Integrated Disease Management Research Articles

Green Strategies of Powdery Mildew Control in Hop: From Organic Products to Nanoscale Carriers.

Humulus lupulus L. is a long-lived, perennial, herbaceous, and dioecious climbing plant. The foremost producers in the European Union are Germany, the Czech Republic, Poland, Slovenia, and Spain. The Spanish cultivated area is concentrated in the province of León. Powdery mildew, caused by Podosphaera macularis, menaces hop production and quality in all hop growing regions located in the Northern hemisphere, colonizing leaves, petioles, inflorescences, and finally cones. In this work, powdery mildew control was monitored, comparing nine fungicide strategies: five organics, two integrated disease management (IDM)-based, with and without Nutragreen® nanoscale carrier, and two conventional treatments (CON) with and without Nutragreen® nanoscale carrier. The organic treatments were able to diminish P. macularis on leaves, but no effect was observed in cones. CON treatments reduced the infection on leaves and cones and increased the cone quantity and quality. Likewise, IDM-based treatments provided satisfactory results as they diminished powdery mildew on leaves and cones. Finally, dose reduction using a Nutragreen® nanoscale carrier showed beneficial effects in the control of powdery mildew compared to the commercial dose. Hence, the use of nanoscale carries permits a 30% reduction in pesticide dose, which optimizes yield and hop quality, reduces risks linked to pesticides, and aids in compliance with public and international policy demands.

Using Computational Methods to Improve Integrated Disease Management for Asthma and Chronic Obstructive Pulmonary Disease: Protocol for a Secondary Analysis.

BackgroundAsthma and chronic obstructive pulmonary disease (COPD) impose a heavy burden on health care. Approximately one-fourth of patients with asthma and patients with COPD are prone to exacerbations, which can be greatly reduced by preventive care via integrated disease management that has a limited service capacity. To do this well, a predictive model for proneness to exacerbation is required, but no such model exists. It would be suboptimal to build such models using the current model building approach for asthma and COPD, which has 2 gaps due to rarely factoring in temporal features showing early health changes and general directions. First, existing models for other asthma and COPD outcomes rarely use more advanced temporal features, such as the slope of the number of days to albuterol refill, and are inaccurate. Second, existing models seldom show the reason a patient is deemed high risk and the potential interventions to reduce the risk, making already occupied clinicians expend more time on chart review and overlook suitable interventions. Regular automatic explanation methods cannot deal with temporal data and address this issue well.ObjectiveTo enable more patients with asthma and patients with COPD to obtain suitable and timely care to avoid exacerbations, we aim to implement comprehensible computational methods to accurately predict proneness to exacerbation and recommend customized interventions.MethodsWe will use temporal features to accurately predict proneness to exacerbation, automatically find modifiable temporal risk factors for every high-risk patient, and assess the impact of actionable warnings on clinicians’ decisions to use integrated disease management to prevent proneness to exacerbation.ResultsWe have obtained most of the clinical and administrative data of patients with asthma from 3 prominent American health care systems. We are retrieving other clinical and administrative data, mostly of patients with COPD, needed for the study. We intend to complete the study in 6 years.ConclusionsOur results will help make asthma and COPD care more proactive, effective, and efficient, improving outcomes and saving resources.International Registered Report Identifier (IRRID)PRR1-10.2196/27065

Reductions in Management Distress Following a Randomized Distress Intervention Are Associated With Improved Diabetes Behavioral and Glycemic Outcomes Over Time.

OBJECTIVETo explore associations between reductions in diabetes distress (DD) and improvements in glycemic outcomes among adults with type 1 diabetes (T1D) in the context of a DD randomized clinical trial.RESEARCH DESIGN AND METHODSAdults with T1D (N = 301) participated in a two-arm trial aimed at reducing DD (DD-focused OnTrack group vs. education-oriented KnowIt group). Mean age was 45.1 years; mean baseline HbA1c was 8.8% (73 mmol/mol). Individuals were assessed at baseline and 9 months later on DD, self-care, HbA1c, and frequency of hypoglycemia. Structural equation models evaluated hypothesized pathways among changes in DD, self-care, and glycemic outcomes in the total sample and by intervention group.RESULTSReductions in DD were significantly and independently associated with better self-care, including fewer missed insulin boluses, more frequent insulin adjustment, improved problem-solving skills, more blood glucose monitoring, and greater adoption of continuous glucose monitoring (all P < 0.05). In turn, better self-care was linked with better glycemic outcomes, including fewer episodes of hypoglycemia and improved HbA1c over time. Fit indices indicated good fit of the model to the data (confirmatory fit index = 0.94, root mean square error of approximation = 0.05), with stronger and more meaningful associations for OnTrack than for KnowIt.CONCLUSIONSIn the context of an intervention to reduce DD for adults with T1D, results indicate that reductions in DD do not affect glycemic outcomes directly but through improvements in self-care behavior. Findings support the importance of integrating disease management with DD interventions to maximize improvements in glycemic outcomes.

Plant defense against a pathogen drives nonlinear transmission dynamics through both vector preference and acquisition

AbstractHost defense against vector‐borne plant pathogens is a critical component of integrated disease management. However, theory predicts that traits that confer tolerance or partial resistance can, under certain ecological conditions, enhance the spread of pathogens and spillover to more susceptible populations or cultivars. A key component driving such epidemic risk appears to be variation in host‐selection behavior of vectors based on infection status of the host. While recent theory has further emphasized the importance of infection‐induced host‐selection behavior by insect vectors for plant disease epidemiology, experimental tests on the relationship between vector host‐selection preference and transmission are lacking. We test how host plant defense—conferred by the PdR1 gene complex—mediates vector host‐selection preference and transmission of the pathogenic bacterium Xylella fastidiosa among grapevine cultivars. We confirmed that PdR1 confers resistance against X. fastidiosa by reducing both pathogen population size and disease severity. We found that vector transmission rates to new hosts exhibited unimodal dynamics over the course of infection when both susceptible and resistant were infected and acted as sources of the pathogen. Transmission from susceptible plants initially increased and then declined as insect vectors avoided severely diseased plants. While transmission from PdR1‐resistant plants also initially increased and then declined as well, this was not due to avoidance by vectors, although the exact mechanism remains unclear. We show that (1) vector preference changes over the course of disease progression, (2) vector preference is clearly important but a poor predictor of transmission, and (3) the post‐latent incubation period—in which plant hosts are infectious but asymptomatic—is likely a key period for vector transmission of X. fastidiosa. Our results suggest that, consistent with theory, defensive traits lengthen the duration of the incubation period, increasing X. fastidiosa transmission. However, defensive traits may over the long‐term ultimately reduce spread possibly through induced resistance. Vector host‐selection preference, host resistance, and transmission are clearly dynamic, changing over the course of disease progression. Understanding these dynamics is critical for broader insights into the epidemiology of vector‐borne plant pathogens, theory development, and deploying disease‐resistant cultivars in an effective and sustainable manner.

Trends in Molecular Diagnosis and Diversity Studies for Phytosanitary Regulated Xanthomonas.

Bacteria in the genus Xanthomonas infect a wide range of crops and wild plants, with most species responsible for plant diseases that have a global economic and environmental impact on the seed, plant, and food trade. Infections by Xanthomonas spp. cause a wide variety of non-specific symptoms, making their identification difficult. The coexistence of phylogenetically close strains, but drastically different in their phenotype, poses an added challenge to diagnosis. Data on future climate change scenarios predict an increase in the severity of epidemics and a geographical expansion of pathogens, increasing pressure on plant health services. In this context, the effectiveness of integrated disease management strategies strongly depends on the availability of rapid, sensitive, and specific diagnostic methods. The accumulation of genomic information in recent years has facilitated the identification of new DNA markers, a cornerstone for the development of more sensitive and specific methods. Nevertheless, the challenges that the taxonomic complexity of this genus represents in terms of diagnosis together with the fact that within the same bacterial species, groups of strains may interact with distinct host species demonstrate that there is still a long way to go. In this review, we describe and discuss the current molecular-based methods for the diagnosis and detection of regulated Xanthomonas, taxonomic and diversity studies in Xanthomonas and genomic approaches for molecular diagnosis.

Induction of Plant Resistance in Tobacco (Nicotiana tabacum) against Tomato Spotted Wilt Orthotospovirus through Foliar Application of dsRNA.

Thrips-transmitted tomato spotted wilt orthotospovirus (TSWV) continues to be a constraint to peanut, pepper, tobacco, and tomato production in Georgia and elsewhere. TSWV is being managed by an integrated disease management strategy that includes a combination of cultural practices, vector management, and growing virus-resistant varieties where available. We used a non-transgenic strategy to induce RNA interference (RNAi)-mediated resistance in tobacco (Nicotiana tabacum) plants against TSWV. Double-stranded RNA (dsRNA) molecules for the NSs (silencing suppressor) and N (nucleoprotein) genes were produced by a two-step PCR approach followed by in vitro transcription. When topically applied to tobacco leaves, both molecules elicited a resistance response. Host response to the treatments was measured by determining the time to symptom expression, and the level of resistance by absolute quantification of the virus. We also show the systemic movement of dsRNA_N from the inoculated leaves to younger, non-inoculated leaves. Post-application, viral siRNAs were detected for up to nine days in inoculated leaves and up to six days in non-inoculated leaves. The topical application of dsRNAs to induce RNAi represents an environmentally safe and efficient way to manage TSWV in tobacco crops and could be applicable to other TSWV-susceptible crops.

Occurrence, Distribution, Economic Importance and Management of Maize Chlorotic Mottle Virus: A Review

Plant virus diseases are serious constraints to the production and productivity of a wide range of crops among which maize chlorotic mottle virus (MCMV) is a serious problem in maize production and productivity. The virus is primarily originated in South America (Peru) and later distributed into many countries of all the continents except Australia and Antarctica. It is transmitted from location to location, and from plant to plant mechanically, through seed, insect vectors, and/or soil. The virus has many host ranges of agricultural crops (Maize, Sorghum, Sugarcane and Finger millet) and wild species (Dinebra retroflexa, Setaria verticillata, Cyperus assimilis, Digitaria ternta and Oplismenus hirtellus). MCMV alone causes 10-15% crop loss and up to 100% loss when it co-infects maize plants with other maize viruses such as maize dwarf mosaic virus, Sugar cane mosaic virus or Wheat streak mosaic virus. No any single disease control measure alone is effective in controlling the MCMV. However, an integrated virus disease management options (the use of disease-resistant crop varieties, proper field sanitation, removal of infection sources, use of virus-free seeds and chemical pesticides to indirectly control insect vectors) play a critical role in controlling the virus. Since the current status of the disease is wide spreading and on increasing trend, intensive MCMV employment, combined with integrated disease management, requires ongoing practice in countries where the virus is prevalent and in those countries that have not yet reported MCMV. Keywords : Integrated management; Insect vector; plant residue; Soil transmission; Zea mays DOI: 10.7176/ALST/87-03 Publication date: April 30 th 2021

Management of spot blotch of barley: an eco-friendly approach

Spot blotch disease caused by the fungus Bipolaris sorokiniana (teleomorph Cochliobolus sativus) is one of the most important fungal diseases of barley. Considering the hazardous effects of fungicidal sprays, an eco-friendly approach was adopted to manage this disease by using botanicals, biocontrol agents and systemic acquired resistance (SAR) chemicals on two barley cultivars, PL426 and PL807. Under in vitro conditions, a 15% solution of neem (Azadirachta indica) and tulsi (Ocimum tenuiflorum) inhibited the growth of B. sorokiniana by 65.48% and 45.37%, respectively. For the bio-agents, Trichoderma harzianum proved to be the best with 60.82% growth inhibition of the pathogen followed by T. viride. The SAR chemicals, maximum disease control was observed when the potted plants were sprayed with salicylic acid (SA) at 0.03% concentration and s-amino-n-butyric acid (BABA) at 0.3% concentration. Similar results were observed for botanicals, bio-control agents and SAR chemicals when tested under field conditions. Considering the economics of these environmentally safe options, it is concluded that the bio-control agent (T. harzianum), plant extracts (neem and tulsi) and SAR chemical (SA) can be used as foliar spray treatments for eco-friendly management of spot blotch of barley in integrated disease management programmes.

The extent and association of chickpea Fusarium wilt and root rot disease pressure with major biophysical factors in Ethiopia

Fusarium wilt and root rot complex are among the major challenges to chickpea production throughout Ethiopia. Previous studies have surveyed economically important chickpea diseases in Ethiopia, but were restricted to the major chickpea growing areas and thus were unable to provide a broad geographic view of disease pressure. In the present study, we focus on understanding the extent of wilt/root rot disease pressure and its correlation with local edaphic and agronomic factors. In 2015 and 2016, we conducted geo-referenced field surveys covering 51 districts representing 17 chickpea growing zones, revealing that diseases were widely distributed in all surveyed areas. Across all surveyed sites, Fusarium oxysporum f. sp. ciceris (Foc) was the predominant species encountered among fungi cultured from plant tissue, representing 69.4% of total isolates. The remaining 30.6% of isolates were other root rot pathogens including Rhizoctonia bataticola, Fusarium solani, Sclerotium rolfslii, Rhizoctonia solani and unidentified fungi. Fusarium wilt and root rot diseases incidence were significantly (P < 0.05) associated with clay soils (vertisols), Desi type chickpea, early planting, flowering and plant maturity. The highest mean percent diseases incidence per m2 (45.65%) was recorded in the Amhara region, West Gojam zone, where heavy clay soils (typical vertisols) predominate and chickpea production is regularly threatened by high diseases pressure. Taken together, the results of this survey highlight factors associated with chickpea wilt and root disease and in doing so provide a framework for integrated disease management, while also nominating agricultural environments where breeding strategies for disease resistance might have greatest impact.

Control of Fungal Diseases in Mushroom Crops while Dealing with Fungicide Resistance: A Review.

Mycoparasites cause heavy losses in commercial mushroom farms worldwide. The negative impact of fungal diseases such as dry bubble (Lecanicillium fungicola), cobweb (Cladobotryum spp.), wet bubble (Mycogone perniciosa), and green mold (Trichoderma spp.) constrains yield and harvest quality while reducing the cropping surface or damaging basidiomes. Currently, in order to fight fungal diseases, preventive measurements consist of applying intensive cleaning during cropping and by the end of the crop cycle, together with the application of selective active substances with proved fungicidal action. Notwithstanding the foregoing, the redundant application of the same fungicides has been conducted to the occurrence of resistant strains, hence, reviewing reported evidence of resistance occurrence and introducing unconventional treatments is worthy to pave the way towards the design of integrated disease management (IDM) programs. This work reviews aspects concerning chemical control, reduced sensitivity to fungicides, and additional control methods, including genomic resources for data mining, to cope with mycoparasites in the mushroom industry.

Genetic Variability and Molecular Evolution of Maize Yellow Mosaic Virus Populations from Different Geographic Origins.

Maize yellow mosaic virus (MaYMV) hosted in various gramineous plants was assigned to the genus Polerovirus (family Luteoviridae) in 2018. However, little is known about its genetic diversity and population structure. In this study, 509 sugarcane leaf samples with mosaic symptoms were collected in 2017 to 2019 from eight sugarcane-growing provinces in China. Reverse-transcription PCR results revealed that four positive-sense RNA viruses were found to infect sugarcane, and the incidence of MaYMV among samples from Fujian, Sichuan, and Guangxi Provinces was 52.1, 9.8, and 2.5%, respectively. Based on 82 partial MaYMV sequences and 46 whole-genome sequences from different host plants, phylogenetic analysis revealed that MaYMV populations are very closely associated with their source geographical regions (China, Africa, and South America). Pairwise identity analysis showed significant variability in genome sequences among MaYMV isolates with genomic nucleotide identities of 91.1 to 99.9%. In addition to codon mutations, insertions or deletions also contributed to genetic variability in individual coding regions, especially in the readthrough protein (P3-P5 fusion protein). Low gene flow and significant genetic differentiation of MaYMV were observed among the three geographical populations, suggesting that environmental adaptation is an important evolutionary force that shapes the genetic structure of MaYMV. Genes in the MaYMV genome were subject to strong negative or purification selection during evolution, except for the movement protein (MP), which was under positive selection pressure. This finding suggests that the MP may play an important role in MaYMV evolution. Taken together, our findings provide basic information for the development of an integrated disease management strategy against MaYMV.

Management of Alternaria Leaf Blight in Pigeonpea through Host Plant Resistance and Micronutrient Application

Background: Pigeonpea [Cajanus cajan (L.) Millsp] is one of the primary grain legume crops grown in India for its high quality vegetable protein, animal feed and fodder. It is affected by various fungal and viral diseases. Among these, leaf blight caused by Alternaria alternata is one of the most destructive diseases and recently the disease of minor importance becomes major one in Tamil Nadu. Use of resistant cultivar is the most effective, economically viable and eco-friendly tool for combating the plant diseases. The micronutrients play a key role in many physiological and biochemical functions of the plants which influences plant pathogenic interaction. The micronutrients viz., Zn.Mn,Cu and Fe found to have greater impact on reducing the plant disease severity. Developing integrated disease management strategy involving disease resistant variety, micronutrient and fungicide application would be the best sustainable method for controlling the pigeonpea leaf blightMethods: Twenty four pigeonpea genotypes along with two local varieties viz., CO5 and CO6 were evaluated in the field for their resistance against Alternaria alternata leaf blight disease, consecutively for three years from 2015-16 to 2017-18 using the disease resistance scale ranging from 0 to 9. Field experiments were also conducted for three consecutive Kharif season from 2015 to 2018 to evaluate the efficacy of the foliar application of different micronutrients and combination fungicide viz., carbendazim 12% + mancozeb 63% on the incidence of leaf blight disease. Result: A total of 24 pigeonpea genotypes were screened for their resistance against leaf blight under field condition. Among these, four genotypes viz., BDN2, IPA 8F, IPA 15F and MA6 were found resistance and nine genotypes were moderately resistant and remaining 11 genotypes showed susceptible reaction to leaf blight. The results of the field experiment on micronutrient and fungicide application revealed that foliar spraying of MnSO 4 @0.2% on 30 days after sowing and carbendazim 12%+ mancozeb 63%@ 1g / lit on 45 days after sowing recorded the lowest leaf blight incidence of 8.1 PDI (Per cent Disease Index) with the highest disease reduction of 76.9% as against 35 PDI in the untreated control plot. The above treatments also recorded the highest grain yield of 905 kg/ ha as against 703 kg/ in the untreated control.

Verticillium dahliae Inoculation and in vitro Propagation Modify the Xylem Microbiome and Disease Reaction to Verticillium Wilt in a Wild Olive Genotype

Host resistance is the most practical, long-term, and economically efficient disease control measure for Verticillium wilt in olive caused by the xylem-invading fungus Verticillium dahliae (Vd), and it is at the core of the integrated disease management. Plant’s microbiome at the site of infection may have an influence on the host reaction to pathogens; however, the role of xylem microbial communities in the olive resistance to Vd has been overlooked and remains unexplored to date. This research was focused on elucidating whether in vitro olive propagation may alter the diversity and composition of the xylem-inhabiting microbiome and if those changes may modify the resistance response that a wild olive clone shows to the highly virulent defoliating (D) pathotype of Vd. Results indicated that although there were differences in microbial communities among the different propagation methodologies, most substantial changes occurred when plants were inoculated with Vd, regardless of whether the infection process took place, with a significant increase in the diversity of bacterial communities when the pathogen was present in the soil. Furthermore, it was noticeable that olive plants multiplied under in vitro conditions developed a susceptible reaction to D Vd, characterized by severe wilting symptoms and 100% vascular infection. Moreover, those in vitro propagated plants showed an altered xylem microbiome with a decrease in total OTU numbers as compared to that of plants multiplied under non-aseptic conditions. Overall, 10 keystone bacterial genera were detected in olive xylem regardless of infection by Vd and the propagation procedure of plants (in vitro vs nursery), with Cutibacterium (36.85%), Pseudomonas (20.93%), Anoxybacillus (6.28%), Staphylococcus (4.95%), Methylobacterium-Methylorubrum (3.91%), and Bradyrhizobium (3.54%) being the most abundant. Pseudomonas spp. appeared as the most predominant bacterial group in micropropagated plants and Anoxybacillus appeared as a keystone bacterium in Vd-inoculated plants irrespective of their propagation process. Our results are the first to show a breakdown of resistance to Vd in a wild olive that potentially may be related to a modification of its xylem microbiome and will help to expand our knowledge of the role of indigenous xylem microbiome on host resistance, which can be of use to fight against main vascular diseases of olive.

Antifungal volatiles from medicinal herbs suppress Fusarium oxysporum f. sp. lycopersici

Medicinal herbs are the potential sources for antimicrobial compounds against soil-borne pathogens. The present investigation focuses on assessing the efficacy of antifungal activity of volatile organic compounds (VOCs) produced by seven different medicinal herbs in the suppression of F. oxysporum f.sp. lycopercisi, the causal agent of wilt disease in tomato plants. Among the seven samples tested in-vitro, the blend of VOCs emitted from mint (Mentha spicata) leaves inhibited the mycelial growth of F. o. f.sp. lycopercisi up to 41.88% followed by lemongrass (39.44%) and nochi leaves (34.66%). The important VOCs emitted by mint and lemongrass samples were identified through Headspace – Gas chromatography coupled with Mass Spectrophotometry (HS-GCMS) which revealed the presence of around 25 different compounds with varied functional groups. Among them -(-) carvone obtained from mint leaves had the highest relative abundance (2.08% peak area at 10.25 RT). In addition, geraniol and citronellol were also present with a peak area percentage of 15.85 at 10.37 RT and 5.27 at 9.97 RT, respectively. Pure compounds of carvone, geraniol and citronellol (Sigma Aldrich) along with plant samples were also tested in vitro for comparison on the inhibition of mycelial growth of F. oxysporum f. sp. lycopercisi. Among the samples, citronellol was found to be the most effective and suppressed the wilt pathogen up to 100% at 500 ppm, followed by carvone (up to 90% inhibition) in the partition plate method. The results indicated that VOCs produced from mint and lemongrass could be explored with an additive effect for the management of F. oxysporum f.sp. lycopercisi along with other Integrated Disease Management (IDM) practices.

Lipid-Based Natural Food Extracts for Effective Control of Botrytis Bunch Rot and Powdery Mildew on Field-Grown Winegrapes in New Zealand.

Synthetic controls of crop pathogens are increasingly associated with harm to the environment and human health, and pathogen resistance. Pesticide residues in crops can also act as non-tariff trade barriers. There is therefore a strong imperative to develop biologically based and natural product (NP) biofungicides as more sustainable alternatives for crop pathogen control. We demonstrate the field efficacy, over multiple seasons, of NP biofungicides, NP1 (based on anhydrous milk fat) and NP2 (based on soybean oil), on two major diseases of winegrapes—Botrytis bunch rot (Botrytis) and powdery mildew (PM). The NPs were integrated into a season-long integrated disease management programme that has produced chemical-residue-free wines. Efficacies for Botrytis control on three different varieties were: 63–97% on Chardonnay, 0–96% for Sauvignon Blanc and 46–58% on Riesling; with 65–98% PM control on Chardonnay and Riesling. NP2 exhibited the significant control of Botrytis latent infections, making it a viable alternative to mid-season synthetic fungicides. Disease control was significantly better than the untreated control and usually as efficacious as the synthetic fungicide treatment(s). Yields and wine quality in NP-treated crops were normally equivalent to those in the synthetic fungicide treatments. The results indicate that NP-mediated disease control of Botrytis and powdery mildew can be obtained in the vineyard, without synthetic fungicide input.

Seed-Borne Fungal Diseases of Maize (Zea mays L.): A Review

&#x0D; Introduction: Maize (Zea mays) is one of the most important cereal crops. It is ranked as 3rd after wheat and rice. Due to its wide adaptability, diversified uses, and low production costs, it has great potential as a cereal crop. In the case of yield losses, various factors are involved. The fungal diseases of maize play a significant role in the reduction of both quantity as well as the quality of maize.&#x0D; Review Results: At the seedling stage, maize suffers from numerous diseases and many of them are seed-borne diseases. Anthracnose stalk rot (Colletotrichum graminicola), Charcoal rot of maize (Macrophomina phaseolina), Crazy top downy mildew disease (Sclerophthora macrospora), Corn grey leaf spot disease (Cercospora zeae-maydis), Aspergillus ear and kernel rot (Aspergillus flavus), Corn smut (Ustilago maydis), Southern corn leaf blight disease (Bipolaris maydis) etc. are important among these diseases.Chemical control of seed-borne pathogens of maize is rather difficult to achieve as a reasonably good. Due to the hazardous environmental effects of chemicals, the Integrated Management of the seed-borne fungal pathogens of corn is mostly preferred. The distribution, disease cycle, symptoms of the damage, effects of environmental factors, economical importance of disease, and integrated disease management options of major seed-borne fungal pathogens of maize have been reviewed in this review article from various currently available sources.&#x0D;

Compatibility studies of indigenous Trichoderma isolates with pesticides

A total of 40 Trichoderma isolates collected from North-Eastern dry zone of Karnataka. Isolates were identified at species level by sequencing of tef1 gene. The gene sequencing results revealed that T. asperellum and Hypocrea lixii were predominantly distributed throughout the surveyed area. Among the isolates sequenced, 27 represents as T. asperellum and nine as Hypocrea lixii, two as T. harzianum and each one as T. afroharzianum and T. asperelloides. Trichoderma isolates expressed the pertinent compatibility with pesticides tested, Carbendazim and Hexaconazole fungicides were not compatible at any given concentration with the isolates. However, maximum compatibility was found in T-45, T-2, T-9 and T-16 isolates against Mancozeb at 0.15 and 0.20 per cent. The recommended dose (RD) of Chlorpyrifos (0.15 %), Imidacloprid (0.03 %) and Acephate (0.1 %) insecticide was found highly compatible with all the isolates. The RD of herbicide 2, 4-D and Glyphosate are more compatible than the Pendimethalin. Among the agrochemicals tested Mancozeb; Chlorpyrifos; Imidacloprid; Acephate; 2, 4-D and Glyphosate are compatible with Trichoderma isolates. The T-45, T-42, T-39 and T-43 isolates were identified as best pesticide tolerant isolates. Incorporation of pesticide tolerant Trichoderma strains in integrated diseases management (IDM) provides added advantages in many perspectives.

English

Maize is an important staple crop for humans and livestock feed in Zambia. A total of 473 maize germplasms were screened under maize lethal necrosis (MLN) artificial inoculation and disease pressure using an alpha lattice design to identify potential tolerant varieties as sources of resistance.&nbsp; The analysis of variance (ANOVA) based on the MLN score range of 1-9 showed that the levels of MLN resistance in the maize germplasms were very low, with almost all the hybrids widely grown in Zambia and germplasms drawn from the genebank found to be highly susceptible. However, the pro vitamin A varieties, GV662A and IICZ3085 showed a moderate level of resistance/tolerance, with disease scores of 4.7 and 5.3, respectively. There is need to enhance development of MLN tolerant maize cultivars by the national maize breeding programme and seed companies to avert the possible calamity posed by the threat of the effects of MLN. In addition, intensive awareness creation among various stakeholders in the maize value chain, systematic monitoring and surveillance of MLN, practicing integrated disease management approaches such as avoiding maize monoculture and continuous cultivations of susceptible maize throughout the year, and practicing maize crop rotation with compatible crops especially legumes that do not serve as hosts for maize chlorotic mottle virus (MCMV)/MLN are recommended. &nbsp; Key words: Maize lethal necrosis, screening, maize germplasm, Zambia.

Real-Time PCR Detection of the Onion Downy Mildew Pathogen Peronospora destructor From Symptomless Onion Seedlings and Soils.

An outbreak of downy mildew disease of onion, caused by Peronospora destructor, in Japan in 2016 necessitated a reevaluation of the primary inoculum sources to optimize disease management. Detection of the P. destructor pathogen in plants with asymptomatic infection and in soil would guide the application of fungicides according to the extent of infection before disease development. Here, we detected P. destructor in both plants and soil using newly developed primer sets (Pd ITS and Pd ITS 614) by both conventional and real-time PCR. Validation by real-time PCR with Pd ITS 614 showed that P. destructor DNA was amplified from symptomless seedlings at 3.7 × 102 to 1.0 × 100 conidium cells/50 mg leaf tissue, suggesting the detection of asymptomatic infection. Real-time PCR with Pd ITS amplified pathogen DNA from field soils at 1.6 × 103 to 8.3 × 101 oospore cells/g of soil. This real-time PCR assay provides a useful tool for identifying and quantifying inoculum sources, which may be the foundation of the design of integrated disease management strategies.

Ramularia leaf spot disease of barley is highly host genotype-dependent and suppressed by continuous drought stress in the field

Since the 1980s, Ramularia leaf spot (RLS) is an emerging barley disease worldwide. The control of RLS is increasingly aggravated by a recent decline in fungicide efficacy and a lack of RLS-resistant cultivars. Furthermore, climate change increases drought periods in Europe, enhances variable weather conditions, and thus will have an impact on severity of plant diseases. Hence, identification of RLS-resistant cultivars and understanding of disease progression under abiotic stress are important aims in integrated disease management under climate change. In the present study, we evaluated quantitative RLS resistance of 15 spring barley genotypes under drought, controlled irrigation and field conditions between 2016 and 2019 and monitored microclimatic conditions within the canopy. We identified genotypes that show robust quantitative resistance to RLS in different field environments. Our findings suggest that long-lasting drought periods create unfavourable conditions for the disease and supports that the extent and duration of leaf wetness is a key factor for RLS epidemics.