Incidence Of Cercospora Leaf Spot Research Articles

Survey of the disease incidence of Cercospora leaf spot of mungbean [Vigna radiata (L.) Wilezek] in Eastern Uttar Pradesh

Survey of the disease incidence of Cercospora leaf spot of mungbean [Vigna radiata (L.) Wilezek] in Eastern Uttar Pradesh

The Multilateral Efficacy of Chitosan and Trichoderma on Sugar Beet

The majority of all fungal formulations contain Trichoderma spp., making them effective biological control agents for agriculture. Chitosan, one of the most effective natural biopolymers, was also reported as a plant resistance enhancer and as a biocide against a variety of plant pathogens. An in vitro three-way interaction assay of T. atroviride, chitosan, and important plant pathogens (such as Cercospora beticola and Fusarium oxysporum) revealed a synergistic effect on fungistasis. Furthermore, chitosan coating on Beta vulgaris ssp. vulgaris seeds positively affected the onset and efficiency of germination. We show that priming with T. atroviride spores or chitosan leads to the induced expression of a pathogenesis-related gene (PR-3), but only supplementation of chitosan led to significant upregulation of phytoalexin synthesis (PAL) and oxidative stress-related genes (GST) as a defense response. Repeated foliar application of either agent promoted growth, triggered defense reactions, and reduced incidence of Cercospora leaf spot (CLS) disease in B. vulgaris. Our data suggest that both agents are excellent candidates to replace or assist common fungicides in use. Chitosan triggered the systemic resistance and had a biocidal effect, while T. atroviride mainly induced stress-related defense genes in B. vulgaris. We assume that both agents act synergistically across different signaling pathways, which could be of high relevance for their combinatorial and thus beneficial application on field.

Development of a Sequential Sampling Plan using Spatial Attributes of Cercospora Leaf Spot Epidemics of Table Beet in New York

Sampling strategies that effectively assess disease intensity in the field are important to underpin management decisions. To develop a sequential sampling plan for the incidence of Cercospora leaf spot (CLS), caused by Cercospora beticola, 31 table beet fields were assessed in the state of New York. Assessments of CLS incidence were performed in six leaves arbitrarily selected in 51 sampling locations along each of three to six linear transects per field. Spatial pattern analyses were performed, and results were used to develop sequential sampling estimation and classification models. CLS incidence (p) ranged from 0.13 to 0.92 with a median of 0.31, and beta-binomial distribution, which is reflective of aggregation, best described the spatial patterns observed. Aggregation was commonly detected (>95%) by methods using the point-process approach, runs analyses, and autocorrelation up to the fourth spatial lag. For Spatial Analysis by Distance Indices, or SADIE, 45% of the datasets were classified as a random pattern. In the sequential sampling estimation and classification models, disease units are sampled until a prespecified target is achieved. For estimation, the goal was sampling CLS incidence with a preselected coefficient of variation (C). Achieving the C = 0.1 was challenging with <51 sampling units, and only observed on datasets with incidence >0.3. Reducing the level of precision, i.e., increasing C to 0.2, allowed the preselected C to be achieved with a lower number of sampling units and with an estimated incidence ([Formula: see text]) close to the true value of p. For classification, the goal was to classify the datasets above or below prespecified thresholds (pt) used for CLS management. The average sample number, or ASN, was determined by Monte Carlo simulations, and was between 20 and 45 at disease incidence values close to pt, and approximately 11 when far from pt. Correct decisions occurred in >76% of the validation datasets. Results indicated these sequential sampling plans can be used to effectively assess CLS incidence in table beet fields.

Effect of Planting Date on Disease Occurrence and Yield of Three Peanut Varieties

Three on-farm verification trials focusing on the different planting dates against major peanut diseases was conducted. The study generally aimed to determine the disease reaction of three peanut varieties namely, Farmers’ variety, NSIC Pn18 and NSIC Pn15 against Cercospora leaf spot (CLS) and rust and determine their potential yield and its productivity using various planting dates (October, November and December). Regardless of variety, the highest disease incidence of CLS and rust was obtained in the month of October while the lowest infection of CLS and rust was obtained from the month of December. The highest yield of Farmers’ variety, NSIC Pn 18 and NSIC Pn15 were obtained when plants were planted during the month of October despite the fact that during this time there was a high incidence of CLS and rust. Among the varieties used, the NSIC Pn 15 consistently and significantly produced the highest yield when grown from October to December. In addition, at least 27.6% yield increase in NSIC Pn 15 was obtained when planted between October to December while a yield increase up to 22% was achieved when NSIC Pn18 was used.

Defense Gene Expression of Vigna radiata (L.) Wilczek., against Cercospora Leaf Spots (CLS)

Most cultivars of Vigna radiata (L) Wilczek grown in Indian subcontinent are susceptible to various biotic and abiotic stresses. Cercospora leaf spot (CLS) is a major biotic stress resulting in poor yield of this crop. Therefore, it is essential to investigate resistance status of different cultivars to CLS and develop effective strategy. Present investigation was focused on the role of biochemical compounds in resistance response of this crop to CLS in naturally grown population and after artificial induction with pathogen derived elicitor. The defense responses in vivo and in vitro were analyzed in the form of phytoalexin genestein, PAL and PR- proteins in their leaves. PR-proteins, PAL and genestein were assayed employing established protocols. In naturally grown population, four cultivars- Kopergaon, TARM-1, TARM-2 and TARM-18 showed lesser accumulation of genestein and lower level of PAL and PR- proteins. However, Pant M-3, ML-1037 and ML-936 showed resistant interaction with very high accumulation of genestein, PAL and PR proteins. Similar trends of accumulation of these biochemicals were observed in in vitro condition after elicitation with pathogen derived elicitor. The correlation study showed that the cultivars with lower defense related expression showed high disease incidence (51-61%) and with higher defense related expression were with less than 5% CLS incidence. It could be stated that PR-proteins, PAL and genestein has prominent role in defense mechanism of mungbean against CLS as biochemical markers and further their utility in early screening for disease resistance of crop plants could be explored.

Incidence of Cercospora Leaf Spot Disease of Groundnut (Arachis hypogaea L.) As Influenced by Sowing Date in Makurdi, Benue state of Nigeria.

Leaf spots of groundnut caused by Cercospora spp is one of the major economic production constraint militating against groundnut production in Nigeria. Field experiments were conducted during the 2011 and 2012 seasons at the Teaching and Research Farm of the Federal University of Agriculture, Makurdi Nigeria to assess the effect of sowing dates on the incidence of Cercospora leaf spot of groundnut The 2 x 4 x 3 factorial (2 groundnut varieties/ 4 sowing dates/ 3 replications) experiment was laid out in a Randomized Complete Block Design (RCBD) and replicated three times. Results indicated no significant effect of Cercoscora leaf spot on the two varieties in 2011 but in Ex-Dakar recorded a significantly (P &lt; 0.05) higher leaf spot incidence compared Borno-Red variety. Sowing groundnut seeds in 14th June to 29th June recorded significantly higher (P &lt; 0.0) leaf spot disease incidence compared with sowing groundnut seeds in May. Ex-Dakar variety recorded higher leaf defoliation compared with Borno-Red variety in 2012 and 2012 seasons. Results indicated that Borno-Red had a significantly (P &lt; 0. 05) higher 100 seed weight in 2011, while Ex-Dakar recorded higher 100 seed weight in 2012. The results has proved that early sowing of groundnut in May can be employed as alternative strategy for the management of leaf spot disease of groundnut in Makurdi, NigeriaKey word: Groundnut, disease incidence, sowing date, leaf defoliation, leaf spot.

Response of Capsicum Genotypes to Cercospora Leaf Spot Disease and Yield as a Result of Natural Infection in the Tropics

ABSTRACTCercospora leaf spot (CLS) disease caused by Cercospora capsici on Pepper (Capsicum spp.) is a major constraint to pepper production. Field experiments were conducted under tropical conditions to evaluate pepper genotypes for reactions to CLS as a result of natural infection in two cropping seasons. Six-week-old pepper seedlings were transplanted to the field and plants were randomly sampled for symptom expression and to isolate the causal organism. Data were collected on disease incidence, severity, and fruit yield. Disease incidence and severity and yield were affected by genotype, season, and the Genotype × Season interaction. Capsicum chinense (Jacq.), cv. Rodo, and C. frutescens L., cv. Ata wewe, were moderately resistant to CLS in both seasons; C. frutescens, cv. NHVI-AB, and C. frutescens, cv. Sombo wewe, produced higher fruit yields in wet and dry seasons, respectively. Production of Capsicum can be undertaken in the dry season with little incidence of Cercospora leaf spot.

Achieving improved control of foliar diseases of sesame (Sesamum indicum L.) intercropped with maize (Zea mays L.) through foliar spray of plant extracts

Field trials were conducted to evaluate the effect of foliar spray of aqueous extracts of Tithonia diversifolia or Ocimum gratissimum on Cercospora leaf spot (CLS) and Alternaria leaf blight (ALB) diseases of sesame intercropped with maize. Spraying regime was at 2 weeks interval from 3 weeks after planting (WAP) until 12 WAP. Extracts of T. diversifolia or O. gratissimum reduced the incidence and severity of both diseases. CLS incidence and severity as well as defoliation was significantly (p < 0.05) reduced below what obtained in the unsprayed intercrop. ALB lesion size was significantly (p < 0.05) reduced by T. diversifolia extract at 8.0% (w/v) from 154.7 mm2 (sole crop) or 13.4 mm2 (unsprayed intercrop) to 4.9 mm2 (sprayed intercrop). T. diversifolia extract at 8.0% (w/v) enhanced higher values of grain yield/plant and incidence of normal seeds, and lower incidence of fungal infection of seeds than in the unsprayed intercrop.

Temporal and Spatial Development of Cercospora Leaf Spot of Faba Bean Influenced by In Situ Inoculum.

The temporal and spatial dynamics of Cercospora leaf spot on susceptible and resistant lines of faba bean grown in or at defined distances from soil with residues infested by Cercospora zonata were examined in South Australia in 2005 and 2006. The disease was first observed on susceptible seedlings 49 days after sowing (DAS) in soil that had been sown with faba bean every 3 years since 1997 (positive soil zone for C. zonata) but was delayed by 1 week in adjacent soil (0 to 16 m away) with no history of cultivation of faba bean (negative soil zone). The incidence of diseased seedlings from 49 to 63 DAS showed a gradient from 4 to 16 m from the infested soil and was significantly greater for susceptible plants grown in the positive versus negative soil zones in field trials conducted in 2005 and 2006 (92 versus 30% in 2005, χ21 = 32.2, P < 0.001; 98 versus 55% in 2006, χ21 = 12.1, P < 0.001). The incidence of Cercospora leaf spot on the resistant line 1322/2 was significantly less (χ26 = 171.7; P < 0.001) than on the susceptible line 'Farah' at that time in both years, with fewer than 5% of the seedlings showing the disease. However, a gradient was shown at 70 to 84 DAS, where disease incidence was significantly greater on line 1322/2 in the positive soil zone than on plants in the negative soil zone in both years (62 and 18%, respectively, with χ21 = 27.9, P < 0.001 in the 2005 trial; and 47 and 6%, respectively, with χ21 = 33.3, P < 0.001 in the 2006 trial). At peak disease severity on Farah, Cercospora leaf spot mean leaf area diseased (%LAD) was severe (85 ± 4.3%) on leaves of the three nodes closest to the soil surface, and much less severe (1 ± 0.6%) in the upper canopy. Defoliation combined with %LAD was used to describe the loss of photosynthetic leaf area (%LPLA) in both cultivars, on both soil zones, in each year. Nonlinear regression analyses using a logistic model described disease development over time on susceptible plants grown in infested soil (e.g., for +12-m blocks within infested soil, y = 2.66 + 46.08/[1 + exp(-0.23 × [X - 40.92])] in 2005 and y = 0.49 + 5.02/[1 + exp(-0.14 × [X - 28.30])] in 2006, where X = DAS and y = %LPLA, with both regressions significant at P < 0.001), whereas an exponential model (e.g., for -12-m blocks from infested soil, y = 0.23 + 0.77 × 1.04X in 2005 and y = 0.44 + 0.56 × 1.04X in 2006, both at P < 0.001) best described disease gradients with increasing distance from the inoculum source. Paired t tests of %LPLA at 77 and 98 DAS showed significant differences in disease severity in the positive versus negative soil zones and a steep gradient in %LPLA from 0 to 4 m from the inoculum source. The role of infested faba bean residue in survival of C. zonata over time was also examined using a pot-bioassay and in situ field assay. When residues were removed from the soil surface or depleted rapidly by animal grazing, the amount of C. zonata inoculum in the soil was significantly less (P < 0.001) than for soil with residue remaining on the soil surface. C. zonata survived in soil and remained infective for at least 30 months after harvest of an infected faba bean crop.

Cercosporiose progression in the agroforestry consortium coffee-rubber trees

Cercospora coffeicola is one of the primary diseases that affect coffee plants. Studies indicate that shaded coffee plants reduce the incidence of this disease and that the management of trees and coffee plants arrangement influence in the dissemination of cercospora. The objective of this study was to evaluate the incidence and severity of C. coffeicola at different distances from double rows of rubber trees (Hevea brasiliensis muell. arg.) at two different sunlight exposures (north and south). This study was conducted in Londrina, Parana, between 2008 and 2010, with adult plants of the IAPAR 59 cultivar (Coffea arabica L.) grown at a spacing of 2.5 m x 1.0 m. The distances between the double rows of rubber trees were 13, 16 and 22 m, compared to plants grown under full sun. The disease incidence was assessed monthly by using a non-destructive method. This analysis was conducted on coffee leaves from the third and fourth pairs of two plagiotropic branches, on eight plants per plot, with five replications. These data were used to calculate the area under the curve for the incidence of the brown eye spot. The highest disease incidence occurred in the coffee plants grown under full sun, whereas lowest disease occurred on plants located at up to two meters away from double rows of rubber trees. The incidence of Cercospora leaf spot increased with the distance from the double rows of rubber trees. The results demonstrate that the mapping of cercospora incidence in shaded coffee plants is essential to determinate the best spacing and plants arrangement.

Brown eye spot incidence in fruits of coffee: different density planting and water managements

The objective of this study was to evaluate the incidence of cercospora leaf spot, on coffee plant fruits, under different irrigation management and planting densities. The trial was carried out at the Federal University of Lavras in the agricultural year 2008/2009 and 2009/2010, and collected 320 fruits per plot. The experimental design was a randomized block with four replicates. The treatments correspond to the densities of 2,500, 3,333, 5,000 and 10,000 plants ha-1 and six subplots: control (T0), irrigation throughout the year when the soil water tension reached values of 20 and 60 kPa (T1 and T2), irrigation when water tension reached values of 20 kPa and 60 kPa and suspended during the months of July and August or when the water deficit was more than 100 mm (T3 and T4) and saw irrigation using software Irriplus (T5). The highest incidence of gray leaf spot, in Lavras/MG depends on the rainfall and rainfall distribution of the agricultural year. There was a significant interaction between irrigation management and planting density, only in the 2010 harvest. In the 2009 harvest, the interaction between irrigation and plant density was not significant due to good rainfall during this period. There was a higher incidence of the disease, on the densities of 3,333 (19.58%) and 5,000 (18.06%) plants ha-1. In the 2010, higher incidence (35.50%) of the disease in control (T0), and the lower incidence in treatments T4 (8.31%) and T5 (12.80%), on the density of 2.500 plants.ha -1.

Effect of sesame (Sesamum indicum L.) population density in a sesame/maize (Zea mays L.) intercrop on the incidence and severity of foliar diseases of sesame

A field study was conducted in Abeokuta, Nigeria, to investigate the effect of different population densities of sesame intercropped with maize, in a single alternate row (1:1) arrangement on the incidence and severity of foliar diseases of sesame during the early and late cropping seasons of 2006 and 2007, respectively. The experiment comprised four treatments, namely sesame planted at 266,666, 177,777 and 133,333 plants/ha intercropped with maize (53,000 plants/ha) and sole sesame at 266,666 plants/ha. Sesame at 133,333 plants/ha + maize showed a lower incidence of Cercospora leaf spot (CLS) and Alternaria leaf blight (ALB) disease and also produced a higher grain yield than the other treatments. The incidence of normal or discolored seeds was not influenced by sesame population density. Significant negative correlations existed between foliar disease incidence and proportion of normal or white/cream colored seeds. Foliar disease incidence was negatively correlated with incidence of abnormal or discolored seeds. Intercropping did not influence maize agronomic characteristics and grain yields.

Incidence and severity of foliar diseases of sesame (Sesamum indicum L.) intercropped with maize (Zea mays L.)

This study evaluates the effects of different row arrangements on incidence and severity of Cercospora leaf spot (CLS) and Alternaria leaf blight (ALB) diseases and seed health of sesame intercropped with maize. Row arrangements were: sesame intercropped with maize in alternate pair of rows (2:2), two rows of sesame intercropped with one row of maize (2:1), sesame intercropped with maize in single alternate rows (1:1) with sole sesame as control. Intercropping maize with sesame reduced the incidence and severity of diseases. Sesame intercropped with maize in a (1:1) ration recorded a significantly lower number of infected leaves by CLS and ALB incidence than other row arrangements. ALB lesion number was between 17 and 20 in the (1:1) arrangement relative to 65–104 and 28–43 in the sole crop and other row arrangements, respectively. ALB lesion size was also reduced in the (1:1) than other row arrangements. Fungal infection of harvested sesame seeds was significantly reduced in the intercrop relative to the sole crop. CLS incidence was significant and negatively correlated with seed weight while defoliation was significant and positively correlated with ALB or CLS incidence. Rainfall was significant and positively correlated with CLS or ALB incidence while intercropping induced microclimatic effects that influenced disease incidence. Grain yield, weight of 1000-seed, number of capsules/plant and weight of seed/plant were significantly higher in the (1:1) row arrangement than the sole crop or other row arrangements. The study demonstrates that intercropping sesame with maize in a single alternate row (1:1) arrangement can be used to reduce foliar diseases of sesame.

Identification of resistance to Cercospora leaf spot of cowpea

Twelve selected cowpea cultivars were screened for resistance to Cercospora leaf spot (CLS) disease caused by Pseudocercospora cruenta and Cercospora apii s. lat. under artificial epiphytotic conditions in a replicated field trial, with the objective of developing a quantitative measure of disease resistance. CLS incidence, leaf spotting score, lesion density, lesion size, proportion of nodes infected, diseased leaf area, conidia number mg−1 and fascicle density were assessed in 12 cowpea genotypes at crop maturity. Proportion of nodes infected and leaf spotting score were best able to quantitatively differentiate between the levels of resistance, and allow the exploitation of quantitative resistance to the disease. Both lesion density and lesion size were important in determining the final leaf spotting score but the former was epidemiologically more important than the latter, indicated by its correlation to most of the CLS symptom measures. There was differential resistance to the P. cruenta and C. apii s. lat. among the cowpea varieties screened. Among the cowpea lines screened, resistance to P. cruenta was more common than resistance to C. apii s. lat. Nevertheless, P. cruenta was considered the more aggressive and epidemiologically more important than C. apii s. lat. on the varieties tested evidenced by the strong correlation of P. cruenta incidence with acropetal spread of CLS, intensity of leaf spotting, conidia number mg−1 and fascicle density. The highly susceptible varieties namely VRB7, Los Banos Bush Sitao no.1 and CB27 were susceptible to both Cercospora pathogens. The cowpea variety VRB-10 was completely resistant to both pathogens and is a useful source of resistance in CLS breeding programmes.

Levels of variability in groundnut (Arachis hypogaea L.) to cercospora leaf spot disease implication for selection

Groundnut (Arachis hypogaea L.) is an important crop both in subsistence and commercial agriculture in arid and semi-arid regions of the world. Leaf spot diseases caused by fungus have been a major destructive disease of groundnut and could cause a yield loss of up to 50 % or more. A two-year experiment was conducted during the cropping seasons of 2002 and 2003 at the Faculty of Agriculture Research Farm, University of Maiduguri, Nigeria. The objective of the study was to determine the reaction of different groundnut varieties to cercospora leaf spot disease to create basis for selection for cercospora leaf spot disease tolerance. The experiment consisted of twenty-four groundnut varieties, laid out in a randomized complete block design (RCBD) with three replications. The analysis of variance (ANOVA) indicated highly significant difference among the groundnut varieties in all the characters studied. The results indicated that ICGV-SM-93531, ICGV-IS-96802, ICGV-IS-96827 and ICGV-IS-96808 had the lowest cercospora leaf spot incidence. The variety ICGV-IS-96808 that produced the highest kernel yield also had the lowest days to 50% flowering and incidentally is among varieties that recorded the lowest leaf spot incidence. The study found tremendous level of variability existing among the groundnut varieties that is essential in crop improvement. This study recommends that development or selection of tolerant varieties to leaf spot should be based on their level of incidence. This will be the only effective measure in decreasing production costs and protect the environment from pollution. Potential therefore exist for selection among the groundnut varieties evaluated for cercospora leaf spot disease tolerance. There is however, a need to undertake further studies in order to determine the type and the number of genes controlling cercospora leaf spot disease tolerance in groundnuts for enhanced breeding strategies.