Biology subjects

Del Ponte, E. M.

Publications and source records attributed to Del Ponte, E. M..

10 recordsLinked to original sources

bioRxiv2026

Epidemic potential of Maravalia cryptostegiae, a classical biological control agent of rubber vine, in Northeastern Brazil

Rubber vines (Cryptostegia madagascariensis and C. grandiflora) are highly invasive weeds in the semi-arid landscapes of many tropical regions. The rust fungus Maravalia cryptostegiae has provided a spetatular and sustainable control of invasive C. grandiflora populations in Australia, after its scientific and quarantine-authorized release in the context of a classical biological control program. The Caatinga biome of Northeastern Brazil is under a devastating invasion by C. madagascariensis. This species is also susceptible to M. cryptostegia but its epidemic potential towards C. madagascariensis in Brazil remains unknown. We developed a weather-driven epidemiological model integrating experimentally derived relationships for infection as a function of temperature and wetness duration and for temperature-dependent latent development. Three infection-response models were fitted to 20 experimental temperature x wetness combinations from the literature and compared using information criteria, grouped cross-validation and a parametric bootstrap. The selected model, in which thermal breadth increases with wetness duration, was best supported (R2 = 0.931; {Delta}AICc [≥] 3.3 relative to the alternatives), and prolonged wetness significantly broadened the thermal range favorable for infection ({gamma} = 0.30 oC h-1; bootstrap P = 0.002). The infection and latent-development models were coupled with 25 years (2001-2025) of hourly NASA POWER data for 65 grid cells representing rubber-vine-infested locations in Northeastern Brazil, with wetness defined as hours with relative humidity equal or greater than 90%. Infection potential was concentrated in March-June (73% of the annual total, peaking in April), coinciding with the regional rainy season, and was highest in the interior of northern and central Ceara. Predicted potential varied more than a hundredfold among grid cells and was lowest along parts of the Ceara coast and the lower Jaguaribe valley, which include some of the largest infestations; the magnitude of these contrasts depended on the humidity threshold used to define wetness. Applied with identical rules to 13 historical release sites in Queensland, Australia, the model reproduced the documented wet-season timing of rust activity, and predicted potential was on average higher at sites with reported high rust impact, although the difference was not statistically significant. These results indicate strong seasonal and geographic structuring of weather-driven epidemic potential and provide testable hypotheses for selecting release periods and locations for M. cryptostegiae in Brazil.

plant biology↗

bioRxiv2026

Yield losses associated with peanut smut incidence in Argentina: a quantitative synthesis across field studies

Peanut smut, caused by Thecaphora frezzii, is an important constraint to peanut production in Argentina, but quantitative estimates of yield losses across environments remain limited. We quantified the relationship between disease incidence and kernel yield using 922 observations from 26 field studies conducted in Cordoba, Argentina, between 2021 and 2025. Study-specific incidence-yield relationships were analyzed using linear regression, random-effects meta-analysis, and linear mixed-effects models. Peanut smut incidence was consistently associated with yield reduction across studies. The estimated damage coefficient ranged from 24.2 to 28.7 kg ha-{superscript 1} per 1% increase in disease incidence, corresponding to a relative yield reduction of 0.74-0.87% of attainable yield. In contrast, attainable yield varied markedly among studies, ranging from 1,370 to 5,409 kg ha-{superscript 1}. Although an exploratory segmented analysis suggested a breakpoint near 12% incidence, subsequent moderator analyses, study- specific regressions, and normalized response curves provided no evidence of a biologically meaningful change in the damage coefficient across incidence or yield classes. These results indicate that differences among environments were primarily associated with attainable yield rather than with changes in the magnitude of disease-associated yield loss. The resulting damage function provides a quantitative basis for yield-loss assessment and disease management in peanut.

plant biology↗

bioRxiv2023

Prevalence of mango postharvest Stem-end rot disease in Cote d'Ivoire and identification of fungal pathogens associated

The Stem-end rot (SER) postharvest disease of mango (Mangifera indica L.) fruits is a significant economic threat to mango production. If suitable conditions are not maintained, it can lead to losses of up to 100 %. Despite its importance, very little information is known about this disease in Cote dIvoire. This research aimed determining the incidence and severity of SER in mango orchards, assess how preharvest climate parameters affect the disease and determine the pathogenic fungi associated with SER. Therefore, mango SER was evaluated on 1500 mango fruits collected from 15 orchards.in Boundiali, Ferkessedougou, Korhogo, Odienne, and Sinematiali departments. Mango SER incidence ranged from 10 % to 30 %, while severity ranged from 5 % to 20 %. No significant differences in these parameters were observed between the different departments (P>0.05). The study also revealed a low correlation between SER disease incidence and mean air temperature (r=0.36) and minimum air temperature (r=0.26) data, indicating that preharvest weather conditions may have a marginal impact on mango SER disease intensity in the postharvest phase. Pathogenic fungi associated with SER were isolated and identified using morphological characteristics and multilocus sequence analysis of the rDNA internal transcribed spacer (ITS) region and the translation elongation factor 1-alpha (tef1-). We identified various fungal species associated with mango SER disease, with Lasiodiplodia species (74%) being the most prevalent (including Lasiodiplodia theobromae, L. euphorbicola, and L. caatinguensis), followed by Colletotrichum gloeosporioides, Curvularia pseudobrachyspora, Diaporthe endophytica and Fusarium mangiferae. However, only Lasiodiplodia species and Diaporthe endophytica induced SER symptoms. This study was the first ever evaluation of mango SER disease and associated fungal pathogens identification in Cote dIvoire. This result will assist researchers in developing a control method for mango SER.

plant biology↗

bioRxiv2023

Lasiodiplodia species associated with mango (Mangifera indica L.) decline in Burkina Faso and influence of climatic factors on the disease distribution

Dieback or decline caused by Lasiodiplodia spp. is a major disease of mango trees (Mangifera indica L.). The main objectives of this study were to identify Lasiodiplodia species associated with mango decline in Burkina Faso, and to asses the climatic and edaphic factors affecting the geographic distribution of the disease in the country. The genetic diversity of 47 Lasiodiplodia isolates was studied based on sequence data of the translation elongation factor 1-alpha gene (tef1-a) and the rDNA internal transcribed spacer region (ITS). Phylogeny analyses grouped the isolates from Burkina Faso with 6 different Lasiodiplodia species, including L. euphorbicola that accounted for 36 of the 47 isolates. Lasiodiplodia isolates tested on mango seedlings induced the typical dieback symptoms. Disease incidence and severity were generally higher in the drier and warmer regions (eastern) of the country. This study provides the required information to establish control strategies against mango decline in Burkina Faso.

microbiology↗

bioRxiv2023

Pyricularia Populations are Mostly Host-Specialized with Limited Reciprocal Cross-Infection Between Wheat and Endemic Grasses in Minas Gerais, Brazil

Wheat blast, caused by Pyricularia oryzae Triticum (PoT), is an emergent threat to wheat production. Current understanding of the evolution and population biology of the pathogen and epidemiology of the disease has been based on phylogenomic studies that compared the wheat blast pathogen with isolates collected from grasses that were invasive to Brazilian wheat fields. Genetic similarity between isolates from wheat and grasses lead to the conclusion that significant cross-infection occurs, especially on signalgrass (Urochloa spp.); and this in turn prompted speculation that its widespread use as forage is a key driver of the diseases epidemiology. We reanalyzed data from those studies and found that all but one of the isolates from non-wheat hosts were members of PoT and the related Lolium-adapted lineage (PoL1), which meant that the Pyricularia populations typically found on endemic grasses had not yet been sampled. To address this shortcoming, we performed a comprehensive sampling of blast lesions in wheat crops and endemic grasses found in and away from wheat fields in Minas Gerais. A total 1,368 diseased samples were collected (976 leaves of wheat and grasses and 392 wheat heads) which yielded a working collection of 564 Pyricularia isolates. We show that, contrary to earlier implications, PoT was rarely found on endemic grasses and, conversely, members of grass-adapted populations were rarely found on wheat. Instead, most populations were host-specialized with constituent isolates usually grouping according to their host-of-origin. With regard to the dominant role proposed for signalgrass in wheat blast epidemiology, we found only one PoT member in 67 isolates collected from signalgrass grown away from wheat fields, and only three members of Urochloa-adapted populations among hundreds of isolates from wheat. Cross-inoculation assays on wheat and a signalgrass used in pastures (U. brizantha) suggested that the limited cross-infection observed in the field may be due to innate compatibility differences. Whether or not the observed level of cross-infection would be sufficient to provide an inoculum reservoir, or serve as a bridge between wheat growing regions, is questionable and, therefore, deserves further investigation.

microbiology↗

bioRxiv2022

A Re-evaluation of phylogenomic data reveals that current understanding in wheat blast population biology and epidemiology is obfuscated by oversights in population sampling

Wheat blast, caused by the Triticum lineage of Pyricularia oryzae (PoT), is a serious disease that first emerged in Brazil and quickly spread to neighboring countries. The recent appearance of this disease in Bangladesh and Zambia highlights a need to understand the population biology and epidemiology of the disease so as to mitigate pandemic outbreaks. Current knowledge in these areas is largely based on analyses of wheat blast isolates collected in Brazil, and their comparison with isolates from non-wheat, endemic grasses. Those studies concluded that wheat blast is caused by a highly diverse P. oryzae population that lacks host specificity and, as a result, undergoes extensive gene flow with populations infecting non-wheat hosts. Additionally, based on genetic similarity between wheat blast and isolates infecting Urochloa species, it was proposed that the disease originally emerged via a host jump from this grass, and the widespread use of Urochloa as a pasture grass likely plays a central role in wheat blast epidemiology. Inconsistencies with earlier phylogenetic studies prompted us to re-analyze the Brazilian data in the context of a comprehensive, global, phylogenomic dataset. We now show that the seminal studies failed to sample the P. oryzae populations normally found on endemic grasses and, instead, repeatedly sampled PoT and P. oryzae Lolium (PoL) members that happened to be present in these hosts. The resulting lack of accurate and representative information about the grass-infecting populations in Brazil means that current conclusions about wheat blasts evolution, population biology and epidemiology are unsubstantiated and could be equivocal.

microbiology↗

bioRxiv2021

Recombination of standing variation in a multi-hybrid swarm drove adaptive radiation in a fungal pathogen and gave rise to two pandemic plant diseases

Adaptive radiations fuel speciation and are characterized by rapid genetic diversification and expansion into new ecological niches. Historically, these processes were believed to be driven by selection on novel mutations but genomic analyses now indicate that standing variation and gene flow often have prominent roles. How "old" variation is combined, however, and its resulting genetic architecture within newly-adapted populations is not well understood. We reconstructed a recent radiation in the fungus, Pyricularia oryzae, that spawned a population pathogenic to eleven grass genera, and caused two new plant diseases: wheat blast - already a serious threat to global agriculture - and gray leaf spot of ryegrasses. We show that the new population evolved in a multi-hybrid swarm using only the standing variation that was present in seven individuals from five distinct, host-specialized lineages. Sexual and parasexual recombination within the swarm reassorted key host-specificity factors and generated more diversity in possibly just a few weeks than existing lineages had accumulated over hundreds to thousands of years. We suggest that the process was initiated by sexual opportunity arising when a fertile fungal strain was imported into Brazil on Urochloa introduced as forage for beef production; and we further contend that the host range expansion was largely fortuitous, with host selection playing little, if any, role in driving the process. Finally, we believe that our findings point to an overlooked role for happenstance in creating situations that allow organisms to skirt rules that would normally hold evolution in check. Commercial Endorsement DisclaimerMention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. Equal Opportunity/Non-Discrimination StatementUSDA is an equal opportunity provider and employer.

evolutionary biology↗

bioRxiv2019

Estimation of a time-varying apparent infection rate from plant disease progress curves: a particle filter approach

The parameters of the simplest (two-parameter) epidemiological models that best fit plant disease progress curve (DPC) data are the surrogate for initial inoculum (y0) and the (constant) apparent infection rate (r), both being useful for understanding, predicting and comparing epidemics. The assumption that r is constant is not reasonable and fluctuations are expected due to systematic changes in factors affecting infection (e.g. weather favorability, host susceptibility, etc.), thus leading to a time-varying r, or r(t). An arrangement of these models (e.g. logistic, monomolecular, etc.) can be used to obtain r between two time points, given the disease (y) data are available. We evaluated a data assimilation technique, Particle Filter (PF), as an alternative method for estimating r(t). Synthetic DPC data for a hypothetical polycyclic epidemics were simulated using the logistic differential equation for scenarios that combined five patterns of r(t) (constant, increasing, decreasing, random or sinusoidal); five increasing time assessment interval ({Delta}t = 1, 3, 5, 7 or 9 time units - t.u.); and two levels of noise ( = 0.1 or 0.25) assigned to y(t). The analyses of 50 simulated 60-t.u. DPCs showed that the errors of PF-derived [Formula] were lower (RMSE < 0.05) for {Delta}t < 5 t.u. and least affected by the presence of noise in the measure compared with the logit-derived r(t). The ability to more accurately estimate r(t) using the novel method may be useful to increase knowledge of field epidemics and identify within-season drivers that may explain r(t) behaviour.

epidemiology↗

bioRxiv2019

Modeling of yield Losses and risk analysis of fungicide profitability for managing Fusarium Head Blight in Brazilian spring wheat

Fusarium head blight (FHB), caused by the Fusarium graminearum species complex, is a serious disease of wheat in Brazil. A review of literature on fungicide efficacy for field trials evaluated in Brazil was conducted to obtain FHB-yield data and explore their relationship. Thirty-seven studies (9 years and 11 locations) met the criteria for inclusion (FHB index [≥] 5% and max-min range [≥] 4 percent points [p.p.]). Studies were group into two production situations: low (Yl [≤] 3,631 kg ha-1) or high (Yh > 3,631 kg ha-1) yield, based on the median of maximum yields across trials. Population-average intercepts, but not the slopes, from fitting a random-coefficients model, differed significantly between Yl (2,883.6 kg ha-1) and Yh (4,419.5 kg ha-1). The calculated damage coefficient was 1.05 %-1 and 1.60 %-1 for Yh and Yl, respectively. A crop model simulated attainable wheat yields for 10 planting dates within each year during a 28-year period, including prior (1980-1989) and after (1990-2007) FHB resurgence. Simulated losses using disease predictions to penalize yield were in general agreement in magnitude with literature reports, for both periods. Economic analysis for scenarios of variable fungicide costs and wheat prices, and one versus two sprays of tebuconazole, showed that the probability of not-offsetting the costs was higher (> 0.75) prior to FHB resurgence than after the 1990. Our approach may be useful for designing of longlasting, yet profitable, contingency tactics to management FHB in wheat. Currently one spray of triazole fungicide during flowering is more likely a profitable decision than applying two sprays, for which there is greater uncertainty.

plant biology↗

bioRxiv2017

Fitness traits of deoxynivalenol and nivalenol-producing Fusarium graminearum species complex strains from wheat

Fusarium graminearum of the 15-acetyl(A)deoxynivalenol(D0N) chemotype is the main cause of Fusarium head blight (FHB) of wheat in south of Brazil. However, 3-ADON and nivalenol(NIV) chemotypes have been found in other members of the species complex causing FHB in wheat. To improve our understanding of the pathogen ecology, we assessed a range of fitness-related traits in a sample of 30 strains representatives of 15-ADON (F. graminearum), 3-ADON (F. cortaderiae and F. austroamericanum) and NIV (F. meridionale and F. cortaderiae). These included: perithecia formation on three cereal-based substrates, mycelial growth at two suboptimal temperatures, sporulation and germination, pathogenicity towards a susceptible and a moderately resistant cultivar and sensitivity to tebuconazole. The most important trait favoring F. graminearum was its 2x higher sexual fertility (> 40% PPI = perithecia production index) than the other species (< 30% PPI); PPI varied among substrates (maize > rice > wheat). In addition, sensitivity to tebuconazole appeared lower in F. graminearum which had the only strain with EC50 > 1 ppm. In the pathogenicity assays, the DON-producers were generally more aggressive (1.5 to 2x higher final severity) towards the two cultivars, with 3-ADON or 15-ADON leading to higher area under the severity curve than the NIV strains in the susceptible and moderately resistant cv., respectively. There was significant variation among strains of a same species with regards asexual fertility (mycelial growth, macroconidia production and germination), which suggest a strain-rather than a species-specific differences. These results contribute new knowledge to improve our understanding of the pathogen-related traits that may explain the dominance of certain members of the species complex in specific wheat agroecosystems.

microbiology↗