Progress Curve Research Articles

Cryo-EM Structure of Recombinantly Expressed hUGDH Unveils a Hidden, Alternative Allosteric Inhibitor.

Human UDP-glucose dehydrogenase (hUGDH) catalyzes the oxidation of UDP-glucose into UDP-glucuronic acid, an essential substrate in the Phase II metabolism of drugs. hUGDH is a hexamer that exists in an equilibrium between an active (E) state and an inactive (EΩ) state, with the latter being stabilized by the binding of the allosteric inhibitor UDP-xylose (UDP-Xyl). The allosteric transition between EΩ and E is slow and can be observed as a lag in progress curves. Previous analysis of the lag suggested that unliganded hUGDH exists mainly as EΩ, but two unique crystal forms suggest that the enzyme favors the E state. Resolving this discrepancy is necessary to fully understand the allosteric mechanism of hUGDH. Here, we used cryo-EM to show that recombinant hUGDH expressed in Escherichia coli copurifies with UDP-4-keto-xylose (UX4O), which mimics the UDP-Xyl inhibitor and favors the EΩ state. Cryo-EM studies show that removing UX4O from hUGDH shifts the ensemble to favor the E state. This shift is consistent with progress curve analysis, which shows the absence of a lag for unliganded hUGDH. Inhibition studies show that hUGDH has similar affinities for UDP-Xyl and UX4O. The discovery that UX4O inhibits allosteric hUGDH suggests that UX4O may be the physiologically relevant inhibitor of allosteric UGDHs in bacteria that do not make UDP-Xyl.

Sensitivity of Septoria lycopersici Speg. isolates to fungicides in Brazil

Disease management using synthetic fungicides is the main strategy used by tomato growers to prevent tomato yield reductions caused by Septoria leaf spot (SLS). Despite the importance of this plant disease, there is little information about the sensitivity of Septoria lycopersici isolates to fungicides. The sensitivity of 94 isolates of S. lycopersici to azoxystrobin, chlorothalonil, tebuconazole, and thiophanate-methyl was assessed in experiments using fungicide-amended 96-well microtiter plates. The highest EC 50 values above 100 mg/L were detected for azoxystrobin, thiophanate-methyl, and tebuconazole. Based on these results, five isolates classified as resistant and five as sensitive to each fungicide were selected for the experiments. Tomato plants were inoculated with sensitive (S) and resistant (R) isolates and sprayed by the fungicides in three greenhouse assays. The differences in the values of the area under the progress curve of Septoria leaf spot (AUDPC), disease severity progress, and progress rates were not so pronounced between tomato plants sprayed and non-sprayed with fungicides. The AUDPC values for plants inoculated with S and R isolates and treated with chlorothalonil, tebuconazole, and thiophanate-methyl ranged from 10 to 320, 0 to 80, and 50 to 150, respectively. For azoxystrobin, the AUDPC values were around 200 in plants inoculated with S and R isolates. There is evidence of reduced sensitivity of individuals of S. lycopersici to azoxystrobin, tebuconazole, and thiophanate-methyl in the population in Brazil. Therefore, tomato growers should rotate and combine fungicides with different mechanisms of action and low-risk of resistance to control SLS.

Ametoctradin + dimethomorph spray frequency affects late blight disease and yield in potato genotypes

AbstractPotato (Solanum tuberosum L.) production is hindered by several diseases, the worst being the late blight disease caused by Phytophthora infestans (Mont) de Bary. This study aimed at determining an appropriate frequency of ametoctradin + dimethomorph ([26.9 + 20.2]%) spray for late blight disease management in potato genotypes. Field experiments were conducted in Bansoa, Cameroon, from August to October in 2019 and 2020 growing seasons The experimental design was a split‐plot design with three replications. Three ametoctradin + dimethomorph spray frequencies (4‐, 7‐, and 10‐day intervals) were tested at the plot level, whereas seven genotypes including Banso, CIPIRA, Desiree, Dosa, Jacob2005, Manate, and Tezelfo were tested at the subplot level. The commonly used fungicide combination, which includes Mancozeb 80% wettable powder supplemented with cymoxanil + chlorotalomil [(30 + 6)%] wettable powder, was sprayed at 3‐day intervals (a total of 18 sprays) and was used as a positive control. Negative control plots were not sprayed. Data were collected on late blight rAUDPC (relative area under the disease progress curve) and yield components. Results showed all fungicide spray frequencies reduced rAUDPC and consequently increased potato yield. The most economically efficient spray frequency was the 7‐day interval with a total of nine sprays, which resulted in an increased net return of $9738 ha−1 with 9.6% profitability against the commonly used fungicide mix. The total number of fungicide sprays could be reduced to six for genotypes Banso and CIPIRA, which showed lower rAUDPC. The mean yield loss associated with unsprayed plots was 93.2%.

Screening Taro Germplasm against Bacterial Blight Incited by Xanthomonas axonopodis pv. dieffenbachia

Sixty-four Taro germplasm accessions from north east India along with two national released varieties were evaluated in natural epiphytotic field condition against bacterial blight incited by Xanthomonas axonopodis pv. dieffenbachia for two consecutive seasons during 2018 and 2019 at an Experimental Farm for Horticultural crops, Assam Agricultural University, Jorhat. The results obtained for the two growing seasons were pooled together. Per cent disease incidence and disease severity ranged from 23.81 (Nepali-2) to 78.57 % (SC-1) and 14.17 (Nepali-2) to 67.50 % (SC-1) respectively. The area under the disease progress curve (AUDPC) which directly corresponds to the bacterial disease infection with time resulting in more susceptibility to the disease ranged from 1612.5 (Sreekiran) to 9812.5 (SC-1). AUDPC was calculated from the per cent disease severity obtained from the first day of disease observation till the last day i.e. from 60 to 240 days after transplanting (DAT). The disease reactions of different germplasm to bacterial blight of colocasia were evaluated based on the disease severity (%) and disease rating scale whereby no cultivars were immune and highly susceptible to the disease. Four accessions viz. Sreekiran, Naga-2, Chandil Pin, Nepali-2 were resistant, twenty-one were moderately resistant, twenty-six were moderately susceptible and fifteen were susceptible. Variety/germplasm resistant to bacterial blight of Taro have not been reported till date. Proper selection of resistant varieties will be useful in breeding programmes and for further crop improvement.

Evaluation of Novel Picolinamide Fungicides (QiI) for Controlling Cercospora beticola Sacc. in Sugar Beet

Studies were initiated to find new effective fungicides to use under field conditions to discover novel approaches for optimizing disease management in sugar beet crops. Cercospora leaf spot (CLS), a prevalent foliar disease in sugar beet crops worldwide, is caused by the fungal pathogen Cercospora beticola Sacc. This disease has become the most prevalent pathogen in sugar beet crops across nearly all European growing regions, including Hungary. The epidemic spread of this disease can cause up to 50% yield loss. The use of fungicides has been a cornerstone in managing CLS of sugar beet due to the limited efficacy of non-chemical alternatives. However, the emergence of fungicide-resistant strains of Cercospora beticola Sacc. in recent decades has compromised the effectiveness of certain fungicides, particularly those belonging to the QoI (FRAC Group 11) and DMI (FRAC Group 3) classes. Hungary is among the many countries where resistance to these fungicides has developed due to their frequent application. Picolinamides represent a novel class of fungal respiration inhibitors targeting Complex III within the Quinoine-Inside Inhibitor (QiI) group. Two innovative fungicides from this class, fenpicoxamid and florylpicoxamid (both classified under FRAC Group 21), were evaluated for their efficacy in managing CLS of sugar beet in Hungary during the 2020 and 2021 growing seasons. Both fungicides were applied as formulated products at various application rates and demonstrated superior efficacy in controlling CLS compared to untreated control plots and the reference fungicides difenoconazole and epoxiconazole. The results consistently demonstrated that all tested application rates of fenpicoxamid and florylpicoxamid effectively controlled CLS in sugar beet, exhibiting a clear dose–response relationship. Disease severity, as measured by the area under the disease progress curve (AUDPC), was significantly correlated with yield reduction but showed no significant association with root sugar content. Moreover, data from both study years indicated that picolinamide fungicides applied at a rate of 75 g ai/ha significantly outperformed difenoconazole (100 g ai/ha) in controlling the CLS of sugar beet. Additionally, higher application rates of picolinamides at 100–150 g ai/ha outperformed epoxiconazole at 125 g ai/ha in disease suppression. Fenpicoxamid is currently registered for use in cereals within Europe, and outside of Europe in Banana against Black Sigatoka (eff. Mycosphaerella fijiensis). Florylpicoxamid, while not yet registered in Europe, is undergoing approval processes in various countries worldwide for a range of crops and is continually being evaluated for potential market introduction. Additional details regarding the efficacy of florylpicoxamid against CLS in sugar beet were presented at ‘The 10th International Conference on Agricultural and Biological Sciences (ABS 2024, Győr-Hungary)’ in 2024.

Comparing Alternative Non-Selective Herbicides in Oregon and New Mexico

Abstract Municipalities are considering alternatives to traditional herbicides for suppressing weeds and vegetation in areas frequented by the public. Two field experiments were conducted to test the efficacy of alternative non-selective herbicides: one in Corvallis, Oregon, on a mixed lawn of perennial ryegrass, annual bluegrass, and broadleaf weeds, and another experiment in Las Cruces, New Mexico, on a predominantly bermudagrass lawn with broadleaf weeds. The experimental objective was to quantify and compare the effects of repeated applications of ten non-selective herbicides to terminate a lawn with mixed vegetation. Applications were made every two weeks for four applications starting on 15 April 2022 in Corvallis and 26 May 2022 in Las Cruces. Data collected included the percent green cover over time calculated using an area under the percent green cover progress curve (AUPGCPC), the percent green cover at the conclusion of the experiment, and the change in monocot and dicot density over the course of the experiment. All treatments resulted in a lower AUPGCPC compared to water only except for mint oil + sodium lauryl sulfate + potassium sorbate. The only treatments with an average percent green cover less than 50% was a combination of ammoniated soap of fatty acids + maleic hydrazide (47% green cover) in Corvallis and pelargonic acid (38%) in Las Cruces, suggesting that more applications would be needed to terminate the lawn under similar circumstances. At the conclusion of the experiment, the water only plots averaged 90% and 93% green cover in Corvallis and Las Cruces, respectively. The change of monocot and dicot densities over the course of the experiment indicated that some of the products tested may be more sensitive to dicots, or in some cases monocots, suggesting a potential for future selective herbicide research in certain locations and climates.

Copper Efficacy Field Trials for Control of Pseudomonas syringae pv. tabaci in Nicotiana tabacum Production

Since 2015, Pseudomonas syringae pv. tabaci tox− has become the most significant foliar disease in the dark tobacco growing regions of Kentucky and Tennessee. Streptomycin sulfate, the main control mechanism that growers utilize to combat this bacterial disease, has evidence of resistance at 200 ppm. Field trials were established to evaluate the efficacy of copper-based products for control of angular leaf spot compared with streptomycin sulfate. Field trials were conducted from 2020 to 2022 at the West Farm of Murray State University in Murray, KY, to evaluate the efficacy of streptomycin sulfate, cuprous oxide, copper sulfate pentahydrate, and copper octanoate. In all years, the moderately susceptible dark tobacco variety KT D8LC was planted and inoculated with a streptomycin-sensitive isolate of P. syringae pv. tabaci. Tobacco treated with five applications of copper octanoate had a lower area under the disease progress curve (AUDPC) than tobacco treated with streptomycin sulfate in 2020 and 2022. Data analysis showed that in one of the three years, tobacco treated with cuprous oxide had a higher yield compared with tobacco treated with streptomycin sulfate. Tobacco treated with cuprous oxide had a higher quality grade index compared with streptomycin sulfate in 2020. Although no treatment eliminated this bacterial disease, copper products, particularly cuprous oxide and copper octanoate, are suitable alternatives to streptomycin sulfate for management of angular leaf spot.

Assessing Broccoli Cultivar Susceptibility to Alternaria brassicicola in Georgia

Alternaria leaf blight and head rot (causal agent: Alternaria brassicicola and other Alternaria species) in broccoli ( Brassica oleracea L. var. italica) can lead to decreased yields, reduced head quality, and postharvest losses. While cultural practices and fungicides can decrease disease severity, further work is needed to determine resistance or susceptibility in commercial cultivars. This study evaluated the susceptibility of 26 cultivars against A. brassicicola in fall 2021 and 2022 at two locations in Georgia (Tifton and Watkinsville). Commonly used cultivars in the eastern United States were selected and grown in a randomized complete block design. Approximately 20 days after transplant, plants were inoculated with a conidial suspension of A. brassicicola and monitored for disease development. Foliar disease severity, foliar area under the disease progression curve (AUDPC), head disease severity, and yield were determined for each cultivar at each location. Significant differences existed among cultivars (year × location) for foliar AUPDC and head disease severity. Foliar AUPDC ranged from 299 to 1,818 for both years and locations, and head disease severity ranged from 1 to 81% across both years and locations. In this study, cultivars ‘Eastern Crown’, ‘Emerald Jewel’, ‘Lieutenant’, and ‘Abrams’ had greater foliar and head disease severity and lower marketable yields in both locations and years. The cultivars ‘Vallejo’, ‘Emerald Pride’, ‘Burney’, ‘Belstar’, ‘Iron Man’, and ‘Marathon’ exhibited low disease severity across both locations and years and maintained greater marketable yields. Proper selection of commercially available cultivars could help growers maintain yields in areas with high A. brassicicola pressure.

Minimized‐rate topramezone programs for goosegrass [Eleusine indica (L.) Gaertn.] control in Florida

AbstractGoosegrass [Eleusine indica (L.) Gaertn.] is one of the most troublesome warm‐season grassy weeds in subtropical climates of the southern United States. Currently, postemergence options are highly limited, and goosegrass control (GC) becomes more difficult as plants mature. Among current options, topramezone can control mature goosegrass. Research conducted in Florida suggests that despite seemingly effective control, recovery may be occurring from surviving roots. Therefore, this study assessed strategies aimed to ensure the persistent removal of mature goosegrass populations of Florida ecotypes. Two greenhouse studies were conducted to evaluate the response of goosegrass at one to three tillers and 4–10 tillers to topramezone applied once at rates from 0.8 to 12.2 g a.i. ha−1 (study 1) and at total rate reduced to 6.1 g a.i. ha−1 applied once or equally divided into two, four, or eight biweekly applications (study 2). Single topramezone applications at 6.1 g a.i. ha−1 provided comparable GC and biomass reduction to single applications at 12.2 g a.i. ha−1. Reduced rate‐based split‐programs of two and four biweekly applications improved GC and its persistence over a single application as evidenced by a >250 increase in GC area under the progress curve and a >20 days increase in days over 80% GC. Among the proposed extended application programs based on the reduced effective rate of topramezone, the most promising consists of four biweekly applications at a 0.125× rate, equivalent to 1.53 g a.i. ha−1.

Field Efficacy of Fungicides for the Management of Rice Neck Blast (Caused by Pyricularia oryzae) in the North‐Western Region of Haryana, India

ABSTRACTNeck blast is one of the most damaging fungal disease of rice, causing severe yield losses in the North‐Western region of Haryana, India. Due to the lack of resistant cultivars commonly grown in Haryana, the management of the disease has relied predominantly on the foliar application of fungicides. Therefore, this study evaluated the field efficacy of various fungicides against rice neck blast in the North‐Western region of Haryana, India, over the kharif seasons of 2020, 2021 and 2022. Fungicides were applied twice per season, at panicle emergence and 10 days later. Among the seven fungicides tested, isoprothiolane 40% EC, propineb 70% WP and difenoconazole 25% EC significantly reduced neck blast severity by 63.2%, 55.2% and 47.3% in 2020; 60.6%, 51.4% and 47.4% in 2021; and 70.0%, 64.9% and 62.5% in 2022, respectively with corresponding reductions in area under disease progress curve values compared with the untreated control. The highest grain yield was recorded for isoprothiolane 40% EC, followed by propineb 70% WP and difenoconazole 25% EC. The greatest increase in grain yield was observed in kharif 2020, whereas the lowest yield in kharif 2022 was associated with moderate total rainfall (284 mm) and high average relative humidity (94.4%) following the appearance of neck blast. These results suggest that these fungicides are effective in reducing rice neck blast and enhancing grain yield in the North‐Western region of Haryana, India.

Severity and Reaction to Bacterial Spot of Tomato Hybrids For Industrial Processing

ABSTRACTThe complexity of phytosanitary control for bacterial spot disease is a major challenge in tomato production for industrial processing. The climatic conditions in Goiás and the number of species causing the disease make this management difficult. Thus, this study aimed to evaluate the severity and reaction to bacterial leafspot of sixteen tomato hybrids for industrial processing under the Cerrado conditions in Goiás. The experiment was carried out in randomised blocks, with sixteen tomato hybrids for industrial processing with five replicates, in Hidrolândia‐GO. Once the bacterial spot presence in the area was verified, a severity assessment was performed weekly with a diagrammatic scale, totalling five assessments. The area under the disease progress curve (AUDPC) was calculated. At 115 days after transplanting (DAT), harvesting was performed manually, and vegetative development, yield, number of fruits with Xanthomonas spp. symptoms and scalding by the sun. Bacterial spot symptoms were observed in all hybrids evaluated. Above all, the symptoms observed in the fruits and leaves do not coincide with the hybrid showing the greatest disease severity. The hybrid CVR 6116 had the highest yield, lowest AUDPC and the lowest number of fruits with bacterial‐spot and sunscald damage symptoms.

Survey, isolation and characterisation of Bipolaris sorokiniana (Shoem.) causing spot blotch disease in wheat under the climatic conditions of the Indo–Gangetic plains of India

Wheat spot blotch has emerged as a disease of significant concern in recent years. The pathogen Bipolaris sorokiniana can infect stems, leaves, roots and seeds, increasing its impact. The pathogen is particularly prevalent in the wheat growing zone of West Bengal, which provides congenial conditions for the growth and development of the pathogen. However, its knowledge under West Bengal conditions is inadequate. To address this issue, isolates of Bipolaris sorokiniana were collected from different locations in West Bengal. The pathogenic species were identified via comprehensive morphological studies supplemented with internal transcribed spacer (ITS)-rDNA sequence analysis and pathogenicity. The disease severity of the twelve isolates collected varied among the surveyed locations, ranging from 44.03% to 81.48 %. The greatest radial growth was observed in BSC11 (50.07 mm), whereas the lowest growth was recorded in BSC9 (6.47 mm) at 96 h after inoculation. Molecular studies confirmed that the isolates were Bipolaris sorokiniana. In pathogenicity assays, BSC11 presented the highest area under the disease progress curve (AUDPC) (380.05) and percent disease index (PDI) among the isolates at 20 dai (38.33 %). The correlation matrix revealed that disease severity was positively correlated with the number of spores (r2 = 0.70), growth rate of mycelia (r2 = 0.77), and lesion size (r2 = 0.74), whereas the length of the spores, incubation period, and latent period were negatively and significantly correlated with disease severity. Establishing the aggressiveness of a pathogen is pivotal in studying host‒ interactions. Our study established BSC11 as a highly virulent pathogen isolate that can be used further for comprehensive analysis of wheat‒Bipolaris sorokiniana interactions.

Allelopathic interactions of Carthamus oxyacantha, Macrophomina phaseolina and maize: Implications for the use of Carthamus oxyacantha as a natural disease management strategy in maize.

Fungicides are used to control phytopathogens but all these fungicides have deleterious effects. Allelopathic interactions can be harnessed as a natural way to control the pathogens but there are no reports that show the allelopathic interactions of donor plant, recipient crop, as well as the target plant pathogen and the material used for inoculum production. So, in the present study, the suitability of Carthamus oxyacantha M. Bieb. was assessed against Macrophomina phaseolina, the cause of charcoal rot in maize. Among the various treatments in pot experiment, a negative control, 3 concentrations of inoculum (1.2×105, 2.4×105, and 3.6×105 colony forming units (CFU) mL-1, 3 concentrations (0.5, 1.0, and 1.5% w/w) of C. oxyacantha along with an autoclaved M. phaseolina (Mp) and C. oxyacantha alone were included to investigate their allelopathic effects on maize, not investigated earlier. Maximum suppression of the disease was observed by 1.5% (w/w) concentration of C. oxyacantha. Soil amendment with C. oxyacantha significantly suppressed the disease incidence (DI) and disease severity index (DSI) in charcoal rot of maize up to 40 and 55%, respectively over the strongest level of inoculum (Mp3). C. oxyacantha not only reduced area under disease incidence progress curve (AUDIPC) and area under disease severity progress curve (AUDSPC), but also improved the morphological, biochemical and physiological parameters of maize. The maximum increase of 48, 65, and 75% in values of shoot length (SL), shoot dry mass (SDM), and root dry mass (RDM), respectively was observed by application of the highest concentration of C. oxyacantha in the treatment Mp1+Co3, over infested control (Mp1). Photosynthetic pigments, such as chlorophyll a, chlorophyll b and carotenoids were increased to 58, 64, and 46%, respectively over Mp1, by the application of C. oxyacantha. Carbon assimilation rate (A), stomatal conductance (gs), rate of transpiration (E), and internal carbon dioxide concentration (Ci) were significantly increased to 58, 48, 48, and 20%, respectively over infested control (Mp3), by application of C. oxyacantha concentration 1.5 (w/w). Moreover, defense enzymes like superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities were boosted up to 27, 28, and 28% over Mp3, respectively. Positive allelopathy of C. oxyacantha towards maize and negative allelopathy towards M. phaseolina makes C. oxyacantha a suitable candidate for charcoal rot disease control in maize.

Identification of Resistance to <i>Puccinia striiformisf</i>. sp. <i>tritici</i> (<i>Pst</i>) in Some Commercial and Elite Bread Wheat Lines

Stripe rust is caused by <i>Puccinia striiformisf</i>. sp. <i>tritici</i> (<i>Pst</i>) threatening wheat production in Ethiopia. The emerged virulent stripe rust races at one point of the world spread to the rest of wheat-producing countries by the wind as well as human travels and damaged popular resistant wheat cultivars thereby posing food insecurity. However, wheat cultivars succumb to new Pst race (s) soon after their release from research centers. This study aimed to determine stripe rust resistance in some Ethiopian commercial and elite bread wheat lines. In 2017, a total of 37 commercial and elite bread wheat lines were exposed to stripe rust in under the disease hot spot areas (Kulumsa and Meraro) Arsi zone Oromia regional state. In the second year (2018), 22 promising lines consisting of 16 commercial bread wheat and 6 elite’s lines were evaluated both at seedling and adult plant growth stages. The seedling test was conducted in the greenhouse at Kulumsa research center using three Pst races. In field evaluations, terminal severity (TRS), coefficient of infection (CI), area under disease progress curve (AUDPC), disease progress rate (DPR), and spike infection (SI) were considered. Of the 37 commercial and elite bread wheat lines, 19 (51.4%) exhibited lower or equal disease reaction compared to the resistant check (Enjoy) across locations and seasons. Eleven bread wheat lines showed both adult plant and seedling resistance. The 37 commercial wheat lines that showed field resistance was further exposed to three Pst races at the seedling stage and 11 exhibited seedling resistance to all races. This study has identified seedling and adult plant resistance in some commercial and elite bread wheat lines to the prevailing Pst races.

Assessing Soybean Cultivar Resistance to Target Spot Using a Detached Leaf Assay

Target spot (TS), caused by the fungus Corynespora cassiicola, is a foliar disease of increasing importance to soybean in the United States. Identifying cultivar resistance to TS is challenging. The objective of this research was to determine the reactions of a diverse collection of soybean genotypes to TS using a detached leaf inoculation method. A detached unifoliate leaf of each soybean genotype was placed in a Petri dish on moist filter paper, wounded at three locations, inoculated with 10 μl of a 105-conidial suspension of C. cassiicola, and incubated at room temperature (23°C). The percent leaf area with TS symptoms (TSS) was measured digitally at 7, 10, 14, and 17 days after inoculation (DAI), and the area under the disease progress curve (AUDPC) was calculated. Thirty-seven soybean genotypes and three soybean cultivars were evaluated in three replicated trials. At 17 DAI, TSS ranged from 2 to 84%. Significant differences occurred between soybean genotypes at each rating time in each trial. Across the three trials, the reaction of most soybean genotypes ranged from resistant to susceptible. These soybean genotypes were evaluated in the field with natural inoculum at two locations in 2022. TS developed late but differed significantly between genotypes, averaging from 0.35 to 3.35% TSS. Field results were not significantly correlated to the detached leaf results. The detached leaf assay is another tool for screening soybean genotypes for resistance to TS but needs field validation. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Development of infectious clones of mungbean yellow mosaic India virus (MYMIV, Begomovirus vignaradiataindiaense) infecting mungbean [Vigna radiata (L.) R. Wilczek] and evaluation of a RIL population for MYMIV resistance.

Yellow mosaic disease (YMD) is a major constraint for the low productivity of mungbean, mainly in South Asia. Addressing this issue requires a comprehensive approach, integrating field and challenge inoculation evaluations to identify effective solutions. In this study, an infectious clone of Begomovirus vignaradiataindiaense (MYMIV) was developed to obtain a pure culture of the virus and to confirm resistance in mungbean plants exhibiting resistance under natural field conditions. The infectivity and efficiency of three Agrobacterium tumefaciens strains (EHA105, LBA4404, and GV3101) were evaluated using the susceptible mungbean genotype PS16. Additionally, a recombinant inbred line (RIL) population comprising 175 lines derived from Pusa Baisakhi (MYMIV susceptible) and PMR-1 (MYMIV resistant) cross was developed and assessed for YMD response. Among the tested Agrobacterium tumefaciens strains, EHA105 exhibited the highest infectivity (84.7%), followed by LBA4404 (54.7%) and GV3101 (9.80%). Field resistance was evaluated using the coefficient of infection (CI) and area under disease progress curve (AUDPC), identifying seven RILs with consistent resistant reactions (CI≤9) and low AUDPC (≤190). Upon challenge inoculation, six RILs exhibited resistance, while RIL92 displayed a resistance response, with infection occurring in less than 10% of plants after 24 to 29 days post inoculation (dpi). Despite some plants remaining asymptomatic, MYMIV presence was confirmed through specific PCR amplification of the MYMIV coat protein (AV1) gene. Quantitative PCR revealed a very low relative viral load (0.1-5.1% relative fold change) in asymptomatic RILs and the MYMIV resistant parent (PMR1) compared to the susceptible parent (Pusa Baisakhi). These findings highlight the potential utility of the developed infectious clone and the identified MYMIV-resistant RILs in future mungbean breeding programs aimed at cultivating MYMIV-resistant varieties.

Timing of Alzheimer's disease biomarker progressions: A two-decade observational study from the Alzheimer's Disease Neuroimaging Initiative (ADNI).

Alzheimer's Disease Neuroimaging Initiative (ADNI) has been pivotal in identifying and refining Alzheimer's disease (AD) biomarkers for clinical trials. This study leverages longitudinal data from participants who have progressed to amyloid-positivity during their study participation to track evolution of biomarkers and cognitive function. We modeled AD biomarker (positron emission tomography [PET], structural, cerebrospinal fluid [CSF], cognition) trajectories before and after observed amyloid-positivity onset time to detect time at which each biomarker had detectable trajectory changes. Analysis of a sub-cohort of the 20-year ADNI study (N=90) recapitulated Alzheimer's progression beginning with amyloid alterations -4.8 to -5.3 years relative to amyloid-positivity, succeeded by neurodegeneration (t=-4.0 to -4.1 years), and CSF tau (t=-0.4 to -0.5 years). Cognitive decline was observed to significantly correspond with emergence of amyloid-positivity (t=0.2 to 2.4 years). Our results corroborate temporal progression curves of AD biomarkers, providing insights on earliest detectable changes in objective and subjective cognitive function assessments.

Selection and application of methanol-utilizing bacteria from tomato leaves for biocontrol of gray mold.

Gray mold, caused by Botrytis cinerea, is a significant threat to tomato production. Traditional chemical control methods have become increasingly ineffective because of the development of resistance. This study aimed to isolate methanol-utilizing bacteria from tomato leaves and evaluate their biocontrol potential against gray mold. To obtain bacterial suspensions, tomato leaf samples were collected and washed. We analyzed the microbial communities of these samples using 16S rRNA amplicon sequencing and identified several methylotrophic strains. Among these, 405 isolated strains were cultivated on a solid low-nutrient inorganic salt medium containing methanol, and 7 strains exhibiting considerable antifungal activity against B. cinerea were identified. Greenhouse tests revealed that two strains-SY163 and SY183-significantly reduced the severity of gray mold on tomato leaves. Disease index scores and the area under the disease progress curve values confirmed the efficacy of these strains as biocontrol agents. Statistical analysis indicated the effectiveness of pre- and co-application of these strains with B. cinerea. Phylogenetic analysis identified Serratia rubidaea as the inhibitory strain. The biocontrol activity is likely mediated through the production of antifungal compounds and suppression of B. cinerea sporulation. This study provides the basis for developing a technology of gray mold suppression by controlling the abundance of S. rubidaea in plant microbial communities.

Response of Nepalese Rice Landraces to Brown Spot [Bipolaris oryzae (Breda de Haan) Shoemaker] at Rampur, Chitwan, Nepal

Brown spot disease, caused by the fungus Bipolaris oryzae, is a common foliar affliction in rice plants, impacting agricultural yields worldwide. A field experiment was conducted to identify brown spot resistant landraces at Rampur, Chitwan during June to November, 2018. A set of 54 rice genotypes comprising of 52 landraces and two checks (resistant and susceptible) were evaluated for resistance to the disease under field condition in alpha lattice design with three replicates. Area under disease progress curve (AUDPC) values varied significantly among the genotypes. Of the tested 54 genotypes, nine genotypes were found moderately resistant, 38 genotypes susceptible and seven genotypes were found highly susceptible. The maximum incidence (64.9%) of pathogen was found in seed of Hodbachhi followed by Sankharika (64.15%). The minimum average incidence of pathogen was found in check Sabitri (4.05%), which was as par with other 28 genotypes. The yield attributing characters were highly significant among the genotypes. Highest grain yield (1.55 t ha-1) was obtained from Ghusara (1.51 t ha-1) followed by Lalbachhi. Lowest grain yield was obtained from Ghuyeni Saro (0.21 t ha-1) followed by Jaguli Mansuli (0.25 t ha-1). All the yield and yield attributing characters were negatively correlated with AUDPC. Seed-borne infection after harvest was highly significant among the genotypes. The results revealed that among the screened genotypes most of the landraces of rice are susceptible to brown spot.

Blend ratios and mixtures of brown patch susceptible and resistant tall fescue cultivars

AbstractBrown patch (Rhizoctonia spp.) is a major disease of turf‐type tall fescue (TF) [Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.]. Many cool‐season turfgrass lawns consist of species mixtures or cultivar blends, but the exact proportion of resistant cultivars in blends and mixtures to effectively reduce disease has not been well documented. A field study was conducted in West Lafayette, IN, and Blacksburg, VA, during 2022 and 2023 to determine the brown patch severity of various blend ratios (0%, 25%, 50%, 75%, and 100% by weight) using a brown patch susceptible and resistant TF cultivar. Additionally, mixtures (90% and 10% by weight, respectively) of TF and Kentucky bluegrass (Poa pratensis L.) with a susceptible and resistant TF cultivar were evaluated. Seasonal appearance/turf quality and brown patch severity were visually determined, and area under the disease progress curve (AUDPC) was calculated. Turf quality and brown patch severity were similar at both locations. Additionally, blends and mixtures containing ≥75% of the resistant cultivar maintained higher average visual quality across both locations compared to the susceptible cultivar alone. Between the two mixtures, the inclusion of a resistant TF cultivar maintained higher canopy density and increased the proportion of TF at both locations. Blends and mixtures containing ≥75% of a resistant cultivar reduced brown patch AUDPC by 71% and 83% in 2022 and 2023, respectively, when compared to the 100% susceptible cultivar. This field study reinforces the importance of selecting resistant TF cultivars to reduce seasonal brown patch symptoms in cool‐season turfgrass lawns.