Area Under The Disease Progress Curve Research Articles

Genetics of downy mildew resistance in indigenous cucumber germplasm

Cucumber (Cucumis sativus L.) is a major Cucurbitaceous vegetable crop widely grown in tropical andsubtropical regions of the world. Downy mildew is the most damaging disease in cucumber worldwide causingsignificant yield loss. The wide diversity in terms of different economically important traits including severityto downy mildew infestation is available in Indian-originated germplasm. To investigate the genetic inheritanceof cucumber downy mildew disease resistance, one resistant genotype (DC-70) from India was crossed with acontrasting susceptible genotype (DC-773). The parents and their progenies were evaluated in both field andnet house conditions for downy mildew disease resistance. Field condition data were recorded 4-times from30 days until the plants die. The lower leaf surface was inoculated 20-25 days after sowing at the seedlingstage by spraying the inoculum. The proportion of infection was recorded 4-times from 8-days to 65-daysafter inoculation, and the per cent disease index and area under the disease progress curve (AUDPC) werecalculated from these proportions. Based on the PDI and AUDPC, it was established that resistance to downymildew in the genotype, DC-70 was controlled by a major gene. Additive-dominance model fits the segregationdata and the additive effect was significant. Finally, the downy mildew disease inheritance pattern indicatedthat it is controlled by a single recessive gene in DC-70, which can be successfully introgressed into desiredelite genotypes to facilitate the downy mildew resistance breeding programme.

Spot blotch disease resistance and heat stress tolerance in spring wheat (Triticum aestivum L.)

Spot blotch caused by Bipolaris sorokiniana is a major disease of wheat in warm and humid regions of Nepal. The fungus has a worldwide distribution but as a pathogen, it is the most aggressive under the conditions of high relative humidity and temperature associated with the low fertility of soils in Nepal. The yield loss due to the disease is very significant in Nepal. This experiment was conducted to identify the genotypes having a good level of resistance against spot blotch. Canopy temperature measurements using infrared thermometry, to assess variation in foliar blight resistance along with heat tolerance as an integrative selection criterion. The experiment set was comprising 52 genotypes and arranged in alpha lattice design with two replications in 2017/-2018 Directorate of agricultural research center, Parwanipur, Bara, Nepal. Each plot size was 8 rows of 3 meters long. Three times disease scoring was done in Flag leaf, and Penultimate leaf method and calculated the Area under the disease progress curve (AUDPC). Other data were analyzed by using R software (4.2.2). Canopy temperature, heading days, days to maturity, plant height, number of grains per spike (NGPS), number of tillers per meter square (NTPM), thousand-grain weight (TGW), and grain yield were found highly significant. The genotype 32 was found the highest yielder (5141 kg/ha) and canopy temperature 16.50 C with a 279; 610 F; F-1AUDPC, respectively.

Evaluation of models based on a generic infection model for controlling early blight in potatoes

TOMCAST and two models (risk hours and critical days) based on a generic infection model (GI model) were evaluated for the timing of fungicide application to control early blight (Alternaria solani) in field experiments. A five-year experiment was conducted at AU Flakkebjerg with the starch potato cultivars Kardal (2016 & 2017), Avarna (2019 & 2020), and Allstar (2021). Barley kernels infested with Alternaria solani were used to inoculate the potatoes. The disease was assessed weekly, starting from the onset of the first symptoms. The impact of disease development was quantified using the area under the disease progress curve (AUDPC), the relative area under the disease progress curve (rAUDPC) as well as starch yield. An economic analysis was done to determine the profitability of the models. Fungicide application significantly suppressed early blight development in comparison to untreated plots. The fungicide-treated plants gave higher yields (10–35%) than the untreated plants. Nevertheless, the models reduced fungicide use by an average of 37–49%, without any yield or economic penalty. Most fungicides were saved with the TOMCAST model, but disease control and yield were generally lower than in plots treated according to the GI-based models. Overall, our study emphasizes the economic importance of early blight and the necessity of applying fungicides to control it. We also show the possibility of significantly reducing fungicide use by using decision support systems. For the first time, we demonstrate the feasibility of using GI models to time fungicide application to control early blight.

Production of New Biopesticides from Cymbopogon citratus for the Control of Coffee Rust (Hemileia vastatrix) under Laboratory and Field Conditions.

One of the diseases with the greatest economic impact on coffee cultivation worldwide and particularly in Peru is coffee rust (Hemileia vastatrix). The search for sustainable control methods as disease management strategies in coffee cultivation is necessary. The objective of this research was to determine the effectiveness of five biopesticides based on lemon verbena (Cymbopogon citratus) for the control of rust applied in laboratory and field conditions to allow the recovery of coffee (Coffea arabica L. var. typica) in La Convención, Cusco, Peru. Five biopesticides (oil, macerate, infusion, hydrolate and Biol) and four concentrations (0, 15, 20 and 25%) were evaluated. The biopesticides were evaluated under laboratory conditions (light and dark) at different concentrations. The design used was completely randomized in a factorial scheme. The biopesticides were incorporated into the culture medium and inoculated with 400 uredospores of rust, and the germination percentage was evaluated. Under field conditions, the biopesticides at the same concentrations were evaluated for 4 weeks after application. Under these field conditions, the incidence, severity and area under the disease progress curve (AUDPC) of selected plants with a natural degree of infection were evaluated. In the laboratory, the results showed that all biopesticides were effective in reducing the germination of rust uredospores to values <1% of germination in relation to the control, which showed values of 61% and 75% in the light and dark, respectively, independent of the concentration used, with no significant differences between them. In the field, 25% oil promoted the best response with values <1% and 0% incidence and severity, respectively, in the first two weeks after application. The AUDPC for this same treatment showed values of 7 in relation to 1595 of the control. Cymbopogon citratus oil is an excellent biopesticide that can be used to control coffee rust.

Optimal timing of fungicide applications on maize, soybean, and beans based on calendar and agrometeorological data

ABSTRACT The objective of this study was to determine the best method to establish optimal timing of fungicide applications on corn (Zea mays), soybean (Glycine max), and bean plants (Phaseolus vulgaris), by comparing results based on the calendar versus agrometeorological data. The experimental design was arranged in randomised blocks with three treatments and eight repetitions. Treatments consisted of control (without application of fungicides), application of fungicides based on the calendar (after establishing the need for chemical control, sprays occurring at intervals of 15 days), or by indication of the AgroDetecta™ programme (based on agrometeorological data). The variables evaluated were: disease incidence and severity, area under the disease progress curve (AUDPC), income components, and economic return. Among the integrated disease management tools investigated, it was concluded that chemical control improves crop health and yield for corn, soybean, and bean plants, especially when timing of treatment application is based on the calendar. The programme AgroDetecta™ showed promise as a decision-making tool for the best timing to spray, but requires adjustments for commercial use.

Varietal resistance of Algerian bread wheat against Fusarium culmorum, the main agent of crown rot on wheat

Fusarium crown rot (FCR) is one of the serious wheat diseases. FC11 is one strain among 34 isolates obtained in a previous study, and identified as Fusarium culmorum strain highly pathogenic. FC11 was assigned the accession number MW151664 by NCBI GenBank. Two resistance/sensitivity tests were conducted on 9 cultivars (cv) of bread wheat. The In vitro test in the oven with the parameters; percentage of germination inhibition (%GI), to determine the tolerance of seedlings germination, and the Area Under the Disease Progress Curve (AUDPC) to test the tolerance to the initial infection of germinated coleoptiles. In in-vivo test in the growth chamber, the disease severity (DS) parameter used to test the cultivars ability to tolerate FCR induced by F. culmorum. The results showed that all cultivars were susceptible to FC11 with a significant decrease in germination and coleoptile emergence rate with GI% and AUDPC values reached up to 68.35, and 68.98% for cv. Boumerzoug and Hidhab, respectively. The cv. Bordj Mehis and Ain Abid showed significant susceptibility to F. culmorum, where length of the vegetative system and fresh weight (RCL% and RCW%) were negatively affected up to 28.66 and 56.66%, respectively. In this work, the cv. Akhamokh showed an interesting level of FCR tolerance among other cultivars tested.

Charcoal Rot Severity and Soybean Yield Responses to Planting Date, Irrigation, and Genotypes

Soybean (Glycine max [L.] Merr.) production is influenced by planting date, but its impact on yield in fields infested with Macrophomina phaseolina (Tassi) Goid. is unknown. A 3-year study was conducted in M. phaseolina-infested fields to assess the effects of planting date (PD) on disease severity and yield using eight genotypes, four of which are reported to be susceptible to charcoal rot (S), and four reported with moderate resistance (MR) to charcoal rot (CR). The genotypes were planted in early April, early May, and early June under irrigated and nonirrigated conditions. There was planting date by irrigation interaction for area under the disease progress curve (AUDPC) where May PD was significantly lower compared to April and June PDs in irrigated environments but not in nonirrigated environments. Correspondingly, yield in April PD was significantly lower than that of May and June. Interestingly, yield of S genotypes increased significantly with each subsequent PD, while yield of MR genotypes remained high across all three PDs. The interaction of genotypes by PD on yield revealed that the MR genotypes DT97-4290 and DS-880 had the greatest yields in May compared to April. While May PD had a decreased AUDPC and an increased yield across genotypes, the result of this research suggests that in fields infested with M. phaseolina, early May to early June planting coupled with appropriate cultivar selection provides maximum yield potential for western Tennessee and mid-southern soybean growers.

Integrated management of late blight of potato in Pokhara, Kaski, Nepal

A field experiments was carried out in Pokhara, Kaski, Nepal, to identify integrated disease management options against late blight of potato under natural epiphytotic conditions.Twelve genotypes of potato, including Janakdev as resistant and Cardinal as susceptible, were evaluated in a randomized complete block design with three replications. Similarly, a two-factor randomized complete block design experiment with three replications was carried out to investigate the interaction effect of planting date and application of chemical, botanical extracts, and a biocontrol agent.Susceptible variety Cardinal was planted in three different dates starting from October 11 at a 15-day interval and received five sprays each of the chemical fungicide Krilaxyl Gold (mancozeb 64% + metalaxyl 8%), 10% V/V extracts of garlic (Allium sativum), neem (Azadirachta indica), and bakaino (Melia azedarach), and Phytoderma (Trichoderma viride) 109 CFU/mL) and water spray as an untreated control.Among the genotypes, CIP384321.15 and Khumal Ujjwal showed the significantly (p&lt;0.01) the lowest mean value of AUDPC (the area under the disease progress curve), whereas susceptible check Cardinal and Khumal Laxmi showed the significantly (p&lt;0.01) the highest mean AUDPC values. Similarly, the 11 October planting with the application of Krilaxyl Gold showed the lowest total AUDPC value (382.65) and the highest total AUDPC value (1533.41). Besides the chemical fungicide, the application of extracts of garlic, bakaino, neem, and phytoderma could significantly reduce the disease and increase tuber yield. These botanical extracts and biocontrol agents can be used in the integrated disease management of potato late blight.

Alternative scoring methods of fusarium head blight resistance for genomic assisted breeding.

Fusarium head blight (FHB) is a fungal disease of wheat (Triticum aestivum.L) that causes yield losses and produces mycotoxins which could easily exceed the limits of the EU regulations. Resistance to FHB has a complex genetic architecture and accurate evaluation in breeding programs is key to selecting resistant varieties. The Area Under the Disease Progress Curve (AUDPC) is one of the commonly metric used as a standard methodology to score FHB. Although efficient, AUDPC requires significant costs in phenotyping to cover the entire disease development pattern. Here, we show that there are more efficient alternatives to AUDPC (angle, growing degree days to reach 50% FHB severity, and FHB maximum variance) that reduce the number of field assessments required and allow for fair comparisons between unbalanced evaluations across trials. Furthermore, we found that the evaluation method that captures the maximum variance in FHB severity across plots is the most optimal approach for scoring FHB. In addition, results obtained on experimental data were validated on a simulated experiment where the disease progress curve was modeled as a sigmoid curve with known parameters and assessment protocols were fully controlled. Results show that alternative metrics tested in this study captured key components of quantitative plant resistance. Moreover, the new metrics could be a starting point for more accurate methods for measuring FHB in the field. For example, the optimal interval for FHB evaluation could be predicted using prior knowledge from historical weather data and FHB scores from previous trials. Finally, the evaluation methods presented in this study can reduce the FHB phenotyping burden in plant breeding with minimal losses on signal detection, resulting in a response variable available to use in data-driven analysis such as genome-wide association studies or genomic selection.

Cercospora Leaf Spot Resistance of Crapemyrtle Cultivars in Tennessee

Crapemyrtle (Lagerstroemia sp.) is a top-selling deciduous flowering tree in the United States, and its salability is often compromised by cercospora (Cercospora lythracearum Heald &amp; F. A. Wolf) leaf spot. To compare cercospora leaf spot resistance, 32 crapemyrtle cultivars belonging to Lagerstroemia indica, Lagerstroemia fauriei, L. indica × L. fauriei, and L. indica × L. fauriei × Lagerstroemia limii and 12 cultivars or unnamed selections belonging to L. indica, L. indica × L. fauriei, L indica × L. fauriei × L. limii, L. limii, and Lagerstroemia subcostata were planted in field plots in 2004 and 2011, respectively. The experiment was a completely randomized block design with three and four replications in the 2004 and 2011 plantings, respectively. Plants were evaluated for cercospora leaf spot disease severity and defoliation using a scale of 0% to 100% foliage affected from August to October of 2015, 2016, and 2017. Area under the disease progress curve (AUDPC) was calculated for the evaluation period of each year. L. fauriei cultivars Fantasy, Kiowa, Townhouse, and Woodlander’s Chocolate Soldier and L. indica × L. fauriei Apalachee from the 2004 planting, and the L. subcostata and L. limii selections from the 2011 planting had lowest cercospora leaf spot disease severity ratings, AUDPC, and defoliation. L. indica × L. fauriei cultivars Choctaw, Miami, Natchez, Osage, Sarah’s Favorite, Tonto, Tuscarora, and Tuskegee, and L. indica × L. fauriei × L. limii Arapaho were moderately resistant to cercospora leaf spot, whereas cultivars belonging to L. indica and L. indica × L. fauriei × L. limii Cheyenne were highly susceptible to cercospora leaf spot. Results from this research may aid breeders, nursery producers, and landscapers in selecting crapemyrtle species and cultivars with cercospora leaf spot resistance.

Nanopartículas de Simonkolleite no tratamento de sementes e controle da mancha bacteriana do tomateiro causada por Xanthomonas hortorum pv. gardneri

ABSTRACT Bacterial spot caused by Xanthomonas spp. (X. vesicatoria, X. euvesicatoria pv. euvesicatoria, X. euvesicatoria pv. perforans, and X. hortorum pv. gardneri) may result in significant losses for tomato crops. Simonkolleite nanoparticles (SK-NPs) has been indicated as a novel approach for plant disease control. The objective of this work was to evaluate SK-NPs (ZnOCl, ZnOCl:Ag, and ZnOCl:Cu at different concentrations) for the in vitro inhibition of X. hortorum pv. gardneri, determining the time of exposure of the products for the bacterial death; the reduction of bacteria recovery on inoculated seeds, and their efficacy to reduce bacterial spot severity in plant. The growth inhibition was evaluated by inhibition zone in culture medium plates, when the diameter of the inhibition zone was measured. The period of exposure of the products to the bacterial suspension tested were 1, 2, 3, 4, or 5 h. Tomato inoculated seeds were treated with SK-NPs. In plant, the preventive and curative effects were evaluated by applying the products two days before or after inoculation, respectively. Disease severity was evaluated and the area under the disease progress curve (AUDPC) was calculated. ZnOCl:Ag, ZnOCl:Cu, and ZnOCl inhibited bacterial growth, and the 5 h exposure time was necessary to reduce bacterial growth. ZnOCl:Ag, and ZnOCl:Cu reduced the bacteria presence in the seeds, and did not affect the seed germination. Both products reduced the AUDPC in the preventive application. The use of SK-NPs ZnOCl:Ag and ZnOCl:Cu showed to be promising to manage tomato bacterial spot.

Resistance Assessment of Hybrid Corn Genotypes to Major Corn Diseases and Its Effects on Disease Epidemic Components in South Sulawesi, Indonesia

The use of resistant varieties is one of approach that can be used in the management of the pathogen development. This study aimed to examine the resistance level of hybrid corn genotypes to the corn major diseases and to determine its effect on the components of the disease epidemic. Testing for the three major diseases was carried out using spreader row plants as an inoculum source. Parameters observed in this study were disease incidence for downly mildew (DM), disease severity for maydis leaf blight (MLB) and leaf rust (LR), disease development model, infection rate, area under the disease progress curve (AUDPC), protection index, and path analysis. The results showed that the HBC01 genotype had the lowest attack intensity to DM, MLB, and LR, namely 35.55%, 37.33%, and 25.33%, respectively. The disease epidemic components also showed that the HCB01 genotype has the lowest AUDPC value and infection rate with the highest protection index against DM, MLB, and LR. Furthermore, relative humidity, temperature, rainfall, and wind velocity were correlated in influencing the development of DM, MLB, and LR. The conclusion is that the hybrid corn genotype greatly influences the development of epidemics of DM, MLB, and LR.

Respostas de plantas de tangor Murcott IAC 221, supridas com cálcio,à infecção por Alternaria alternata

Abstract Alternaria brown spot - ABS (Alternaria alternata) causes lesions on fruits, leaves and branches of mandarins. The cost of fungicide application is high and alternative managements for the control need to be studied. We aimed to evaluate calcium (Ca) nutrition to mitigate the effects of ABS. Murcott IAC 221 tangor plants were nourished with calcium nitrate at three different concentrations (30, 150 and 300 mg Ca L-1), and the N content was standardized in the nutrient solution of the treatments (245 mg L-1 of N) with ammonium nitrate. In vitro and in vivo tests were installed, evaluating the severity and area under the disease progress curve (AUDPC), total proteins, peroxidase (POX), catalase (CAT), superoxide dismutase (SOD) and hydrogen peroxide (H2O2), during four times. In all evaluations a negative correlation was observed between leaf Ca content and the severity and AUDPC of ABS. On the other hand, there was a positive correlation between N and the occurrence of the disease. In the treatment with the lowest concentration of calcium there was accumulation of H2O2 and hypersensitivity reaction (HR), with low detoxification of H2O2 by CAT. There is potential for use of calcium supply to plants of Murcott IAC 221 tangor as an alternative management against the fungus A. alternata.

Validation of Novel spot blotch disease resistance alleles identified in unexplored wheat (Triticum aestivum L.) germplasm lines through KASP markers

BackgroundDuring the last few decades, the diverse sources of resistance, several genes and QTLs for spot blotch resistance have been identified. However, a large set of germplasm lines are still unexplored that have the potential to develop highly resistant wheat cultivars for the target environments. Therefore, the identification of new sources of resistance to spot blotch is essential for breeding programmes to develop spot blotch resistant cultivars and sustain wheat production. The association mapping panel of 294 diverse bread wheat accessions was used to explore new sources of spot blotch disease resistance and to identify genomic regions using genome wide association analysis (GWAS). The genotypes were tested in replicated trials for spot blotch disease at three major hot spots in India (Varanasi in UP, Pusa in Bihar, and Cooch Behar in West Bengal). The area under the disease progress curve (AUDPC) was calculated to assess the level of resistance in each genotype.ResultsA total of 19 highly and 76 moderately resistant lines were identified. Three accessions (EC664204, IC534306 and IC535188) were nearly immune to spot blotch disease. The genotyping of all accessions resulted in a total of 16,787 high-quality polymorphic SNPs. The GWAS was performed using a Compressed Mixed Linear Model (CMLM) and a Mixed Linear Model (MLM). A total of seven significant MTAs, common in both the models and consistent across the environment, were further validated to develop KASP markers. Four MTAs (AX-94710084, AX-94865722, AX-95135556, and AX-94529408) on three chromosomes (2AL, 2BL, and 3BL) have been successfully validated through the KASP marker.ConclusionsThe new source of resistance was identified from unexplored germplasm lines. The genomic regions identified through GWAS were validated through KASP markers. The marker information and the highly resistant sources are valuable resources to rapidly develop immune or near immune wheat varieties.

Pathogenicity of Asymptomatically Residing Fusarium Species in Non-Gramineous Plants and Weeds to Spring Wheat under Greenhouse Conditions.

Despite significant efforts in recent decades to combat Fusarium head blight (FHB), this disease remains one of the most important and widely studied diseases of wheat and other cereal plants. To date, studies have focused on small grain cereals as hostplants for these pathogens, but it was recently discovered that asymptomatic non-gramineous plants and weeds can serve as alternative sources of fungi associated with FHB. The aim of this study was to evaluate the pathogenicity of Fusarium avenaceum, F. culmorum, F. graminearum and F. sporotrichioides isolated from non-gramineous plants and weed species to spring wheat under greenhouse conditions. A total of 91 Fusarium isolates, including 45 from weeds and 46 from non-gramineous plants were floret inoculated at mid anthesis. The FHB incidence and severity (%) of inoculated heads and the area under the disease progress curve (AUDPC) were calculated. To determine yield losses, the weight of 1000 grains (TGW) was evaluated. Results of the research showed that FHB severity (%) values in Fusarium spp.-inoculated heads from non-gramineous plants varied from 9.3% to 69.6% and AUDPC values ranged from 161.5% to 1044.6%. TGW was most significantly reduced by the F. culmorum isolates BN26r and BN39fl from Brassica napus and isolates BV15.1l and BV142.1pe from Beta vulgaris (37%, 30%, 28.8% and 31.8% respectively, compared to the water control). In Fusarium-inoculated heads from weeds, FHB severity values ranged from 6.2% to 81.0% and AUDPC values varied from 134.2% to 1206.6%. TGW was most significantly decreased by CBP1401r isolate from Capsella bursa-pastoris (52%). The study results suggest that the pathogenicity of Fusarium species isolated from different hosts to wheat more strongly depends on the Fusarium species and strain than the hostplant. Under greenhouse conditions, F. culmorum strain groups obtained from weeds, non-gramineous plants and Triticum were more pathogenic to wheat than the water control and other Fusarium species.

Potential and Metabolic Pathways of Eugenol in the Management of Xanthomonas perforans, a Pathogen of Bacterial Spot of Tomato.

Bacterial spot of tomato continues to pose a significant problem to tomato production worldwide. In Florida, bacterial spot of tomato caused by Xanthomonas perforans is one of the most important diseases responsible for tomato yield loss. This disease is difficult to control, and new strategies are continually being investigated to combat the devastating effect of this disease. Recent efforts focusing on essential oils based on small molecules have spurred interests in the utilization of this class of chemicals for disease management. In this study, we evaluated the efficacy of eugenol for the management of bacterial spot of tomato caused by X. perforans. In the greenhouse experiments, eugenol applied as a foliar spray significantly (p < 0.5) reduced bacterial spot disease compared to the untreated control. In the field experiments, the area under the disease progress curve (AUDPC) was significantly (p < 0.5) lower in the plots treated with eugenol or eugenol combined with the surfactant Cohere than in the untreated control plots, and it was comparable to the copper-based treatments. To provide additional insights into the possible pathways of eugenol activities, we applied a liquid chromatography mass spectrometry (LC-MS)-based metabolomic study using a thermo Q-Exactive orbitrap mass spectrometer with Dionex ultra high-performance liquid chromatography (UHPLC) on X. perforans strain 91−118 treated with eugenol. Our results showed that eugenol affected metabolite production in multiple pathways critical to bacterial survival. For example, treatment of cells with eugenol resulted in the downregulation of the glutathione metabolism pathway and associated metabolites, except for 5-oxoproline, which accumulation is known to be toxic to living cells. While the peaks corresponding to the putatively identified sarmentosin showed the most significant impact and reduced in response to eugenol treatment, branched-chain amino acids, such as L-isoleucine, increased in production, suggesting that eugenol may not negatively affect the protein biosynthesis pathways. The results from our study demonstrated the efficacy of eugenol in the management of bacterial spot of tomato under greenhouse and field conditions and identified multiple pathways that are targeted.

In Vitro Evaluation of the Development of Fusarium in Vanilla Accessions

Vanilla is an economically important crop for low-lying humid tropical regions. World demand for natural vanilla is increasing, but cultivated plants face serious phytosanitary problems. The disease known as Fusarium wilt is mainly related to the fungus Fusarium oxysporum f. sp. vanillae, and for its management, the pathogen–host relationship must be understood. Four in vitro multiplied vanilla accessions were evaluated: two Vanilla planifolia from Colombia and Mexico, one from V. odorata, and one (1) F1 hybrid (V. rivasii × V. trigonocarpa). In addition, three isolates of Fusarium from different symptomatic plants present in small-scale agroforestry systems: (1Fov) F. oxysporum f. sp. vanillae from leaf, (2Fov) F. oxysporum f. sp. vanillae from root and (3Fs) F. solani also from root. Plants with two months of growth were inoculated in vitro by immersion of roots, and the development of Fusarium wilt was recorded for 15 days, using a severity scale to describe symptoms and to calculate the area under the disease progress curve (AUDPC). No statistical differences were found when analyzing the interaction between Fusarium isolates and vanilla accessions. However, when independently analyzing the design factor Fusarium isolates, there were significant differences; the 1Fov isolate of F. oxysporum f. sp. vanillae induced the highest symptoms as well as death in some plants of all accessions, while F. solani was considered a secondary pathogen. There were no statistical differences for the vanilla accessions factor, but the values of AUDPC and symptoms observed suggest a slight resistance in all the accessions. Therefore, it is suggested to explore the vanilla gene pool to generate multiplication material with resistance genes and to contribute with genetic improvement to successfully integrate the management of Fusarium wilt in commercial systems.

New Genomic Regions Identified for Resistance to Spot Blotch and Terminal Heat Stress in an Interspecific Population of Triticum aestivum and T. spelta.

Wheat is one of the most widely grown and consumed food crops in the world. Spot blotch and terminal heat stress are the two significant constraints mainly in the Indo-Gangetic plains of South Asia. The study was undertaken using 185 recombinant lines (RILs) derived from the interspecific hybridization of 'Triticum aestivum (HUW234) × T. spelta (H+26)' to reveal genomic regions associated with tolerance to combined stress to spot blotch and terminal heat. Different physiological (NDVI, canopy temperature, leaf chlorophyll) and grain traits (TGW, grain size) were observed under stressed (spot blotch, terminal heat) and non-stressed environments. The mean maturity duration of RILs under combined stress was reduced by 12 days, whereas the normalized difference vegetation index (NDVI) was 46.03%. Similarly, the grain size was depleted under combined stress by 32.23% and thousand kernel weight (TKW) by 27.56% due to spot blotch and terminal heat stress, respectively. The genetic analysis using 6734 SNP markers identified 37 significant loci for the area under the disease progress curve (AUDPC) and NDVI. The genome-wide functional annotation of the SNP markers revealed gene functions such as plant chitinases, NB-ARC and NBS-LRR, and the peroxidase superfamily Cytochrome P450 have a positive role in the resistance through a hypersensitive response. Zinc finger domains, cysteine protease coding gene, F-box protein, ubiquitin, and associated proteins, play a substantial role in the combined stress of spot blotch and terminal heat in bread wheat, according to genomic domains ascribed to them. The study also highlights T. speltoides as a source of resistance to spot blotch and terminal heat tolerance.

High-Throughput Plant Phenotyping (HTPP) in Resource-Constrained Research Programs: A Working Example in Ghana

In this paper, we present a procedure for implementing field-based high-throughput plant phenotyping (HTPP) that can be used in resource-constrained research programs. The procedure relies on opensource tools with the only expensive item being one-off purchase of a drone. It includes acquiring images of the field of interest, stitching the images to get the entire field in one image, calculating and extracting the vegetation indices of the individual plots, and analyzing the extracted indices according to the experimental design. Two populations of groundnut genotypes with different maturities were evaluated for their reaction to early and late leaf spot (ELS, LLS) diseases under field conditions in 2020 and 2021. Each population was made up of 12 genotypes in 2020 and 18 genotypes in 2021. Evaluation of the genotypes was done in four locations in each year. We observed a strong correlation between the vegetation indices and the area under the disease progress curve (AUDPC) for ELS and LLS. However, the strength and direction of the correlation depended upon the time of disease onset, level of tolerance among the genotypes and the physiological traits the vegetation indices were associated with. In 2020, when the disease was observed to have set in late in medium duration population, at the beginning of the seed stage (R5), normalized green-red difference index (NGRDI) and variable atmospheric resistance index (VARI) derived at the beginning pod stage (R3) had a positive relationship with the AUDPC for ELS, and LLS. On the other hand, NGRDI and VARI derived from images taken at R5, and physiological maturity (R7) had negative relationships with AUDPC for ELS, and LLS. In 2021, when the disease was observed to have set in early (at R3) also in medium duration population, a negative relationship was observed between NGRDI and VARI and AUDPC for ELS and LLS, respectively. We found consistently negative relationships of NGRDI and VARI with AUDPC for ELS and LLS, respectively, within the short duration population in both years. Canopy cover (CaC), green area (GA), and greener area (GGA) only showed negative relationships with AUDPC for ELS and LLS when the disease caused yellowing and defoliation. The rankings of some genotypes changed for NGRDI, VARI, CaC, GA, GGA, and crop senescence index (CSI) when lesions caused by the infections of ELS and LLS became severe, although that did not affect groupings of genotypes when analyzed with principal component analysis. Notwithstanding, genotypes that consistently performed well across various reproductive stages with respect to the vegetation indices constituted the top performers when ELS, LLS, haulm, and pod yields were jointly considered.

Control of leaf anthracnose of peach palm with fungicides: a valid strategy for seedling nurseries, but not for young plantations

This work aimed to evaluate the efficacy of fungicides for controlling anthracnose (Colletotrichum gloeosporioides) on peach palm (Bactris gasipaes var. gasipaes) seedlings in nursery beds and in newly planted peach palms in the field. The nursery experiment included two fungicide combinations: [thiophanate-methyl + chlorothalonil (TM + C) and pyraclostrobin + epoxiconazole (P + E)], three application intervals (7, 14, and 21 days), and an additional nontreated control. The two field experiments with newly planted peach palms tested the fungicide combinations TM + C at 15-day intervals for 12 months after transplanting, comparing to the control without fungicide application. The severity of anthracnose was assessed, and it was used for calculating the area under the disease progress curve (AUDPC). The fungicides TM + C and E + P applied at 7-days intervals were effective in the control of anthracnose in peach palm seedlings, resulting in the lowest severities and AUDPC. The fungicide TM + C reduced the maximum disease severity and AUDPC under field conditions. However, differences in the final severity of anthracnose and stem diameter were not significant compared to the control. Therefore, the use of fungicides for control of anthracnose in the field is not necessary.