Determining Alfalfa Resistance and Yield Losses Associated with Verticillium Wilt Infestations
- Y. A. Papadopoulos,
- B. R. Christie and
- G. J. Boland
Twenty-four alfalfa (Medicago sativa L.) cultivars and experimental synthetics were evaluated for resistance to verticillium wilt (Verticillium albo-atrum Reinke & Berth) in controlled environments (utilizing aseptically grown seedlings prior to inoculation with V. albo-atrum) and field conditions to determine the ability of controlled environment methods to evaluate disease resistance and the influence of verticillium wilt on alfalfa forage production. Foliar disease symptoms first appeared in the field prior to the second cut of the first production year (1 yr after planting). Substantial differences in foliar disease symptoms and reductions in healthy plant populations and herbage dry matter yield were detected among the entries by the third harvest of the second production year. Field disease ratings were positively correlated with growth chamber disease ratings and negatively correlated with herbage dry matter yield. Twenty to 56% of the variation in herbage yield among cultivars in the V. albo-atrum infested field was attributed to the influence of disease as determined by correlation analysis. The results indicate that controlled environment evaluations of cultivar resistance to verticillium wilt of alfalfa were in agreement with the cultivars' reaction in the field following natural infection and that verticillium wilt causes substantial yield reduction in susceptible cultivars. It is estimated that alfalfa cultivars should possess levels of resistance comparable to that of the check cultivar Vertus to avoid yield losses due to verticillium wilt.
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