Factors influencing the infectivity of oospores of Peronosclerospora sorghi (Weston & Uppal) C.G. Shaw /
| Main Author: | |
|---|---|
| Other Authors: | , , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1980.
|
| Subjects: | |
| Online Access: | Link to ProQuest copy Link to OAKTrust copy ProQuest, Abstract |
| Abstract: | The effect of soil moisture, soil temperature and soil pH on sorghum downy mildew (SDM) disease incidence (DI) was evaluated. In the field, when sorghum and maize hosts were planted at different dates during the cropping season, sorghum had a high DI at the beginning of the planting season followed by a sharp decrease at later planting dates. Maize responded differently. There was an increase in DI each successive planting date. Soil environments prevailing within a period of one week subsequent to planting were very crucial for the initiation of infection. The highest rate of infection for a susceptible sorghum cultivar was reached at soil temperatures of 19.5 ± 3C and a soil matric water potential of around -0.7 bars during this period. For susceptible maize, the optimum infection rate was obtained at 25 ± 3.5C and with a soil matric water potential of around -0.7 bars. In the greenhouse, when different matric water potentials and soil temperature regimes were used, the optimum infection rate occurred at approximately -0.7 bars and at a temperature of 25 ± 3C and 30 ± 3C for sorghum and maize, respectively. DI was drastically suppressed at the matric water potential of -0.3 and -0.1 bars corresponding to the soil water field capacity and soil saturation. The pH did not appear to constitute a critical factor. In the field , there was no change of soil pH at different dates of sowing. In the greenhouse, infection occurred on seedlings growing in soil within a pH range of 5.5 to 8.3. Soil with different textural composition were artificially infested with a uniform oospore population of Peronosclerospora sorghi in the greenhouse. Data show that DI was correlated (r=+0.790) with the soil bulk density. But an even higher significant (P=0.01) correlation (r = +0.889) existed when sand particle content of soils were plotted against DI. When the effect of predetermined oospore density and soil dilution on SDM incidence was investigated, the DI was greatest at 1:2 soil-sand mixture (v/v) artificially infested with 80 oospores per gram of the mixture. In the field, the DI of sorghum and maize cultivars planted on high and low inoculum density plots was more a reflection of the time of seeding rather than the amount of inoculum present... |
|---|---|
| Item Description: | "Major subject: Plant Pathology." Typescript (photocopy). Vita. |
| Physical Description: | xiii, 93 leaves : illustrations, graphs ; 29 cm |
| Bibliography: | Includes bibliographical references (leaves 84-92). |