Tomato?

“…Djianaporalino et al (2011) reported the reproduction of M. incognita in a tomato variety that carry the corresponding R gene, supporting the shifting of avirulence to virulence. In fact new virulent strains have been reported in many regions of the world where tomato is growing in a large acreage (Tzortzakakis et al 2005;Verdejo-Lucas et al 2009;Devran and Söğüt 2010), indicating significant reduction of the durability of R genes in tomato production. Tomato is a top crop species in which numerous molecular markers and maps have been developed by the last few years (Foolad 2007).…”

A case of infection on the scion of grafted tomatoes by the root-knot nematode Meloidogyne javanica

“…Rotation of resistant tomato with susceptible has been already proved successful for reducing M. javanica infestations in greenhouse conditions of Crete (Tzortzakakis et al, 2000). Further research is also required in accessing the susceptibility of tomato rootstocks to resistance breaking pathotypes of Meloidogyne, which have been found infecting resistant tomatoes in both field and experimental conditions (Tzortzakakis et al, 1999(Tzortzakakis et al, , 2000(Tzortzakakis et al, , 2005.…”

Identification of the economically important plant parasitic nematodes in vineyards areas of Izmir and Manisa provinces by morphological and molecular techniques

“…Benzer diğer bir çalışmada Kök-ur nematodlarının moleküler olarak tek bireyden tanımlanması için teşhis anahtarlarının oluşturulması amacıyla üç farklı M. arenaria popülasyonu kullanılmış ve bu örneklerde 420 bp DNA bandı elde edilmiştir (Adam et al, 2007). Devran & Söğüt (2009) (Zijlstra et al, 2000;Tzortzakakis et al, 2005). Batı Akdeniz Bölgesi'nde Kök-ur nematodu türlerinin moleküler tanımlanmaları amacıyla yürütülen çalışmada M. javanica' ya ait 28 popülasyonun tamamında beklenen 670 bp DNA bandını elde etmişlerdir (Devran & Söğüt, 2009).…”