Epidemiological Factors Affecting Brown Spot (Physoderma maydis) Progression in Maize (Zea mays L.)
Chetna Mahajan
Department of Plant Pathology, Chaudhary Sarwan Kumar Himachal Pradesh Krishi Vishvavidyalaya, Palampur-176062, Himachal Pradesh, India.
Rakesh Develash
Department of Plant Pathology, Chaudhary Sarwan Kumar Himachal Pradesh Krishi Vishvavidyalaya, Palampur-176062, Himachal Pradesh, India.
Shikha Sharma
Department of Plant Pathology, Chaudhary Sarwan Kumar Himachal Pradesh Krishi Vishvavidyalaya, Palampur-176062, Himachal Pradesh, India.
Devinder Kumar Banyal
Department of Plant Pathology, Chaudhary Sarwan Kumar Himachal Pradesh Krishi Vishvavidyalaya, Palampur-176062, Himachal Pradesh, India.
Vanshdeep Dhanda *
Department of Entomology, Chaudhary Sarwan Kumar Himachal Pradesh Krishi Vishvavidyalaya, Palampur-176062, Himachal Pradesh, India.
Piyush
Department of Plant Pathology, Chaudhary Sarwan Kumar Himachal Pradesh Krishi Vishvavidyalaya, Palampur-176062, Himachal Pradesh, India.
*Author to whom correspondence should be addressed.
Abstract
Brown spot of maize (Zea mays L.) caused by Physoderma maydis is an emerging disease whose development is influenced by several host- and pathogen-related factors. The present study was undertaken under controlled polyhouse conditions using a whorl inoculation technique to elucidate the role of host age, pathogen culture age, inoculum load, and sub-culturing on disease development. Host susceptibility increased with plant age with maximum disease progression in 50-days old plants, whereas, reduced severity at later stages suggested the onset of age-related resistance. Among varying culture ages, 14-days old culture exhibited peak virulence with disease severity (26.85%) and apparent infection rate of (0.04 r/day). A sporangial concentration of 1×106 sporangia/ml resulted in maximum average disease index (39.51%) and shortest average incubation period of 13.0 days establishing as optimal inoculum load. Among varying sub-culturing of the pathogen, highest average disease index (22.22%) was recorded in the maize plants inoculated with 1st sub-culture. Furthermore, these findings elucidate age-related resistance and define optimal inoculation factors, offering practical insights for timing of management interventions and supports the development of durable resistance through targeted breeding strategies in maize.
Keywords: Maize, Physoderma maydis, inoculum load, host age, pathogenicity