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  • Author or Editor: F.L. Pfleger x
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Asparagus offcinalis L. `Mary Washington' seedlings inoculated with Glomus fasciculatum (Thaxter) Gerd. and Trappe emend. Walker and Koske showed increased growth after 9 weeks, compared with noninoculated plants. Phosphorus supplementation (25 g·m-3) increased seedling growth of inoculated and noninoculated plants throughout the 26 weeks of the experiment. However, after 9 weeks, there were no differences in growth of inoculated, non-P-supplemented plants and noninoculated, P-supplemented plants. Fern height, fern and crown weight, and bud numbers correlated positively to the percentage of G. fasciculatum root infection.

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Abstract

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.

Open Access

Pea root rot is a serious economic threat to pea production in the Great Lakes region. The primary causal organism is Aphanomyces euteiches Drechs., which is responsible for an estimated 10% annual crop loss. A fall oat (Avena sativa) rotation before spring pea planting reduces disease severity. To better understand the beneficial effect of oat on A. euteiches, isolated individual pathogen lifecycle stages of zoospores, mycelium, and oospores were treated in culture with oat extract. Resulting mycelial mats were dried and weighed. Treatment with 90%, 70%, 50%, and 30% oat extract resulted in significant spore germination and mycelial growth of A. euteiches. In the presence of nutrient solution, oat extract concentrations of 90%, 70%, 50%, and 30% significantly enhanced spore germination and mycelial growth of the pathogen. These results demonstrate that the use of oat extract results in dosage dependent germination and growth of A. euteiches.

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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