Area Under The Disease Progress Curve Values Research Articles

Systematic Evaluation of Groundnut Genotypes for Resistance to Cercospora Leaf Spot Disease

The present study assessed peanut genotypes for resistance to Cercospora leaf spot (CLS), with a focus on disease severity and defoliation across different growth stages. Based on Percent Incidence Data (PID) and defoliation scores, genotypes were classified as susceptible, moderately resistant, or resistant. Disease progression was measured through the Area under the Disease Progress Curve (AUDPC), revealing significant variation in resistance among the genotypes. Most genotypes, including 21CG001, 21CG002, 21CG003, 21CG004, 21CG006, ATTOCK 19, and 20AK012, exhibited high PID and defoliation levels, with AUDPC values indicating susceptibility. Their PID ranged from 23.96 to 31.72 at 50 days after sowing (DAS) and from 44.84 to 56.97 at 70 DAS. Genotypes 21CG005, 20AK004, and ATTOCK 19 showed the highest PID and defoliation levels, with AUDPC values over 320, categorizing them as highly susceptible. Conversely, genotypes 21CG007, 21CG008, 20AK001, and 20AK010 demonstrated the lowest PID, minimal defoliation, and AUDPC values below 250, indicating strong resistance. In vitro trials further highlighted variability in lesion characteristics, with genotypes 20AK012, BARI 16, and 20AK010 showing the most severe symptoms, including rough lesion textures and types ranging from minute chlorotic spots to mature black lesions. Overall, genotypes 21CG007, 21CG008, 20AK001, and 20AK010 exhibited high resistance, while ATTOCK 19, 20AK004, and 21CG005 were highly susceptible. These findings underscore the importance of selecting resistant genotypes for effective CLS management in peanut cultivation.

Determining the optimal ratio of resistant to susceptible bentgrass cultivars to reduce dollar spot severity

AbstractDollar spot, caused by Clarireedia spp., is the most prevalent disease on creeping bentgrass golf fairways. Interseeding newer dollar spot‐resistant cultivars into susceptible bentgrass stands could reduce dollar spot severity and the need for resultant fungicide use. This study was conducted to determine the optimal ratio of resistant to susceptible cultivars in a blend that will result in dollar spot reduction. Greenhouse experiments were conducted on cultivar blend ratios (0%, 10%, 25%, 50%, 75%, 90%, 100%) of dollar spot‐resistant (Pure Select, 007XL, Coho) and susceptible (Penncross) bentgrass challenged with inoculation of two Clarireedia spp. isolates. Disease severity was determined using visual estimates and digital image analysis. Dollar spot severity was significantly influenced by the Clarireedia isolate, with a fungicide‐resistant isolate being more aggressive and producing more disease than a sensitive one. Dollar spot severity was highest on Penncross alone, with no statistical differences observed among the resistant cultivar monostands. Mean disease severity of the blended cultivar ratios was divided into three statistically different groups—low resistance (10% and 25%), medium resistance (50% and 75%), and high resistance (90% and 100%). Compared to Penncross, blending a 10% resistant cultivar reduced AUDPC (area under the disease progress curve) values by 2% and 3% in Experiments 1 and 2, respectively, while blending a 90% resistant cultivar yielded 20% and 32% reductions. These results indicate dollar spot severity decreases as the ratio of the resistant cultivar in a stand increases, and blending resistant cultivars into susceptible has the potential for reducing disease.

Screening of rice genotypes against brown leaf spot (Bipolaris oryzae) (Breda de Haan) shoemaker, under field and laboratory conditions at Banke, Nepal

A field experiment was carried out to screen 60 rice genotypes against brown leaf spot disease caused by Bipolaris oryzae with Sabitri as a resistant check and Mansuli as a susceptible check at Banke, Nepal. The field experiment was laid out in a randomized completed block design, and the seed infection screening was done in a laboratory with a completely randomized design. The disease assessment was done by calculating disease severity, the area under the disease progress curve (AUDPC), and the seed infection rate. The disease severity and AUDPC significantly varied for the tested genotypes. Based on the AUDPC and disease severity values, this study observed that one genotype was moderately resistant, 11 were susceptible, and 48 were highly susceptible. From our experiment, rice genotypes were primarily susceptible rather than resistant; thus, for the next-generation breeding program for brown leaf spot-resistant genotypes, more landraces should be screened from diverse environments of Nepal.

Sowing Date and Seed Rate Influence on Septoria Leaf Blotch Occurrence in Winter Wheat

Septoria leaf blotch (SLB), caused by Zymoseptoria tritici, is one of the most important foliar diseases of wheat. The management of this disease is assisted by selecting a sowing time and seeding density that is less favorable to the pathogen. The aim of this research was to evaluate the severity of SLB on winter wheat cv. ‘Etana’ sown at three different sowing times and three seed rates. The severity assessments were performed on the upper two leaves three times during the growth stages using the phenological growth stage key developed by the Biologische Bundesanstalt, Bundessortenamt, and Chemical industry (BBCH), namely stages 37–41, 59–65, and 75. The area under the disease progress curve (AUDPC) was evaluated in each plot. In 2022, seed rates showed significant differences (p = 0.0047), while sowing times did not show significant differences. In contrast, both seed rate and sowing time showed significant effects in 2021 (p = 0.0004 for sowing time and p < 0.0001 for seed rate). During the 2021 growth stage BBCH 75, late sowing times exhibited a significant reduction in SLB on the first leaf. The reduction ranged from 47.0% to 52.6% compared to the optimal sowing time, and from 59.2% to 66.2% compared to the early sowing time. At optimal sowing times (between 11 September and 25 September), seed rates of 400 and 450 seeds/m2 resulted in a low SLB. At late sowing times in 2022, a lower SLB (43.2% compared to the early sowing time) was obtained from seed rates of 400 seeds/m2. No significant interaction was observed between sowing time and seed rate across both study years. In the absence of interaction, the effects of sowing time and seed rate on SLB severity were independent and not additive. In 2022, the highest values of AUDPC were recorded for the early sowing time and the highest seed rate. Increasing the seed rate (450 seeds m−2) gave higher AUDPC at early sowing time with significant differences compared to other seed rates at optimal or late sowing times. In conclusion, our findings highlight the significant influence of sowing time and seed rate on SLB severity in winter wheat. Understanding these factors can inform agricultural practices to better manage SLB. Future research should explore additional agronomic practices and environmental factors to develop comprehensive strategies for SLB management.

Assessment of wheat genotypes for spot blotch (Bipolaris sorokiniana Sacc.) resistance under artificial epiphytotic conditions in the inner terai of Nepal

Spot blotch, caused by (Bipolaris sorokiniana Sacc.) is a significant fungal disease leading to economic losses in wheat (Triticum aestivum), especially in regions with low soil fertility and warm, humid climates, such as the inner Terai of Nepal. A field experiment was conducted at the National Maize Research Program (NMRP), Rampur, Chitwan, during winter of 2021/022 with an aim of identifying wheat genotypes with spot blotch resistance under artificial epiphytotic conditions. Each genotype was sown in a single 2-meter long row alongside susceptible check genotypes (Agra and Morocco) at every 20th row. Aqueous spore suspension of B. sorokiniana was applied twice in border rows during the booting stage at 15-day intervals. Disease severity was assessed four times at five-day intervals using a double-digit scale based on the percentage blighted area on the flag and penultimate leaf, and the area under the disease progress curve (AUDPC) was calculated. The results categorized 43 genotypes as resistant, 127 as moderately resistants, 135 as moderately susceptible, 66 as susceptible, and 7 as highly susceptible based on AUDPC. Cluster analysis identified cluster 3 comprising 17 genotypes as superior in terms of disease resistance as well as agronomic parameters. NRN-34 emerged as the top-ranked genotype within this cluster, followed by NAL-73, NAL-94, NAL-12, NRN-34, NAL-57, NAL-43, NAL-82, and NAL-35, exhibiting lower AUDPC values and higher yield-attributing character values. This study will aid breeders in developing spot blotch-resistant and high-yielding wheat varieties by incorporating the identified promising genotypes into further breeding programs.

Development and validation of a standard area diagram set to assess corn grey leaf spot severity and foliar fungicide control efficacy

AbstractGrey leaf spot (GLS), caused by Cercospora spp., has become a very important foliar disease for second‐crop corn season, mainly in South America. Therefore, this study aimed to develop and validate a standard area diagram set (SADs) to estimate the severity of GLS and to apply the SADs established in this study to evaluate the efficacy of fungicides for GLS control in field trials. The SADs with nine levels of severity (0.5; 2; 5; 10; 20; 30; 40; 50 and 60%) improved accuracy, precision and reliability. To evaluate the control of GLS in corn, two experiments spraying chemical fungicides were conducted, one in Rio Verde (GO) (experiment A) and another in Chapadão do Sul (MS) (experiment B). Both experiments were conducted in randomized block design, with 10 treatments and four replicates. For the severity assessment, the SADs elaborated in this study was used. From this severity data over time, disease progress curves, area under the disease progress curve (AUDPC), and yield were obtained. Based on the AUDPC and yield values, all treatments differed from the control. The fungicide fluxapyroxad + pyraclostrobin + mefentrifluconazole had the highest value, giving 72.8% control efficacy and the highest yield maintenance of 43.5%. The other treatments had an intermediate control efficacy and yield. The SADs proposed here is a useful tool for improving visual assessments of GLS severity on corn leaves and fungicides can be used for integrated disease management.

Produtos alternativos isolados e associados a fungicida em diferentes épocas de semeadura no controle do oídio da soja

ABSTRACT: Soybean (Glycine max) is the most important legume cultivated in the world. With the aim of studying alternative products isolated and associated with fungicide on the efficiency of controlling powdery mildew (Microsphaera diffusa), in two sowing seasons, field experiments were conducted in Ponta Grossa, PR, Brazil, during the 2016/2017 and 2017/2018 seasons. The treatments were: 1- control (water), 2- Bacillus subtilis lineage QST, 3- Bacillus subtilis lineage QST associated with fungicide, 4- 1% chitosan, 5- 1% chitosan associated with fungicide, 6- sulfur, 7- sulfur associated with fungicide, 8- sodium hypochlorite, 9- sodium hypochlorite associated with fungicide, 10- fungicide (2 applications) and 11- fungicide (3 apllications). In all fungicide treatments, azoxystrobin + benzovindiflupyr with adjuvant was used. The variables evaluated were: powdery mildew severity and yield. The severity data made it possible to calculate the area under the disease progress curve (AUDPC). AUDPC values were higher in the second sowing season. Sulfur, chitosan and B. subtilis, isolated, reduced AUDPC, but when associated with the fungicide they obtained superior results. Sulfur, whether or not associated with the fungicide, provided less severity of the disease. The fungicide applied three times showed better control than two applications. The highest yield averages were, obtained in the first sowing season. There was no difference between the treatments during sowing in October for yield, this was affected by the treatments, only in the second sowing season, highlighting the sulfur associated with the fungicide.

Multi-environment evaluation of rice genotypes: impact of weather and culm biochemical parameters against sheath blight infection.

Sheath blight caused by Rhizoctonia solani is one of the major diseases of rice, causing widespread crop losses. The use of semi-dwarf rice varieties in the ongoing nutrient-intensive rice cultivation system has further accentuated the incidence of the disease. An ideal solution to this problem would be identifying a stable sheath blight-tolerant genotype. A multi-environment evaluation of 32 rice genotypes against sheath blight infection was conducted over six seasons across two locations (Agricultural Research Farm, Institute of Agricultural Sciences, Banaras Hindu University (28.18° N, 38.03° E, and 75.5 masl), for four years during the wet seasons (kharif) from 2015 to 2018 and two seasons at the National Rice Research Institute (20°27'09" N, 85°55'57" E, 26 masl), Cuttack, Odisha, during the dry season (rabi) of 2019 and the kharif of 2019, including susceptible and resistant check. Percent disease index data were collected over 4 weeks (on the 7th, 14th, 21st, and 28th day after infection), along with data on other morphological and physiological traits. The resistant genotypes across seasons were the ones with a higher hemicellulose content (13.93-14.64) and lower nitrogen content (1.10- 1.31) compared with the susceptible check Tapaswini (G32) (hemicellulose 12.96, nitrogen 1.38), which might explain the resistant reaction. Three different stability models-additive main effect and multiplicative interaction (AMMI), genotype + genotype x environment (GGE) biplot, and multi-trait stability index (MTSI)-were then used to identify the stable resistant genotypes across six seasons. The results obtained with all three models had common genotypes highlighted as stable and having a low area under the disease progress curve (AUDPC) values. The ideal stable genotypes with low disease incidence were IC 283139 (G19), Tetep (G28), IC 260917 (G4), and IC 277274 (G10), with AUDPC values of 658.91, 607.46, 479.69, and 547.94, respectively. Weather parameters such as temperature, rainfall, sunshine hours, and relative humidity were also noted daily. Relative humidity was positively correlated with the percent disease index.

Estimation of Genetic Parameters and Identification of Leaf Blast-Resistant Rice RILs Using Cluster Analysis and MGIDI

Rice blast disease, caused by the fungus Magnaporthe oryzae, poses a significant threat to rice cultivation. One effective way to deal with this disease is to identify and introduce resistant varieties using different breeding methods. This study utilized a population of 153 recombinant inbred lines (RILs) derived from the crossing of the Shahpasand (SH) and IR28 varieties, characterized by susceptibility and resistance to leaf blast, respectively. In combination with 12 control varieties, these genotypes were subjected to an extensive evaluation of disease severity (5 stages), the area under the disease progress curve (AUDPC), type, and the infection rate in 2021 and 2022. Analysis of variance revealed significant genetic variation, highlighting the potential of the RIL population for identifying and selecting resistant lines. Employing cluster analysis and the multi-trait genotype-ideotype distance index (MGIDI), 17 lines were identified as the most resistant over a two-year evaluation period. The average AUDPC for these resistant lines was estimated at 2.435 ± 0.114, and lines 17 and 111 had the lowest AUDPC (1.526 and 1.630, respectively) and showed the least infection in two years. Conversely, lines 42 and 43 showed the highest AUDPC values (255.312 and 248.209) along with heightened sensitivity. The use of MGIDI yielded a substantial selection differential (SD) of −59.12% for traits related to leaf blast disease resistance, demonstrating the effectiveness of this method. Furthermore, new recombinant populations are expected to be developed in future plant breeding projects by crossing the most susceptible and resistant lines, which will be new sources of resistance to this disease.

Differential susceptibility of two Citrullus amarus pollenizer watermelons to five species of Pythium and Globisporangium.

Pollenizer watermelon (Citrullus amarus) must be planted alongside triploid watermelon cultivars to provide a source of pollen. Early season death of pollenizer watermelon cultivars SP-6 and SP-7 was observed in a research field in Charleston County, South Carolina, in April 2022, 3 to 4 weeks after transplanting. Disease incidence was 15% and 12% for the two cultivars, respectively. Two species of Pythium, P. myriotylum (four isolates) and P. aphanidermatum (three isolates), and three species of Globisporangium, G. ultimum (one isolate), G. irregulare (one isolate), and G. spinosum (four isolates), were recovered from 13 of 17 plants cultured and identified based on the sequences of the cytochrome c oxidase subunit I gene. Pythium spp. were recovered from both cultivars, while Globisporangium spp. were recovered only from SP-7. In pathogenicity tests, SP-7 had lower area under the disease progress curve (AUDPC) values than SP-6 with one isolate each of four species and lower AUDPC values than seedless watermelon Estrella with one isolate each of two species. Mean AUDPC values did not differ between Estrella and SP-6 with any isolate. AUDPC values were greater with G. ultimum on all three cultivars than with one isolate of G. spinosum and both isolates of P. myriotylum and P. aphanidermatum. Susceptibility of the new cultivar SP-7 to Pythium and Globisporangium spp. differs from susceptibility of SP-6. These results will help growers choose which pollenizer cultivar to plant.

Field Screening of Cotton Genotypes for Resistance to Cotton Leaf Curl Disease (CLCuD) in Sindh

Cotton leaf curl disease (CLCuD) caused by Begomovirus(s) is economically important disease of cotton in Pakistan. Management of CLCuD using natural sources of resistance has great significance and is recognized as long term management strategy. In present study, we evaluated resistant potential of 33 cotton genotypes in agro-ecosystem of Sindh, Pakistan within thrice repeated experiments. Observations were taken at interval of 30 days after sowing on incidence and severity of CLCuD under field conditions. Then the disease index was calculated from values of initial observations on incidence and severity of the disease at each time point and finally Area Under the Disease Progress Curve (AUDPC) was calculate for the disease index and presented as semi-quantitative estimate of the disease. Results showed that there was significant difference among AUDPC values of the disease index of tested genotype (LSD=41666, P=0,0000 and LSD=70297, P= 0.0000) during 2018 and 2019, respectively. Significantly highest AUDPC value was recorded in BT.CIM-678 (664109) followed by CRIS-585 (277732) and CRIS-613 (133917) and CRIS-522 (159272) during 2018. The remaining genotypes gave significantly lower AUDPC values. Similar results were obtained during next year of experiment. Therefore, it is concluded that cultivation of BT.CIM-678, CRIS-585, CRIS-613 and CRIS-522 should be avoided in agro-ecosystem of Sindh. Further studies should be conducted for eco-friendly management of the disease.

Tree Architecture and Powdery Mildew Resistance of Yellow-flowering Magnolias in Tennessee, USA

Magnolias (Magnolia sp.) are economically important woody ornamental plants; however, plant damage associated with frost and powdery mildew (Microsphaera alni and Phyllactinia corylea) disease is a major production challenge. To understand the tree architecture and powdery mildew resistance, 26 yellow-flowering magnolias (Magnolia sp.) were evaluated in McMinnville, TN, USA (USDA Plant Hardiness Zone 6b). One-year-old containerized trees were planted in a field plot during Mar 2006, with 4.6-m plant-to-plant and 3.7-m row-to-row spacing. The experiment was a completely randomized block design with three single-plant replications. Plant height and canopy diameter were measured on Dec 2016 and Feb 2018, and the apical dominance ratio (i.e., indicating tree architecture) was calculated by dividing the height by the canopy diameter. Plants were evaluated for powdery mildew severity and defoliation using a scale of 0% to 100% of the total plant canopy affected or defoliated, respectively, from Aug to Oct of 2016 and 2017. The area under the disease progress curve (AUDPC) was calculated for the evaluation period of each year. The plant apical dominance ratio ranged from 1 to 3, with ‘Gold Cup’ and ‘Sun Spire’ having the highest value, and ‘Lois’, ‘Gold Star’, ‘Golden Gala’, ‘Solar Flair’, ‘Stellar Acclaim’, ‘Sun Ray’, ‘Sunburst’, and ‘Sundance’ having the lowest value (i.e., relatively round shape). Of the 26 cultivars, Sundance, Sun Spire, Sun Ray, and Gold Cup had the lowest powdery mildew severity (10% to 33% in 2016 and 40% to 60% in 2017), AUDPC, and defoliation. Cultivars Anilou, Gold Star, Golden Pond, Golden Rain, Golden Sun, Green Bee, Honey Liz, Judy Zuk, Koban Dori, Lois, Solar Flair, Stellar Acclaim, and Yellow Bird were highly susceptible to powdery mildew (>80% disease severity) and had the highest AUDPC values. Results of this research may aid breeders, nursery producers, and landscapers when selecting yellow-flowering magnolia cultivars with desirable tree architecture and resistance to powdery mildew.

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.

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<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<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.

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.

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.

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.

Evaluation of wheat (Triticum aestivum L.) genotypes for spot blotch (Bipolaris sorokiniana Sacc) resistance in terai condition of Nepal

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. The experiment set was received from CIMMYT comprises 52 genotypes and arranged in alpha lattice design with two replications in 2017/18 at National Wheat Research Program, Bhairahawa, Nepal, and Regional Agricultural Research Station, Parwanipur, Bara, Nepal. Each plot size was 8 rows of 2 meters long. Three times disease scoring was done in the double-digit method and calculated the Area under the disease progress curve (AUDPC). Other data were analyzed by using R software (4.2.2). Heading days, days to maturity, plant height, number of grains per spike (NGPS), number of tillers per meter square (NTPM), mean AUDPC, thousand-grain weight (TGW), and grain yield were found highly significant. The genotype 8HLBSN47 was found the highest yielder (4996kg/ha) with a 304 mean AUDPC value. Seventeen genotypes (15.3%) found the lowest mean AUDPC, Penultimate leaf AUDPC, Flag leaf AUDPC, and the highest number of tillers per square meter, number of grains per spike, thousand-grain weight, and grain yield.

Development of winter wheat leaf blotches depending on meteorological conditions

Tan spot (caused by Pyrenophora tritici-repentis) and Septoria tritici blotch (caused by Zymoseptoria tritici) are the most widespread winter wheat leaf blotches in Latvia. Precipitation and air temperature are important factors in the development of fungal diseases. The aim of the present research was to clarify the development of leaf blotches in winter wheat depending on meteorological conditions. A field trial was conducted at the Research and Study farm “Peterlauki” (Latvia) of the Latvia University of Life Sciences and Technologies in 2018–2021. The disease impact during the vegetation periods was estimated by calculating the area under the disease progress curve (AUDPC). The severity of leaf blotches in winter wheat leaves differed significantly during the four vegetation seasons. Tan spot was the dominant disease in 2018, 2019 and 2021 (respectively 2.12%, 18.7% and 4.1% in the untreated variant at the time of grain ripening (GS 75–79)), when weather conditions were dry and warm. The first symptoms of tan spot were observed already at GS 31–32, but rapid development of the disease began at the time of grain ripening (GS 73–79 depending on year). In such conditions, Septoria tritici blotch started later and its progression was slower than that of tan spot. Septoria tritici blotch dominated in 2020 (11.4% in the untreated variant at GS 75–79), when precipitation amount was high. The first symptoms were observed at GS 31–32, but rapid disease development started at GS 73 (2.7% in untreated variant) which coincided with rainfall. The differences in average AUDPC values during investigation years fluctuated within a range of 13–142 units for tan spot and 1–57 units for Septoria tritici blotch. The research was supported by the EIP–Agri project “The development of the decision–making support system for restriction of the diseases, affecting leaves and ears of winter wheat”.

Performance of Wheat (Triticum aestivum L.) Genotypes for Spot Blotch (Bipolaris sorokiniana Sacc.) Resistance in Terai Condition of Nepal

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. The experiment set was received from CIMMYT comprises 52 entries and arranged in alpha lattice design with two replications in 2017/18 at National Wheat Research Program, Bhairahawa, Nepal, and Regional Agricultural Research Station, Parwanipur, Bara, Nepal. Each plot size was 8 rows of 2 meters long. Three times disease scoring was done in the double-digit method and calculated the Area under the disease progress curve (AUDPC). Other data were analyzed by using R software (4.2.2). Heading days, days to maturity, plant height, number of grains per spike (NGPS), number of tillers per meter square (NTPM), mean AUDPC, thousand-grain weight (TGW), and grain yield were found highly significant. The genotype 8HLBSN47 was found the highest yielder (4996kg/ha) with a 304 mean AUDPC value. Seventeen genotypes (15.3%) found the lowest mean AUDPC, Penultimate leaf AUDPC, Flag leaf AUDPC, and the highest number of tillers per square meter, number of grains per spike, thousand-grain weight, and grain yield. Keywords: AUDPC, spot blotch, genotypes, HLBSN