A Chitosan formulation Elexa™ induces downy mildew disease resistance and growth promotion in pearl millet

Abstract

A commercially developed aqueous Chitosan formulation Elexa was used in different concentrations viz., 1:5, 1:10, 1:15, 1:19 and 1:25 as seed soaking treatment to pearl millet for 3, 6 and 9 h duration to test for its effect on germination and vigor index. Among the treatments used 1:19 for 6 h soaking recorded maximum germination and seedling vigor. Seed treatment, foliar spray and combination of seed treatment and foliar spray were tested for control of downy mildew disease caused by Sclerospora graminicola in pearl millet under greenhouse and field conditions. Metalaxyl at the rate of 2.1% a.i. in the form of Apron 35 SD seed treatment was used as check. Under greenhouse conditions seed treatment offered 48% protection. Foliar spray was carried out to two, seven and 14-day-old seedlings and there was marked reduction in downy mildew disease incidence. Maximum protection of 67% was recorded with foliar spray to 2-day-old seedlings. With the combination of seed treatment and foliar spray to 2-day-old seedlings offered 71% protection. Under field conditions Elexa treatments were evaluated for their effect on incidence and severity of downy mildew disease. Seed treatment reduced downy mildew severity to 42.5% and recorded 38% protection, whereas foliar spray to 7-day-old seedlings gave 67% protection and reduced severity to 25%. Combination of seed treatment and foliar spray to 7-day-old seedlings recorded 69% protection and reduced severity by 23%. The nature of disease control mechanisms has been investigated and the results indicated that it is due to induction of systemic resistance. The induction of resistance was observed as early as 24 h time gap between the inducer treatment and pathogen inoculation and the maximum resistance developed at 24–48 h time gap and maintained thereafter. Elexa treated to pearl millet seeds offered growth promoting effect under greenhouse conditions and recorded increase in plant height, earhead length and seed weight. Hence, it is inferred that Elexa is a good downy mildew disease management commercial formulation and also exhibits growth-promoting effects in pearl millet.