Meloidogyne enterolobii nematode threatens cotton production in Brazil

A new study published by experts Jorge Bleno da Silva Verssiani (Staphyt Brasil), Rafael Galbieri (IMAmt, Mato Grosso Cotton Institute), and Juvenil Enrique Cares (UnB, University of Brasília) has identified the Meloidogyne enterolobii nematode parasitizing cotton in Brazil and emphasized the particularly "aggressive" nature of this nematode species.

From left to right: Jorge Bleno da Silva Verssiani, Rafael Galbieri, and Juvenil Enrique Cares

In cotton plants, the researchers noted that Meloidogyne enterolobii creates notably larger root galls compared to those caused by other root-knot nematode species. "We acknowledge that nematode control using chemical or biological nematicides doesn't guarantee effective control," they admitted.

"The best possible approach is developing cultivars with genetic resistance, when available, to ensure efficient nematode management. The current cotton seed market offers five cultivars resistant to M. incognita. This resistance is governed by major effect genes (oligogenic inheritance), determined by two QTLs (quantitative trait loci) located on chromosomes 11 and 14," the study explained.

Meloidogyne enterolobii is known for its ability to cause disease in cultivars. It carries resistance genes to major root-knot nematodes in crops such as potato, sweet potato, tomato, bell pepper, cowpea, and soybean. Now, the experts highlighted that this soil pest is attacking cotton even in cultivars with M. incognita resistance genes, demonstrating that the new M. enterolobii variant can both infect and multiply.

"In the US, M. enterolobii populations were found parasitizing cotton and soybean in North Carolina. In Brazil, the recently detected cotton-affecting variant remains limited in field occurrence, with four confirmed cases," revealed IMAmt researcher Rafael Galbieri, who presented these findings during the 38th Brazilian Nematology Congress.

Only certain agriculturally important crops, such as corn, sorghum, wheat, oats, garlic, peanuts, castor bean, passion fruit, and Crotalaria spectabilis, have been reported as non-hosts or poor hosts for M. enterolobii. Therefore, the researchers recommend management strategies based on rotation with these crops in infested areas.

"Currently, no commercial cotton cultivars with M. enterolobii resistance are available. Additionally, there are no registered nematicide products for managing this nematode in major crops like cotton, soybean, and beans. Prevention remains the best control strategy for M. enterolobii in cotton," they emphasized.

To achieve this, they recommend preventing nematode entry into cotton cultivation areas, cleaning agricultural machinery before entering new plots, properly disposing of machine-washing wastewater, cleaning boots and shoes as they can be sources of nematode inoculum, and using poor host cover crops to reduce multiplication.

"Regular field inspections for early detection of potential nematode outbreaks are crucial. If nematode presence is suspected, proper diagnosis can be conducted by specialized laboratories using isozyme electrophoresis and molecular markers," they said in conclusion.

(Editing by Leonardo Gottems, reporter for AgroPages)