Studies on correlation between Glomus fasciculatum spore density, root colonization and Meloidogyne incognita infection on Lycopersicon esculentum

In vitro (pot conditions) and in vivo (nursery beds) experiments were carri ed out to correlate Glomus fasciculatum spore density (1, 2, 4, 8 and 16 sp ores/g soil), root colonization of Lycopersicon esculentum and root infecti on of Meloidogyne incognita. In vitro experiments revealed that mycorrhizal root colonization and formation of chlamydospores were positively correlat ed with spore density, although the rate of increase in root colonization a nd subsequent chlamydospore formation declined at eight spores/g soil and a bove. The nematode populations, egg masses/plant and root gall index were n egatively correlated with spore density. Further, at least two spores/g soi l were required for 50 % root colonization under pot conditions. However, u nder nursery conditions, four spores/g soil were required to obtain 50 % ro ot colonization which reduced nematode populations in root (in terms of egg masses/plant) by 59 and 61 %, respectively. It was observed that new flush of roots from precolonized roots after chlamydospore formation (45-60 DAS) were infected by root-knot nematode juveniles.