White Mold Disease Research Articles

Evidence of white mold disease caused by Neonectria candida on Morchella importuna

Morels (Morchella sp. pl.) are valuable mushrooms, and their applications in the pharmaceutical and food industries has steadily increased in China.White mold disease is a common and severe disease in the culturing of morels, which is mainly manifested as white villous mycelial infection on the fruiting bodies of these mushrooms. However, the causal agent is not yet known. Therefore, this study aims to identify, at the species level, the causal pathogen of this disease via morphological and molecular methods and then to confirm its pathogenicity through Koch’s postulates. The pathogen was identified as Neonectria candida. Healthy ascocarps were inoculated with N. candida, which produced the initial disease symptoms with white mold appearing at the inoculation sites. The same pathogen was then isolated again from diseased ascocarps. To our knowledge, this is the first report of Morchella importuna ascocarps with white mold disease caused by N. candida in China. Moreover, this report will inform the establishment of sustainable management strategies for white mold disease in morels.

Molecular Characterization, Etiology of Sclerotinia sclerotiorum, an Emerging Fungal Pathogen of White Mold Disease in Eggplant and its Biocontrol Using Soil Bioagents

Molecular Characterization, Etiology of Sclerotinia sclerotiorum, an Emerging Fungal Pathogen of White Mold Disease in Eggplant and its Biocontrol Using Soil Bioagents

Integrated Transcriptomics-Proteomics Analysis Reveals the Response Mechanism of Morchella sextelata to Pseudodiploöspora longispora Infection.

Morels (Morchella spp.) are valuable and rare edible mushrooms with unique flavors and high nutritional value. White mold disease occurring during cultivation has seriously affected the quality and yield of morels in China. In this study, the fungus causing white mold disease in morels was isolated, purified, and identified as Pseudodiploöspora longispora by morphology and molecular biology. In addition, research has shown that P. longispora infection causes wrinkled and rupturing asci, loosened cell walls, and obvious membrane breakage accompanied by severe cytoplasmic leakage in M. sextelata. Interestingly, research has shown that infection with P. longispora can induce the production of an unknown substance in the cells of M. sextelata, which accumulates on the cell membrane, leading to membrane breakage. Furthermore, integrated transcriptomics-proteomics analysis revealed the response mechanism of M. sextelata to P. longispora infection. The results indicate that DEGs and DEPs can be significantly enriched in pathways involved in oxidoreductase activity; peroxisomes, lipid transport, and metabolism; cell wall assembly; and integral components of membranes. Further electron microscopy analysis clarified the important role of changes in the cell membrane and cell wall in the response of mycelia to biological stress. This study clarified the response mechanism of M. sextelata to P. longispora, laying a foundation for further clarifying the infection mechanism of P. longispora.

Release of ‘Kikatiti’ a multiple disease resistant pinto bean cultivar with superior productivity in Tanzania identified from evaluation of the Durango Diversity Panel

Abstract‘Kikatiti’ pinto bean (Phaseolus vulgaris L.) (Reg. no. CV‐361, PI 705149) was developed by the dry bean breeding program at the University of Nebraska, Agricultural Research Division, and submitted for release in 2021 by the Sokoine University of Agriculture in Morogoro as an upright indeterminate pinto bean with high yield potential and multiple disease resistance across bean production environments in Tanzania. Kikatiti was officially released in 2024 by the National Seed Committee. Kikatiti is an F7:8 derived line developed using the pedigree breeding method in Nebraska. The exceptional performance of Kikatiti in Tanzania was first identified by evaluation of the Durango Diversity Panel (DDP), which consisted of 200 accessions in on‐station trials conducted in Arusha and Mbeya. Kikatiti was identified as accession DDP‐094 (advanced breeding line NE2‐09‐3). Kikatiti yielded 1584 kg ha−1 across 5 years of trials in Tanzania and matured in 89 days. Kikatiti is resistant to bean rust conferred by the Ur‐3 and Ur‐11 genes, resistant to all strains of Bean common mosaic virus and Bean common mosaic necrosis virus conferred by the I and bc‐3 genes, moderately resistant to common bacterial blight conferred by the SAP6 quantitative trait locus, avoids white mold disease due to its upright architecture, and is moderately susceptible to angular leaf spot disease. Kikatiti has large seed size (35.9 g 100 seeds−1), and in on‐farm trials, farmers ranked Kikatiti above local pinto cultivars for its performance and market potential. Kikatiti has the potential to expand pinto bean production across East Africa.

Non-proteinogenic amino acids mitigate oxidative stress and enhance the resistance of common bean plants against Sclerotinia sclerotiorum.

White mold, caused by the necrotrophic fungus Sclerotinia sclerotiorum, is a challenging disease to common bean cultivation worldwide. In the current study, two non-proteinogenic amino acids (NPAAs), γ-aminobutyric acid (GABA) and ß-alanine, were suggested as innovative environmentally acceptable alternatives for more sustainable management of white mold disease. In vitro, GABA and ß-alanine individually demonstrated potent dose-dependent fungistatic activity and effectively impeded the radial growth and development of S. sclerotiorum mycelium. Moreover, the application of GABA or ß-alanine as a seed treatment followed by three root drench applications efficiently decreased the disease severity, stimulated plant growth, and boosted the content of photosynthetic pigments of treated S. sclerotiorum-infected plants. Furthermore, although higher levels of hydrogen peroxide (H2O2), superoxide anion (O2 •-), and malondialdehyde (MDA) indicated that S. sclerotiorum infection had markedly triggered oxidative stress in infected bean plants, the exogenous application of both NPAAs significantly reduced the levels of the three studied oxidative stress indicators. Additionally, the application of GABA and ß-alanine increased the levels of both non-enzymatic (total soluble phenolics and flavonoids), as well as enzymatic (catalase [CAT], peroxidases [POX], and polyphenol oxidase [PPO]) antioxidants in the leaves of S. sclerotiorum-infected plants and improved their scavenging activity and antioxidant efficiency. Applications of GABA and ß-alanine also raised the proline and total amino acid content of infected bean plants. Lastly, the application of both NPAAs upregulated the three antioxidant-related genes PvCAT1, PvCuZnSOD1, and PvGR. Collectively, the fungistatic activity of NPAAs, coupled with their ability to alleviate oxidative stress, enhance antioxidant defenses, and stimulate plant growth, establishes them as promising eco-friendly alternatives for white mold disease management for sustainable bean production.

How can an in vitro incompatibility of Trichoderma-based products and herbicides impact the parasitism and control of white mold (Sclerotinia sclerotiorum (Lib.) De Bary)?

The integration of management methods for both diseases and weeds depends on the compatibility between the tools. Biological control represents an important strategy to cope with the integrated management of white mold (Sclerotinia sclerotiorum) through parasitism of sclerotia. However, its application in the field is more cost-effective if combined with the herbicide in a tank mix, as long as the products are compatible. Therefore, we aimed at (i) evaluating two compatibility test methodologies (constant exposure and different times) and (ii) two soybean crop seasons to infer the compatibility of Trichoderma-based products. In vitro bioassays were performed to assess the compatibility between herbicides (Haloxifope-p- methyl, Glyphosate N-ammonium salt, Fluasifope-p-butyl, Fomesafem, Chlorimuron ethyl and Imazapyc + Imazapyr) and two biocontrol agents (Trichoderma asperellum and Trichoderma harzianum). Thus, the recommended spray volume for each herbicide was added to the PDA culture medium (Potato-Dextrose-Agar) and then deposited in the center of the plate a disc of mycelium from each antagonist isolate (constant exposure). The tests with time of exposure were marked at times 0, 2, 4, 8 and 16 h (simulating tank mixing) and at the spp of each time were plated on PDA medium. For both tests, the mycelial growth and conidiogenesis of Trichoderma spp. were observed. The combination of herbicide and biocontrol was also tested in the field and sclerotia parasitism, white mold incidence and plant yield were assessed in two field trials. The constant exposure of the antagonists to herbicides revealed that no herbicide was compatible with the T. asperellum or T. harzianum. While in test, exposure time exhibited compatibility with either T. asperellum or T. harzianum, within a period of 2 to 8 h. Conclusively, the integration of biocontrol agents with the herbicide imazapique + imazapyr exhibited significant reductions in white mold disease incidence and conidia germination, along with effective parasitism of S. sclerotiorum and even the least compatible herbicide (glyphosate) resulted in significant reduction in the disease incidence and sustained yield when compared to the untreated control. Therefore, the integration of the biocontrol agent for white mold should always be considered, and the tank mixing of it with the herbicide represents a cost-effective alternative for the grower.

Estimation of Peanut Southern Blight Severity in Hyperspectral Data Using the Synthetic Minority Oversampling Technique and Fractional-Order Differentiation

Southern blight significantly impacts peanut yield, and its severity is exacerbated by high-temperature and high-humidity conditions. The mycelium attached to the plant’s interior quickly proliferates, contributing to the challenges of early detection and data acquisition. In recent years, the integration of machine learning and remote sensing data has become a common approach for disease monitoring. However, the poor quality and imbalance of data samples can significantly impact the performance of machine learning algorithms. This study employed the Synthetic Minority Oversampling Technique (SMOTE) algorithm to generate samples with varying severity levels. Additionally, it utilized Fractional-Order Differentiation (FOD) to enhance spectral information. The validation and testing of the 1D-CNN, SVM, and KNN models were conducted using experimental data from two different locations. In conclusion, our results indicate that the SMOTE-FOD-1D-CNN model enhances the ability to monitor the severity of peanut white mold disease (validation OA = 88.81%, Kappa = 0.85; testing OA = 82.76%, Kappa = 0.75).

Cobweb disease on Morchella sextelata caused by Hypomyces spp. in Sichuan province, China

Morels (Morchella spp.) are commercially important edible mushrooms with high nutritional and medicinal value. There are more than twenty provinces in China that cultivate Morel mushrooms. As of 2023, white mold disease on cultivated Morchella sextelata has become a disease of concern in Sichuan Province, China, with a disease incidence of 12.13%. The ascocarp infected with white mold disease appears covered with a dense white mycelia of a foreign fungus and disintegrates soon after. However, the causal agent is not yet known. Therefore, this study aims to confirm both the causal pathogen by using Koch's postulates and to further establish, at the species level, the identity of this organism via morphological and molecular methods. The pathogens were later identified as Hypomyces rosellus and Hypomyces aurantius. Healthy ascocarps were inoculated with H. rosellus and H. aurantius, which produced the initial disease symptoms with white mold appearing at the inoculation sites, and H. aurantius showed stronger pathogenicity than H. rosellus; the same pathogens were then isolated again from diseased ascocarp. To our knowledge, this is the first report of the ascocarp cobweb disease of cultivated M. sextelata caused by H. rosellus in China. Our work may be beneficial, especially for designing control measures for ascocarp cobweb disease in the commercial cultivation of M. sextelata.

Exploring the Mycovirus Sclerotinia sclerotiorum Hypovirulence-Associated DNA Virus 1 as a Biocontrol Agent of White Mold Caused by Sclerotinia sclerotiorum.

Sclerotinia sclerotiorum is a necrotrophic fungal pathogen causing white mold on many important economic crops. Recently, some mycoviruses such as S. sclerotiorum hypovirulence-associated DNA virus 1 (SsHADV-1) converted S. sclerotiorum into a beneficial symbiont that helps plants manage pathogens and other stresses. To explore the potential use of SsHADV-1 as a biocontrol agent in the United States and to test the efficacy of SsHADV-1-infected United States isolates in managing white mold and other crop diseases, SsHADV-1 was transferred from the Chinese strain DT-8 to United States isolates of S. sclerotiorum. SsHADV-1 is readily transmitted horizontally among United States isolates of S. sclerotiorum and consistently conferred hypovirulence to its host strains. Biopriming of dry bean seeds with hypovirulent S. sclerotiorum strains enhanced resistance to white mold, gray mold, and Rhizoctonia root rot. To investigate the underlying mechanisms, endophytic growth of hypovirulent S. sclerotiorum in dry beans was confirmed using PCR, and the expression of 12 plant defense-related genes were monitored before and after infection. The results indicated that the endophytic growth of SsHADV-1-infected strains in plants stimulated the expression of plant immunity pathway genes that assisted a rapid response from the plant to fungal infection. Finally, application of the seed biopriming technology with SsHADV-1-infected hypervirulent strain has promise for the biological control of several diseases of wheat, pea, and sunflower.

Simulations of multiple breeding strategy scenarios in common bean for assessing genomic selection accuracy and model updating.

The aim of this study was to evaluate the accuracy of the ridge regression best linear unbiased prediction model across different traits, parent population sizes, and breeding strategies when estimating breeding values in common bean (Phaseolus vulgaris). Genomic selection was implemented to make selections within a breeding cycle and compared across five different breeding strategies (single seed descent, mass selection, pedigree method, modified pedigree method, and bulk breeding) following 10 breeding cycles. The model was trained on a simulated population of recombinant inbreds genotyped for 1010 single nucleotide polymorphism markers including 38 known quantitative trait loci identified in the literature. These QTL included 11 for seed yield, eight for white mold disease incidence, and 19 for days to flowering. Simulation results revealed that realized accuracies fluctuate depending on the factors investigated: trait genetic architecture, breeding strategy, and the number of initial parents used to begin the first breeding cycle. Trait architecture and breeding strategy appeared to have a larger impact on accuracy than the initial number of parents. Generally, maximum accuracies (in terms of the correlation between true and estimated breeding value) were consistently achieved under a mass selection strategy, pedigree method, and single seed descent method depending on the simulation parameters being tested. This study also investigated model updating, which involves retraining the prediction model with a new set of genotypes and phenotypes that have a closer relation to the population being tested. While it has been repeatedly shown that model updating generally improves prediction accuracy, it benefited some breeding strategies more than others. For low heritability traits (e.g., yield), conventional phenotype-based selection methods showed consistent rates of genetic gain, but genetic gain under genomic selection reached a plateau after fewer cycles. This plateauing is likely a cause of faster fixation of alleles and a diminishing of genetic variance when selections are made based on estimated breeding value as opposed to phenotype.

Morphologically and Molecularly Identification of the Fungus that Causes White Mold Disease on Eggplant and Cucumber

This study aimed to isolate the causal agent of white mold on eggplant caused by the fungus Sclerotinia sclerotiorum, and it was examined microscopically and molecularly. The pathogenicity of 16 isolates of the pathogenic fungus was evaluated from soil and plant residues, eggplant and cucumber plants (ScE1– ScE8) and (ScC1 – ScC8), respectively, from fields in different areas of Baghdad governorate of Baghdad (Abi Ghraib/Zidan, Al-Yusufiyah, Mada’in/Tuwaitha and Jadiriyah / University of Baghdad). The results of testing the pathogenicity of isolates of the pathogenic fungus showed that all isolates had a significant effect in reducing the percentage of seed germination compared to the control treatment in which the germination rate was 100%. The isolate ScE2 isolated from eggplant plants significantly outperformed the rest of the isolates, followed by isolates ScE1, ScC2, ScE3, ScE4, ScE2 and ScE5, followed by the rest of the isolates with a significant effect, the percentage of germination for the rest of the isolates ranged between 20-30%. The identificationof the two most pathogenic isolates was confirmed by PCR technology on eggplant and cucumber based on the ITS1 and ITS4 gene. The two isolates were deposited in (NCBI) under accession numbers MZ424307 and MZ424308.

Invitro analysis of antifungal effects of botanicals on sclerotinia sclerotiorum causing white mold disease

White mold, Sclerotinia sclerotiorum, is a devastating fungal plant pathogen that has affected many crop species worldwide. Using chemicals to control the disease has been practiced over the years, whose prolonged application has negatively impacted the environment, thus finding an organic solution is crucial. The analysis quantifies the effect of 5 different local plants that have been proven to have fungicidal properties; Artemisia vulgaris L., Azadirachta indica L., Zingiber officinale Roscoe, Allium sativum L., and Lantana camara L. Poisoned food technique was used to study the inhibition effect, carried out by inoculating and growing the fungus on PDA media infused with botanical extracts. The data of mycelial mat diameter was recorded till the control plates were fully occupied. The growth-inhibiting capacity was found as 100% by Allium sativum, 28% & 43% by Azadirachta indica, 22.44% & 44% by Zingiber officinale, and 16.33% & 8.55% by Lantana camara at 10% and 20% concentrations respectively. Only a slight difference between the overall inhibition effect of the two concentrations was found with 37.22% inhibition by 20% concentration and 33.38% inhibition by 10% concentration. No inhibition effect was observed from Artemisia vulgaris which could be due to heat neutralization of the active constituent during sterilization. Further research needs to be conducted using the botanical with different sterilization techniques. This in-vitro study identified garlic as a critical antifungal alternative to conventional fungicides. Field experiments need to be done to prove its effectiveness.

Small Cationic Cysteine-Rich Defensin-Derived Antifungal Peptide Controls White Mold in Soybean.

White mold disease caused by a necrotrophic ascomycete pathogen Sclerotinia sclerotiorum results in serious economic losses of soybean yield in the USA. Lack of effective genetic resistance to this disease in soybean germplasm and increasing pathogen resistance to fungicides makes white mold difficult to manage. Small cysteine-rich antifungal peptides with multi-faceted modes of action possess potential for development as sustainable spray-on bio-fungicides. We have previously reported that GMA4CG_V6 peptide, a 17-amino acid variant of the MtDef4 defensin-derived peptide GMA4CG containing the active γ-core motif, exhibits potent antifungal activity against the gray mold fungal pathogen Botrytis cinerea in vitro and in planta. GMA4CG_V6 exhibited antifungal activity against an aggressive field isolate of S. sclerotiorum 555 in vitro with an MIC value of 24 µM. At this concentration, internalization of this peptide into fungal cells occurred prior to discernible membrane permeabilization. GMA4CG_V6 markedly reduced white mold disease symptoms when applied to detached soybean leaves, pods, and stems. Its spray application on soybean plants provided robust control of this disease. GMA4CG_V6 at sub-lethal concentrations reduced sclerotia production. It was also non-phytotoxic to soybean plants. Our results demonstrate that GMA4CG_V6 peptide has potential for development as a bio-fungicide for white mold control in soybean.

Integrating de novo QTL-seq and linkage mapping to identify quantitative trait loci conditioning physiological resistance and avoidance to white mold disease in dry bean.

White mold (WM), caused by the ubiquitous fungus Sclerotinia sclerotiorum, is a devastating disease that limits production and quality of dry bean globally. In the present study, classic linkage mapping combined with QTL-seq were employed in two recombinant inbred line (RIL) populations, "Montrose"/I9365-25 (M25) and "Raven"/I9365-31 (R31), with the initial goal of fine-mapping QTL WM5.4 and WM7.5 that condition WM resistance. The RILs were phenotyped for WM reactions under greenhouse (straw test) and field environments. The general region of WM5.4 and WM7.5 were reconfirmed with both mapping strategies within each population. Combining the results from both mapping strategies, WM5.4 was delimited to a 22.60-36.25 Mb interval in the heterochromatic regions on Pv05, while WM7.5 was narrowed to a 0.83 Mb (3.99-4.82 Mb) region on the Pv07 chromosome. Furthermore, additional QTL WM2.2a (3.81-7.24 Mb), WM2.2b (11.18-17.37 Mb, heterochromatic region), and WM2.2c (23.33-25.94 Mb) were mapped to a narrowed genomic interval on Pv02 and WM4.2 in a 0.89 Mb physical interval at the distal end of Pv04 chromosome. Gene models encoding gibberellin 2-oxidase proteins regulating plant architecture are likely candidate genes associated with WM2.2a resistance. Nine gene models encoding a disease resistance protein (quinone reductase family protein and ATWRKY69) found within the WM5.4 QTL interval are putative candidate genes. Clusters of 13 and 5 copies of gene models encoding cysteine-rich receptor-like kinase and receptor-like protein kinase-related family proteins, respectively, are potential candidate genes associated with WM7.5 resistance and most likely trigger physiological resistance to WM. Acquired knowledge of the narrowed major QTL intervals, flanking markers, and candidate genes provides promising opportunities to develop functional molecular markers to implement marker-assisted selection for WM resistant dry bean cultivars.

Variation in oxalic acid production, mycelial compatibility and pathogenicity amongst isolates of Sclerotinia sclerotiorum causing white mold disease

Variation in oxalic acid production, mycelial compatibility and pathogenicity amongst isolates of Sclerotinia sclerotiorum causing white mold disease

A cAMP phosphodiesterase is essential for sclerotia formation and virulence in Sclerotinia sclerotiorum.

Sclerotinia sclerotiorum is a plant pathogenic fungus that causes white mold or stem rot diseases. It affects mostly dicotyledonous crops, resulting in significant economic losses worldwide. Sclerotia formation is a special feature of S. sclerotiorum, allowing its survival in soil for extended periods and facilitates the spread of the pathogen. However, the detailed molecular mechanisms of how sclerotia are formed and how virulence is achieved in S. sclerotiorum are not fully understood. Here, we report the identification of a mutant that cannot form sclerotia using a forward genetics approach. Next-generation sequencing of the mutant's whole genome revealed candidate genes. Through knockout experiments, the causal gene was found to encode a cAMP phosphodiesterase (SsPDE2). From mutant phenotypic examinations, we found that SsPDE2 plays essential roles not only in sclerotia formation, but also in the regulation of oxalic acid accumulation, infection cushion functionality and virulence. Downregulation of SsSMK1 transcripts in Sspde2 mutants revealed that these morphological defects are likely caused by cAMP-dependent inhibition of MAPK signaling. Moreover, when we introduced HIGS construct targeting SsPDE2 in Nicotiana benthamiana, largely compromised virulence was observed against S. sclerotiorum. Taken together, SsPDE2 is indispensable for key biological processes of S. sclerotiorum and can potentially serve as a HIGS target to control stem rot in the field.

Incidence of white mould of bean and characterization of its causal pathogen, Sclerotinia sclerotiorum in Kashmir valley, India

White mould caused by Sclerotinia sclerotiorum affects the quality and quantity of bean crop. The aims of this study were to evaluate the incidence and severity of white mould disease in four districts of Kashmir valley and to characterize the morphological variability of 60 Sclerotinia sclerotiorum isolates from bean plants. Three bean fields per village and five villages per district were chosen randomly for sampling. The highest incidence among surveyed areas was found in Ganderbal (37.94%) and lowest in Shupiyan (19.98%). The disease severity was highest in district Ganderbal (15.54%) and lowest in district Shupiyan (7.94%). Single spore method was used to isolate the fungus. Sixty isolates of the causal organism were isolated from bean plants collected from the surveyed areas and pathogenecity test was carried out following Koch’s postulates. Morphological characters of the different isolates, like number of sclerotia per Petri plate, time required for formation of the first sclerotium and average weight and shape of the sclerotia were studied. Among sixty isolates of S. sclerotiorum isolated from bean, it was observed that 25% of the isolates had abundant mycelium, 25% had irregular mycelium, half of the isolates had thin mycelium. 75% of the isolates had white colour and 25% had beige coloration. 25% of the isolates had a round shape, and 75% had a diverse shape. Sclerotia were detected in 50% of the cases in a regular pattern along the colony edge, 25% spread throughout the colony, and 25% in concentric circles. The mean number of sclerotia per colony ranged from 11.68 (SS55) to 32.32 (SS26). The mean number of days for formation of the first sclerotium ranged from 9.3 (SS30) to 17.7 (SS60). The average weight of sclerotia ranged from 0.0918 (SS58) to 0.2475 (SS21). The variation in disease incidence across different sites and the morphological variation of the isolates can be due to differences in genetic constitution as well as environmental conditions.

Bacillus lipopeptide-mediated biocontrol of peanut stem rot caused by Athelia rolfsii.

Peanut (Arachis hypogaea L.) is a widespread oilseed crop of high agricultural importance in tropical and subtropical areas. It plays a major role in the food supply in the Democratic Republic of Congo (DRC). However, one major constraint in the production of this plant is the stem rot (white mold or southern blight) disease caused by Athelia rolfsii which is so far controlled mainly using chemicals. Considering the harmful effect of chemical pesticides, the implementation of eco-friendly alternatives such as biological control is required for disease management in a more sustainable agriculture in the DRC as in the other developing countries concerned. Bacillus velezensis is among the rhizobacteria best described for its plant protective effect notably due to the production of a wide range of bioactive secondary metabolites. In this work, we wanted to evaluate the potential of B. velezensis strain GA1 at reducing A. rolfsii infection and to unravel the molecular basis of the protective effect. Upon growth under the nutritional conditions dictated by peanut root exudation, the bacterium efficiently produces the three types of lipopeptides surfactin, iturin and fengycin known for their antagonistic activities against a wide range of fungal phytopathogens. By testing a range of GA1 mutants specifically repressed in the production of those metabolites, we point out an important role for iturin and another unidentified compound in the antagonistic activity against the pathogen. Biocontrol experiments performed in greenhouse further revealed the efficacy of B. velezensis to reduce peanut disease caused by A. rolfsii both via direct antagonism against the fungus and by stimulating systemic resistance in the host plant. As treatment with pure surfactin yielded a similar level of protection, we postulate that this lipopeptide acts as main elicitor of peanut resistance against A. rolfsii infection.

Response of dark red kidney beans to nitrogen on irrigated, sandy soil

AbstractThere is a lack of nitrogen response research on dark red kidney beans (Phaseolus vulgaris L.). This is of particular importance as most cultivars form nodules and are commonly grown on sandy soil. The objectives of this study were to determine the effects of nitrogen rates and irrigation amounts on leaf area index, white mold occurrence, yield, and N uptake of dark red kidney beans. The study occurred at the University of Wisconsin Hancock Agricultural Research Station over two growing seasons (2020 and 2021), across four N rates, three irrigation levels, and five cultivars. Preceding crop for each study year was potato and field corn, respectively. More heavy rainfall events that may lead to leaching were observed in 2021. Neither irrigation effect nor general cultivar difference was observed on bean yield, disease resistance, and nitrogen use across the 2 years. Bean yield was significantly influenced by N rates across the five cultivars in 2020 but not in 2021, with 56 kg ha−1 more total N uptake at the lowest N rate in 2021. This highlights large site‐year influences on N supply from fixation. Furthermore, although greater N application did lead to greater yield in 1 year, it was also associated with greater white mold disease pressure and lower partial factor productivity (PFP). Thus, there is economic risk in N application to dark red kidney beans on irrigated sandy soil from reduced quality (mold damage) and lower N use efficiency (indicated by lower PFP), although site‐year effects remain unknown.

Airborne versus soilborne inoculum: White mould, where do you come from?

AbstractIdentifying the sources of fungal inoculum that induces epidemics is instrumental to managing crop health in a more efficient way by implementing prophylactic methods and by using better targeted biocontrol and fungicide applications. For some phytopathogenic fungi, this identification is hampered by the multiplicity of inoculum types. This is the case for Sclerotinia sclerotiorum, the agent of white mould, which can produce ascospores disseminated via the atmosphere, sclerotia stored in the soil and mycelium in plant debris of a large variety of hosts. The present study aims to assess the relative importance of airborne and soilborne inocula in white mould disease development and its persistence across two crop seasons. S. sclerotiorum isolates were collected from air, soil and carrot plants during two crop seasons in south‐western France and genotyped with 16 microsatellite markers. Among the 490 isolates, 162 clonal lineages were identified. The genetic characteristics did not differ significantly among isolates collected from air, soil and carrots. The epidemics of white mould on carrots were initiated either by airborne inoculum or by soilborne inoculum. It also appears that some isolates from airborne inoculum persisted from year to year.