2. FOCUS:
PSRSR and impact on soybean
The disease cycle of PSRSR
Resistance to PSRSR
Conclusion
3. 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
4. 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
5. PSRSR AND IMPACT ON SOYBEAN: symptoms
Dorrance et al, 2007
Stem rotSeedling damping
off
Root rot
Stunted growth and reduced standing
Tyler, 2007
6. Spring
Under favorable
wet high
moisture and
warm
temperature
conditions
oospores
germinate and
form mycelia
Mycelia
produce
sporangia
which
releases
zoospores
DISEASE CYCLE PHYTOPHTHORA SOJAE
Causing the Phytophthora root and stem rot
(PRSR) of Soybean
(Glycine max).
Rufus Akinrinlola PLPT
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°C
Optimum
temperature
8. RESISTANCE TO
PSRSR
R-GENE MEDIATED RESISTANCE.
ROOT RESISTANCE.
PARTIAL RESISTANCE.
Dorrance et al, 2007
9. RESISTANCE TO PSRSR
R-gene mediated resistance.
Involves 14Rps
Expressed as HR
It’s race specific
Active from germination
Wu et al, 2010; Dorrance et al, 2007
11. 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
12. RESISTANCE TO
PSRSR
Root resistance
Expressed in the root
It is quantitatively inherited
It is an incomplete resistance
It involves several genes
13. 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
15. 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.
Editor's Notes
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.]
The optimum temperature for
disease development is 25 to 30°C (77 to 86°F).
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.]
The optimum temperature for
disease development is 25 to 30°C (77 to 86°F).
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.