RESISTANCE AGAINST PHYTOPHTHORA ROOT AND STEM

(PSRSR) ROT OF SOYBEAN

RUFUS AKINRINLOLA

FOCUS:

PSRSR and impact on soybean The disease cycle of PSRSR Resistance to PSRSR Conclusion

PSRSR AND IMPACT ON SOYBEAN

Phytophthora soybean root and stem rot (PSRSR)

PSRSR is caused by Phytophthora sojae

First discovered in 1948 Indiana

PSRSR is a soilborne disease

Affects all stages of growth

Optimum temperature: 25-30°C

Favored by high humidity and rainfall

Dorrance et al, 2007

PSRSR AND IMPACT ON SOYBEAN

Impacts on soybean PSRSR could attack all soybean parts PSRSR causes seed rot, seedling damping off, root and stem

rot.

Causes stunted growth and reduced standing

Yield loss may be up to 50%

PSRSR could wipe out susceptible varieties

PSRSR destroys upto 300 000acres of soybean in Ohio (1970s)

Worldwide annual loss close to $2 billion (Tyler, 2007) Dorrance et al, 2007

PSRSR AND IMPACT ON SOYBEAN: symptoms

Dorrance et al, 2007

Stem rotSeedling damping off

Root rot

Stunted growth and reduced standing

Tyler, 2007

Spring Under favorable wet high moisture and warm temperature conditions oospores germinate and form mycelia

Mycelia produce sporangia which releases zoospores

DISEASE CYCLE PHYTOPHTHORA SOJAECausing the Phytophthora root and stem rot

(PRSR) of Soybean (Glycine max).

Rufus Akinrinlola PLPT 802

Dead infected plants residues remain in the soil and overwinter for the next growing season

Wind and rain splash spread sporangia and other infective propagules from infected plant to initiate secondary infection in uninfected susceptible host

Secondary inoculum source

Summer

Fall

Oospores overwinter in soil and debris during hatch conditions

Oogonium form by sexual crossing of hypha and produces the survival oospores in the soil

Winter

Zoospores swim towards root exudates of young soybean root tips initiating primary infection

Attachment, encystment and penetration on zoospores into root surface induce root rot and hyphal colonization of the stem induces stem rot

Hyphal tips of Mycelia can also colonize root tips and induce infection

25 - 30°COptimum temperature

Plant description

polycyclic

RESISTANCE TO PSRSR

R-GENE MEDIATED RESISTANCE.

ROOT RESISTANCE.

PARTIAL RESISTANCE.

Dorrance et al, 2007

RESISTANCE TO PSRSR

R-gene mediated resistance.

Involves 14Rps

Expressed as HR

It’s race specific

Active from germinationWu et al, 2010; Dorrance et al, 2007

RESISTANCE TO PSRSR: R-gene mediated resistance

RESISTANCE TO PSRSR

Partial resistance.

Race non-specific/horizontal tolerance

It’s stable and heritable

It’s a multi-genic trait

Limits lesion expansion

Limits severity of root rot

Limits yields losses Dorrance et al, 2007; Wu et al, 2010

RESISTANCE TO PSRSR

Root resistance

Expressed in the root

It is quantitatively inherited

It is an incomplete resistance

It involves several genes

CONCLUSION

Phytophthora soybean root and stem rot is a major soilborne disease of soybean

Annual losses due to the disease worth $2billion

It affects all parts of soybean

The disease is polycyclic in cycle and mostly initiated by zoospores

It’s majorly controlled through resistant varieties

R-gene resistance, partial and root resistance are the major resistance

Commination of both partial and R-gene mediated resistance gives the best protection

QUESTIONS ?

REFERENCES Dorrance, A. E., Robertson, A. E., Cianzo, S., Giesler, L. J., Grau, C. R., Draper, M. A., ... & Anderson, T.

R. (2009). Integrated management strategies for Phytophthora sojae combining host resistance and seed treatments. Plant Disease, 93(9), 875-882.

Dorrance, A. E., Mills, D., Robertson, A. E., Draper, M. A., Giesler, L., & Tenuta, A. (2007). Phytophthora root and stem rot of soybean. The Plant Health Instructor, 1.

Tyler, B. M. (2007). Phytophthora sojae: root rot pathogen of soybean and model oomycete. Molecular plant pathology, 8(1), 1-8.

Wu, X. L., Zhao, J. M., Sun, S., Yang, F., Wang, Y. C., Gai, J. Y., & Xing, H. (2010). A survey of soybean germplasm for resistance to Phytophthora sojae. Euphytica, 176(2), 261-268.