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Tolerance to Phytophthora Rot in Soybean: I. Studies of the Cross ‘Ripley’ ✕ ‘Harper’
Author(s) -
McBlain B. A.,
Zimmerly M. M.,
Schmitthenner A. F.,
Hacker J. K.
Publication year - 1991
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/cropsci1991.0011183x003100060002x
Subject(s) - biology , hypocotyl , phytophthora megasperma , cultivar , horticulture , root rot , phytophthora , phytophthora sojae , botany , phycomycetes , inoculation
The pathogen Phytophthora megasperma Drechs. f. sp. glycinea T. Kuan & D.C. Erwin ( Pmg ) was shown to be the causative agent of a seed rot, damping off, and root and stem rot of susceptible cultivars of soybean [ Glycine max (L.) Merr.]. Genetic control Ping has been partitioned into two classes: hypocotyl resistance and tolerance. The hypocotyl‐susceptible ‘Ripley’ was observed to have a very tolerant reaction to Pmg in the field and in Race 4 slantboard tests in 1984. This study examined inheritance of tolerance in the cross Ripley ✕ ‘Harper’ (a caltivar with a low level of tolerance), evaluated Ripley as a donor parent of Pmg tolerance, and determined the value of the slant‐beard test on single plants. Tolerance to Pmg (using the slant board with Race 4) was inherited quantitatively ( h 2 = 54%). The slant‐board test had single‐plant escapes that reduced ability to select superior F 2 plants. It was a sensitive test if 20 or more plants were tested per line. Slant‐beard and field tolerance data did not correlate as well as expected ( r = 0.34, P < 0.01). Eighteen percent of the F 2 lines from this cross were no inter than Ripley and at least as tolerant as Harper based on field tolerance scores. Less than 1% of the F 2 lines were as early or earlier than Harper and as tolerant as Ripley. Ripley is not a good donor parent for Midwestadapted caltivars tolerant to all prevalent races. One line was identiffed which has earliness, indeterminate stem termination, and Riple's tolerance for Races 1,3, and 4.