Agronomic and Molecular Marker Mapping of Brown Stem Rot, Phytophthora Root Rot, and Powdery Mildew Resistance in Soybean PDF Download

Author: David Glenn Lohnes
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Languages : en
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Book Description
Diseases are a major factor limiting the yield of soybean (Glycine max (L.) Merr.). Brown stem rot of soybean, caused by Phialophora gregata (Allington and Chamberlain) W. Gams, and phytophthora root rot, caused by Phytophthora sojae Kaufmann & Gerdemann, are major diseases of soybean in Illinois. A gene for resistance to powdery mildew, caused by Microsphaera diffusa Cke. & Pk., has also been found to be linked to a gene for phytophthora resistance. A field study was conducted to determine yield differences between isolines carrying different alleles at the locus for powdery mildew resistance, greenhouse experiments were performed to study the inheritance of brown stem rot resistance, and laboratory experiments were conducted in attempts to find molecular markers linked to brown stem rot, phytophthora, and powdery mildew resistance in soybean. When isolines carrying alleles for powdery mildew resistance are compared, the resistant isolines yielded 7% more than the adult-plant resistant isolines. With this yield advantage, it would be advantageous to use complete resistance to powdery mildew as a marker to select for phytophthora resistance in a soybean breeding program. Classification of reaction to brown stem rot of soybean populations indicates that a Clark isoline contains Rbs3, and that a germplasm line deriving resistance from PI 90.138 contains Rbs1 and another unknown resistance gene. Molecular marker analysis of Harosoy and a Harosoy brown stem rot isoline did not produce any polymorphic markers. Clark, Harosoy, and Williams were screened with several RAPD primers to determine the random amplified polymorphic DNA (RAPD) variability present between these cultivars. The percentage of RAPD products in common was 94% for Clark and Williams, 90% for Clark and Harosoy, and 84% for Harosoy and Williams. The material cost of running a single RAPD reaction ranged from 21 to 76 cents. Linkage analysis of the restriction fragment length polymorphism and disease classification revealed that the loci studied are in classical linkage group 19 and RFLP linkage group J, in the most likely order Rps2 Rmd Rj2 pA233 pA724 pK375. This is the most agronomically important gene-dense region of the soybean molecular map identified to date.