Abstract
ABSTRACT Meloidogyne enterolobii (=M. mayaguensis) is an emerging plant pathogen capable of inducing root galls and yield reduction in a wide range of host species. This pathogen has also been reported as a global threat for tomato (Solanum lycopersicum) crop production mainly due to its ability to overcome the resistance meditated by the Mi-1 gene. Despite the potential importance of this nematode, sources of resistance to M. enterolobii are not yet available for breeding purposes. The main objective of the present work was to evaluate a large Solanum (section Lycopersicum) germplasm (comprising nine species and one botanic variety) aiming to identify useful sources of resistance to M. enterolobii. In the first screening assay, 101 accessions and the susceptible standard S. lycopersicum ‘Santa Cruz’ were inoculated and evaluated under controlled conditions. The phenotypic criteria used for evaluation were the number of root galls, gall index, number of eggs, and the reproduction factor. Plants of the 20 selected accessions were cultivated in 0.4 L pots filled with sterile soil. Inoculation procedures were identical to the first assay, but with higher inoculum pressure (3,300 eggs per plant). Three accessions with superior tolerance levels to M. enterolobii were identified viz. S. lycopersicum ‘Yoshimatsu’, S. lycopersicum ‘CNPH 1246’ and S. pimpinelifolium CGO 7650 (= CNPH 1195). These accessions were re-evaluated against a distinct M. enterolobii population as well as against two other root-knot nematode species (M. javanica and one M. incognita race 1). Under higher inoculum pressure, ‘Yoshimatsu’ was found to be resistant to M. javanica and M. incognita race 1, but susceptible to M. enterolobii from guava. The other two sources displayed susceptibility to all three nematodes. Additional germplasm screening is needed since no source of stable genetic resistance to M. enterolobii was found so far.
Highlights
Meloidogyne enterolobii (=M. mayaguensis) é um patógeno de plantas capaz de induzir galhas e reduzir produtividade de uma vasta gama de espécies hospedeiras
O principal objetivo do presente trabalho foi avaliar um amplo germoplasma de Solanum composto por nove espécies e uma variedade botânica, objetivando identificar fontes de resistência a M. enterolobii
M. enterolobii has been reported as a potential threat for tomato crop in tropical and subtropical areas, especially due to its ability to overcome the resistance meditated by the Mi-1 gene (Yang & Eisenback, 1983)
Summary
Meloidogyne enterolobii (=M. mayaguensis) é um patógeno de plantas capaz de induzir galhas e reduzir produtividade de uma vasta gama de espécies hospedeiras. Meloidogyne enterolobii is a new invasive root-knot nematode species with an extremely wide host range, which includes the original host pacara earpod tree (Enterolobium contortisiliquum) as well as guava (Psidium guajava), acerola (Malpighia glabra), weed and ornamental plants, tomato (Solanum lycopersicum) and many vegetable crops (Yang & Eisenback, 1983; Carneiro et al, 2001). Introgression of the Mi-1 gene into commercial tomato cultivars was a very important breeding achievement, avoiding yield and quality losses caused mainly by mixed infections of M. incognita and M. javanica, a common feature observed in many producing areas of the world. This gene is not effective to M. hapla and against isolates of M. brasiliensis (Charchar et al, 2010). In tomato cultivars and rootstocks (with and without the Mi-1 gene), M. enterolobii is able to induce stunting and extensive root galling, which might result in drastic yield and quality losses (Pinheiro et al, 2009)
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