HISTO-PATHOLOGICAL OBSERVATION OF RESISTANT AND SUSCEPTIBLE MAIZE (ZEA MAYS L.) GENOTYPES UNDER EXSEROHILUM TURCICUM STRESS

Northern Corn Leaf Blight (NCLB) is the most common fungal disease in the temperate climate zone including Azad Kashmir.It is caused by the fungus Exserohilum turcicum, which produces spores that colonizes maize leaf surface.This pathogen damages the leaf structure, causing chlorosis and loss of photosynthetic activity.Compromised maize germplasm demonstrates a variety of NCLB symptoms as well as mechanisms of disease resistance.Planting resistant maize varieties has been demonstrated to be the most effective method of NCLB management.In this report, histochemical studies were conducted to identify the genetic source of maize resistance to E. turcicum.Plant susceptibility to NCLB was evaluated on a scale of 0-5.Leaves sample were visually assessed based on symptoms conferring to NCLB stress.Pathogenic assessments explore 3 highly susceptible (HS), 3 highly resistant (HR), 1 resistant (R), 14 moderately resistant (MR) and 9 moderately susceptible (MS) genotypes.The reaction of each tested genotype was again confirmed/evaluated using histochemical observations.Data was recorded for number of infections (NI), fungal colony area (FCA), necrotic area (NA), and the calculated hypersensitivity index (HI).Leaf samples were collected at 10-and 20-days post infection (dpi), allowing comparison of early and full progression of the disease.Results at 10 dpi demonstrated that resistant genotypes had few-to-no infections while demonstrating the highest necrotic area.The largest NA was measured in genotypes Karamat-Bar (3456.66m),NCEV-1530-11 (726.57m), and SZP-13200 (625.68m).Smallest FCAs were observed in Karamat-Bar (50.67m),NCEV-1530-11 (59.12m), and SZP-13200 (97.68 m) at10dpi.Resistance was indicated by HI, which was the highest in Karamat-Bar (93.37%),SZP-13200 (93.09%), and NCEV-1530-11 (90.36%).Histo-chemical screening identified as susceptible genotypes showed larger NA (16m in Soan-3) and greater FCAs (Soan-3 3943.04m,Ghuari 2302.73m, and Kissan 1947.14m)respectively.These genotypes exhibited the lowest HI (2.6% in Soan-3, 2.51% in Ghuari, and Razzaq et al.: Histo-pathological observation of resistant and susceptible maize (Zea mays L.) genotypes under Exserohilum turcicum stress -6690 -