A modified Environmental Shift Technique based on use of a disease index (scoring) gave consistent separation between susceptible and moderately resistant pea (Pisum sativum L.) genotypes to Aphanomyces euteiches Drech. root rot in 3 tests. A moderately high association (r = −0.63 to −0.83) between disease index and percentage of plant survival was found in segregating populations. Minnesota 108, moderately resistant to A. euteiches, produced adventitious roots readily at an early stage. Root rot resistance and number of adventitious roots were inherited independently. Broad sense heritability (BSH) ranging between 0.45 and 0.57 for resistance to A. euteiches root rot, and between 0.39 and 0.44 for resistance to Rhizoctonia solani Kuehn stem rot, varied by parental combination, experiment, and method of estimation. However, heritability based on gain by selection in the F3 ranged from 0.28 to 0.46 and from 0.21 to 0.44 for resistance to A. euteiches and R. solani, respectively. Frequency distribution of resistant and susceptible plants suggested quantitative inheritance of resistance to both diseases. Recurrent selection, in which each cycle includes one intermating, selfing, and testing generation, is suggested to improve and transfer resistance.
‘Andover’ parsnip (Pastinaca sativa L.) is being released for commercial fresh-market and home garden production as a cultivar with desirable root type and resistance to field and storage attack by Itersonilia perplexans Derx. (1-4), which causes a foliar leaf spot, and, in storage, a root canker followed by root deterioration. The disease is commonly known as parsnip canker. A need for resistance to deterioration in storage gave rise to the breeding program. It was found that canker was a major reason for this deterioration, although other organisms are known to be involved.