Area Under Disease Progress Curve Research Articles

Herbicide safener isoxadifen-ethyl associated with increased Goss's wilt severity in corn (Zea mays).

Goss's bacterial wilt and leaf blight (Goss's wilt), caused by the bacterium Clavibacter nebraskensis, is a corn disease that has been a top ten yield-reducing disease in North America in the past 15 years. Isoxadifen-ethyl is an herbicide safener that effectively increases cytochrome P450 activity in corn which enhances a plant's metabolism of herbicide molecules. Recent research found a potential link between isoxadifen-ethyl and increased Goss's wilt severity. The application of isoxadifen-ethyl increased (P = 0.014-0.046) area under disease progress curve (AUDPC) by 19%, 7%, and 9% at three environments, independent of accompanying herbicide or herbicide application timing. However, no significant differences in incidence of systemic wilt or corn grain yield occurred among treatments at any environment. These data provide evidence for an association between isoxadifen-ethyl safener and Goss's wilt in corn. The reason for this association is unknown, but the safener may affect plant or pathogen physiological mechanisms. While the increased disease severity did not result in decreased grain yield in these experiments, an increase in pathogen inoculum due to higher disease severity could influence Goss' wilt epidemics in future years. © 2024 Society of Chemical Industry.

Chitosan-Coated Fosetyl-Al Nanocrystals efficacy on Nicotiana tabacum colonized by Xylella fastidiosa.

Xylella fastidiosa (Xf) is a quarantine plant pathogen capable of colonizing the xylem of a wide range of hosts. Currently, there is no cure able to eliminate the pathogen from a diseased plant, whereas several integrated strategies have been implemented for containing the spread of Xf. Nanotechnology represents an innovative strategy based on the possibility of maximizing the potential antibacterial activity by increasing the surface-to-volume ratio of nanoscale formulations. Nanoparticles based on Chitosan and/or Fosetyl-Al have shown different in vitro antibacterial efficacy against Xf subspecies fastidiosa (Xff) and pauca (Xfp). This work demonstrated the uptake of Chitosan-Coated Fosetyl-Al nanocrystals (CH-nanoFos) by roots and their localization in the stems and leaves of olea europaea plants. Additionally, the antibacterial activity of Fosetyl-Al, nano-Fosetyl, nano-chitosan, and Chitosan-Coated Fosetyl-Al nanocrystals (CH-nanoFos) was tested on Nicotiana tabacum cv. SR1 (Petite Havana) inoculated with Xff, Xfp, or Xf subsp. multiplex (Xfm). The bacterial load was evaluated with qPCR, and the results showed that CH-nanoFos was the only treatment able of reducing the colonization of Xff, Xfm, and Xfp in tobacco plants. Additionally, the Area Under Disease Progress Curve (AUDPC), used to assess symptoms development in tobacco plants inoculated with Xff, Xfm, and Xfp and treated with CH-nanoFos, showed a reduction in symptom development. Furthermore, the twitching assay and bacterial growth under microfluidic conditions confirmed the antibacterial activity of CH-nanoFos.

A new bacterial consortia for management of Fusarium head blight in wheat

Fusarium head blight (FHB) is a significantly important disease in cereals primarily caused by Fusarium species. FHB control is largely executed through chemical strategies, which are costlier to sustainable wheat production, resulting in leaning towards sustainable sources such as resistance breeding and biological control methods for FHB. The present investigation was aimed at evaluating newly identified bacterial consortium (BCM) as biocontrol agents for FHB and understanding the morpho-physiological traits associated with the disease resistance of spring wheat. Preliminary evaluation through antagonistic plate assay and in vivo assessment indicated that BCM effectively inhibited Fusarium growth in spring wheat, reducing area under disease progress curve (AUDPC) and deoxynivalenol (DON), potentially causing type II and V resistance, and improving single spike yield (SSPY). Endurance to FHB infection with the application of BCM is associated with better sustenance of spike photosynthetic performance by improving the light energy harvesting and its utilization. Correlation and path-coefficient analysis indicated that maximum quantum yield (QY_max) is directly influencing the improvement of SSPY and reduction of grain DON accumulation, which is corroborated by principal component analysis. The chlorophyll fluorescence traits identified in the present investigation might be applied as a phenotyping tool for the large-scale identification of wheat sensitivity to FHB.

Reaction of Selected Citrus Cultivars to Pseudocercospora Leaf and Fruit Spot Disease Under Natural Infection in Northern Uganda

Citrus is an important crop among many resource constrained subsistence farmers living in rural areas of Uganda. Citrus production is affected mainly by drought, declining soil fertility, pests and diseases. Among diseases, citrus leaf and fruit spot disease caused by fungus Pseudocercospora angolensis is currently one of the major constraints to the production of citrus in Uganda where millions of people rely on the crop for nutritional security and household income. The disease can lead to 50-100% fruit yield loss depending on environmental conditions, disease management and weather conditions. In order to identify resistance to P. angolensis, a study was conducted to identify variability for citrus leaf and fruit spot resistance from adapted commercial cultivars as an initial step in developing integrated disease management strategy. Six cultivars were assessed. The screening was under natural infection conditions in disease hot spots in northern Uganda in 2014a and 2014b seasons. The results showed significance difference (p < 0.01) for Area Under Disease Progressive Curve (AUDPC) for number of leaves with P. angolesnis symptoms and number of lesions. Subsequently, the study identified Kuno as resistant and Tangelo as less susceptible to Pseudocercospora leaf and fruit spot infection, and they could be recommended for citrus leaf and fruit spot disease control.

Marker trait association analysis to unravel genomic regions associated with Stemphylium disease reaction in lentil

This study investigates the response of lentil genotypes to Stemphylium blight disease over two cropping years, 2021 and 2022. In addition, this research aims to assess the marker-trait association between Stemphylium disease progress and the selected SSRs. Visual symptoms were assessed using Hashemi's disease scoring system, leading to the calculation of disease parameters such as Percent Disease Index (PDI) and Area Under Disease Progress Curve (AUDPC). The results revealed variations in disease progress among genotypes, with some exhibiting low disease indices, particularly genotype IC241072. Genetic diversity analysis using SSR markers identified 30 alleles and grouped genotypes into four clusters. Principal Coordinate Analysis (PCoA) confirmed the genetic distances among genotypes. Marker-trait association analysis linked the microsatellite locus LCSSR04_130362_118bp to Stemphylium blight resistance, supported by the identification of a TCP family transcription factor in close proximity. The validation of the association indicated a significant difference between resistant and susceptible alleles. This comprehensive approach combining field screening, genetic diversity analysis, and marker-trait associations provides valuable insights into the genetic basis of Stemphylium blight resistance in lentil genotypes, offering potential candidates for future breeding programs.

Early boosting of genetically improved Falcataria moluccana with mycorrhiza for better growth and disease tolerance

Falcataria moluccana is a widespread species that grows rapidly in Indonesia and produces timber used for carpentry. Nonetheless, this species is especially susceptible to gall rust disease. To find plants that can handle rust, a mix of breeding with progeny experiments and forest management methods, like arbuscular mycorrhiza (AM), were used. The point of this study is to find out if adding AM changes how F. moluccana seedlings grow and how they react to gall rust disease, both those that have been improved and those that have not. We will also look at the response by calculating the area under disease progress curves (AUDPC) value for rust disease to grow in F. moluccana seedlings. The experimental design comprised four different treatments, including varying quantities of mycorrhizae, as well as four different seed sources. For the mycorrhizal inoculation experiments, there was a control group and three treatment groups. The treatment groups got 5, 10, and 15 g of mycorrhiza per polybag, respectively. The seeds used in this study were sourced from two unimproved families, namely Java and Solomon, as well as two genetically improved families, F63 and F77. This study revealed that mycorrhizal application affects the growth of F. moluccana seedlings and significantly reduces both disease incidence and severity. The application of mycorrhiza reduces the disease incidence and severity; the AUPDC value of seedlings with mycorrhiza added is four times lower than that of seedlings without mycorrhiza. The disease severity was highest for the unimproved Solomon seedlings, despite the fact that the source of seeds had little impact on the disease incidence. Meanwhile, the genetically improved seedlings demonstrated lower disease incidence and severity rates than seedlings without improvement, with an AUPDC value nearly half that of the unimproved seedling. In terms of diameter and height, F. mollucana seedlings derived from various seed sources were remarkably diverse, and seedlings with improvements grew much better than seedlings without improvements. This study shows how arbuscular mycorrhiza affects how well improved and unimproved F. moluccana seedlings deal with gall rust disease.

Identification of resistant sources against bakanae disease in short grained aromatic rice (Oryza sativa)

An experiment was conducted during rainy (kharif) seasons of 2019 and 2020 at the research farm of ICAR Indian Agricultural Research Institute, New Delhi to screen 90 genotypes of scented short grained rice (Oryza sativa L.) for Fusarium fujikuroi resistance. Genotypes Kankjeer A, Lectimanchi-A, Sumati, Pankhali-203, GR-102, NWGR- 3042, Geetanjali, R 1432-261-105-2-1-2, Khaskani, C-4-63-G, Calrose 76, JJ 92, Koliha, Hari Shankar, Kusuma, IR 74717-3-3-1-3, IR 74725-115-3-3-3, IR 74728-134-1-1-3, Hansraj, Anterved and GAR-1 were identified as moderately resistant with the disease rating of 3 in both the years of evaluation. Further, a set of genotypes with different disease response was evaluated for different parameters including root length, shoot length, number of fibres/threads in roots, days of symptom appearance and area under disease progress curve (AUDPC). Disease severity was observed to be significantly correlated (r = 1.0) with AUDPC and days required for the symptom appearance (r = 0.95). Results indicated that apart from the disease severity, AUDPC could also be considered as a one of the component for the bakanae disease resistance. The resistant sources identified in the present study can be utilized in rice breeding programme against bakanae disease.

Multivariate analysis of the effects of weather variables on white rust epidemics and yield reduction of mustard over multiple growing seasons

AbstractThree shrinkage regression and two machine‐learning approaches were evaluated to derive models for the prediction of epidemiological characteristics of white rust of mustard, using data from 112 epidemics in the field. Four epidemiological characteristics were considered: (a) crop age at first appearance of disease, (b) crop age at highest disease severity, (c) highest disease severity in a growing season and (d) area under disease progress curve (AUDPC), along with (e) crop yield to measure the effects of disease on crop performance. We developed models using weather indices to predict these variables using five different approaches: ANN, Elastic Net, LASSO, random forest and ridge regression. One model was developed for each sowing date corresponding to each dependent variable. Two hundred different models were developed. All models performed well at the calibration stage for most of the five variables at all sowing dates. However, at the validation stage, ANN‐derived models outperformed (R2val ~ 1.00, nRMSEV ~0.00 and MBEV ~0.00 in most cases) the three shrinkage regression‐derived models in predicting all five variables. Predictions by random forest‐ and LASSO‐derived models were acceptable for AUDPC and crop yield. Evaluation metrics (including R2val, nRMSEV and MBEV) suggested that ENET‐ and ridge‐derived models do not perform satisfactorily, whereas ANN‐derived models yielded reliable results and thus generate robust predictions. The present work constitutes a systematic effort to compare modelling methods for disease and yield prediction and illustrates the relevance of weather variables in predicting multiple epidemiological variables, and of multiple disease variables as predictors of actual crop yield.

Behavior of rust in new and old inner leaves in Conilon coffee

Coffee rust (Hemileia vastatrix) epidemics are studied in detail in Coffea arabica where a single lesion can cause defoliation, in contrast to the same disease in Coffea canephora, in which the infected leaves remain on the plant. The objective of this study was to compare the progress of coffee rust based on its incidence in young and old inner leaves in different genotypes of Conilon coffee. For this purpose, a field experiment was performed in Vila Valério, state of Espírito Santo. The incidence of rust disease was evaluated during twelve months in plant genotypes 143 (ENCAPA 8131), 02 (ENCAPA 8111), G35 (Verdebrás), and Verdinho HP grown in fields. With data on rust incidence collected during one year, it was possible to determine the disease progress curve and calculate the area under disease progress curve (AUDPC) for each genotype. The data were obtained from the young and old leaves and statistically compared.  Rust was more prevalent in old inner coffee leaves. The Gompertz model gave the best adjustment to the disease progress curve. Genotype 143 was the most resistant. Infected leaves on the plants could be an important inoculum source to be considered in the management of rust in Conilon coffee.

Employing different parameters of disease epidemics for screening and assessment of tomato genotypes against early blight disease

Early blight is the most devastating fungal disease that infects tomato (Solanum spp.) caused by Alternaria spp. Screening of a panel of fifty-one tomato lines comprising some wild relatives for resistance against early blight was carried out under uninoculated natural field conditions and under artificially controlled conditions where the latter was found to be more informative. Disease intensity was recorded at different time intervals under both conditions following Pandey’s 5-point scale to find out the percent disease intensity (PDI) and area under disease progress curve (AUDPC). Under the influence of constant inoculum load, disease intensity was found to increase with the age of plants. A positive association was shared between PDI and AUDPC while resistance was found to be negatively correlated with AUDPC. A parallelism in genotype performance was found for screening results and AUDPC under both conditions. Resistant genotypes can be utilized in future breeding schemes for producing hybrids resistant to early blight.

Determining morphological and biochemical indices to select for smut-resistant sugarcane varieties

ABSTRACT In Sri Lanka, smut in sugarcane (Saccharum spp. hybrid) is caused by Sporisorium scitamineum and results in significant crop yield and economic losses. Current field evaluation methods to identify smut resistance in sugarcane are time consuming and do not show an association between disease resistance and the resistance mechanisms. This research was conducted to identify morphological and biochemical characters as selection indices of smut-resistant varieties to strengthen the existing varietal selection program. Fifty accessions were selected from the sugarcane germplasm collection and tested for their resistance to S. scitamineum by the standard inoculation method. The disease incidence and Area Under Disease Progress Curve (AUDPC) were assessed in the first two crop cycles. Pearson correlation coefficients were used to identify relationships of AUDPC with evaluated nine morphological and biochemical characteristics. Principal component analysis (PCA) was used to identify the indices associated with smut resistance and select the superior sugarcane varieties. Significant negative correlations (P < 0.05) were detected between AUDPC and total phenols in the leaves, bud hardness, foliage inclination angle (FIA) and number of scale leaves in the buds. The tested nine morphological and biochemical indices formed four major clusters by PCA with a cumulative contribution rate of 66%. The findings revealed that total phenols in the leaf, bud hardness, FIA and the number of scale leaves in the bud are useful, simple and non-laborious indices to determine sugarcane smut resistance in varietal selection.

Screening of onion (Allium cepa) genotypes to find out novel resistant source against purple blotch (Alternaria porri)

Purple blotch caused by Alternaria porri (Ellis) Cif., 1930 causes huge losses to bulb crop and seed crop of onion (Allium cepa L.). This is a major disease affecting successful onion production in majority of the onion growing areas. To identify resistant source against purple blotch, 34 onion genotypes with good marketable yield based on field evaluation trial in 2017 and allied species Pusa Soumya were screened under protected conditions during kharif, 2018 at insect proof net house facility of ICAR-Indian Agricultural Research Institute, New Delhi. The pure culture of Alternaria porri, isolated from infected leaf samples of onion crop raised under natural epiphytotic conditions during kharif, 2017. Highest change of disease severity index was observed between 1–2 weeks post inoculation (WPI) while highest disease severity index was recorded at 5 WPI suggesting that preventive measures must be employed as soon as disease symptoms appear in the field. The disease severity index ranged from 0.10–33.33 at 1 WPI, which increased to 9.33–89.33 at 5 WPI. The cultivated allied species Pusa Soumya was identified as novel resistance source with DSI value less than 10.0% at 5 WPI. Four genotypes exhibited moderately susceptible reaction, while 20 genotypes were susceptible and 10 genotypes were highly susceptible. The area under disease progress curve (AUDPC) value ranged from 22.33–240.17. Pusa Soumya had the lowest value and among onion lines Arka Kirtiman was found promising. Three onion genotypes had low relative AUDPC value and can effectively be utilized in resistance breeding programme. The average daily temperature between 20–25°C and relative humidity above 75% was found ideal for disease development.

Partial Resistance Components and Morphological Traits Aid Selection of Resistant Wheat Genotypes against Spot Blotch

Spot blotch caused by Bipolaris sorokiniana results substantial yield losses (15-80%) in an Indian subcontinent. Wheat varietal improvement through breeding followed by evaluation of elite germplasms against a particular disease is crucial method to manage diseases. Fifty diverse wheat genotypes and two susceptible checks viz., Sonalika and Nepal 297 were evaluated under artificial epiphytotic condition against spot blotch at NWRP, Bhairahawa, Nepal in 2017-18 and 2018-19. Evaluation was based on partial resistance components viz., lesion sizes, lesion types (chlorotic/ necrotic), lesion characteristics (sporulating/ non-sporulating) and area under disease progress curve (AUDPC) and morphological traits viz. lesion mimic, leaf angle, leaf tip necrosis and plant height. Statistical analysis revealed that genotypes with smaller lesion size (&lt;1 cm), small dark brown to black lesions with or without chlorosis/ necrosis and non sporulating lesions had lower AUDPC (&lt;225). Similarly genotypes with erect to semi erect leaf (leaf angle 1-2), medium to high leaf tip necrosis (2-4), low percentage of lesion mimic (0-22.5%) were found resistant (AUDPC&lt;225) to moderately resistant (AUDPC value 226-315). Moreover AUDPC showed strong and positive correlation with lesion sizes (0.76), lesion types (0.84) and lesion characteristics (0.54). Twenty genotypes were found resistant (AUDPC&lt;225), could be used as new resistance sources in breeding program. However genotypes viz., KACHU/BECARD//WBLL1*2/BRAMBLING/3/ATTILA*2/PBW65//MURGA, FRET2*2/SHAMA//TNMU/3/FRET2*2/SHAMA/4/UP2338*2/KKTS*2//YANAC/5/FRET2*2/SHAMA//PARUS/3/FRET2*2/KUKUNA, KACHU#1//PI610750/SASIA/3/KACHU/4/MUU#1//PBW343*2/KUKUNA/3/MUU/5/KACHU#1//PI610750/SASIA/3/KACHU, BORL14//KFA/2*KACHU and KFA/2*KACHU//QUELEA were found excellent based on partial resistance components and morphological traits. These genotypes could be further evaluated for yield potential in multi environment and better performing genotypes could be released as resistant varieties for spot blotch.

Cultivar and Fungicide Evaluations for Cercospora Leaf Spot Control in Organic and Conventional Table Beet Production

Cercospora leaf spot (CLS), caused by the fungal pathogen Cercospora beticola, is the most destructive foliar disease of table beet (Beta vulgaris ssp. vulgaris) in Wisconsin, USA, and globally. Under conducive conditions, symptomatic lesions on the leaf expand and coalesce forming large necrotic areas that can ultimately lead to complete defoliation. This damage reduces productivity and threatens the ability to mechanically harvest. CLS damage also detracts from the visual appeal of fresh market bunched beets to such an extent that growers risk buyer rejection if CLS severity is observed to be greater than 5%. Fungicide use for CLS control is threatened by the emergence of resistant C. beticola strains, and the application of host resistance is constrained by limited knowledge of cultivar reaction to CLS in table beet. This study aimed to address the knowledge gaps of fungicide efficacy and cultivar reaction by conducting replicated field trials in multiple table beet growing environments across Wisconsin. Broad variation for resistance to CLS was observed among the 10 included cultivars. The mean area under disease progress curve (AUDPC) across environments for the most susceptible cultivar was 267% greater than the most resistant cultivar. Spearman correlations between environments for mean cultivar AUDPC value ranged from 0.71 to 0.99, revealing consistent cultivar CLS reactions across environments. Although susceptible cultivars surpassed 5% severity in all environments, the resistant cultivars remained below this threshold in six of the 10 environments. By comparison with resistant sugar beet (Beta vulgaris ssp. vulgaris) cultivars, however, all tested table beets appeared susceptible to CLS, highlighting the potential for a CLS breeding effort in table beet. Neither of the evaluated Organic Materials Review Institute–listed treatments were effective at limiting CLS disease progress, whereas both tested conventional fungicides significantly reduced disease severity over the nontreated plots. These findings may provide helpful guidance to table beet growers affected by CLS in Wisconsin and beyond.

The severity and yield effects of the chocolate spot disease in faba bean affected by intercropping and nitrogen input.

Study the disease suppression efficiency, yield losses rate, and yield benefits of intercropped faba bean against chocolate spot under nitrogen (N) input, to clarify the effectiveness of intercropping faba beans in controlling chocolate spot and its contribution to yield increase. Four N input levels and disease suppression treatments were discovered when faba bean-wheat intercropped was used. Adding N enhanced the chocolate spot's the area under disease progression curve (AUDPC) by 27.1-69.9%. In contrast to monoculture, intercropping reduced the AUDPC of the chocolate spot by 32.4-51.0% (P<0.05). Interestingly, the relative control efficacy (RCE) of intercropping at the EShan site was better. With disease suppression or non-suppression, N input increased grain yield loss and its components in faba bean. The total yield advantage effect (TE) and disease-suppressed yield recovery effect (DSE) of faba bean intercropped at the two experimental sites were significantly increased under N input (N1 and N2 level). The proportion of recovery yield due to intercropping suppressed disease (DSE/TE ratio) in Eshan (52.1%) was higher than that in Xundian (40.9%), and the DSE of intercropping played an indispensable role in the two sites. Regression analysis of AUDPC and grain yield loss amount showed that one unit increase in chocolate spot AUDPC could cause a grain yield loss of 0.38-0.86 kg·ha-1 . The partial land equivalent ratio(pLER) of intercropping faba beans at the EShan site was>0.33. In conclusion, intercropped faba bean with nitrogen treatment (45~90 kg·ha-1 ) was the best choice for maximizing the intercropping disease control effect. This article is protected by copyright. All rights reserved.

The Potential of Rhizophagus intraradices, Bacillus thuringiensis Bt BMKP and Silica for Anthracnose Disease Control in Shallot

Anthracnose caused by &lt;em&gt;Colletotrichum gloeosporioides&lt;/em&gt; is a prevalent disease that poses a significant threat to shallot production in Indonesia. To mitigate this issue, the use of biological agents presents an alternative for disease control, reducing the inherent risks associated with the use of chemical pesticides. Therefore, this study aimed to determine the potentiality and mechanism of the biological agents (&lt;em&gt;Rhizophagus intraradices&lt;/em&gt; and &lt;em&gt;Bacillus thuringiensis&lt;/em&gt;) combined with silica. These agents were evaluated both individually and in combination to suppress the development of anthracnose in Tajuk variety shallot. The study was conducted in the laboratory and greenhouse, arranged in a completely randomized design with six treatments and three replications. The ability to suppress pathogenic fungi was determined based on &lt;em&gt;in vitro&lt;/em&gt; antagonism tests of &lt;em&gt;B. thuringiensis&lt;/em&gt;, disease severity, area under disease progress curve (AUDPC), plant height, number of leaves, number of tillers and the percentage of mycorrhizal fungal infections. Furthermore, the mycorrhizal infection on plant roots was observed using staining methods. The results showed that the &lt;em&gt;Bt&lt;/em&gt; BMKP isolate was included in the &lt;em&gt;B. thuringiensis&lt;/em&gt; strain RC9 group with the capacity to inhibit &lt;em&gt;C. gloeosporioides&lt;/em&gt; &lt;em&gt;in vitro&lt;/em&gt; by 18.88%. The combination treatment of &lt;em&gt;R. intraradices&lt;/em&gt;, &lt;em&gt;B. thuringiensis&lt;/em&gt; and silica reduced infection from anthracnose by 15.52% compared with control. These three treatments also significantly increased the agronomic performance of shallot up to six weeks after planting compared to control and other treatments.

Wheat Genotype Evaluation for Spot Blotch Disease Resistance: Unveiling Resilient Varieties

Spot blotch, caused by Bipolaris sorokiniana (Sacc.) Shoemaker is a major disease of wheat (Triticum aestivum L.), in all the six agro climatic zones of India. Estimation of losses due to this disease vary from location to location, due to diverse environmental conditions. The use of resistant cultivars is the most effective, long-lasting, cost-effective, and environmentally friendly technique for sustainable disease control. The experiment was conducted at Crop Research Centre, Chirodi farm of Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut (U.P.). Among the tested varieties, disease index and AUDPC values varied significantly for both years’ data viz. 2021-22 and 2022-23. In this experiment 32 wheat varieties were screened against B. sorokiniana under artificial epiphytotic conditions in the field. Each variety were sown in two row of three-meter length with three replications, two line of susceptible check RAJ 4015 was sown at every ten genotypes of interval. Among 32 wheat varieties, two varieties were found to be resistant, eleven varieties were found moderately resistant, fourteen varieties were found moderately susceptible and five varieties were found susceptible, none of the variety was found immune and highly susceptible against spot blotch disease. Area Under Disease Progress Curve (AUDPC) calculated for the thirty- two wheat varieties on the basis of disease index. AUDPC varies from 212.90 to 1143.9 and 198.80 to 1144.90 during the 2021-22 and 2022-23 years’ data. The pooled mean, Area Under Disease Progress Curve varied from 205.85 to 1144.40, showing the fast progress of disease in all genotypes.  It was observed that different wheat varieties expressed varied type of disease response against B. sorokiniana.

Management of Stemphylium Blight of Lentil by the Application of Different Dose of Chemical and Biological Fungicides

Field experiment was conducted at Plant Pathology block of Grain Legumes Research Program, Khajura, Banke during 2018 to evaluate the different doses of chemical and biological fungicides against Stemphylium blight disease of Lentil. The experimental design was laid in Randomized Complete Block design in field condition with three replications. Altogether 3 fungicides, 2 chemical {Saff (Carbendazim 12%+ Mancozeb 63%); Farm guard (Chlorothalonil 75% WP} at the dose of 1.5 gm, 2 gm and 2.5 gm per liter water and one biological {Commericial Phytoderma (Trichoderma harzianum) at the dose of 2.5 gm, 3 gm and 3.5 gm per liter water along with no fungicide application (control) was evaluated. Lowest mean disease severity (28.89) was obtained when Farm guard (Chlorothalonil @ 2.5 gm/ water) was applied followed by Saff (30) at the same dose. Highest mean disease severity (43.33) was obtained when no fungicide was applied. Similarly lowest Area Under Disease Progress Curve (AUDPC) (204.2) was obtained when Saff @ 2.5 gm/lit water was applied followed by Chlorothalonil (210) at the same dose. Highest AUDPC (291.7) was obtained in control plot. In case of grain yield Chlorothalonil @2gm per liter water obtained highest yield (836 kg/ha) with highest yield increase percent (34.6%). Lowest grain yield was obtained from control plot (546 kg/ha) followed by Trichoderma (624 kg/ha) when sprayed at 2.5 gm per liter water. Thus, from the study it is concluded that Chlorothalonil @ 2 gm when applied timely for three times can manage the Stemphylium blight disease.

Association of Tomato Chlorosis Virus Complicates the Management of Tomato Yellow Leaf Curl Virus in Cultivated Tomato (Solanum lycopersicum) in the Southern United States

Tomato (Solanum lycopersicum L.) production in the USA has been severely impacted by the tomato yellow leaf curl virus (TYLCV). Furthermore, a complex association of whitefly-transmitted TYLCV (genus, begomovirus) and tomato chlorosis virus (ToCV, genus, crinivirus) were recently identified in tomato. Several tomato cultivars were developed and commercialized with intermediate resistance (IR) against TYLCV-IL (Israel), the predominant strain of TYLCV found in Georgia, USA. TYLCV-resistant cultivars were tested in open field conditions against multiple whitefly-transmitted viruses in Georgia under natural disease pressure during the fall of 2022. The area under disease progress curve (AUDPC) over time showed a steady increase in disease severity among all cultivars. Further analysis of infected samples using high throughput sequencing (HTS) and quantitative PCR (qPCR) revealed the presence of TYLCV and ToCV in symptomatic upper and lower leaves, respectively. Moreover, the presence of both viruses in upper and lower leaves was determined. A mixed infection of both viruses, TYLCV and ToCV, resulted in severe disease development which may enhance the commercial tomato plants to break resistance and lead to decreased fruit quality and marketable yields.

Elucidating Late Leaf Spot Disease Progression and Resistance Components in Different Groundnut (Arachis hypogaea L.) Cultivars towards Phaeoisariopsis personata

Late Leaf Spot (LLS) disease is caused by Phaeoisariopsis personata, a devastating disease that significantly affects groundnut (Arachis hypogaea L.) production worldwide. This research aimed to investigate the disease progress in resistant and susceptible groundnut genotypes under green house conditions with artificial inoculations. The four popularly growing groundnut cultivars in Andhra Pradesh i.e., Kadiri-6 (K6), Dharani, Harithandra and Lepakshi (K-1812) were evaluated in this study. The disease severity scale, percent disease index (PDI), Area under disease progression curve (AUDPC) and the epidemic rate (rate) were estimated by using the linear model. Highest disease severity was observed in K6 (88.19 %) and Dharani (85.19 %) with greater disease progression rate was observed in K6 (0.13) and Dharani (0.12) cultivars. However, the lowest disease progression was observed in Lepakshi (0.04) and Harithandhra (0.08) cultivars. Enhanced resistance to LLS was reported with Harithandhra and Lepakshi cultivars due to slower epidemic rate, longer incubation and latent periods with smaller lesions.