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Characterization and management of g...

Stewart, Silvina.

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Characterization and management of genetic diversity in Phytophthora sojae populations.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Characterization and management of genetic diversity in Phytophthora sojae populations./
Author:	Stewart, Silvina.
Description:	153 p.
Notes:	Source: Dissertation Abstracts International, Volume: 72-09, Section: B, page: .
Contained By:	Dissertation Abstracts International72-09B.
Subject:	Agriculture, Plant Culture. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3458373
ISBN:	9781124702124

Characterization and management of genetic diversity in Phytophthora sojae populations.
Stewart, Silvina.

Characterization and management of genetic diversity in Phytophthora sojae populations. - 153 p.

Source: Dissertation Abstracts International, Volume: 72-09, Section: B, page: .

Thesis (Ph.D.)--Iowa State University, 2011.

Phytophthora root and stem rot (PRR) of soybean, caused by Phytophthora sojae, has been managed traditionally through breeding for resistance. Breeding efforts have focused on incorporating major Rps gene resistance into soybean lines but the pathogen is rapidly and continuously evolving, the complexity of pathotypes is increasing, and the durability of the Rps in the field is short.

ISBN: 9781124702124Subjects--Topical Terms:

1018669
Agriculture, Plant Culture.

Characterization and management of genetic diversity in Phytophthora sojae populations.
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020 $a 9781124702124
035 $a (UMI)AAI3458373
035 $a AAI3458373
040 $a UMI $c UMI
100 1 $a Stewart, Silvina. $3 1684977
245 1 0 $a Characterization and management of genetic diversity in Phytophthora sojae populations.
300 $a 153 p.
500 $a Source: Dissertation Abstracts International, Volume: 72-09, Section: B, page: .
500 $a Adviser: Alison E. Robertson.
502 $a Thesis (Ph.D.)--Iowa State University, 2011.
520 $a Phytophthora root and stem rot (PRR) of soybean, caused by Phytophthora sojae, has been managed traditionally through breeding for resistance. Breeding efforts have focused on incorporating major Rps gene resistance into soybean lines but the pathogen is rapidly and continuously evolving, the complexity of pathotypes is increasing, and the durability of the Rps in the field is short.
520 $a It has been suggested that a large reservoir of genetic diversity exists in populations of P. sojae, however, only a few studies have tried to characterize this diversity using genetic markers. In this study, we assessed diversity of P. sojae in Iowa using microsatellite (SSR) markers (Objective 1). Forty MGLs (multilocus SSR genotypes) and 19 pathotypes were found, with a genotypic and pathotype diversity (D) of 0.96 and 0.86, respectively. Low observed heterozygosity (Ho= 0.027) and a high inbreeding coefficient (F=0.944) were found as expected in this homothallic species. Data suggest that multiple pathotypes and genotypes of P. sojae may infect a single plant in the field. Furthermore, at least one of the seven populations of P. sojae recovered from a commercial soybean field showed some level of outcrossing.
520 $a It has also been hypothesized that the deployment of specific resistant genes result in changes in the pathotype structure of the P. sojae populations. An alternative way to prolong the life of a resistance gene in the field is to generate disruptive selection by rotating major resistant genes through time and space. To test this hypothesis, we monitored pathotype and genetic shifts in P. sojae populations in a four year soybean cultivar rotation (Objective 2). We recovered new pathotypes and MGLs from rotation treatments at the second sampling date, indicating P. sojae has the ability to evolve quickly. We found cultivar rotation affected the genetic structure of the P. sojae population, but pathotype shift was not a function of cultivar rotation.
520 $a A third strategy used to control PRR is through the use of partial resistance (PR), which allows the host to tolerate infection by P. sojae better when compared to a fully susceptible host. PR is also effective against all physiological races of the pathogen. Thus, tolerance should be more stable than single-gene resistance because of lack of selection pressure imposed on the pathogen. Few cultivars with high levels of PR are currently available, because this type of resistance is polygenic, and thus harder to recognize and introgress in a good agronomical type. Our goal was to develop an easier and more objective method that could be used by soybean breeders to screen for PR (Objective 3). The inoculation method we propose uses rice infested with P. sojae as an inoculum source and the evaluation is done by dry root weight instead of the customary 1--10 scale used in the standard layer test. For the variables evaluated, the rice method did not differ statistically from the layer test, and it has the advantage that it is cheaper, set up is less time consuming, and more than one pathotype can be used in a single test ensuring that no Rps gene masks the partial resistance while screening. The six soybean cultivars used in the study ranked as expected for PR based on the published information and on the information supplied by company. Partial resistance ratings were negatively and significantly correlated to corrected dry root weight (r= -0.975, P < 0.0001).
590 $a School code: 0097.
650 4 $a Agriculture, Plant Culture. $3 1018669
650 4 $a Agriculture, Plant Pathology. $3 1028950
690 $a 0479
690 $a 0480
710 2 $a Iowa State University. $b Plant Pathology. $3 1272632
773 0 $t Dissertation Abstracts International $g 72-09B.
790 1 0 $a Robertson, Alison E., $e advisor
790 1 0 $a Harrington, Thomas $e committee member
790 1 0 $a Cianzio, Silvia $e committee member
790 1 0 $a Braum, Edward $e committee member
790 1 0 $a Yang, Xiao-Bing $e committee member
790 $a 0097
791 $a Ph.D.
792 $a 2011
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3458373