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Inheritance of Phytophthora Root Rot Resistance in Two Diploid Alfalfa Species 1
Author(s) -
Havey M. J.,
Maxwell D. P.
Publication year - 1987
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1987.0011183x002700020019x
Subject(s) - biology , medicago sativa , phytophthora megasperma , backcrossing , ploidy , botany , inoculation , medicago , resistance (ecology) , root rot , phycomycetes , phytophthora , mycelium , horticulture , agronomy , genetics , gene
Phytophthora root rot [caused by Phytophthora megasperma Drechs. f. sp. medicaginis (Pmm)] is a major cause of decline of alfalfa ( Medicago sativa L.) grown in poorly drained soils. Diploid (2n = 2x= 16) Medicago species have been described as sources of resistance to diseases of cultivated tetraploid (2n=4x=32) alfalfa and are a potential source of resistance to Pmm. The objective of this project was to study the inheritance of resistance to Pmm in plant introductions of diploid M. falcata L. (PI 410970) and M. sativa subsp, × varia (Martyn) Arcangeli (PI 325408). Plants were grown in the greenhouse in pots containing a peat‐sand mix (1:1, v/v) and inoculated at 8 weeks with a chopped mycelial suspension of Pmm. Plants resistant and susceptible to Pmm were retained from both diploid Medicago species for use in inheritance studies. Segregations of 3:1 (resistance:susceptibility) in F 1 families and backcrosses to the susceptible parent indicated that resistance to Pmm in M. falcata was conditioned by a dominant allele at either of two independently segregating loci, designated as Pm 3 and Pm 4 . Resistance to Pmm in M. sativa subsp, × varia was heritable, but no mode of inheritance is proposed because unexplained segregation ratios were observed in the backcross to the resistant parent. These results demonstrate that M. falcata is a source of a simply inherited resistance to Pmm.