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Ontario Grain Farmer Magazine

Virulence of Phytophthora sojae and soybean resistance to phytophthora root rot (PRR) in Ontario

Principal Investigator

Allen Xue

Research Institution

Agriculture and Agri-Food Canada (AAFC)

External Funding Partners

Manitoba Pulse & Soybean Growers (MPSG)

Project Start

April 2012

Project End

May 2015

Objectives

  • Determine the predominant races of Phytophthora sojae in Ontario.
  • Identify sources of major gene resistance to the new and predominant races of P. sojae and sources of partial resistance (multi-gene resistance) and tolerance to PRR.
  • Develop molecular markers for the new and major resistance genes for marker assisted selection (MAS) for introduction of new resistance genes and for gene pyramiding in future soybean cultivars for Ontario.

Impact

  • The identification of Phytophthora root rot (PRR), resistance will accelerate the breeding of resistant soybean varieties for Ontario.
  • The introduction of PRR resistant soybeans will improve the production efficacy and greater economical return to producers through efficient use of pesticides used in production.

Scientific Summary

Phytophthora root rot (PRR), caused by the fungus Phytophthora sojae, is a destructive disease of soybean in Ontario. Although the improvement of PRR resistance has been one of the major priorities of soybean breeding in Ontario, the disease has become widely spread and increased in severity in central and eastern Ontario and western Quebec where most of the short-season soybean (2200-2800 HU) is grown. Several resistance genes that are commonly used in soybean breeding in Ontario are RPS1a, Rps1c, and Rps1k, which provide resistance to Race 1, the predominant P. sojae race in Ontario from 1965-1973. There has been no survey for P. sojae races in Ontario since 1990. The resistance breeding cannot be successful without knowing the pathogen race structure and population dynamic of the major races of P. sojae in the regions and effective sources of resistance to these new races. Our preliminary research demonstrates that the racial profile of the P. sojae in Ontario has changed since the last survey in the 1980s and new and more virulent races might have developed in response to the release of resistant cultivars, thus shortening the effective life-span of these cultivars. In addition, these new races of P. sojae can have virulence against resistance genes that are not currently present in soybean cultivars or breeding lines, rendering these genes ineffective even before use in a breeding program.

This project will continue a race survey initiated in 2011 to determine the predominant races of P. sojae in Ontario; to conduct greenhouse and field experiments to evaluate up to 100 soybean cultivars and germplasm released in Canada for their reactions to major P. sojae races and for partial resistance (multi-gene resistance) and tolerance under field epidemical conditions; and to conduct a crossing program between PRR resistant lines and high-yielding but susceptible cultivars in Ontario and to use marker assisted selection (MAS) techniques for introduction of new resistance genes and for gene pyramiding in future Canadian soybean cultivars.