Tomato Mi-gene Resistance-Breaking Populations of Meloidogyne Show Variable Reproduction on Susceptible and Resistant Crop Cultivars

Abstract

Sixteen Meloidogyne isolates from tomato fields in California grown with resistant cultivars were multiplied on resistant tomato in a greenhouse. Of these resistance-breaking isolates, one was identified as M. javanica, and all others as M. incognita. The reproduction of the M. javanica isolate and four M. incognita isolates on six resistant tomato cultivars and on susceptible and resistant cultivars of pepper, sweetpotato, green bean, cotton, and cowpea was evaluated and compared to an avirulent M. incognita population in greenhouse pot trials. On resistant tomato cultivars, there were minor but significant differences between the resistance-breaking Meloidogyne isolates and between the different tomato cultivars. Of the other resistant crop cultivars, pepper was resistant to all isolates and green bean to all M. incognita isolates, while cotton and cowpea allowed reproduction of one of the resistance-breaking M. incognita isolates. The resistant sweetpotato cv. Bonita behaved like resistant tomato, allowing reproduction of all five resistance-breaking isolates but not of the avirulent M. incognita. Our results showed that variability exists among resistance-breaking Meloidogyne isolates, and that isolates overcoming resistance in tomato may also be virulent on resistant sweetpotato.

Identification and Characterization of a Virulent Meloidogyne incognita Population Breaking Tomato Mi-1-Mediated Resistance in Indiana

“…Tomatoes are the most popular crops grown in high tunnels, and they are highly susceptible to RKNs. Growing resistant cultivars has been frequently employed to mitigate yield losses caused by RKNs in the production of processing tomatoes [19]. The resistance in all of the commercially available RKN-resistant tomato cultivars is derived from a single dominant Mi-1 gene, which has been used for more than 70 years.…”

“…Here, we report the identification and characterization of a virulent population of M. incognita, capable of overcoming Mi-1 resistance, from tomatoes grafted on resistant rootstock in a high tunnel in Indiana. This makes Indiana the third state in the United States to report Mi-1-resistance-breaking M. incognita populations, following California [19,25] and Georgia [23]. Growing resistant tomato cultivars or rootstocks may partially contribute to the occurrence of Mi-1-resistance-breaking populations of M. incognita, although virulent populations were also found in tomato fields with no history of growing resistant cultivars [23].…”

“…Meanwhile, the lack of diversity in the sources of resistance in tomatoes has led to the emergence of virulent RKN populations that can overcome Mi-1 resistance and reproduce on resistant tomato cultivars or rootstocks regardless of the soil temperatures. Such virulent populations of M. incognita in tomato fields have been reported in California and Georgia in the US [19,[23][24][25]. Virulent populations of M. incognita were also found in other parts of the world, including Europe and Asia, under laboratory and field conditions [26][27][28][29].…”

“…To our knowledge, all of the commercial tomato cultivars or rootstocks with resistance against RKNs derive their resistance from a single dominant gene, Mi-1, which confers resistance against the three important RKN species: M. incognita, M. javanica and M. arenaria [17][18][19]. It is worth noting that Mi-1-mediated resistance is significantly compromised when the soil temperature is above 28 • C, and J2s of M. incognita, M. javanica or M. arenaria can successfully infect, survive and develop into adult females and lay eggs on the tomato plants carrying the Mi-1 resistance gene [18].…”

Performance of biological and chemical nematicides in different soils to control Meloidogyne incognita in tomato plants

“…It was introgressed from the wild tomato species Lycopersicum peruvianum (Medina Filho & Stevens, 1980). Increasingly, resistance-breaking strains of M. incognita have been found in processing tomato production fields in California (Kaloshian et al, 1996;Ploeg et al, 2018).…”