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A survey of sorghum downy mildew in sorghum in the Sudano-Sahelian Savanna zones of Nigeria
AS Kutama, BS Aliyu, AM Emechebe
Bayero Journal of Pure and Applied Sciences , 2009,
Abstract: An extensive survey was conducted across the 13 states constituting the Sudan and Sahel savanna agro-ecological zones of Nigeria to determine the occurrence and distribution of sorghum downy mildew in sorghum during the 2008 growing season. The survey was conducted at two different stages of the crop development; seedling and dough stage. The first survey was in early July while the second was carried out in late September. Three farmers’ fields were critically investigated at every stop on a road system. During the first survey, a total of 97 farmers’ fields in 36 locations were investigated while 110 sorghum fields in 37 locations were visited in the second survey. Average incidence (%) of the disease was obtained from a sample of 100 plants selected using simple random sampling technique from each of the three farms visited per stop. Results of the survey (16.20 and 9.64% and 3.28 and 1.16% during the first and second visits in the Sudan and Sahel savanna AEZs respectively) indicated that the disease was present only at the seedling stage and virtually absent at flowering stage .In the areas where it was noticed at the juvenile stage the incidence was more prevalent in the Sudan than in the sahel savanna regions. The results also revealed that there was a relationship between soil type (which was mostly sandy loam) and disease incidence. Disease incidence was relatively higher on sandy loam soil than other soil types. The prevalence was generally low, but efforts should be made towards controlling the spread of the disease further. Farmers should be advised to use improved cultural practices like early sowing, seed dressing with the sole aim of reducing the disease.
Reaction of Pearl Millet Infected with Downy Mildew (Sclerospora Graminicola (Sacc.) Schroet) Intercropped Cowpea with on Days to 50% Heading and Grain Yield in the Savanna Zone of Northern Nigeria
AG Gaya, SA Adebitan, AU Gurama
Bayero Journal of Pure and Applied Sciences , 2012,
Abstract: Field trials were carried out at the Teaching and Research farm of Kano University of Science and Technology Wudil with three pearl millet varieties in 2003, 2004 and 2005 rainy seasons to find out the reaction of cowpea intercropped with pearl millet infected with downy mildew on days to 50% heading and grain yield. The experiment was a 3 x 2 factorial in randomized blocks of six plots with three pearl millet varieties (LCIC 9702, Ex-Borno and Zango) and each variety was intercropped with a cowpea and planted sole making six treatments. Data collected on days to 50% heading and grain yield were subjected to T-test for the separation of means of sole and intercropped to bring out the differences between them at 1% and 5% levels of significance. Results showed that intercropped LCIC pearl millet variety had significantly (P≤0.05) more days to 50% heading than other varieties either planted sole or intercropped in 2004. Similarly, from the combined result, it showed that intercropped LCIC pearl millet variety had significantly (P≤0.05) more days to 50% heading than other varieties either solely planted or intercropped. Maximum grain yield was however obtained from sole Zango and intercropped LCIC 9702 pearl millet varieties. Combined result shows only intercropped LCIC 9702 had significantly (P≤0.05) maximum grain yield than other pearl millet varieties. It is imperative to grow sole LCIC 9702 pearl millet variety than intercropped with cowpea for less number of days to 50% heading. But for maximum grain yield, it is advisable to grow sole Zango and intercrop LCIC 9702 with cowpea.
Diagrammatic scale to assess downy mildew severity in melon
Michereff, Sami J;Noronha, Mariss?nia A;Lima, Gaus SA;Albert, ígor CL;Melo, Edilaine A;Gusm?o, Luciana O;
Horticultura Brasileira , 2009, DOI: 10.1590/S0102-05362009000100015
Abstract: the downy mildew, caused by pseudoperonospora cubensis, is an important melon disease in northeast brazil. considering the lack of standard methods for its assessment, a diagrammatic scale was developed with 2, 4, 8, 16, 32, 64, 82, and 96% of affected leaf area. the scale was then checked for its accuracy, precision, and reproducibility in estimating downy mildew severity. the diagrammatic scale was validated by eight disease raters; using 50 leaves with different severity levels, previously measured using the software assess?. two evaluations were performed on the same set of leaves, but in a different sequence order, by the same raters, within a 15-day interval. the accuracy and precision of each rater was determined by simple linear regression between the actual and the estimated severity. the scale provided good levels of accuracy (means of 87.5%) and excellent levels of precision (means of 94%), with absolute errors concentrated around 10%. raters showed great repeatability (means of 94%) and reproducibility (>90% in 90.3% of cases) of estimates. therefore, we could conclude that the diagrammatic scale presented here was suitable for evaluating downy mildew severity in melon.
Influence of Host Management on Downy Mildew Control in Onion
Shabeer Ahmad,Hakim Khan
Pakistan Journal of Biological Sciences , 2001,
Abstract: The interactive effect of three different levels of NPK fertilizer, plant population and irrigation was studied on downy mildew severity and yield of onion. The lowest disease severity was recorded in treatment where NPK 120:90:60 kg/ha, coupled with plant population 0.5 million/ha and eight irrigations. In this treatment the yield and bulb size were also the highest. However, number of bulbs was lower than some other treatments indicating the non-significant effect of disease
Effect of Fungicide Synergy on Downy Mildew Control in Onions  [PDF]
Shabeer Ahmad,Hakim Khan
Pakistan Journal of Biological Sciences , 2000,
Abstract: The synergistic effect of four different fungicides was studied on severity of onion downy mildew under natural field conditions during 1998-99. Area Under Disease Progress Curve (AUDPC) was the highest in treatment where no fungicide was applied. However, it was the lowest in Dithan M-45 + Ridomil. In this treatment bulb yield, bulb size and number of bulbs were also the highest, indicating that fungicide application reduced the disease severity and stabilized onion productivity.
Weather based forecasting model for incidence of downy mildew of pearl millet in Coimbatore  [cached]
Indian Phytopathology , 2011,
Abstract: Analysis of simple correlation and multiple correlation and regression between the incidence of downy mildew in pearl millet and weather factors like rainfall (avg.55.3mm) and minimum temperature (avg.21.45° C) showed positive correlation to the development of downy mildew incidence one week before diseases incidence compared to other weather parameters. The prevalence of rainfall (avg. 45.30mm) and minimum air temperature (avg.20.832C) during the vegetative phase (30 days after sowing) suggested maximum incidence of downy mildew at Coimbatore. One unit increase of independent variables like temperature (min.) and rainfall increases downy mildew incidence to 0.41 and 0.48 per cent and 9.14 and 0.32 per cent at 30DAS respectively.
Chinese sorghum germplasm evaluated for resistance to downy mildew and anthracnose
Louis K. Prom,John E. Erpelding,Noe Montes-Garcia
Communications in Biometry and Crop Science , 2007,
Abstract: Forty Chinese sorghum [Sorghum bicolor (L.) Moench] accessions maintained by the USDA-ARS, Plant Genetic Resources Conservation Unit, Griffin, Georgia were evaluated for multiple disease resistance. The level of sorghum downy mildew (SDM) infection with systemic infection and local lesion development for infected plants was low to very high. Accessions PI511832, PI563519, PI563521, PI563850, PI610677 and P 610724 were the most resistant to sorghum downy mildew, whereas PI610692 and PI610720 were the most susceptible SDM. Thirty-three of the 40 sorghum accessions tested were susceptible to anthracnose. Four accessions, PI430471, PI563905, PI563924 and PI563960, were uniformly resistant to anthracnose. No sorghum accession exhibited resistance to both downy mildew and anthracnose. Because resistance was observed for anthracnose or downy mildew within the subset of the Chinese germplasm collection, additional screening of the collection could help identify accessions conferring resistance to multiple diseases to enhance sorghum improvement
Studies on pathogenicity in Plasmopara halstedii (sunflower downy mildew)  [PDF]
Nachaat Sakr
International Journal of Life Sciences , 2010, DOI: 10.3126/ijls.v4i0.3481
Abstract: Studies on morphological and genetic variabilities as well as alterations in pathogenicity were carried out in Plasmopara halstedii (sunflower downy mildew) isolates of several races. Aggressiveness was analyzed in one sunflower inbred line showing a high level of quantitative resistance. Viability analyses were performed on oval and spheric zoosporangia. Genetic relationships were detected between the pathogen isolates using 12 EST-derived markers. There were significant differences between pathogen isolates for aggressiveness criteria. Based on virulence and aggressiveness reaction for P. halstedii to D3 line of sunflower, there were two groups as more aggressive and less virulent isolates of 100 and 3xx races, and less aggressive and more virulent isolates of 7xx races. The oval zoosporangia for more aggressive isolates of races 100 and 3xx produced more zoospores than the oval ones for less aggressive isolates of races 7xx. The isolates of races 714, 704 and 314 had an intermediary genetic position between the two isolates of races 100 and 710. It is concluded that the relationship between aggressiveness and oval zoosporangia viability may be established in P. halstedii . No correlation was detected between pathogenicity traits and EST genotypes. Key words: aggressiveness; D3 line of sunflower; EST-derived markers; oval zoosporangia; spheric zoosporangia; virulence DOI: 10.3126/ijls.v4i0.3481 International Journal of Life Sciences Vol.4 2010 pp.48-59
Effect of Intercropping Bulb Onion and Vegetables on Purple Blotch and Downy Mildew
R.D. Narla,J.W. Muthomi,S.M. Gachu,J.H. Nderitu
Journal of Biological Sciences , 2011,
Abstract: Field experiments were conducted over two growing seasons to determine the effectiveness of vegetable intercrops in the management of downy mildew (Peronospora destrutor) and purple blotch (Alternaria porri) of bulb onion. Vegetable intercrops evaluated, were carrot (Daucus carota), spider plant (Cleome gynandra) and French bean (Phaseolus vulgarisHowever, further studies are necessary to determine the optimal spatial arrangements of onion and vegetable intercrops in foliar disease management.
Control of Downy Mildew on Protected Cucumber Plants With Film Forming Antitranspirants
Wafaa M. Haggag
Journal of Biological Sciences , 2002,
Abstract: Downy mildew in cucumber plants, caused by Pseudoperonospora cubensis, was reduced by foliar spraying of antitranspirants film Kaolin nu-film, bio-film, folicote and Polyacrylamide Anti-Stress 550. In greenhouse test, antitranpirants proved to be effective treatments in reducing disease incidence, severity and pathogen sporulation when applied prior or post to inoculation. Among these compounds, Kaolin and Nu-Film (1.0 %) were more effective in reducing spores counts, germination and infection as well as downy infected area and lesions number. Scanning electron microscope examination showed that, Kaolin antitranspirant inhibited zoospores germination, growth and development as well as had become collapsed and lost its turgidity when applied either pre or post inoculation. Although, spraying of Bio-Film and Polyacrylamide Anti-Stress 550 antitranspirants, at 1 and 3%, resulted also in better disease control. Under protected cultivation and natural infection conditions, all antitranspirants showed a remarkable effectiveness on the reduction of disease severity and pathogen density when applied twice at 45 and 75 days after sowing in cucumber leaves. Furthermore, all tested antitranspirants, significantly increased the cucumber plant height and yield. Kaolin strongly protected cucumber against downy mildew and yield increased. Conclusively, antitranspirants film can be used as effective treatments for the control of downy mildew disease in cucumber plants under plastic houses.
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