Mango anthracnose disease: the current situation and direction for future research

Mango anthracnose disease (MAD) is a destructive disease of mangoes, with estimated yield losses of up to 100% in unmanaged plantations. Several strains that constitute Colletotrichum complexes are implicated in MAD worldwide. All mangoes grown for commercial purposes are susceptible, and a resistant cultivar for all strains is not presently available on the market. The infection can widely spread before being detected since the disease is invincible until after a protracted latent period. The detection of multiple strains of the pathogen in Mexico, Brazil, and China has prompted a significant increase in research on the disease. Synthetic pesticide application is the primary management technique used to manage the disease. However, newly observed declines in anthracnose susceptibility to many fungicides highlight the need for more environmentally friendly approaches. Recent progress in understanding the host range, molecular and phenotypic characterization, and susceptibility of the disease in several mango cultivars is discussed in this review. It provides updates on the mode of transmission, infection biology and contemporary management strategies. We suggest an integrated and ecologically sound approach to managing MAD

Hosts of Colletotrichum

The taxonomy of Colletotrichum has undergone profound changes over the past decade, with ca. 340 species now recognised, and grouped into 20 species complexes (16 previously described and four proposed in this work). Over that period, the volatility of the taxonomic framework posed difficulties to the aetiology of anthracnose diseases along with uncertainty on cross-infection potential, quarantine rules, pesticide management and plant breeding strategies. Now that the Colletotrichum taxonomy is stabilising (still several new species being named, but no longer representing major pathogens), there is a point on reviewing the knowledge on the aetiology of anthracnose diseases in a global way, pointing out the relative importance of each Colletotrichum species for each host/crop and identifying areas/crops where information is missing (and there are several crops for which nothing is known regarding Colletotrichum species in modern terms). Based on 3400 host species-Colletotrichum species occurrence records (considering only records of Colletotrichum spp. identified in modern terms), we have listed over 760 host (plants) species and analysed the information available on the Colletotrichum species reported from them, the symptoms caused and the geographic distribution and pathological relevance. Whereas some of these hosts are wild plants, this work is mostly focused on cultivated plants and therefore on the aetiology of anthracnose diseases globally. In the context of Colletotrichum fungi, this compilation provides downstream users of Mycology, namely those in areas such as Plant Pathology, Plant Protection and Plant Breeding, with updated information on the main causal agents of anthracnose in each crop/plant species in each location, or alternatively with an alert on the lack of information on the identity of the species of Colletotrichum relevant for a given crop in a given location.info:eu-repo/semantics/publishedVersio

Incidence of leaf blight disease of Egusi melon in South-west Nigeria

Egusi melon ( Citrullus lanatus (Thumb) Mansf.) is an important vegetable crop grown for edible seeds and oil in West Africa. Leaf Blight Disease (LBD) is one of the major constraints to its production, with potential to cause economic damage. The objective of this study was to investigate the incidence and distribution of leaf blight on Egusi melon in Southwestern Nigeria. A survey of LBD of Egusi melon was conducted in 2015 and 2016, in five southwestern States of Nigeria (Ogun, Oyo, Osun, Ekiti and Ondo States). Twenty plants each, were randomly sampled from 150 farms comprising 30 farms each, from each State. The distribution of different Egusi melon varieties planted was recorded. \u201cBara\u201d cv. was the most cultivated variety (51.6%); followed by \u201cBojuri\u201d (30.4%) and \u201cSerewe\u201d (18%). Leaf blight was observed in most farms in the five States, from 73% in Osun and Oyo states to 83% in Ondo State. Disease incidence and severity varied with locations and cultivars, and ranged from 0.0-87.5\ub118% and 1.0\ub10-4.5\ub10.8 in Osun State to 20.0\ub119 - 95.0\ub14.5% and 2.3\ub11.5 - 5.0\ub10 in Ondo State. Out of the twelve fungal pathogens from ten genera isolated from infected plants, only Colletotrichum truncatum , C. gloeosporioides and Lasiodiplodia theobromae caused Leaf blight on Egusi melon.Le melon Egusi ( Citrullus lanatus (Thumb) Mansf.) Est une importante culture l\ue9gumi\ue8re cultiv\ue9e pour les graines et l\u2019huile comestibles en Afrique de l\u2019Ouest. La maladie de br\ufblure foliaire (LBD) est l\u2019une des principales contraintes \ue0 sa production, avec le potentiel de causer des dommages \ue9conomiques. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9tudier l\u2019incidence et la distribution de la br\ufblure foliaire du melon Egusi dans le Sud-ouest du Nig\ue9ria. Une enqu\ueate sur la LBD du melon Egusi a \ue9t\ue9 faite en 2015 et 2016, dans cinq \uc9tats du sud-ouest du Nig\ue9ria (\uc9tats d\u2019Ogun, Oyo, Osun, Ekiti et Ondo). Vingt plantes dans chaque \uc9tat ont \ue9t\ue9 \ue9chantillonn\ue9es au hasard dans 150 fermes comprenant 30 fermes chacune, de chaque \uc9tat. La distribution des diff\ue9rentes vari\ue9t\ue9s de melons Egusi plant\ue9es a \ue9t\ue9 enregistr\ue9e. \uabBara\ubb cv. \ue9tait la vari\ue9t\ue9 la plus cultiv\ue9e (51,6%); suivi de \uabBojuri\ubb (30,4%) et \uabSerewe\ubb (18%). La br\ufblure foliaire a \ue9t\ue9 observ\ue9e dans la plupart des exploitations agricoles des cinq \uc9tats, passant de 73% dans les \uc9tats d\u2019Osun et d\u2019Oyo \ue0 83% dans l\u2019\uc9tat d\u2019Ondo. L\u2019incidence et la gravit\ue9 de la maladie variaient selon les emplacements et les cultivars, et allaient de 0,0-87,5 \ub1 18% et 1,0 \ub1 0-4,5 \ub1 0,8 dans l\u2019\uc9tat d\u2019Osun \ue0 20,0 \ub1 19 - 95,0 \ub1 4,5% et 2,3 \ub1 1,5 - 5,0 \ub1 0 dans l\u2019\uc9tat d\u2019Ondo . Sur les douze agents pathog\ue8nes fongiques de dix genres isol\ue9s de plantes infect\ue9es, seuls Colletotrichum truncatum , C. gloeosporioides et Lasiodiplodia theobromae ont caus\ue9 la br\ufblure foliaire du melon Egusi

Pathogenicity of Colletotrichum coccodes causing anthracnose disease and its effect on growth and yield of sweet potato [Ipomoea batatas (L.) Lam]

The disease causing ability of Colletotrichum coccodes and the effect of anthracnose on growth and yield of sweet potato accessions were evaluated in a two-year field trial. Field layout was a randomized complete block design with 16 sweet potato accessions replicated thrice. Young leaves of sweet potato accessions were sprayed with an inoculum concentration of 2.1 × 107 in a two-split application in the field with growth, yield, and disease indices recorded. Pathogenicity of C. coccodes was significantly highest among four accessions; OW4, SE10, SE12 and SPK-004 with abundant necrosis on leaves and stems of inoculated plants. Disease incidence varied between 2.48% - 52.83%, and 2.77% - 50.73%, during the 2018 and 2019 planting seasons respectively, with host response ranging from being susceptible to resistant. Accessions OW5 and OS15 had significantly lower disease incidence and severity than other treatments (p = 0.031 and 0.28 respectively) and also produced the highest yield ranging between 15.84 - 17.29, and 14.88 - 15.72 t/ha-1, in 2018 and 2019, respectively. This study has shown that anthracnose causes significant reduction in expected yield in sweet potato cultivation and also identified two resistant sweet potato accessions that can be useful sources in breeding for resistance to the disease

Evolution des infections naturelles sur les mangues, les avocats et les bananes en Côte d’Ivoire et principaux champignons responsables

Objectif: Les altérations fongiques constituent une des causes majeures des pertes post récolte des fruits frais en Côte d’Ivoire. L’objectif de cette étude était d’analyser les infections naturelles qui apparaissent sur les fruits dans les principales zones de production du pays, et d’identifier les principaux agents pathogènes responsables.Méthodologie et résultats: L’étude a consisté à la collecte, de manière aléatoire, des fruits dans les zones Centre, Sud, Est et Nord du pays, à la notation quotidienne des infections naturelles apparues sur les fruits, sur une durée de 6 à 9 jours et à l’isolement ainsi que l’identification des champignons qui leur sont associés. Les résultats ont montré une évolution du taux cumulé des infections naturelles de tous les fruits et la présence de 16 groupes morphologiques dont les plus dominants sont ceux à thalle gris (93,75%) au niveau de la mangue, ceux à thalle noir cotonneux (73,53%) pour l’avocat et ceux à thalle rose (81,25%) pour la banane. L’identification a montré une diversité de champignons pathogènes dont les principaux genres sont : Colletotrichum, Fusarium, Aspergillus, Phoma, Penicillium, Curvularia, Botryodiplodia et Rhizoctonia.Conclusion et application des résultats: Les fruits frais subissent après récolte l’impact des champignons pathogènes par les infections qu’ils causent. Ces infections augmentent au fur et mesure que les fruits murissent. Ces résultats constituent une bonne base pour le renforcement des stratégies de lutte. Toutefois, des études complémentaires, notamment pathogéniques et moléculaires des principaux champignons, sont nécessaires pour mieux les connaître et envisager, ainsi, des méthodes intégrées de lutte plus inclusives.Mots clés: Fruits, post-récoltes, infections, champignons pathogènesEnglish AbstractObjective: Fungal alterations are one of the major causes of post-harvest losses of fresh fruit in Côte d'Ivoire. The objective of this study was to analyze the natural infections that appear on fruits produced in the main production areas of the country, and to identify the main pathogens.Methodology and results: The study consisted of random fruit collection in the main growing areas, daily recording of natural infections on the fruit over a period of 6 to 9 days and isolation of the associated fungi. The results showed an evolution of the cumulative rate of natural infections of all fruits and the presence of 16 morphological fungal groups of which the most dominant are those with grey thallus (93.75%) in mango, those with cottony black thallus (73.53%) for avocado and those with pink thallus (81.25%) for banana. Identification showed a diversity of pathogenic fungi including the genera Colletotrichum, Fusarium, Aspergillus, Phoma, Penicillium, Curvularia, Botryodiplodia and Rhizoctonia.Conclusion and application of results: Fresh fruits quality are influenced by pathogenic fungi through the infections they cause after harvest. These results provide a good basis for control strategy enhancement. However, additional studies, including pathogenic and molecular components of the main fungi, are needed to better understand them and thus consider more inclusive integrated control methodsKeywords: Fruits, post-harvest, infections, pathogenic fung

Mangiferin as a Biomarker for Mango Anthracnose Resistance

Mangos (Mangifera indica L.) are tropical/subtropical fruits belonging to the plant family Anacardiaceae. Anthracnose is the most deleterious disease of mango both in the field and during postharvest handling. It is most commonly caused by the Colletotrichum gloeosporioides complex. Mangiferin, a xanthanoid compound found in at least twelve plant families worldwide (Luo et al., 2012), is present in large amounts of the leaves and edible mangos. Even though this compound plays a pivotal role in the plant’s defense against biotic and abiotic stressors, no correlations been made between the compound and mango anthracnose resistance. Mangos were collected, grouped according to their countries of origin, and evaluated for their mangiferin concentrations at four different stages of development. Extracts of interest were then tested against different strains of C. gloeosporioides. The results demonstrated that mangiferin concentrations are significantly different at different stages in fruit development. The antifungal assays were inconclusive

High-yielding Anthracnose-resistant Stylosanthes for Agricultural Systems

Livestock Production/Industries,

Plant Diseases

Plant pathogens, the causal agent of infectious plant diseases, influence our lives more than just as an economic impact through yield lost. The study of plant pathogens has given rise to the development of new sciences, new technologies for plant breeding, and the agrochemical industry for pesticide developments. Yet, all our actions and efforts to suppress or eradicate them constantly pressures these various organisms to evolve and adapt for survival. Therefore today, when facing climate changes, accelerated transport of plants and plant products, and world population growth, we have to ask quo vadis phytopathology. Like Alice in Wonderland “If we wish to go anywhere we must run twice as fast as that” so we need to constantly broaden our knowledge. However, today’s literature abounds with knowledge about plant pathogens. Hence, this book intends to present to the reader all the latest material and knowledge about plant pathogens, changes or refinements in plant disease epidemiology, and new approaches and materials used for plant pathogen control. Hopefully, this book will be of interest to those working within the field and looking for an up-to-date introduction. We hope it also interests students and thereby, will influence the future development of phytopathology and our better coexistence with plant pathogens

Morphologische und molekulare Charakterisierung des Pathogens Colletotrichum gloeosporioides an Gaultheria mit dem Ziel der Erschließung von Resistenzquellen

Gaultheria procumbens L. ist in der Herbstvermarktung eine der bedeutendsten Zierpflanzen. Die winterharte, mehrjährige und sich über Rhizome bzw. Samen vermehrende Art der Familie Ericaceae kann massiv vom ubiquitär vorkommenden pilzlichen Pathogen Colletotrichum gloeosporioides befallen werden. Hat sich der Erreger einmal im Bestand etabliert, kann dies mitunter zu Totalausfällen führen, in deren Folge die Betriebe den Anbau der Gaultherien aufgeben müssen. Eine Bekämpfung der Mykose stellt sich als besonders schwierig heraus, da das Pathogen latent in der Pflanze vorkommt und Fungizide nur in der juvenilen Phase erfolgversprechend eingesetzt werden können. Ältere Pflanzen erzeugen zudem einen sehr dichten Bestand, sodass das Fungizid nicht mehr an die Stängelbasis gelangen kann, wo das Pathogen hauptsächlich lokalisiert ist. Eine Alternative zum Einsatz von Pflanzenschutzmitteln stellt die Züchtung dar. Mit der Nutzung pflanzengenetischer Ressourcen besteht die Möglichkeit der Entwicklung krankheitsresistenter Formen. Daher lagen die Schwerpunkte dieser Arbeit (1) in der Sammlung, Erhaltung, Vermehrung und Hybridisierung von Gaultheria-Arten, (2) in der Charakterisierung des Pathogens für die Entwicklung eines reproduzierbaren und praktikablen Resistenztests sowie (3) in der Resistenzevaluierung ausgewählter Gaultheria-Arten. Insgesamt konnten 23 der 33 im Gewächshaus kultivierten Gaultheria-Arten erfolgreich auf Anderson-Medium mit Phytohormonzusätzen (9 μM/l Zeatin, 5,7 μM/l Indol-3-essigsäure) als In-vitro-Sprosskultur etabliert werden. Mit Hilfe von 185 Random Amplified Polymorphic DNA Markern erfolgte eine Verwandtschaftsanalyse in der Gattung Gaultheria, die die Basis für anschließende Artkreuzungen bildete. In deren Folge konnten drei interspezifische Hybriden aus G. myrsinoides x G. procumbens gewonnen und molekulargenetisch über RAPD Marker bestätigt werden. In-vitro-Untersuchungen zur Langzeitlagerung von Gaultheria-Pollen machten deutlich, dass Pollen von G. procumbens bei einer dreimonatigen Lagerung bei -20 °C noch bis zu 50 % und bei G. shallon bis zu 70 % keimfähig bleiben kann. Mit zeitlich zunehmender Tiefkühllagerung verringerte sich die Keimrate und ging nach sechs Monaten gegen Null. Hinsichtlich des Pathogens C. gloeosporioides erfolgten Analysen zur Morphologie, Genetik und Virulenz. Anhand der Sequenzanalyse der rDNA-ITS-Region von 30 Isolaten und des Abgleichens der Sequenzen mit veröffentlichten Sequenzen der NCBI Datenbank via BLAST konnte gezeigt werden, dass neben C. gloeosporioides auch C. acutatum an Gaultheria vorkommt. Weiterführende Untersuchungen zum pathogenen Potential ergaben, dass C. acutaum apathogen ist. In einem PCR-basierten Nachweis von C. gloeosporioides aus infiziertem Pflanzenmaterial unter Anwendung von Additiven und Touch-Down-PCR konnten nur unspezifische Amplifikate erzeugt werden. In der Bewertung morphologischer Merkmale wie radiales Myzelwachstum, Koloniefarbe, Myzelstruktur, Setaen- und Konidienmassebildung sowie der Konidienlänge und -breite waren große Differenzen zwischen den 27 untersuchten Isolaten zu beobachten. Es wurden weiterhin Versuche zur Lokalisierung des Erregers an latent befallenen Gaultheria-Trieben durchgeführt mit dem Ergebnis, dass sich das Pathogen hauptsächlich im Wurzelbereich der Pflanze akkumuliert. Diese Resultate bildeten die Grundlage für Substratinfektionsversuche. Inokuliertes Substrat ermöglichte dabei innerhalb von vier Wochen eine Infizierung der Pflanze. Mit den Resistenztestungen über die etablierte Methode der Stängelgrundapplikation konnte eine Art (G. shallon) gegenüber dem hoch virulenten Isolat (P-14) als gering anfällig eingestuft werden. Die Arten G. procumbens, G. pumila und G. hispida reagierten auf das hoch virulente Pathogen mit starken Symptomausprägungen und wurden daher als sehr anfällig eingeordnet.Gaultheria procumbens L. is an important horticultural species in Germany. It is cultivated and used as an ornamental plant for the fall season. The perennial and hardy Ericaceous shrub propagates via seeds and rhizomes. Over the last years, German Gaultheria producers have suffered from enormous losses up to collapses of the whole crop due to the infection with the fungus Colletotrichum gloeosporioides. Only frequent applications of fungicides in the juvenile phase prevent the expansion of the pathogen. In older plants the application of fungicides is less effective and preventive, since the fungus colonizes the lower stem part which cannot be reached by fungicides. An alternative to the application of fungicides is the use of plant genetic resources as disease resistance donors and the development of resistant cultivars. Therefore, the focus of this work was (1) on the collection, maintenance, reproduction and hybridization of different Gaultheria species, on (2) the characterization of the pathogen for the development of a reproducible and practicable resistance test as well as (3) on the evaluation of resistance in selected Gaultheria species. Overall, out 23 of 33 Gaultheria species cultivated in the greenhouse were successfully established on Anderson's medium as in vitro shoot cultures. In further cultivations on Anderson's medium supplemented with phytohormons (9 μM/l zeatin, 5,7 μM/l indole-3-acetic-acid) more shoots were successfully established from shoot segments than from shoot tips. Genetic relationships in the genus Gaultheria were analysed using 185 Random Amplified Polymorphic DNA markers and formed the basis for interspecific hybridisations. Three interspecific hybrids of G. myrsinoides x G. procumbens were molecularly identified by RAPD markers. Studies on the long-term storage of Gaultheria pollen in vitro revealed that pollen from G. procumbens stored for up to three months at -20 °C retains 50 % and from G. shallon 70 % germinating rate. With temporal increasing cold storage germinating rate decreased and went to zero after six months. Concerning to the pathogen C. gloeosporioides the morphological and genetic variability plus its virulence potential were investigated. Based on sequence analysis of the rDNA ITS region in comparison to published sequences in the BLAST database, C. gloeosporioides and C. acutatum were shown to infect Gaultheria. Studies on the pathogenic potential confirmed that C. acutatum is non-pathogenic. In a PCR-based detection of C. gloeosporioides in infected Gaultheria plant material no specific amplicons were obtained, when applying additives and touch-down PCR programmes. The evaluation of morphological characteristics such as radial mycelial growth, colony color, and structure of mycelium, setae formation and mass propagation of conidia as well as their length and width indicated huge differences between the 27 tested isolates. Further experiments were performed on latently infected Gaultheria shoots. They demonstrated that the pathogen accumulates mainly in the root zone of the plant. These results formed the basis for substrate infection experiments, in which contaminated substrate led to an infection of Gaultheria plants within four weeks. Resistance tests showed that G. shallon was less susceptible against a highly virulent isolate (P-14) than G. procumbens, G. pumila and G. hispida when applying a spore suspension at the stem base