Abstract
ABSTRACT: To investigate the degree of parasitism of two populations of Meloidogyne exigua, the gall index (GI) and the reproduction factor (RF) of M. exigua races 1 (Est E2) and 2 (Est E1) were analyzed in 47 progenies on F3:4 or F4:5 generation derived from the crossing between Coffea arabica cv. Catuaí Amarelo and Timor Hybrid. C. canephora cv. Apoatã IAC 2258 and C. arabica cv. Catuaí Vermelho IAC 144 were used as resistance and susceptibility checks, respectively. The genotypes that were classified as resistant or susceptible by RF were similarly classified by GI, showing a close relationship between both methodologies. The data also indicated no differences in virulence between the nematode populations, since the progenies showed similar resistance reactions to the M. exigua races 1 and 2. According to GI from the 47 mother plants evaluated, 27 progenies (57.4%) were classified as resistant to M. exigua races 1 and 2, with GI ranging from 0.0 to 1.4 and 20 progenies (42.6%) were susceptible with GI from 2.6 to 4.4. These results showed that most of the evaluated germplasm was very promising in relation to the development of new Arabica coffee cultivars with resistance to M. exigua.
Highlights
Most of the Brazilian coffee crop is comprised by susceptible cultivars to Meloidogyne exigua Goeldi, 1887
Considering that the plant resistance to root knot nematode (RKN) can be races and / or species specific (ROBERTS, 2002) and the occurrence of high intraspecific variability in populations of M. exigua coffee parasites (CARNEIRO & COFCEWICZ, 2008, MUNIZ et al, 2008), the objectives of this research were: i) to investigate the degree of parasitism of two races of M. exigua; ii) to compare the nematode coffee resistance methodology based on the gall index (GI) and the reproduction factor (RF) and iii) to assess the resistance of 47 germoplasms on F3:4or F4:5 generation derived from the crossing between C. arabica cv
Meloidogyne exigua populations The initial nematode populations were obtained from coffee roots parasitized by M. exigua collected from Campinas, SP (Est E2, race 1) and São Sebastião do Paraíso, MG (Est E1, race 2) and the race test was determined according to MUNIZ et al(2008)
Summary
Most of the Brazilian coffee crop is comprised by susceptible cultivars to Meloidogyne exigua Goeldi, 1887. The parasitism of this species of root knot nematode (RKN) has been causing decreases of 20 to 68% in the production of susceptible coffee trees infested by nematodes (BARBOSA et al, 2004). Several management strategies have been recommended to minimize the damage caused by RKN in coffee (CAMPOS & SILVA, 2008); genetic resistance is the most effective method to cultivate coffee in infested soils. The first three are derived from the Timor Hybrid, the penultimate of Icatu x Catuaí and the Approved 11.30.20 Returned CR-2020-0721.R1 by the author. V.51, n.7, latter is derived from BA-10 (PEREIRA & BAIÃO, 2015; SERA et al, 2017). The grafting cultivar of C. canephora Apoatã IAC 2258 is highly resistant (FAZUOLI et al, 2002)
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