EFFECTS OF NaCl SALINITY ON GROWTH OF SOME COTTON VARIETIES AND THE ROOT ROT PATHOGENS

Salinity is one of the predisposing factors to plant disease and increase the severity of the plant disease. An experiment was conducted to determine the effect the different levels of NaCl salinity on growth of Cotton (Gossypium hirsutum L.) varieties (CIM-598, CIM-599, CIM-602, CIM-573 and CIM-554) and its root rot pathogens. These varieties of Cotton were grown under different salinity levels @ 0, 30, 60, 90, 120 and 150mM NaCl (corresponding to 1.91, 5.72, 9.54, 13.43, 16.43, and 20.98 dS.m -1 ). The salinity reduced the root and shoot growth significantly. Root weight was the most limiting growth parameter. On the basis of 50% reduction of root weight, the in hand cotton varieties were found to follow following salt tolerance order, CIM-598 > CIM-602 > CIM-554 > CIM-573 > CIM – 599 (166.6) (142.4) (132.5) (119.1) (94.4)…mM NaCl The results of 3-way ANOVA showed that salinity treatment (P < 0.008, F = 3.21) and fungal type (P < 0.001, F = 238.47) significantly affected the colonization of root rot fungi while all varieties of cotton behaved more or less similarly and didn’t differ significantly (p < 0.364, F = 1.086) in colonization. The interactions amongst the three factors were highly significant indicating the fact that the intensity of colonization was an interactive function of salinity varietal specificity and nature of the root rot fungi. There was somewhat irregular trend of decline of colonization with salinity. However, maximum colonization was apparent in control and 30 mM NaCl treatment and minimum in 120 mM NaCl salinity. There was no significant difference in varietal response to fungal colonization (39.92- 45.91%). Fusarium sp. had, however, relatively higher colonization (64.98%). M. phaseolina had the moderate (48.18%) and R. solani, the least (15.38%) colonization.