Identification of soybeans having resistance to phytophthora sojae

Abstract

The invention provides soybean plants having a novel determinant, Rps 8 , for resistance to Phytophthora sojae . The invention also provides methods for identifying germplasms that are either heterozygous or homozygous for Rps 8 using marker assisted selection. Genetic markers with known chromosomal location that are associated with the Rps 8 gene are used to confirm Rps 8 -derived Phytophthora sojae resistance in germplasms. Marker assisted selection also used when introgressing Rps 8 -derived soybean Phytophthora sojae resistance into non-resistant soybean germplasm or less resistant soybean germplasms.

1 . A method for introgressing Rps8-derived  Phytophthora sojae  resistance into non-resistant or less resistant soybean germplasm comprising:
 (A) crossing at least one Rps8 soybean plant having an Rps8 gene with at least one non-resistant or less resistant soybean germplasm lacking said Rps8 gene, to form a segregating population;   (B) screening soybean from said segregating population for the presence of said Rps8 gene to determine if one or more soybean from said segregating population contains said Rps8 gene; and   (C) selecting one or more soybean from said segregating population containing said Rps8 gene,   wherein the presence of said Rps8 gene confers Rps8-derived  Phytophthora sojae  resistance to all  P. sojae  pathotypes vir1a, 1b, 1c, 1d, 1k, 2, 3a, 3b, 3c, 4, 5, 6 and 7.   
     
     
         2 . The method of  claim 1 , wherein the screening in step B comprises:
 (i) analyzing genomic DNA of soybean from said segregating population for the presence of a combination of molecular markers on major linkage group F which are associated with Rps8 locus, whereby detecting the presence of the molecular markers provides an indication that the Rps8 gene is present in the analyzed soybean; and   (ii) confirming the presence of the Rps8 gene in the analyzed soybean by inoculating the analyzed soybean with one or a combination of  P. sojae  pathotypes vir1a, 1b, 1c, 1d, 1k, 2, 3a, 3b, 3c, 4, 5, 6 or 7 to which the soybean would be susceptible if the soybean did not have Rps8-derived  P. sojae  resistance and selecting resistant soybean,   wherein the resistant soybean from said segregating population contain said Rps8 gene.   
     
     
         3 . The method of  claim 2 , wherein the molecular markers are selected from the group consisting of Satt516, Satt595, Satt114, Satt334, Sat — 317, Sat — 197, Satt510, Satt335 and Satt144. 
     
     
         4 . The method of  claim 3 , wherein the molecular markers are Satt516 and Satt114. 
     
     
         5 . The method of  claim 1 , wherein the Rps8 soybean plant of step (A) is selected from the group consisting of: PI 399073 or a descendant thereof; HFX01-602 or a descendant thereof, OX-99128 or a descendant thereof, OX-98317 or a descendant thereof, and OX-99218 or a descendant thereof. 
     
     
         6 . The method of  claim 1 , wherein the screening in step B comprises inoculating the soybean from said segregating population with one or more  P. sojae  pathotypes selected from the group consisting of pathotypes vir1a, 1b, 1c, 1d, 1k, 2, 3a, 3b, 3c, 4, 5, 6 and 7 to which the non-resistant or less resistant soybean germplasm is susceptible and selecting resistant soybean, wherein the resistant soybean from said segregating population contain said Rps8 gene. 
     
     
         7 . The method of  claim 6 , wherein the  P. sojae  pathotypes are those present in one or more  P. sojae  isolates selected from  P. sojae  race 1, race 4, race 17, race 25 or race 30. 
     
     
         8 . The method of  claim 6 , wherein the one or more  P. sojae  pathotypes have virulence to Rps3a, Rps3b, or Rps3c, but not Rps8. 
     
     
         9 . The method of  claim 1 , wherein the screening in step B comprises:
 (a) detecting in the soybean from said segregating population a first nucleic acid which is genetically linked to Rps8 locus, wherein said Rps8 locus is mapped to major linkage group F and is located between molecular markers Satt114 and Satt516; and   (b) identifying a soybean having said first nucleic acid;   (c) inoculating the identified soybean of (b) with one or a combination of  P. sojae  pathotypes vir1a, 1b, 1c, 1d, 1k, 2, 3a, 3b, 3c, 4, 5, 6 or 7 to which the identified soybean would otherwise be susceptible if the identified soybean did not have Rps8-derived  P. sojae  resistance, and selecting resistant soybean;   wherein the resistant soybean from said segregating population contain said Rps8 gene.   
     
     
         10 . The method of  claim 9 , wherein the first nucleic acid is a marker selected from the group consisting of:
 (a) Satt 114, Satt 516, Satt595, Satt334, Sat — 317, Sat — 197, Satt510, Satt335, Satt144; and   (b) a marker linked to a marker of (a).   
     
     
         11 . The method of  claim 9 , wherein detecting the first nucleic acid comprises: restriction fragment length polymorphisms (“RFLP”) analysis, single sequence repeats (“SSR”) analysis, random amplified polymorphic DNA (“RAPD”) analysis, or amplified fragment length poymorphisms (AFLPs) analysis. 
     
     
         12 . The method of  claim 1 , wherein the screening in step B comprises:
 (a) detecting a first locus on the genome of the soybean from said segregating population which is genetically linked to Rps8 locus, wherein the first locus maps to major linkage group F and is located between molecular marker Satt114 and Satt516; and selecting a soybean from said segregating population having said first locus; and   (b) determining that the soybean from said segregating population that has said first locus does not have Rps3.   
     
     
         13 . The method of  claim 12 , wherein the first locus is linked to a marker selected from the group consisting of Satt 516, Satt595, Satt334, Sat — 317, Sat — 197, Satt510, Satt335, Satt 114 and Satt144. 
     
     
         14 . The method of  claim 1 , further comprising the step of determining that the at least one Rps8 soybean plant of step (A) and the at least one non-resistant or less resistant soybean germplasm of step (A) lack Rps3. 
     
     
         15 . An Rps8 gene, wherein said Rps8 gene confers soybean resistance to all  Phytophthora sojae  pathotypes vir1a, 1b, 1c, 1d, 1k, 2, 3a, 3b, 3c, 4, 5, 6, 7, and wherein said Rps8 gene is within an Rps8 locus that maps to a region of soybean major linkage group F that is flanked by molecular marker Satt516 and a molecular marker selected from the group consisting of Satt114, Satt334, Sat — 317, Satt335, Satt510, Satt144 and Sat — 197. 
     
     
         16 . The Rps8 gene of  claim 15 , wherein the Rps8 locus maps to a region of soybean major linkage group F that is flanked by molecular marker Satt516 and Satt114. 
     
     
         17 . A method for the production of an inbred soybean cultivar adapted for conferring, in hybrid combination with a suitable second inbred, Rps8-derived resistance to  Phytophthora sojae  pathotypes vir1a, 1b, 1c, 1d, 1k, 2, 3a, 3b, 3c, 4, 5, 6 and 7, comprising:
 selecting a first donor parental line possessing the desired Rps- 8  derived  Phytophthora sojae  resistance said first donor parental line having an Rps8 gene that maps to linkage group F;   crossing the first donor parental line with a second parental line, which is high yielding in hybrid combination, to produce a segregating plant population of genetically heterogeneous plants;   screening the segregating plant population for the Rps8 gene;   selecting plants from the segregating plant population having the Rps8 gene; and   breeding by self crossing the selected plants containing the Rps8 gene until a line is obtained which is homozygous for Rps8 gene to give Rps8-derived resistance to  Phytophthora sojae  pathotypes vir1a, 1b, 1c, 1d, 1k, 2, 3a, 3b, 3c, 4, 5, 6 and 7 in hybrid combination.   
     
     
         18 . The method of  claim 17 , wherein the first donor parental line is selected from the group consisting of: PI 399073 or a descendant thereof, HFX01-602 or a descendant thereof, OX-99128 or a descendant thereof; OX-98317 or a descendant thereof; and OX-99218 or a descendant thereof. 
     
     
         19 . A soybean plant having Rps8-derived resistance to  Phytophthora sojae  produced by introgression of a soybean germplasm containing an Rps8 gene in its genome with a soybean germplasm lacking the Rps8 gene in its genome, wherein the presence of said Rps8 gene confers Rps8-derived  Phytophthora sojae  resistance to all  P. sojae  pathotypes vir1a, 1b, 1c, 1d, 1k, 2, 3a, 3b, 3c, 4, 5, 6 and 7. 
     
     
         20 . The soybean plant of  claim 19 , wherein the introgression comprises:
 (A) crossing a soybean germplasm containing an Rps8 gene in its genome with a soybean germplasm lacking the Rps8 gene in its genome, to form a segregating population;   (B) screening soybean from said segregating population for the presence of the Rps8 gene to determine if one or more soybean from said segregating population contains the Rps8 gene; and   (C) selecting one or more soybean from said segregating population containing the Rps8 gene.   
     
     
         21 . The soybean plant of  claim 20 , wherein the screening in step B comprises:
 (i) analyzing genomic DNA of soybean from said segregating population for the presence of a combination of molecular markers on major linkage group F which are associated with Rps8 locus, whereby detecting the presence of the molecular markers provides an indication that the Rps8 gene is present in the analyzed soybean; and   (ii) confirming the presence of the Rps8 gene in the analyzed soybean by inoculating the analyzed soybean with one or a combination of  P. sojae  pathotypes vir1a, 1b, 1c, 1d, 1k, 2, 3a, 3b, 3c, 4, 5, 6 or 7 to which the soybean would be susceptible if the soybean did not have Rps8-derived  P. sojae  resistance and selecting resistant soybean,   
       wherein the resistant soybean from said segregating population contain the Rps8 gene. 
     
     
         22 . The soybean plant of  claim 21 , wherein said segregating population is formed from crossing a soybean germplasm containing an Rps8 gene in its genome selected from the group consisting of: PI 399073 or a descendant thereof, HFX01-602 or a descendant thereof; OX-99128 or a descendant thereof; OX-98317 or a descendant thereof; and OX-99218 or a descendant thereof; with a soybean germplasm lacking the Rps8 gene in its genome. 
     
     
         23 . A method for producing a hybrid soybean plant line having Rps8-derived resistance to  Phytophthora sojae  pathotypes vir1a, 1b, 1c, 1d, 1k, 2, 3a, 3b, 3c, 4, 5, 6 and 7, comprising:
 identifying one or more molecular markers in an Rps8 soybean plant to be used as a donor plant, wherein the one or more molecular markers are linked to an Rps8 locus that maps to a region of linkage group F that is flanked by molecular marker Satt516 and a molecular marker selected from the group consisting of Satt114, Satt334, Sat — 317, Satt335, Satt510, Satt144 and Sat — 197; and   introgressing Rps8-derived resistance to  Phytophthora sojae  into a recipient soybean plant which is non-resistant or less resistant to one or more  P. sojae  pathotypes vir1a, 1b, 1c, 1d, 1k, 2, 3a, 3b, 3c, 4, 5, 6 and 7, by performing marker assisted selection to provide a hybrid soybean plant having Rps8-derived resistance to  Phytophthora sojae.      
     
     
         24 . The method of  claim 23 , wherein said introgressing comprises:
 providing F2 plants from a segregating F2 plant population derived from selective breeding, the selective breeding including a first cross between the donor plant and the recipient soybean plant to yield a heterozygous F1 plant population, and self-fertilizing one or more plants from the heterozygous F1 plant population to yield a segregating F2 plant population;   selecting F2 plants having the one or more molecular markers in their genome;   backcrossing the selected F2 plants with plants from the recipient soybean plant to yield backcrossed F1 generation plants, and   selecting plants from the backcrossed F1 generation plants that have the one or more molecular markers in their genome to provide the hybrid soybean plant having Rps8-derived resistance to  Phytophthora sojae.      
     
     
         25 . The method of  claim 24 , wherein the one or more molecular markers are selected from the group consisting of:
 (a) Satt 114, Satt 516, Satt595, Satt334, Sat — 317, Sat — 197, Satt510, Satt335, Satt144, and   (b) a marker linked to a marker of (a).