Inheritance of Phytophthora Root Rot Resistance in Alfalfa
1973
Lu, Nancy Shyh-Jane | Barnes, D. K. | Frosheiser, F. I.
The inheritance of Phytophthora root rot resistance was determined in alfalfa (Medicago sativa L.) for five clones from the variety ‘Lahontan’ and six clones from ‘Vernal’ and Vernal-type varieties. A heterozygote-diallel crossing scheme was used as the basis for genetic analysis. Parent clones were selfed, intercrossed, and testcrossed to two susceptible clones. Degree of resistance was determined by type of root-rot lesion. Susceptibility appeared to be conditioned by one tetrasomic gene, Pm, with incomplete dominance. The nulliplex condition produced highly resistant plants. The simplex condition produced a moderate degree of resistance. Duplex, triplex, and quadruplex plants were increasingly more susceptible. Resistance in the Lanhontan and Vernal-type varieties appeared to be controlled by the same gene.
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