Turcicum Leaf Blight Resistance in Maize: Field Screening of New Inbreds and Hybrids

This paper presents identification of sources of Turcicum Leaf Blight (TLB) resistance in maize. Maize is affected by more than 60 diseases, of which 16 are major ones. TLB, caused by E. turcicum, is considered a serious disease where climatic conditions are cool with high relative humidity. Severe losses in grain yield ranging from 25 to 90 per cent have been reported in India. Seventy two hybrids developed by line x tester design along with 18 parents and three checks were screened against turcicum leaf blight (TLB) under artificial epiphytotics during rainy season of the years, 2015 and 2016. Disease score and percent disease indexes were recorded at tasseling and 20 days after tasseling (DAT). Nineteen hybrids with a disease score of 0, 33 hybrids with a score of 1 and 20 with a score of 2 at tasseling were categorised as resistant. The range of per cent disease index (PDI) was between 0 per cent and 28.6 per cent. At 20 days after tasseling (DAT), one hybrid with a disease score of 1, fifteen hybrids with 2 were found to be highly resistant and resistant, respectively. Twenty nine scored disease score 3 indicating moderate resistance. Twenty four hybrids registered susceptible, (score of 4) while three hybrids recorded highly susceptible reaction (disease score 5). After 20 DAT, the PDI ranged from 20.40 to 68.57 per cent. Thirty four hybrids showed less than 45 per cent disease index falling under moderately tolerant category and twenty six hybrids showed more than 50 per cent disease index falling under susceptible category. After 20 DAT, parents PDM-8, PDM-60 and PDM-254 had disease index of <10% indicating their resistance to TLB. The inbreds, PDM-4611, PDM-1, PDM-32 IDM-, PDM-36 and PDM-83 recorded disease index of more than 50% while, PDM-259, PDM-127, PDM-51 and PDM-52 recorded disease index of more than 35% but less than 50% indicating they are highly susceptible to TLB. The results suggested the possibility of improving resistance against TLB further through population improvement approach, preferably by reciprocal recurrent selection.