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Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982. http://hdl.handle.net/2142/70581 (UMI)AAI8209643 Agriculture, Plant Pathology Whatley, Thomas Lamar 2014-12-15T23:52:11Z 2014-12-15T23:52:11Z 10000-01-01 1982 1982 Microplot and large plot studies indicated the cultivars 'Harosoy' and 'Williams' inoculated with Glomus etunicatus (GE) were susceptible to Phytophthora root rot caused by Phytophthora megasperma var. sojae (PMS); however, at soil phosphorus (P) levels equal to a Bray P1 of 19 or 75 kg/ha plant heights and yields were greater and significantly greater for final height and yield with a soil P1 of 75 kg/ha with application of both GE and PMS rather than PMS alone. Tolerance of PMS due to GE at Bray P1 levels of 75 kg/ha or less may be caused by improved P nutrition but no tolerance existed at higher P levels. Root dry weight of soybeans grown in 150 cc tubes increased to an optimum level of P and decreased with additional P, exclusive of PMS. In a large plot experiment leaflet P increased with increasing soil P; however, without PMS dry matter and yield increased to the 444 kg/ha level of added P and decreased insignificantly at the 888 kg/ha P level. However, at 0, 444, 888 kg/ha added P Phytophthora root rot reduced dry matter 10, 54 and 51%, stand 19, 53 and 51%, yield 13, 39 and 39%, respectively. In plots with reduced plant populations due to high P and PMS the remaining stressed plants were unable to compensate for the yield of the missing plants. In greenhouse susceptibility studies resistance to PMS race 1 contained in 'Harosoy 63' was not sufficient to prevent root dry weight losses due to PMS race 1 at high P levels. Reductions in root dry weight caused by PMS and high P were additive. When both root halves of a split root experiment were infested with PMS the low P side had a significantly greater root weight than the high P side. Under disease stress low P may permit greater root growth than high P. In the field losses associated with PMS may not be aleviated by resistant cultivars. Made available in DSpace on 2014-12-15T23:52:11Z (GMT). No. of bitstreams: 1 8209643.pdf: 1833879 bytes, checksum: 92d57c60d17fe25258914011c2c46c0c (MD5) Previous issue date: 1982 Embargo set by: Seth Robbins for item 70747 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs U of I Only 60 p. The Effects of Glomus Etunicatus and Soil Phosphorus on Phytophthora Root Rot of Soybean text Plant Pathology Plant Pathology University of Illinois at Urbana-Champaign Dissertation Ph.D.