Reaction of a heterozygous tomato hybrid bearing the Mi‐1.2 gene to 15 Meloidogyne species

Abstract

| INTRODUC TI ONRoot-knot nematodes (RKN) of the genus Meloidogyne are among the main sanitary problems of the tomato (Solanum lycopersicum) crop worldwide (Seid et al., 2015). So far, 18 Meloidogyne species have been detected in Brazil affecting a wide range of crops, including tomato and other vegetables, fruit trees, soybeans, coffee, cotton, and beans (Carneiro et al., 2016). Most of these RKN species can naturally infect tomato plants either across large geographic regions or in more restricted areas. However, the predominant Meloidogyne species infecting tomato worldwide are M. javanica, M. incognita, M. arenaria, M. hapla, and more recently M. enterolobii (= M. mayaguensis) (Brito et al., 2007; El-Sappah et al., 2019).Abstract Many root-knot nematode (RKN) species (Meloidogyne spp.) are polyphagous and cultivated tomato (Solanum lycopersicum) is one of their preferential hosts, leading to significant losses. It is known that the dominant Mi-1.2 gene in tomato confers resistance to the three most important RKN species-M. incognita, M. javanica, and M. arenaria, and minor species-M. ethiopica, M. hispanica, and M. luci. However, little information is available about resistance of tomatoes carrying this gene to other tomato-infecting RKN species. In this study, resistance conferred by the Mi-1.2 gene/ locus was evaluated against populations of 15 Meloidogyne species, employing tomato cultivars Santa Clara (homozygous recessive mi-1.2/mi-1.2, susceptible) and Debora Plus (heterozygous Mi-1.2/mi-1.2, resistant). Debora Plus was susceptible only to M. enterolobii and M. hapla, and was resistant to the other Brazilian populations of M. arenaria, M. ethiopica, M. exigua, M. hispanica, M. incognita, M. inornata, M. izalcoensis M. javanica, M. konaensis, M. luci, M. morocciensis, M. paranaensis, and M. petuniae. Mi-1.2 is located on tomato chromosome 6 within a cluster of seven homologous genes of the nucleotide-binding site leucine-rich repeat (NBS-LRR) family; further research is required to confirm if this multiple Meloidogyne spp. resistance phenotype is controlled exclusively by Mi-1.2 or by combined action of other closely linked genes. This evaluation of resistance of the Debora Plus cultivar to several Meloidogyne species suggests that the Mi-1.2 gene/locus may reduce losses induced by a wide range of Meloidogyne spp. Further studies using additional resistant cultivars and other populations of Meloidogyne spp. are needed to confirm these results. K E Y W O R D S aggressiveness, root-knot nematode species, Solanum lycopersicum, susceptibility

Enzymatic and Molecular Identification of Meloidogyne Species in Tomato Orchards in Paraguay

“…It is known that the dominant Mi-1.2 gene in tomato confers resistance to the three most important RKN species M. incognita, M. javanica, and M. arenaria, and minor species-M. ethiopica, M. hispanica, and M. luci, infect various crops in Brazil (8). Hence, the importance of identifying the different species of Meloidogyne.…”

“…in these studies has relied upon the characterization of adult female perineal patterns using several morphometric and morphological features of juveniles. However, it is possible to confuse M. incognita with other related species (e.g., M. paranaensis, M. izalcoensis, and M. inornate) attending the female perineal pattern [8,10]. Here, we obtained RKN females of all samples [20], and perennial pattern morphology suggested the presence of M. incognita and M. javanica.…”

“…Because over 100 Meloidogyne species have been reported [7], their identification at the species level remains challenging for many researchers [6]. There are specific preventive strategies that can be included in a nematode management plan, such as the use of resistant plants to control different Meloidogyne species [8]. Both enzymatic and molecular techniques have been commonly used to improve the accuracy of RKN species diagnosis.…”

Role of Two Transcription Factors (TGA 1a and TGA 2.1) in the Mi-1-Mediated Resistance of Tomato to the Root-Knot Nematode Meloidogyne javanica

“…The Mi-1.2 gene, like other resistance (R) genes, encodes a coiled-coil domain nucleotide binding site leucine-rich repeat (CC-NLR) protein [18]. Mi-1.2 provides resistance not only against M. incognita, M. arenaria, and M. javanica [19][20][21][22], but also against different phloem-feeding insect pests, such as the potato aphid Macrosiphum euphorbiae, the whitefly Bemisia tabaci, and the tomato psyllid Bactericerca cockerelli [23][24][25]. Additionally, Mi-1.2-like genes can be relevant for resistance in crop plants other than tomato [26,27].…”

Host suitability of pepper cultivars to (a)virulent root-knot nematodes isolates

“…In tomato, Mi-1.2 gene is the most important resistant gene for controlling RKNs and is widely used in commercial tomato cultivars (Devran & Söğüt, 2014;Seid et al, 2015). Mi-1.2 gene provides effective protection against the three most destructive RKNs, Meloidogyne incognita Kofoid & White,1919), Chitwood, 1949, Meloidogyne arenaria (Neal, 1889) Chitwood, 1949and Meloidogyne javanica (Treub, 1885 Chitwood, 1949 (Tylenchida: Meloidogynidae) (Williamson & Hussey, 1996) as well as other RKN species (Aydınlı & Mennan, 2019;Gabriel et al, 2020;Santos et al, 2020). However, the resistance mediated by Mi-1.2 is lost at high soil temperatures and can be overcome by Mi-1.2-virulent RKN isolates (Dropkin, 1969;Kaloshian et al, 1996;Tzortzakakis et al, 2005;.…”