SINGLE AND COMBINED EFFECTS OF Meloidogyne incognita AND Fusarium oxysporum f. sp. lycopersici ON TOMATO (Solanum lycopersicum) IN MAKURDI, NIGERIA

Abstract

Most of the diseases caused by nematodes are debilitating. However, when they interact with other pathogenic organisms the disease scope is drastically altered. Simultaneous multiple disease infections are not uncommon in most tomato fields in Makurdi, Benue State. However, there is paucity of information on effects of concomitant infections on the agronomic performance of tomato involving Meloidogyne incognita and Fusarium oxysporum in the study area. This study was carried out to investigate the effects of nematode-fungus disease complex at different population densities under simulated micro plot conditions in Makurdi, Nigeria. Experiments were carried out in 2014 and 2015 at the Teaching and Research Farms of Federal University of Agriculture, Makurdi. Two weeks after planting (WAP), seedlings of tomato cv. Roma VF were inoculated with Meloidogyne incognita using 0, 2,500 or 5,000 eggs, solely and in combination with Fusarium oxysporum fungal inocula at three levels; 1,000, 10,000 or 100,000 conidia/ml by applying 5 ml of spore suspension per micro plot except in the control. Results showed that although single inoculation of either pathogens significantly (P<0.05) reduced plant growth, M. incognita reduced plant growth more. F. oxysporum inoculated at 1,000, 10,000 and 100,000 conidia/ml reduced plant height at 6 WAP by 14.2, 18.2 and 15.1 % in 2014 and by 15.2, 14.3 and 13.1 % in 2015, respectively. In the presence of the nematodes however, height of tomato plants at 6 > WAP was 14.6 cm (2014) and 15.2 cm (2015) representing percentage reductions of 43.3 % and 35.8 %, respectively. The least fruit yields were observed in plants infected with combined inocula of M. incognita (5000 eggs) and F. oxysporum at 1000, 10,000 and 10,000 conidia/ml, representing 59.4, 61.5 and 65.8 % yield reduction, respectively in 2014, and 67.0, 67.8 and 73.3 %, respectively in 2015. The study concluded that the yield of Fusarium wilt-resistant tomato variety, cv. Roma VF was sub[1]optimal in the presence of the root-knot nematode. Further percentage reductions in its vegetative growth were also indicative of a possible synergistic activity targeted at the efficiency of the tomato host plant. Further studies on the dynamics of the population densities of the two pathogens at various intervals of the development of the host will further elucidate our understanding of the nematode-fungus disease complex.