EDAPHIC OVERHEATING AS A POSSIBLE INDUCER OF Alternaria sp. INFECTION IN TOMATO SEEDLINGS

Abstract

Alternaria sp infection of tomato (Lycopersicon esculentum Mili.) plants is rather common in mature, senescent plants. However, in the State of Morelos, México, a severe damage caused by this pathogenic fungus has been detected at the bottom of the stem in
young tomato plants, which had been recently transplanted. This problem was studied in the tomato cultivar Floradade during the 1990 Summer, planted in a black clay soil (vertisol) at Zacatepec, Morelos. A week after transplantig, all plants showed stem injuries (necrosis) at soil level. It was found that the soil surface reached 47°C while the air and leaf temperatures were 34°C and 29°C. Hence, we suggest that the high soil temperature can induce premature tissue senescence of young stems in direct contact with soil which in tum allowed the Alternaria infection.