effect of watering regime and soil temperature on ... · 9-17°c wale, 2005 12-16°c carnegie et...
TRANSCRIPT
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EFFECT OF WATERING REGIME AND SOIL
TEMPERATURE ON INFECTION OF POTATO
ROOTS BY SPONGOSPORA SUBTERRANEA F.
SP. SUBTERRANEA
Chris Slabbert, Jacquie van der Waals
Department of Plant and Soil Sciences,
University of Pretoria
Potato Pathology Programme @ UP
INTRODUCTION
Soil-borne inoculum important, but environmental factors are most important in determining final disease intensity
Soil temperature (?)
Soil moisture – very important for motility of
zoospores
IMPORTANT TEMPERATURES FOR INFECTION OF POTATOES BY SPONGOSPORA SUBTERRANEA F. SP. SUBTERRANEA
Minimum temp.
Optimal temp.
Maximum temp.
≈9⁰C 12-16⁰C ≈25⁰C
Temperature Reference
Optimal temperature 14-20°C Kole, 1954
12-13°C Hims, 1976
>20°C Hughes, 1980
12.5°C de Boer et al., 1985
12°C van de Graaf et al., 2005
9-17°C Wale, 2005
12-16°C Carnegie et al., 2010
16-17°C (root hairs) Kole, 1954
17°C (root gall formation) van de Graaf, et al., 2007
Maximum temperature 22-25°C Kole, 1954
Minimum temperature <11°C Kole, 1954
9°C van de Graaf et al., 2005
12°C (root galls) Van de Graaf, et al., 2007
IRRIGATION MANAGEMENT
Most important environmental factor for infection is free soil moisture
Avoid over-irrigation or water logging during tuber initiation
M. Steyn M. Steyn
SIGNIFICANCE OF PROPOSED PROJECT
Powdery scab previously considered disease of cool, wet climates
FOUND IN MOST POTATO GROWING REGIONS IN SOUTH AFRICA
Cannot extrapolate data from elsewhere to SA
Is the pathogen is able to adapt to prevailing environmental conditions?
Imperative to conduct studies in South Africa, with South African Sss samples
Collection of
infected tubers
Inoculum
preparation
Inoculate soil (CRD)
Control pots uninoculated
Plant with mini-tubers of
susceptible cultivar
Incubate at
10, 15, 20,
25 and
30˚C
Wilting point,
saturation point and
fluctuating water
content
Sample roots two
weeks after
emergence
DNA Extraction
Microscopy
Spongospora subterranea f. sp. subterranea DNA in the roots of potato plants grown at different
temperatures, samples taken 14 days after inoculation.
Spongospora subterranea f. sp. subterranea DNA in the roots of potato plants grown at
saturation point, samples taken 2-12 days after inoculation.
Spongospora subterranea f. sp. subterranea DNA in the roots of potato plants grown at field
capacity, samples taken 2-12 days after inoculation.
Spongospora subterranea f. sp. subterranea DNA in the roots of potato plants grown at
fluctuating soil moisture, between field capacity and soil saturation, samples taken 2-12
days after inoculation.
Field capacity Fluctuating wilting point Saturation point
DAP Incidence
DNA
Quantity
(pg/µl) DAP Incidence
DNA
Quantity
(pg/µl) DAP Incidence
Quantity
(pg/µl)
2 0% 0,0000 2 0% 0,0000 2 50% 0,0028
4 50% 0,0033 4 0% 0,0000 4 50% 0,0077
6 0% 0,0000 6 100% 0,0068 6 100% 0,2965
8 100% 0,0034 8 50% 0,0102 8 100% 0,0071
10 50% 0,6109 10 50% 0,0011 10 100% 0,0191
12 50% 0,0051 12 100% 0,9314 12 100% 0,0039
Optimal temperature and soil
moisture for root infection
Temperature:
• Most infection at 15⁰C, then 20⁰C (literature: 17⁰C)
• Least root infection: 30⁰C < 25⁰C < 10⁰C
Soil moisture:
• Earliest and greatest infection at Saturation point > Fluctuating soil moisture > Field capacity
• Applications: • Choose planting date so that temperatures during initial root development are >20⁰C
• Use irrigation scheduling – allow soil moisture content to fluctuate
IMPORTANCE FOR INDUSTRY
Knowledge of conditions favourable for disease development = integral part of risk assessment
Ultimate goal: Better disease management and more sustainable potato production