Department of Plant Sciences

Tomato is grown in about 0.15m hectares in India with replacement of the determinate open pollinated local cultivars with the F1 hybrids from Europe with semi determinate and indeterminate growth habit. There is a quantum jump in increase in yield from 25 t ha-1 to 55 t ha-1 in the open field cultivation (Anonymous, 2002). But the cultivation of F1 hybrids, developed in Europe for greenhouse cultivation in open field cultivation, nutritional problems hitherto not noticed were observed. Among them, the predominant nutrient disorder is magnesium deficiency, which is noticed in all the F1 hybrids resulting in reduction in yield by 15-20 per cent, smaller fruit size from 3rd picking and poor colour resulting in 20-25 per cent loss in marketable yield. According to Graham (1984) in modern cultivars nutrient efficiency is low since the plant breeding centers tend to be located in areas of fertile soils. Since breeding is conducted under low or zero selection pressure for nutrient efficiency factors especially the common limitation of NPK and Mg are overcome by adequate fertilizer application. Besides the fast growth rate of F1 hybrids makes the soil which were found adequate for magnesium for comparatively slow growing open pollinated tomatoes, deficient for the hybrids (Graham, 1984) since growth rate also decides the occurrence of nutrient disorders. An additional factor in the occurrence of magnesium deficiency as a new disorder is the need for magnesium in seeds (Welch, 1986) since with doubling of yield seed production also is doubled. The reduction in size and poor color are related to the low chlorophyll production due to reduced supply of magnesium. Hence a study was initiated to survey the farmer's field, to establish the extent of occurrence of Mg deficiency, its effect on yield and quality of tomatoes.