In Brazil, Meloidogyne exigua is one of the most important pathogens that attack coffee plants. Morphological, biochemical, molecular and physiological variabilities have been observed in M. exigua, but the expression of these variabilities in coffee genotypes is not well known. To evaluate the effect of M. exigua on 25 Coffea spp. genotypes, populations exhibiting distinct esterase phenotypes and host suitability variations were selected. Thus, coffee seedlings at the stage of 3-4 sets of two leaves were inoculated with 5000 eggs of either population, with each treatment including six replicates. The evaluation occurred 110 days after inoculation, by counting galls and eggs per root system and measuring root fresh weight. According to the genotypes' reaction, three groups of Coffea spp. were detected: fourteen expressed susceptible reaction, six segregated and five were immune to M. exigua populations. The segregating genotypes behaved in a different way in relation to the four populations. Thus, the utilization of different populations showing this variability is fundamental for a breeding program that aims to develop resistant cultivars.
Root-knot nematode; resistance; variability; coffee
