Phenotypic Evaluation of Maize Cultivars for Bacterial Stalk Rot Disease Reaction Caused by Dickeya zeae under Glasshouse Conditions in Telangana, India

Abstract

Background: Bacterial stalk rot (BSR), caused by Dickeya zeae, is an important bacterial disease of maize, and the identification of resistant germplasm is required for sustainable disease management. Aims: The present study was conducted to evaluate the phenotypic response of maize lines and commercial hybrids to bacterial stalk rot (BSR), caused by Dickeya zeae, under glasshouse conditions. Study Design: Completely randomised design experiment. Place and Duration of Study: Institute of Biotechnology, PJTAU, Rajendranagar, Hyderabad-500030. Methodology: Bacterial stalk rot (BSR), caused by Dickeya zeae, is an economically important disease of maize and may cause severe yield losses ranging from 27% to 98%. The cultivation of resistant maize genotypes is considered an effective and sustainable strategy for managing BSR. The present study evaluated the BSR disease reaction of 12 maize cultivars, comprising six lines from the Maize Research Unit, Professor Jayashankar Telangana Agricultural University (PJTAU), six commercially cultivated hybrids and the susceptible check CM 600, under controlled glasshouse conditions. Plants were artificially inoculated with the aggressive D. zeae isolate DZ-KR1 using the hypodermic syringe method at 41 days after sowing. Disease severity was assessed using the 1-9 scale developed by ICAR-IIMR, Ludhiana, and the Percent Disease Index (PDI) was calculated. The experiment included 13 genotypes under two treatments: pathogen inoculation and sterile distilled water  control. Results: All maize lines and private hybrids produced characteristic bacterial stalk rot symptoms, whereas the control plants did not show any symptoms. A 100% disease incidence was observed among all maize lines and hybrids under 80% relative humidity and 32°C temperature conditions within seven days of inoculation. The highest Percent Disease Index was recorded in Syngenta Hybrid NK 30 and the lowest in Pioneer Hybrid 3302, with values ranging from 94.30% to 79.97%, respectively. Conclusion: This study demonstrated that none of the evaluated maize lines or commercial hybrids cultivated in Telangana showed resistance to D. zeae. These findings indicate the need to screen a wider range of maize germplasm to identify novel sources of resistance.