Rodrigo V. Silva

Effects of silicon on the penetration and reproduction events of Meloidogyne exigua on coffee roots

Considering that the root-knot nematode Meloidogyne exigua has caused great yield losses to coffee production in Brazil, this study aimed to determine whether the penetration and the reproduction events of this nematode on the roots of plants from two coffee cultivars with different levels of basal resistance to this nematode could be affected by silicon (Si). Coffee plants from the cultivars Catuai and IAPAR 59, which are susceptible and resistant, respectively, to M. exigua, were grown in pots containing Si-deficient soil that was amended with either calcium silicate (+Si) or calcium carbonate (-Si). The Si concentration on the root tissue significantly increased by 159 and 97% for the +Si plants from the cultivars Catuai and IAPAR 59, respectively, compared to the -Si plants of these cultivars. The population of M. exigua, the number of galls and the number of eggs were significantly reduced on the roots of the +Si plants of the cultivars Catuai and IAPAR 59 compared to the -Si plants of these cultivars. It was concluded that the development and reproduction events of M. exigua were negatively impacted on the roots of coffee plants supplied with Si.

Preservação da capacidade reprodutiva de Meloidogyne exigua em mudas de pimentão

Coffee is the host-type of Meloidogyne exigua and significant inoculum production on this plant takes a long time. The objective of this study was to evaluate the reproduction of five M. exigua populations on coffee comparatively with reproduction on pepper, and the possible occurrence of physiological selectivity after successive generations on pepper. In the selectivity test, one population was maintained on coffee and pepper for 30 months and reproduction was evaluated 10 times, at 90 day intervals. The number of galls and eggs was always higher in pepper roots than in coffee ones. The reproductive rate in pepper was four times higher than in coffee. There was no difference in nematode reproduction in coffee between the two inoculum sources, coffee and pepper, during 30 months. Pepper proved to be a better host than coffee for the rearing of M. exigua, including those populations unable to reproduce in tomato roots, since pepper plants are easy to manage under green-house conditions and nematode reproduction is faster than in coffee. Therefore, pepper should be used to rear M. exigua since the nematode does not lose its ability to infect coffee.