Major emerging problems with minor meloidogyne species

Root-knot nematodes (Meloidogyne spp.) represent one of the most polyphagous genera of plant-parasitic nematodes. To date, close to 100 valid species are recognized. In contrast to the size of the genus, the majority of past research focused on a small number of species, i.e., the so-called 'major' species M. arenaria, M. hapla, M. incognita, and M. javanica. This review highlights recent work aimed at 'minor' root-knot nematodes: M. chitwoodi, M. fallax, M. minor, M. enterolobii (=M. mayaguensis), M. exigua, and M. paranaensis. Some of these species have been described only recently. After a brief profile of each species, identification methods and their application in Meloidogyne spp. are summarized. Intraspecific variation and its impact on plant resistance breeding are discussed and interactions between M. enterolobii and Fusarium solani are highlighted as an example of synergistic interactions with other plant pathogens. Future research on Meloidogyne spp. is not only shaped by recent breakthroughs such as completing the genome sequences of M. hapla and M. incognita, but is also influenced by changes in agriculture. Taken together, the aim of this review is to draw attention to previously neglected and newly described Meloidogyne spp. that are developing into major problems for agriculture in tropical and temperate climates.