Lieceng Zhu

Document Type

Thesis - University Access Only

Award Date

2001

Degree Name

Master of Science (MS)

Department / School

Plant Science

Abstract

Fusarium head blight (FHB, also scab), caused by Fusarium graminearum Schwabe (telemorph Gibberella zeae (schwein.) Petch; synonym= G. saubinetti), is a major threat for wheat in the humid and semihumid regions of the world. We have observed that wheat plants develop less FHB when subjected to early season drought stress and/or heat stress. The objective of this study was to investigate the response of wheat plants to pre-anthesis drought and/or heat stress in FHB development. Four hard red spring wheat lines or cultivars, ND2710, Wheaton, Russ and 2375, were used in this study. These genotypes are different in their resistance or susceptibility to F. graminearum. Three simultaneous experiments were conducted under controlled conditions in the greenhouse and growth chambers. Experiment 1 (Chapter 1) used a single cultivar to evaluate the effect of different levels of drought stress applied at different pre-anthesis plant growth stages. In experiment 2 (Chapter 2), four cultivars were used to investigate genotypic response to pre-anthesis drought stress and FHB development. Experiment 3 (Chapter 3) was designed to evaluate the interactions of preanthesis heat stress and drought stress and their effect on FHB development. In all experiments, drought stress was applied by withholding water from the plants until the soil moisture content reached the desired level (35% pot capacity, 30% pot capacity, and 3 days after 30% pot capacity). Heat stress was applied in Experiment 3 by transfening the plants from a growth chamber set at 20/15°C to a growth chamber set at 30/20°C. Plants were transferred to the hot chamber when they reached boot stage and were left until inoculation time in one trial and for 3 days in another trial before being returned to the 20/l 5°C growth chamber. FHB was induced by artificial inoculation with F. graminearum using a point inoculation method or by spray inoculation. The results of the experiments indicated that drought stress, either separate or combined with heat stress together, reduced the level of FHB in spring wheat. Drought stress reduced the FHB severity across all the four genotypes and trials except in the trial 3. The levels of reduction seemed to be affected by levels of stress and by genotypes but not by the imposing stage. The severe and intermediate level of drought stress caused more reductions in FHB severity than the mild level of stress. The reduction in FHB severity induced by the pre-anthesis drought stress was at a greater degree in the moderate susceptible cultivar 2375 and Russ than the resistant line ND2710 and susceptible cultivar Wheaton. The influence of the stresses seemed mainly on the development of the disease rather than initial establishment of infection on the wheat plants. Drought stress also reduced kernel damage. However, the reductions of the kernel damage appeared to vary among trials and genotypes. Heat stress did not affect FHB severity when imposed from booting stage until inoculation in the growth chamber trial 1. However, heat stress applied for three days at booting stage in the growth chamber trial 2 tended to reduce FHB severity. Among all the four genotypes, Russ was most sensitive to heat stress in FHB development. Heat combined with drought stress might also reduce the level of FHB development in the FHB susceptible cultivar Wheaton. Although all levels of drought stress, heat stress and heat combined with drought stress affected wheat plants adversely, the intennediate level of early season drought stress did not reduce spike weights significantly when the plants was inoculated with F. graminearum. Compared to non-stressed control plants, drought stressed plants had less reduction in spike weight under FHB epidemics due to the lower level of FHB severity.

Library of Congress Subject Headings

Wheat -- Diseases and pests
Fusarium diseases of plants
Wheat -- Effect of drought on
Wheat -- Effect of temperature on

Format

application/pdf

Number of Pages

98

Publisher

South Dakota State University

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