Underground threat

Carrot plants (

L.) cultivar Nantes collected from a commercial field in Rio Paranaíba, Alto Paranaíba region, state of Minas Gerais, were analyzed in the Nematology laboratory of Embrapa Hortaliças in Brasília-DF. Severely infected plants showed symptoms of chlorosis, reduced growth and an abundance of galls on the roots. Examination of the galls showed the presence of a population of nematodes of the genus Meloidogyne. The microscopic study of the perineal configuration of females from this population showed different characteristics when compared to the most common species of root-knot nematodes (

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), indicating that the population is a new species of Meloidogyne infecting carrots in Brazil.

Detailed morphological and morphometric studies of this new species conducted at Virginia Polytechnic Institute and State University, Blacksburg-VA and host circle conducted at Embrapa Hortaliças, revealed different morphological characteristics and host circle, which confirmed its distinction from the four common species of nematodes. galls widely disseminated in Brazil. The unique perineal pattern of the female and the presence of numerous rings in the head region of males, females and juveniles of this new species are important characteristics that differentiate it from other described species of the genus. “Carrot root-knot nematode” is suggested as the common name of the nematode, which is considered the first report of a new species of root-knot nematode infecting carrots in Brazil. The scientific name of this species will be defined later after its description. The nematode also has a great ability to infect tomato cultivars in greenhouse conditions.

The “carrot root-knot nematode” could become a serious parasite in the future due to its great ability to infect carrots and tomatoes, two of the most important vegetables cultivated extensively in the country, although there is still no report of the spread of this species outside the type locality, the region of Alto Paranaíba-MG. The “carrot root-knot nematode” infects the Nantes cultivar, but does not infect the Alvorada, Brasília, Carandaí and Kuronan cultivars. In addition to the ‘Nantes’ carrot, the nematode can also infect different tomato cultivars such as Rutgers, Santa Clara and Kada in greenhouse conditions. Differential indicator plants such as peanut 'Florrumer', cotton 'Deltapine 16', tobacco 'NC 95', watermelon 'Chaleston Gray', sweet corn 'Golden Cross Bantan' and pepper 'California Wonder' were considered non-hosts of the nematode which, together with the carrot cultivars Alvorada, Brasília, Carandaí and Kuronan, they can be used in crop rotation with 'Nantes' carrot and tomato cultivars, to control the nematode.

Additional research is necessary to select resistant tomato cultivars, carry out studies with a wide range of hosts to determine susceptible plants and evaluate the effects of the interaction of this species with other soil pathogens such as fungi and bacteria. It is also important to carry out surveys to understand the geographic distribution of the nematode beyond the type locality and estimate economic losses caused by this species in other vegetables and large crops susceptible to this new species of Meloidogyne.

The description of the “carrot root-knot nematode” included an important contribution from Dr. Jonathan D. Eisenback, Professor of Nematology, Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA. The description of this new Meloidogyne species will be published in the journal Nematology in 2004.

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Embrapa Vegetables

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