Meloidogyne arenaria is a species of plant pathogenic nematodes. This nematode is also known as the peanut root knot nematode. The word "Meloidogyne" is derived from two Greek words that mean "apple-shaped" and "female". The peanut root knot nematode, M. arenaria is one of the "major" Meloidogyne species because of its worldwide economic importance. M. arenaria is a predominant nematode species in the United States attacking peanut in Alabama, Florida, Georgia, and Texas. The most damaging nematode species for peanut in the USA is M. arenaria race 1 and losses can exceed 50% in severely infested fields. Among the several Meloidogyne species that have been characterized, M. arenaria is the most variable both morphologically and cytologically. In 1949, two races of this nematode had been identified, race 1 which reproduces on peanut and race 2 which cannot do so. However, in a recent study, three races were described (races 1, 2, and 3). López-Pérez et al (2011) had also studied populations of M. arenaria race 2, which reproduces on tomato plants carrying the Mi gene and race 3, which reproduces on both resistant pepper and tomato.
History Meloidogyne arenaria has the same history as the other root knot nematodes. Meloidogyne spp were originally grouped together with the cyst nematodes (Heterodera spp) but they were later separated after they were confirmed to be significantly different from each other. The changes that were made when discovering Meloidogyne spp of nematodes are described below:
1855 – Reverend Miles Joseph Berkeley (clergyman) noted galls on cucumbers in greenhouse in England. This was the first official report of nematodes that caused galls on plant roots. 1871 – Schmidt described Heterodera schactii, the sugarbeet cyst nematode. 1872 – Greeff described Anguillula radicicola – a nematode that caused galls on cereals and grasses, but this was actually Ditylenchus and not a root knot nematode. 1879 – Cornu described a root-knot nematode as Anguillula marioni. 1884 – Muller decided root-knot nematode was the same as Greeff's root-galling nematode and that both should be Heterodera – Heterodera radicicola. 1887 – Goeldi – Brazil – described a root knot on coffee – Meloidogyne exigua. 1932 – Goodey decided that use of Heterodera radicicola was incorrect according to International Rules of Zoological Nomenclature as original H. radicicola was not a root-knot nematode. He renamed it Heterodera marioni. 1949 – Chitwood removed them from Heterodera because they differed from cyst nematodes. Since the oldest name for the genus was Goeldi's Meloidogyne exigua, that name had precedence. Chitwood described five species based on perineal patterns, M. arenaria being one of the five.
Distribution Crop damage by this nematode is mostly faced in warmer regions and it is rarely found in areas where the average monthly temperatures approach freezing. The peanut root knot nematode, race 1 is found in all areas where peanuts are grown.
Economic importance The peanut root-knot nematode is the most serious nematode pest of the crop and questionably the most serious soil-borne disease problem. For example, the nematode is present in almost all fields where the crop is grown in Florida and economic damage is estimated to occur in greater than 50% of these fields. Individual peanut fields heavily infested with the root-knot nematode have sustained yield losses greater than 75%. In addition to causing considerable damage alone, it also increases the severity and incidence of other soil-borne diseases such as southern stem rot and Cylindrocladium blackrot. M. arenaria is C-rated pest in California.
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