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Systemic Infection of Maize by Fusarium Verticillioides Under Three Temperature Regimes

Adriana Murillo-Williams

出版	Iowa State University, 2005
URL	http://books.google.com.hk/books?id=O9I9NwAACAAJ&hl=&source=gbs_api

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Fusarium verticillioides (Sacc.) Nirenberg is important in maize (Zea mays L.) production because it causes ear rot, seedling decay, stalk rot, and fumonisin contamination in kernels. Pathways for kernel infection and ear rot by F. verticillioides include silks, insect wounds, and systemic infection. In previous studies, the frequency of systemic transmission of the fungus was variable, and this was attributed to environmental factors. In this study, the effect of temperature on systemic development of F. verticillioides was investigated during vegetative and reproductive stages of plant development. There were three temperature treatments designed to simulate the seasonal progression in Iowa. Treatments consisted of: a) average temperature (based on the average weekly temperatures); b) low temperature (two standard deviations below average); and c) high temperature (two standard deviations above average). Maize seeds were inoculated with a GFP (green fluorescence protein)-expressing strain of F. verticillioides and grown in growth chambers. Temperature treatments were imposed when plants reached V6 stage (vegetative-stage experiments), or when they reached VT (reproductive-stage experiments). F. verticillioides was reisolated from primary roots, mesocotyls and belowground internodes at all temperatures regimes. Reisolation of the inoculated strain declined acropetally in aboveground internodes at all temperature regimes. There was a significantly higher incidence systemic development of F. verticillioides in aboveground tissues at the high temperature regime than at the low and average temperature regimes in the vegetative-stage and reproductive-stage experiments. Mean kernel infection with the seed inoculated strain was 7.5%. There was no evidence of a treatment effect on the number of infected kernels (either symptomatic or asymptomatic) and ear peduncles that yielded the inoculated strain. Overall, the influence of high temperature on systemic movement of F. verticillioides was significant. The inoculated strain can be isolated from higher internodes in plants at physiological maturity. Other environmental factors may interact with temperature in ways that influence systemic movement of F. verticillioides and it subsequent movement into the kernels.