SummaryRoot-knot nematodes, Meloidogyne spp., cause great losses to coffee crops in Brazil and worldwide. However, little is known about the physiological changes that these pathogens induce in coffee plants. The present work aimed to compare the physiological variables of coffee seedlings (Coffea arabica ‘Catuaí Vermelho IAC 144’) infected with Meloidogyne paranaensis or M. exigua with healthy coffee plants. Nematode-infected plants showed reductions in height and starch content in roots compared to healthy plants. In addition, the infected plants had a reduction in transpiration, stomatal conductance and CO2 concentration. However, only the coffee seedlings infected with M. paranaensis showed reduction in the rate of photosynthesis. Nematode-infected plants had lower leaf contents of P, K, Mn and Fe when compared to healthy plants. However, only coffee seedlings parasitised by M. paranaensis exhibited lower levels of Ca in the leaves. Therefore, M. paranaensis and M. exigua, with emphasis on M. paranaensis, alter the normal coffee seedling physiology.
Climate change greatly influences coffee production, especially in areas infested with plant‐parasitic nematodes. In this study, coffee genotypes showed differences in their morphological and physiological characteristics when subjected to a water deficit and parasitism by Meloidogyne paranaensis. The cultivar IPR 100 had the largest superficial and volumetric root system area, even when parasitized. The two progenies (MG 0179‐1 and MG 0179‐3) and the cultivar Catuaí IAC 62 had a similar surface area (p < .05) when parasitized. However, the root surface area and volume of MG 0179‐3 increased by 96% and 400%, respectively, when parasitized by M. paranaensis. On the other hand, Catuaí IAC 62 had a 31% reduction in root surface area. Catuai 62 and IPR 100 showed higher sensitivity to drought when parasitized because of the increased photochemical sensitivity and reduction in photochemical quenching. In MG 0179‐1 and MG 0179‐3, an increase in non‐photochemical quenching occurred in response to stress, indicating that these progenies use a photochemical response to protect photosystem II. In this work, MG 0179‐3, which is resistant to M. paranaensis, was remarkable because, interestingly, the infestation caused an increase in its root surface area. In addition, MG 0179‐3 had relatively good photochemical performance under water deficit and M. paranaensis parasitism.
SummaryMeloidogyne paranaensis is one of the most important pathogenic nematode species on coffee. Our aim with this study was to characterise the resistance of genotype ‘16-6-1’, derived from germplasm ‘Amphillo’ of Coffea arabica to M. paranaensis. Second-stage juveniles penetrated the roots of ‘16-6-1’ in lower numbers and at a slower pace as compared to the susceptible genotype. The strong blue fluorescence observed in the resistant, but not in the susceptible genotype suggested that resistance responses occurred as early as 2 days after inoculation (DAI). Late responses involved the degradation of the giant cell at 14 DAI onwards in the resistant genotype, whereas nematode and giant cell development progressed normally in the susceptible genotype. Our results suggested that the resistance of genotype ‘16-6-1’ is related to early and late defence responses. These results may be used to develop molecular markers linked to the resistance genes to use in breeding programmes.
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