Pseudocercospora Leaf Spot Research Articles

First Report of Resistance to Pyraclostrobin in Pseudocercospora spp. from Blackberry (Rubus fruticosus) in Georgia, United States

Pseudocercospora leaf spot is frequently observed in blackberry production in the southeastern United States. To manage the impacts of leaf spot diseases, blackberry growers in the southeastern United States typically rely on the application of single-site fungicides, including the quinone outside inhibitors (QoIs) (FRAC 11) pyraclostrobin and azoxystrobin. In recent years, despite the regular application of chemical fungicides to manage leaf spots, blackberry growers and extension personnel in Georgia have noticed relatively poor control of these diseases. To investigate potential control failures due to fungicide resistance development, Pseudocercospora were isolated from symptomatic leaves collected from blackberry ( Rubus fruticosus) in five commercial fields in southeastern Georgia. Using a mycelial growth inhibition assay, isolates were screened for resistance to pyraclostrobin. Among the 13 isolates tested, 12 were determined to be resistant to the fungicide. Subsequent sequencing of the cytochrome b gene indicated the presence of the G143A mutation in all fungicide-resistant isolates. The identification of fungicide resistance in 12 of 13 isolates and 4 of 5 examined commercial blackberry sites in Georgia suggests that resistance to this fungicide may be prevalent among Pseudocercospora on blackberry in Georgia and that future fungicide resistance monitoring efforts in Georgia blackberry plantings may be warranted. This represents the first report of QoI fungicide resistance in Pseudocercospora spp. from blackberry.

Diagnosis of Neem Leaf Diseases Using Fuzzy-HOBINM and ANFIS Algorithms

This paper proposes an approach to detecting diseases in neem leaf that uses a Fuzzy-Higher Order Biologically Inspired Neuron Model (F-HOBINM) and adaptive neuro classifier (ANFIS). India exports USD 0.28-million worth of neem leaf to the UK, USA, UAE, and Europe in the form of dried leaves and powder, both of which help reduce diabetes-related issues, cardiovascular problems, and eye disorders. Diagnosing neem leaf disease is difficult through visual interpretation, owing to similarity in their color and texture patterns. The most common diseases include bacterial blight, Colletotrichum and Alternaria leaf spot, blight, damping-off, powdery mildew, Pseudocercospora leaf spot, leaf web blight, and seedling wilt. However, traditional color and texture algorithms fail to identify leaf diseases due to irregular lumps and surfaces, and rough ridges, as the classification time involved takes as long as a week. The proposed F-HOBINM algorithm recognizes the leaf intensity through the leaky capacitor, and uses subjective intensity and physical stimulus to interpret the diagnosis. Further, the processed leaf images from the HOBINM algorithm are applied to the ANFIS classifier to identify neem leaf diseases. The experimental results show 92.18% accuracy from a database of 1,462 neem leaves.

Evaluation of Cowpea (Vigna unguiculata) Genotypes for Fodder Yield and Resistance against Leaf Spot (Pseudocercospora cruenta)

Cowpea, Vigna unguiculata (L.), is an important grain legume grown in the tropics and constitutes a valuable source of protein in the diets of millions of people. Some abiotic and biotic stresses adversely affect its productivity. Among biotic factors, Pseudocercospora leaf spot is a widespread disease claim significant losses to the crop. Present studies consisted of two experiments, i.e., the pot experiment was carried out under glasshouse conditions and another experiment was conducted under field conditions. Eight local cowpea genotypes viz., CP-383, CP-162, CP-145, CP-271, CP-219, IT84-552, SS-92 and IT82E-715 were evaluated for yield parameters, green fodder yield and their reaction against Cercospora leaf spot disease compared with the commercially approved variety ‘Rawan 2003' for two ‘Kharif’ seasons. The lowest disease index (2.76 %) was recorded in CP-383 followed by statistically similar resistance shown by check variety, CP 2003 (4.07%) and CP-219 (4.53%). The highest susceptibility with disease index (18.32%) was exhibited by IT84-552. The genotypes differed significantly on the basis of length, thickness and branching of vines, number and size of their leaves. The accession CP-383 out-performed the other accession lines in green fodder yield during both the years and can be ranked as the best gene resources for future breeding programmes.

Evaluation of Cowpea (Vigna unguiculata) Genotypes for Fodder Yield and Resistance against Leaf Spot (Pseudocercospora cruenta)

Cowpea, Vigna unguiculata (L.), is an important grain legume grown in the tropics and constitutes a valuable source of protein in the diets of millions of people. Some abiotic and biotic stresses adversely affect its productivity. Among biotic factors, Pseudocercospora leaf spot is a widespread disease claim significant losses to the crop. Present studies consisted of two experiments, i.e., the pot experiment was carried out under glasshouse conditions and another experiment was conducted under field conditions. Eight local cowpea genotypes viz., CP-383, CP-162, CP-145, CP-271, CP-219, IT84-552, SS-92 and IT82E-715 were evaluated for yield parameters, green fodder yield and their reaction against Cercospora leaf spot disease compared with the commercially approved variety ‘Rawan 2003' for two ‘Kharif’ seasons. The lowest disease index (2.76 %) was recorded in CP-383 followed by statistically similar resistance shown by check variety, CP 2003 (4.07%) and CP-219 (4.53%). The highest susceptibility with disease index (18.32%) was exhibited by IT84-552. The genotypes differed significantly on the basis of length, thickness and branching of vines, number and size of their leaves. The accession CP-383 out-performed the other accession lines in green fodder yield during both the years and can be ranked as the best gene resources for future breeding programmes.

Identification and Characterization ofPseudocercosporaSpecies Causing Grapevine Leaf Spot in China

AbstractPseudocercosporais an important plant pathogenic genus causing leaf spots on grapevine leaves and other hosts worldwide. A survey of vineyards in four provinces of China was carried out to identify the causal agent of Pseudocercospora leaf spot. A phylogenetic analysis based on a combination ofLSU,ITSandACTloci, coupled with morphology, showed thatPseudocercospora vitisis the sole causal agent of this leaf spot disease. This study represents the first attempt to identify and characterize the cercosporoid species causing Pseudocercospora leaf spot in China using morphological and molecular approaches.

포도 캠벨얼리의 무가온 하우스재배시 지역별 갈색무늬병 발생차이

Pseudocercospora leaf spot was major disease of grape cultivar `Campbell Early` in Korea. Leaf spot first appeared in early June and rapidly dispersed to other leaves through rainy season. Disease progress of leaf spot by Pseudocercospora vitis in plastic green house, in the two provinces (Gimje and Gimcheon), were investigated in 2007. Differences of Infected leaves (%) between cultivation systems were observed in field and plastic green house, but there was no difference between provinces. Micro environmental factors, such as temperature and relative humidity, were correlated with infected leaves by PROC REG procedure of SAS (Statistical Analysis System). As a result, regression model best described ($R^2

Screening of mulberry germplasm lines against Powdery mildew, Myrothecium leaf spot and Pseudocercospora leaf spot disease complex

Fifty-six indigenous and 29 exotic mulberry varieties were screened against powdery mildew, Myrothecium leaf spot, Pseudocercospora leaf spot for a period of three years under field conditions. The percent disease index (PDI) was recorded during the peak season of the diseases. Out of 85 germplasm lines studied four-germplasm lines viz. Thailand lobed (0.43), M. multicaulis (2.63), Italian (2.83) and M. australis (4.56) were found highly resistant; nine lines were resistant; 43 lines were moderately resistant and 29 were susceptible to the disease complex. Powdery mildew showed significant positive correlation with Pseudocercospora leaf spot. Highly resistant varieties may be utilized for future disease resistance breeding programme to evolve multiple disease resistant mulberry varieties.

A Comparative Study Between Detached Leaf and Plastic Growth Pouches Techniques on the Infection of Pseudocercospora Leaf Spot Disease of Cowpea Cultivars (Vigna unguiculata L. Walp) in Northeast Thailand

This glasshouse experiment was carried out in the 2004 at the Department of Agricultural Production, Faculty of Technology, Mahasarakham University, Mahasarakham 4400, Northeast Thailand to compare amounts of infection of Pseudocercospora leaf spot disease in leaves of cowpea cultivars being screened between detached leaf and plastic growth pouches techniques. The experiment was laid in a factorial arranged in a Randomized Complete Block Design (RCBD) with four replications. KVC7, IT81D-1228-14-1 and KKU25 cowpea cultivars were used as factor A, detached leaf and plastic growth pouches techniques were used as factor B and four levels of the concentrations of the spores of the disease, i.e., 0, l x 10(4), 5 x 10(4) and 1 x 10(5) of disease forming units mL(-1) of distilled water were used as factor C. The results showed that KVC7 and IT81D-1228-14-1 cultivars possessed immune and high resistant properties against the disease, respectively, whereas KKU25 cultivar ranked as a susceptible cultivar. Detached leaf technique gave higher amount of infection of the disease than plastic growth pouches technique and the differences were highly significant. A plentiful amount of Infected disease was attained with an inoculation rate of l x 10(5) forming units mL(-1) of distilled water, which was considered too high and the most appropriate concentrations for use lie on both concentrations, i.e., 1 x 10(4) and 5 x 10(4) forming units mL(-1) of distilled water. An interaction among factors AxBxC was severely found with KKU25 cultivar, particularly on day 28 after inoculation, whilst other two cultivars gave a minute amount of disease incidences (%) where detached leaf technique gave much higher disease incidences than plastic growth pouches technique, thus detached leaf technique should be of higher advantages.

Inheritance characteristics of F1 and F2 offsprings obtained from full diallele crosses of five cowpea cultivars (Vigna unguiculata L. Walp) against pseudocercospora leaf spot disease.

The experiment was carried out at the Experimental Farm, Department of Agricultural Technology, Mahasarakham University, Mahasarakham Province in the 2005 (February to April) for F1 offsprings and also at the Experimental Farm, Khon Kaen University, Khon Kaen Province, Northeast Thailand for F2 offsprings (July to October), i.e., four experiments were carried out, each location had two experiments. The research aimed to investigate inheritance characteristics of F1 and F2 offsprings derived from full diallele crosses of five cowpea cultivars (20 pairs of crosses) against a pathogenic disease of Pseudocercospora cruenta (Sacc,) Deighton. The first two experiments were carried out under field and glasshouse conditions at Mahasarakham University for F1 offsprings and the other two experiments were carried out at Khon Kaen University for F2 offsprings. A Chi square test method was used to justify dominant genes on the infection of the disease. The results showed that the cowpea plants of F1 and F2 offsprings gave only one pair of dominant gene that had its complete dominant effect over recessive gene of the cowpea offsprings.

An Evaluation on Intensity of Infection of Pseudocercospora Leaf Spot Disease of Cowpea Cultivars (Vigna unguiculata L. Walp), With Respect to Infector Rows, Dates of Inoculation and Cultivars, Grown Under Field Conditions in Northeast Thailand

This investigation was carried out at the Experimental Farm, Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand to evaluate intensity of infection of Pseudocercospora Leaf Spot disease of cowpea cultivars, grown under field conditions with the use of Yasothon soil series (Oxic Paleustults). The experimental design used was a strip split plot design with four replications. The experiment consisted of three factors, i.e., with and without infector rows (Factor A), with and without inoculation and inoculated dates, i.e. none inoculation, inoculated at days 15 and 30 after sowing of seeds in main plots (Factor B) and three cowpea cultivars of KVC7, KKU25 and IT81D-1228-14-1 (Factor C). The results showed that the use of infector rows of cowpea plants (KKU25) being sown at 15 days before sowing seeds of cowpea cultivars in main plots gave a similar intensity of disease as those infector rows being sown at 30 days before sowing seeds of cowpea cultivars in main plots but significantly higher than without infector rows. Pathogenic disease being inoculated to the cowpea plants at 15 days after the sowing of seeds in main plots gave significantly higher intensity of disease than none inoculation. The establishment of infector rows at 15 days ahead of the sowing of seeds in main plots together with an inoculation of the disease at 15 days after the sowing of seeds in main plots gave the best results in evaluating amount of the infected disease. Thus infector rows surrounded the main plots are required whenever trials on disease evaluation are taken place.