Chemical and Histological Differences of Corn (Zea mays L.) Responsive to Harpophora maydis Infection

Abstract

Harpophora maydis (Cephalosporium maydis) is considered to be the most destructive pathogens causing late wilt disease of maize in Egypt. Pathogen isolation was carried out through five Governorates (Kafr El-Sheikh, Behera, Dakahlya, Menia and Sohage). Five isolates were differed in their virulence based on their pathogencity test with five cultivars (SC.10, SC.123, TWC.310, Giza-2 and Balady). The maize (SC.10) was resistant against all the isolates. While the Balady showed higher susceptibility. Isolate No.5 isolated from Sohage was the most virulent isolate (25.75%), while isolate No.4 was the least virulent isolated from Menia (1.6%). Moreover, under artificial infection, phenol contents were higher in the susceptible cultivar compared to resistant one at 30, 60 and 90 days from planting. Sugar contents measured at 30, 60 and 90 days from planting were significantly high (33.64 mg 10g-1 fresh weight) with susceptible cultivars relative to resistant one (23.18 mg 10g-1). Linear increment of phenol contents and sugars was observed with the resistant cultivar compared to susceptible one, but sugar contents were decreased after 60 days. Phenol contents were higher in resistant cultivar, while interestingly sugar contents were higher in susceptible one. For results of light microscope, thickness of sheath bundle of infected plants in resistant cultivar was higher than susceptible one, and increased over age with noninfected plants. Additionally, thickness of sheath layer in resistant and susceptible was affected after infestation process. So, phenol contents may play an essential role in resistance process against late wilt disease and sugar contents with susceptibility process.