Disease Progress Curve Research Articles

Screening of Rice Genotypes for Resistance Against Bacterial Blight Disease

A study was undertaken at V. C. Farm, Mandya, Karnataka, India during 2020 to screen the genotypes against BLB under natural field conditions. Host Plant resistance is an important component of an integrated management program for this disease. Among the 102 rice genotypes screened under natural epiphytotic condition at Zonal Agricultural Station, V. C. Farm, Mandya, none of them were found immune against bacterial leaf blight. So, in the study, plants were assessed by measuring disease severity (% of leaf diseased) and area under the disease progress curve (AUDPC). The pathogenicity of Xoo was tested on IRRI rice cultivars, inoculation was conducted at the maximum tillering stage, and the lesion length was measured after 14 days of inoculation. An attempt was made to phenotypically characterize a set of 102 Genotypes from IRRI for BLB resistance by artificially inoculaton using clipping method. Out of the 102 genotypes and two checks tested, it was observed that five entries viz., IRGC 125853, IRGC 126264, IRGC 132357, IRGC 122088 IRGC 125658 and Improved Samba Mahsuri were highly resistant with score of 1. Only one entry (IRGC 125754) was resistant with score of 3, 33 lines being moderately resistant with score of 5 and 43 lines were susceptible with score of 7. 20 lines and also the susceptible check Jyothi-PTB 39, had the highest susceptibility with a phenotypic score of 9.

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

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

Dissecting genomic regions and underlying sheath blight resistance traits in rice (Oryza sativa L.) using a genome-wide association study.

The productivity of rice is greatly affected by the infection of the plant pathogenic fungus Rhizoctonia solani, which causes a significant grain yield reduction globally. There exist a limited number of rice accessions that are available to develop sheath blight resistance (ShB). Our objective was to identify a good source of the ShB resistance, understand the heritability, and trait interactions, and identify the genomic regions for ShB resistance traits by genome-wide association studies (GWAS). In the present study, a set of 330 traditional landraces and improved rice varieties were evaluated for ShB resistance and created a core panel of 192 accessions used in the GWAS. This panel provides a more considerable amount of genetic variance and found a significant phenotypic variation among the panel of rice accessions for all the agro-morphological and disease-resistance traits over the seasons. The infection rate of ShB and disease reaction were calculated as percent disease index (PDI) and area under the disease progress curve (AUDPC). The correlation analysis showed a significant positive association between PDIs and AUPDC and a negative association between PDI and plant height, flag leaf length, and grain yield. The panel was genotyped with 133 SSR microsatellite markers, resulting in a genome coverage of 314.83 Mb, and the average distance between markers is 2.53 Mb. By employing GLM and MLM (Q + K) models, 30 marker-trait associations (MTAs) were identified with targeted traits over the seasons. Among these QTLs, eight were found to be novel and located on 2, 4, 8, 10, and 12 chromosomes, which explained the phenotypic variation ranging from 5% to 15%. With the GWAS approach, six candidate genes were identified. Os05t0566400, Os08t0155900, and Os09t0567300 were found to be associated with defense mechanisms against ShB. These findings provided insights into the novel donors of IC283139, IC 277248, Sivappuchithirai Kar, and Bowalia. The promising genomic regions on 10 of 12 chromosomes associated with ShB would be useful in developing rice varieties with durable disease resistance.

Propagation and shelf-life of weed pathogenic fungi in alternative media and their effectiveness in billygoat (Ageratum conyzoides L)

Control of billygoat (Ageratum conyzoides L) currently uses herbicides, on the other hand, control using pathogenic fungi is environmentally friendly, but for mass propagation and storage, alternative media are needed. The aim of the study was to determine the best type of alternative media for fungal growth and shelf life, as well as its effectiveness against billygoat. The treatment tested involves a combination of two factors: the type of pathogenic fungi (Curvularia lunata or Fusarium oxysporum) and the type of medium (rice washing water or tofu liquid waste). A completely randomized design was used for the in vitro test, while in planta test used a randomized block design with each experimental unit repeated five times. The observed variables were conidia density, number of colonies, incubation period, disease symptoms, disease intensity, and area under the disease progress curve (AUDPC), as well as weed height, number of leaves, fresh and dry shoot, and root weights. The results showed that the conidia density of F. oxysporum was 57% better in rice washing water than in tofu wastewater. The best shelf life for the fungus was four weeks. The use of rice washing water for F. oxysporum and C. lunata effectively delayed the incubation period by 77 and 71% respectively, suppressed disease intensity by 90 and 88%, and AUDPC by 94 and 93% compared to the control. The F. oxysporum grown on rice washing water media was able to reduce the number of leaves, fresh and dry weight of billygoat by 25, 30, and 20% compared to the control, respectively.

Propagation and shelf-life of weed pathogenic fungi in alternative media and their effectiveness in billygoat (Ageratum conyzoides L)

Control of billygoat (Ageratum conyzoides L) currently uses herbicides, on the other hand, control using pathogenic fungi is environmentally friendly, but for mass propagation and storage, alternative media are needed. The aim of the study was to determine the best type of alternative media for fungal growth and shelf life, as well as its effectiveness against billygoat. The treatment tested involves a combination of two factors: the type of pathogenic fungi (Curvularia lunata or Fusarium oxysporum) and the type of medium (rice washing water or tofu liquid waste). A completely randomized design was used for the in vitro test, while in planta test used a randomized block design with each experimental unit repeated five times. The observed variables were conidia density, number of colonies, incubation period, disease symptoms, disease intensity, and area under the disease progress curve (AUDPC), as well as weed height, number of leaves, fresh and dry shoot, and root weights. The results showed that the conidia density of F. oxysporum was 57% better in rice washing water than in tofu wastewater. The best shelf life for the fungus was four weeks. The use of rice washing water for F. oxysporum and C. lunata effectively delayed the incubation period by 77 and 71% respectively, suppressed disease intensity by 90 and 88%, and AUDPC by 94 and 93% compared to the control. The F. oxysporum grown on rice washing water media was able to reduce the number of leaves, fresh and dry weight of billygoat by 25, 30, and 20% compared to the control, respectively.

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.

Exploring the association between latent Plasmopara viticola infection and downy mildew epidemic in commercial vineyards: Application of qPCR assay

AbstractIt is critical to quantify latent Plasmopara viticola infections in commercial vineyards rapidly and accurately to estimate the potential for grapevine downy mildew (GDM) epidemics. In this study, a well‐established quantitative PCR (qPCR) assay was employed to quantify the amount of P. viticola in asymptomatic grapevine leaves from various commercial vineyards in the Ningxia Hui Autonomous Region (Ningxia), China. The qPCR revealed efficient detection of P. viticola, with 56.6% and 95.8% of the asymptomatic leaves testing positive to the pathogen in 2018 and 2019, respectively. The molecular disease index (MDI), which offers insights into the progression of latent infection preceding the appearance of visible GDM symptoms, showed relatively modest values in the initial phases. However, it increased variably as grapevines grew. The disease index progress curve and the relative area under the disease progress curve revealed that all assessed vineyards experienced different degrees of epidemics after the initial GDM observation, with most vineyards experiencing more severe GDM epidemics in 2019 than in 2018. Bayesian and non‐linear regression analyses demonstrated that MDI data matched well with occurrence of GDM at early, mid and late stages of disease, and the overall accuracy of predictions exceeded 50%, 64% and 70%, respectively. Furthermore, latent infection levels were positively correlated with subsequent assessments of disease progression (p < 0.001). This study provides evidence for the interrelation between latent P. viticola infections and development of GDM epidemics under field conditions. This insight has substantive implications for the formulation of effective disease management strategies.

Genetic analysis of basal stalk rot resistance introgressed from wild Helianthus petiolaris into cultivated sunflower (Helianthus annuus L.) using an advanced backcross population.

Sclerotinia sclerotiorum is a serious pathogen causing severe basal stalk rot (BSR) disease on cultivated sunflower (Helianthus annuus L.) that leads to significant yield losses due to insufficient resistance. The wild annual sunflower species H. petiolaris, commonly known as prairie sunflower is known for its resistance against this pathogen. Sunflower resistance to BSR is quantitative and determined by many genes with small effects on the resistance phenotype. The objective of this study was to identify loci governing BSR resistance derived from H. petiolaris using a quantitative trait loci (QTL) mapping approach. BSR resistance among lines of an advanced backcross population (AB-QTL) with 174 lines developed from a cross of inbred line HA 89 with H. petiolaris PI 435843 was determined in the field during 2017-2019, and in the greenhouse in 2019. AB-QTL lines and the HA 89 parent were genotyped using genotyping-by-sequencing and a genetic linkage map was developed spanning 997.51 cM and using 1,150 SNP markers mapped on 17 sunflower chromosomes. Highly significant differences (p<0.001) for BSR response among AB-QTL lines were observed disease incidence (DI) in all field seasons, as well as disease rating (DR) and area under the disease progress curve (AUDPC) in the greenhouse with a moderately high broad-sense heritability (H 2) of 0.61 for the tested resistance parameters. A total of 14 QTL associated with BSR resistance were identified on nine chromosomes, each explaining a proportion of the phenotypic variation ranging from 3.5% to 28.1%. Of the 14 QTL, eight were detected for BSR resistance in the field and six were detected under greenhouse conditions. Alleles conferring increased BSR resistance were contributed by the H. petiolaris parent at 11 of the 14 QTL.

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

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

Efficacy of Biocontrol Agents Coniothyrium minitans and Bacillus amyloliquefaciens for Managing Sclerotinia sclerotiorum in Indiana Soybean

Sclerotinia sclerotiorum is a soilborne pathogen of soybean that causes Sclerotinia stem rot, also called white mold. Sclerotinia stem rot can cause significant yield losses under cool and wet environmental conditions. Two biofungicides, Coniothyrium minitans and Bacillus amyloliquefaciens, are currently available and labeled to limit or suppress S. sclerotiorum in soybean. These biofungicides can be applied in place of synthetic foliar fungicides to provide an alternative mode of action for the control of Sclerotinia stem rot. However, limited information is available regarding the efficacy of C. minitans and B. amyloliquefaciens as biocontrol agents of S. sclerotiorum in soybean. To assess the effectiveness of C. minitans and B. amyloliquefaciens as biocontrol agents of S. sclerotiorum, dual culture and soil plate assays were conducted, along with experiments in the growth chamber and field. Degradation of sclerotia following treatment with C. minitans in the soil plate assay confirmed that the primary mode of action is mycoparasitism. In the growth chamber, B. amyloliquefaciens at 14.03 liters/ha applied using the dip method significantly reduced Sclerotinia stem rot lesion length over the nontreated control and resulted in the lowest lesion area under the disease progress curve. When B. amyloliquefaciens and C. minitans were applied in the field, no differences were observed between treatments for soybean moisture, test weight, or yield in Indiana. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

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

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

Phytophthora Root and Crown Rot of Lavender: New Host-Pathogen Relationships Involving Six Species of Phytophthora and Three Species of Lavandula.

Phytophthora root and crown rot has become a major threat to the lavender industry worldwide. Isolations from symptomatic plants between 2015 and 2019 revealed a number of potential causal agents in the United States. In this study, we tested nine species of Phytophthora and four species of Lavandula and used Koch's Postulates to prove pathogenicity for six new host-pathogen relationships and confirm two pathogenic relationships for the first time in the United States. A total of 10 experiments were conducted with each consisting of two independent trials. Only host-pathogen combinations that occurred in the field were evaluated. All isolates used in these experiments were recovered from diseased lavender plants or, for one isolate, soil associated with a diseased plant sent to our lab or the Clemson University Plant and Pest Diagnostic Clinic for diagnosis. Experiments were conducted over 3 years, 2017 to 2019, in a research greenhouse under relatively uniform environmental conditions following a standard protocol. Plants were evaluated weekly for foliage symptom severity, and, at the end of each trial, plants were scored for final foliage symptom severity and root rot severity, area under the disease progress curve was calculated, fresh plant mass was weighed, and isolation of pathogens from roots was attempted. These studies successfully demonstrated for the first time pathogenicity of Phytophthora nicotianae, P. palmivora, and P. cinnamomi to hybrid lavender (Lavandula × intermedia), P. nicotianae to sweet lavender (L. heterophylla), and P. cryptogea and P. drechsleri to English lavender (L. angustifolia). In addition, a soil isolate of P. tropicalis was shown to be potentially pathogenic to L. × intermedia. Our results also documented for the first time in the United States pathogenicity of P. palmivora and P. citrophthora to L. angustifolia. We were not able to confirm pathogenicity for three host-pathogen relationships: P. megasperma on English lavender, P. cactorum on hybrid lavender, and P. nicotianae on Spanish lavender (L. stoechas). Results from this study expand the list of Phytophthora species causing root rot on lavender (Lavandula species) in the United States and elsewhere.

Differential gene effectiveness and blast disease progression in MAS derived NILs in the background of aromatic rice landrace Mushk Budji

Mushk Budji is a premium quality scented rice landrace of Kashmir, which is highly susceptible to rice blast cause by Magnaporthe oryzae with more than 70% grain yield loss. Near-isogenic lines (NILs), namely, SKUA-27-4-40-9, SKUA-27-20-10-2 and SKUA-27-13-5-1, for the blast resistance genes, Pi54, Pi1and Pita were successfully developed in the background of Mushk Budji. Marker-assisted foreground selection was carried out using gene-based and closely linked markers viz., Pi54 MAS (Pi54), RM224 (Pi1) and YL155/87 (Pita). The background analysis was done with 90 genome-wide distributed SSR markers linked to previously tagged SNPs, which helped in estimating the recurrent parent genome (RPG) recovery in the NILs. An area under the disease progress curve (AUDPC) was drawn to test the effectiveness of the individual-resistance genes in the developed NILs. A differential reaction pattern exhibited by the individual genes helped validate the respective genes’ effectiveness under the Kashmir conditions. The Pi54 and Pita were found to be effective in conferring resistance towards M. oryzae infection in the NILs of Mushk Budji.

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

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

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

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

Combined application of effective Trichoderma, Pseudomonas and arbuscular mycorrhiza spp. reduced soil-borne diseases and boosted growth in cotton

BackgroundThe most common soil-borne diseases in cotton are root rot and wilt, which are caused by Rhizoctonia solani (Taub) Butler and Fusarium oxysporum f. sp. vasinfectum, respectively. These two diseases significantly reduce plant stand and production. Under extreme circumstances, the application of fungicides does not provide satisfactory management of these diseases and also pollutes the environment. The effect of biocontrol agents, their combinations and fungicides on root rot and wilt management and plant growth in Gossypium hirsutum and G. arboreum cultivars CSH-3129 and CICR-3 were studied during 2017–18 and 2018–19.ResultsOut of six isolates of Trichoderma spp., T. asperellum (Th-11) was the most effective for inhibiting the mycelial growth of R. solani and F. oxysporum f. sp. vasinfectum (64.4–100%). The combined seed treatment of T. asperellum (Th-11, c.f.u. 2 × 108/g) + Pseudomonas fluorescens (c.f.u. 2 × 108/g) + arbuscular mycorrhizal fungi (AMF; 1200 IP/g) resulted in the highest plant vigour index in CSH-3129 (890.9%) and CICR-3 cultivars (393.5%) at 15 days after treatment. Ninety days after sowing, the combined seed treatments of T. asperellum (Th-11) + P. fluorescens + AMF followed by T. asperellum (Th-11) + P. fluorescens showed the lowest area under the disease progress curve in CICR-3 and CSH 3129. Two-year pooled results indicated that the combined seed treatment with T. asperellum (Th-11) + P. fluorescens + AMF reduced the root rot disease by 51 and 57.5% in CICR-3 and CSH-3129 cultivars, respectively, under field conditions.ConclusionThe present investigation suggested that combined application of the most effective strains of T. asperellum (Th-11) @10 g/kg + P. fluorescens @10 g/kg and AMF @20 g/kg can effectively manage root rot and wilt diseases up to 60 days after sowing and enhance plant growth under field conditions. However, the application rates of these biocontrol agents vis-à-vis load of pathogen inoculum in the field must be further evaluated for improved and long-term effects.

Development of a Greenhouse Method to Evaluate the Peanut Resistance to Athelia rolfsii

Peanut stem rot (also known as white mold), caused by the fungus Athelia rolfsii, is one of the most damaging soilborne pathogens for U.S. peanut production. The disease is mainly controlled by fungicides and by adopting cultivars with moderate resistance. Field evaluation is the main approach for evaluating plant resistance, but it is costly and labor-intensive. Reliable methods for in vitro or greenhouse evaluations are desirable. Greenhouse, growth chamber, and in vitro methods have been tried to assess resistance, but they generally do not correlate well with field results. In this study, we developed a reliable method to assess resistance to stem rot on peanut under greenhouse conditions. Stem cuttings were taken from 60-day-old plants and placed into a cup filled with potting mix. Cuttings were inoculated with active A. rolfsii mycelial plugs above the soil line, with mycelium directly contacting the stem. Inoculated cuttings were put in a mist chamber to keep humidity high. Highly significant differences in disease resistance among genotypes were found at 7 days after inoculation ( P &lt; 0.05). Moreover, evaluations done at 3, 5, 7, and 9 days after inoculation and the area under the disease progress curve were significantly correlated with field evaluations of the same genotypes. This greenhouse assay is a step forward to screen peanut germplasm more efficiently for stem rot resistance. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

Didymella fabae Punith.: mating type occurrence, distribution and phenotyping of the anamorph Ascochyta fabae Speg. in Tunisia.

Faba bean ascochyta blight, caused by Ascochyta fabae Speg. (teleomorph: Didymella fabae Punith.), is one of the most devastating diseases of the crop. It can cause yield losses that reach 95% in conducive weather conditions. Surveys were carried out in five regions of Tunisia: Beja, Bizerte, Jendouba, Kef and Tunis-Cap Bon. A total of 513 fungal isolates were collected from 2011 to 2013. A molecular characterization was conducted to identify the mating type of each individual using a mating type specific PCR. Results revealed that the two mating types MAT1-2 and MAT1-1 coexisted in all surveyed regions. An imbalance in favor of MAT1-2 was observed particularly in Bizerte and Jendouba regions (sex ratio was 18:85 and 32:80, respectively). Moreover, morphological and pathogenic characterization of 122 isolates among the collection revealed a significant variability in conidia type (one celled or two celled conidia) frequency, in conidia mean size and in aggressiveness toward Badii faba bean cultivar (incubation period, IP; percentage necrotic leaf area, S; and area under disease progression curve, AUDPC). A principal component analysis (PCA) performed on morphologically studied parameters (frequency of conidia cell number and conidia mean size) identified three groups of isolates based on morphological traits: one celled (1C) and two celled (2C) conidia rates, one celled and two celled conidia length and width (1L, 1W, 2L and 2W, respectively). A second PCA using aggressiveness parameters (IP: Incubation period, S1, S4 and S9: percentage of necrotic leaf area respectively 5, 20 and 45 days after inoculation) identified three distinct pathogenic groups: poorly pathogenic AG1, moderately pathogenic AG2 and highly pathogenic AG3. Morphological and pathogenic groups and mating type data were used to conduct a multiple factorial correspondence analysis (MFCA) which revealed a correlation between the variables studied. Five groups were identified, each associated with a morphological and pathogenic trait and mating type. The most pathogenic group belonged to MAT1-2 suggesting that in locations where MAT1-2 is prevalent the epidemic risk is more important.

Evaluating Options to Increase the Efficacy of Biocontrol Agents for the Management of Pantoea spp. Under Field Conditions.

Center rot of onion is caused by a complex of plant pathogenic Pantoea species, which can lead to significant yield losses in the field and during storage. Conventional growers use foliar protectants such as a mixture of copper bactericides and an ethylene-bis-dithiocarbamate (EBDC) fungicide to manage the disease; however, organic growers have limited management options besides copper-protectants. Biocontrol agents (BCAs) provide an alternative; however, their efficacy could be compromised due in part to their inability to colonize the foliage. We hypothesized that pretreatment with peroxide (OxiDate 2.0: a.i., hydrogen peroxide and peroxyacetic acid) enhances the colonizing ability of the subsequently applied BCAs, leading to effective center rot management. Field trials were conducted in 2020 and 2021 to assess the efficacy of peroxide, BCAs (Serenade ASO: Bacillus subtilis and BlightBan: Pseudomonas fluorescens), and an insecticide program (tank mix of spinosad and neem oil) to manage center rot. We observed no significant difference in foliar area under the disease progress curve (AUDPC) between the peroxide pretreated P. fluorescens plots and only P. fluorescens-treated plots in 2020 and 2021. Peroxide pretreatment before B. subtilis application significantly reduced the foliar AUDPC as compared with the stand-alone B. subtilis treatment in 2020; however, no such difference was observed in 2021. Similarly, peroxide pretreatment before either of the BCAs did not seem to reduce the incidence of bulb rot as compared with the stand-alone BCA treatment in any of the trials (2020 and 2021). Additionally, our foliar microbiome study showed comparatively higher P. fluorescens retention on peroxide pretreated onion foliage; however, at the end of the growing season, P. fluorescens was drastically reduced and was virtually nonexistent (<0.002% of the total reads). Overall, the pretreatment with peroxide had a limited effect in improving the foliar colonizing ability of BCAs and consequently a limited effect in managing center rot.