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  • Author or Editor: T. H. King x
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Abstract

Resistance in Pisum sativum to Aphanomyces euteiches was evaluated in the laboratory by the number of oospores formed in excised root tips inoculated with zoospores of the pathogen. Significantly lower mean numbers of oospores formed in root tips of 3 moderately resistant breeding lines than in those of 3 susceptible cultivars. Results were reproduceable if test procedures were adequately controlled. A sample size of 40 root tips gave 95% confidence in detecting a 40 oospore/root tip difference between means of resistant and susceptible genotypes.

Lower mean numbers of oospores formed in excised root tips of genotypes which were resistant in greenhouse tests. Inoculum concentrations of 10 to 100 zoospores/plant caused severe disease in susceptible cv. New Era, while greater amounts of inoculum were needed to cause comparable disease in 2 resistant breeding lines.

Open Access

Abstract

Minnesota 494-A11 is a unique source of common pea (Pisum sativum L.) germ-plasm. It has moderate to high resistance to common root rot caused by Aphanomyees euteiehes Drechs. (3, 6) and high resistance to fusarium wilt races 1, 2 and 6 caused by Fusarium oxysporum Linford f. sp. pisi Snyd. & Hans. It is intermediate in reaction to race 5 of that organism (7). It also has moderate tolerance to fusarium root rot caused by Fusarium solani and to root rot caused by Pythium ultimum. However, it does not have resistance to Rhizoctonia solani. No other genotype of P. sativum is known to have the above combination of resistanee/tolerance to so many soil-borne pathogens.

Open Access