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Title:The Effects of Glomus Etunicatus and Soil Phosphorus on Phytophthora Root Rot of Soybean
Author(s):Whatley, Thomas Lamar
Department / Program:Plant Pathology
Discipline:Plant Pathology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Agriculture, Plant Pathology
Abstract: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.
Issue Date:1982
Description:60 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982.
Other Identifier(s):(UMI)AAI8209643
Date Available in IDEALS:2014-12-15
Date Deposited:1982

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