The study examined interactions between morogo plants, arbuscular mycorrhizal fungi (AMF) and Fusarium species. Morogo refers to traditional leafy vegetables that, together with maize porridge, are dominant staple foods in rural areas of the Limpopo Province such as the Dikgale Demographic Surveillance Site (DDSS). Morogo plants grow either as weeds (often among maize), occur naturally in the field or are cultivated as subsistence crops by rural communities. Botanical species of morogo plants consumed in the DDSS were determined. Colonisation of morogo plant roots by AMF and Fusarium species composition in the immediate soil environment were investigated in four of eight DDSS subsistence communities, Isolated AMF were shown to belong to the genera Acaulospora and Glomus. Twelve Fusarium species were isolated from soil among which Fusariurn verticilliodes and Fusarium proliferaturn occurred predominantly. Greenhouse pot trials were conducted to examine the effect of AMF on morogo plant growth (cowpea; Mgna unguiculata) and Fusarium proliferatum levels in soil, Interaction between plants and AMF, as well as tripartite interactions of cowpea plants, AMF and Fusarium proliferatum were investigated. Non-inoculated cowpea plants served as controls for the following inoculations of cowpea in pots: (i) Fusarium proliferatum; (ii) commercial AMF from Mycoroot (PTY) Ltd. (a mixture of selected indigenous Glomus spp referred to commercial AMF for the purpose of this study); (iii) indigenous AMF obtained from DDSS soil (referred to iocal AMF for the purpose of this study); (iv) commercial AMF plus Fusarium proliferatum; (v) local AMF plus Fusariurn proliferatum. Results showed reduced root colonization by local as well as commercial AMF when Fusarium proliferatum were present. Local AMF significantly enhanced cowpea growth while commercial AMF apparently reduced the level of Fusarium proliferatum in the rhizosphere and surrounding soil. Results suggest that AMF may have potential as biological growth enhancers and bioprotective agents against Fusarium proliferatum. / Thesis (M. Environmental Science (Water Science))--North-West University, Potchefstroom Campus, 2007.

The study examined interactions between morogo plants, arbuscular mycorrhizal fungi (AMF) and Fusarium species. Morogo refers to traditional leafy vegetables that, together with maize porridge, are dominant staple foods in rural areas of the Limpopo Province such as the Dikgale Demographic Surveillance Site (DDSS). Morogo plants grow either as weeds (often among maize), occur naturally in the field or are cultivated as subsistence crops by rural communities. Botanical species of morogo plants consumed in the DDSS were determined. Colonisation of morogo plant roots by AMF and Fusarium species composition in the immediate soil environment were investigated in four of eight DDSS subsistence communities, Isolated AMF were shown to belong to the genera Acaulospora and Glomus. Twelve Fusarium species were isolated from soil among which Fusariurn verticilliodes and Fusarium proliferaturn occurred predominantly. Greenhouse pot trials were conducted to examine the effect of AMF on morogo plant growth (cowpea; Mgna unguiculata) and Fusarium proliferatum levels in soil, Interaction between plants and AMF, as well as tripartite interactions of cowpea plants, AMF and Fusarium proliferatum were investigated. Non-inoculated cowpea plants served as controls for the following inoculations of cowpea in pots: (i) Fusarium proliferatum; (ii) commercial AMF from Mycoroot (PTY) Ltd. (a mixture of selected indigenous Glomus spp referred to commercial AMF for the purpose of this study); (iii) indigenous AMF obtained from DDSS soil (referred to iocal AMF for the purpose of this study); (iv) commercial AMF plus Fusarium proliferatum; (v) local AMF plus Fusariurn proliferatum. Results showed reduced root colonization by local as well as commercial AMF when Fusarium proliferatum were present. Local AMF significantly enhanced cowpea growth while commercial AMF apparently reduced the level of Fusarium proliferatum in the rhizosphere and surrounding soil. Results suggest that AMF may have potential as biological growth enhancers and bioprotective agents against Fusarium proliferatum. / Thesis (M. Environmental Science (Water Science))--North-West University, Potchefstroom Campus, 2007.

Some yeast strains under certain conditions secrete polypeptide toxins which are inhibitory to sensitive fungal cells into the medium. These yeast strains are termed as killer yeasts and their toxins are designated as killer proteins or killer toxins. Killer proteins are classified into 11 typical types (K1-K11). These toxins have different killing mechanisms on sensitive cells. Some of them hydrolyze major cell wall component, beta-1,3- glucans. As mammalian cells lack cell walls research and development of novel highly selective antifungals are mostly focused on the agents which target the components of the fungal cell wall. K5 type killer protein was characterized in our labarotory previously. This protein is an exo beta-1,3-glucanase which is stable at pH&amp / #8217 / s and temperatures appropriate for its biocontrol usage. Beta-1,3-glucan hydrolyzing activity of the K5 type killer protein highlighted the potential use of this protein as a selective antifungal agent. According to CLSI methodology, antifungal activity of the K5 type yeast killer protein was tested against 6 fungal strains causing postharvest spoilage in citrus fruits and found to be effective on Botrytis cinerea, Penicillium digitatum, Penicillium italicum whereas non effective on Colletotrichum gloeosporoides, Phythophythora citrophthora, Alternaria citri. The MIC values of the toxin for B.cinerea, P.digitatum, P.italicum were found to be 16 mikrogram/ml while IC 50 values of the toxin were 2.12, 3.31, 2.57 mikrogram/ml respectively. The results showed that K5 type yeast killer protein would be used as a novel and selective agent against B.cinerea, P.digitatum and P.italicum.

L’aglio è coltivato a livello mondiale nelle regioni temperate, secondo la FAO nel 2016 1.5 milioni di ettari sono stati destinati a questa coltura. A partire dal 2002 Fusarium proliferatum è stato segnalato come principale agente causale del marciume secco dell’aglio in post raccolta. I sintomi sono identificabili come macchie necrotiche sui bulbilli e in presenza di forti infezioni è possibile osservare la presenza di micelio bianco. F. proliferatum è un patogeno in grado di produrre Fumonisina B1 e B2, micotossine che potrebbero accumularsi all’interno dei bulbi ed essere tossiche per il consumatore. In Italia nel 2012 il 30% del raccolto è stato perso a causa di questo patogeno. Essendo la Fusariosi una malattia emergente a livello mondiale in letteratura si trovano ancora scarse informazioni sul suo sviluppo a livello di campo e sulle strategie di contenimento. 1. Allo scopo di verificare la quantità di inoculo fungino presente nell’ambiente si è proceduto all’analisi dei suoli in presemina con specifica attenzione alla quantificazione e all’identificazione delle specie fungine presenti. A tale scopo è stata eseguita: la conta delle Unità Formanti Colonia per grammo di terreno (UFC/g) su terreni specifici per l’isolamento del genere Fusarium spp. per grammo di terreno. Le identificazioni sono state eseguite al microscopio ottico e confermate successivamente con metodi molecolari. 2. Per seguire l’avanzamento della malattia durante la stagione colturale, invece, si è proceduto al campionamento in tre fasi fenologiche (inizio formazione dei bulbilli BBCH 15, ingrossamento dei bulbilli BBCH 45, maturazione di raccolta BBCH 49) con caratterizzazione dei sintomi, isolamento e riconoscimento dei funghi associati al marciume. 3. Per verificare la correlazione tra andamento meteo e incidenza delle specie fungine associate al marciume secco, sono stati raccolti i dati di meteorologici relativi al totale delle piogge, ai gradi giorno, all’umidità relativa media e alla temperatura media nei quadrati corrispondenti alle aziende agricole oggetto di studio. I dati sono stati correlati attraverso il coefficiente di correlazione di Pearson con i valori di gravità e incidenza della malattia stimati a fine stagione colturale. 4. Per verificare l’insorgenza dalla malattia nella fase di post raccolta si è proceduto con campionamenti di bulbi in conservazione, posa in piastra di bulbilli sintomatici e asintomatici e calcolo dell’incidenza delle specie fungine associate ai sintomi del marciume. 5. Al fine di verificare la possibile presenza di fumonisine nei campioni analizzati durante la stagione colturale e nel post raccolta, si è proceduto all’analisi attraverso HPLC di estratti di aglio. 6. Per individuare possibili strategie di controllo della malattia durante la stagione colturale sono stati eseguiti test di efficacia di prodotti chimici e biologici in vitro e in campo. I prodotti chimici sono stati provati su PDA modificato inoculato centralmente con F. proliferatum, mentre per gli agenti di biocontrollo sono state allestite prove di coltura duale. La prova in campo, invece, è stata eseguita all’interno di un campo sperimentale a strip plot. L’aglio delle diverse tesi è stato conservato in cella frigorifera per 9 mesi, per valutare la persistenza dei prodotti utilizzati alla concia. I risultati ottenuti hanno dimostrato che F. proliferatum e F. oxysporum sono le specie maggiormente associate al marciume dell’aglio durante la stagione colturale. L’andamento delle due specie è complementare e varia a seconda dell’andamento meteorologico della stagione colturale. F. proliferatum è correlato positivamente con l’aumento della temperatura e delle piogge, mentre F. oxysporum sembra prevalere nelle stagioni meno piovose ed ha mostrato correlazione positiva con la gravità dei sintomi rilevati in campo sulle corone. La carica micotica di Fusarium nel terreno rimane costante negli anni di analisi, facendo presupporre un maggiore ruolo del seme nella trasmissione della malattia. Per quanto riguarda il post raccolta, invece, F. proliferatum risulta la specie isolata con maggiore frequenza dai bulbilli e si correla positivamente ai sintomi rilevati sugli spicchi, confermando il suo ruolo come agente causale del marciume secco durante lo stoccaggio. F. oxysporum, invece, colonizza in prevalenza le radici e la parte basale della pianta dividendo il patosistema in due subsistemi: F. proliferatum-bulbi; F. oxysporum-radici. F. proliferatum è stato isolato anche dagli spicchi asintomatici con frequenza del 25%, ed è stato possibile rilevare la presenza di fumonisine con l’avanzare del tempo di stoccaggio in cella. Essendo il fungo presente anche sugli spicchi asintomatici maggiori studi saranno necessari per garantire la sicurezza dei consumatori. Infine, dalle prove di concia in campo è emerso che il principio attivo Tebuconazolo, riduce la comparsa dei sintomi da Fusarium, ma non in modo risolutivo. Ciononostante, una volta che il prodotto viene riportato a temperatura ambiente dopo lo stoccaggio in cella refrigerata, l’incidenza di F. proliferatum aumenta nuovamente con possibilità di sviluppo di danni al prodotto da commercializzare. / Since 2002, Fusarium proliferatum has been reported as the main causal agent of garlic dry rot during the postharvest stage, but information on the development of the disease throughout the production chain was nearly absent. Dry rot has caused huge economic losses in the past few years (up to 30 % of the yield), symptoms are visible on bulbs during storage as necrotic spots and in the most severe attacks, white mycelium may become visible on cloves. Few pest management strategies were tested in the recent past, but none were satisfactory. Due to the economic effect that this pathogen can have on local productions, the thesis aimed to deeply investigate the pathosystem with a field to fork approach and to test new strategies to control fungal infections. First of all, the work focused on garlic (Allium sativum L.) cropping season, intending to clarify the role of F. proliferatum in bulb infection as well as the impact of crop growing conditions on the development of the pathogen. A 3-year study was conducted in Piacenza (northern Italy) by sampling six garlic farms with different dry rot history (three highly contaminated and three low contaminated). Soil samples were recovered at sowing time for the counting of fungal colony-forming units (CFU). Plant samples were collected at three relevant growth stages, from April to July, for which disease severity assessment and fungi isolations were performed. Fusarium was the most frequently isolated genus, and F. proliferatum and F. oxysporum the dominant species during the garlic cropping season. F. oxysporum was dominant in the first year of the study, but F. proliferatum registered the highest incidence in all the farms tested. F. oxysporum incidence was correlated with dry weather, whereas F. proliferatum was enhanced in rainy years. To conclude, F. proliferatum is confirmed to be associated with garlic bulbs, even at crop’s early growth stages and symptoms are visible mainly on roots and basal plates at the field stage, related to F. oxysporum. Then, the focus was made in detecting the presence of F. proliferatum on garlic bulbs during prolonged storage, and to identify other fungal species associated with garlic dry rot. Moreover, fumonisin contamination in symptomatic and asymptomatic cloves were detected. Samples of 100 plants were collected over three production seasons in six farms located in Northern Italy at three-time points (at harvest, processing, and 6 months storage at –4° C). Results obtained lead to think that Fusarium–garlic pathosystem is split into two parts: basal plate/root and bulb. F. proliferatum had the highest incidence in infected bulbs and was confirmed as the causal agent of postharvest dry rot in garlic (mean incidence: 35.4%). F. oxysporum co-occurred with F. proliferatum but symptoms were visible only on basal plate/root. Dry rot incidence slightly increased during cold storage (from 14.6% at processing to 18.4% at 6-month storage); although, F. proliferatum incidence was stable during cold storage, fumonisin were produced from harvest through storage. Cloves showing symptoms were more contaminated compared to those asymptomatic, both by the fungus (mean incidence 39% vs 25.3%) and the toxin (287.0 vs 24.4 µg kg-1). Therefore, cold storage limits garlic dry rot, but health concerns related to fumonisin should be seriously considered. Regarding disease management, garlic crop is commonly propagated by plant parts (cloves). To protect garlic crop from early growth stages it is important to find commercial products able to control the pathogen growth on seedlings. The experiment aimed to test in vitro and in vivo the efficacy of triazoles and biocontrol agents (BCAs) against F. proliferatum and F. oxysporum. In in vitro trials, the best performance was achieved by propiconazole+prochloraz (100%), followed by tebuconazole (88.9%). BCAs were less effective but still showed great capacity to control the pathogen with maximum growth inhibition of 80% (Trichoderma harzianum +T. gamsii). In both cases, temperature influenced the capacity to control the pathogen with minimum effect at 25°C compared to lower temperatures. In vivo bacterial BCAs showed a similar capacity to control Fusaria compared to chemical products (mean of severity index 18.6% and 11.7%, respectively) and did not show side effects on root length. In vitro and in vivo results are comparable, except for Trichoderma, with the worst performances in terms of disease severity on plants. Finally, a field trial was designed to verify the efficacy of chemical and biological active ingredients as seed coating both at crop stage and postharvest, simulating the entire production chain, by taking into account visible symptoms and incidence of fungi. All products tested reduced the severity of symptoms on basal plates at the field stage, but none of them was able to reduce Fusarium incidence. A postharvest analysis conducted on bulbs demonstrated the efficacy of Tebuconazole, B. subtilis, and Trichoderma+B. subtilis in reducing the number of cloves showing symptoms per bulb (mean 34.3% vs control 45.8%). Moreover, Tebuconazole was able to reduce the incidence of F. proliferatum by 48% with respect to untreated control. The trial highlighted also that the incidence of F. proliferatum increased by 37% when garlic bulbs were kept for 15 days at room temperature simulating storage at consumers houses. Results obtained in the trial are promising and seed coating had a positive effect on garlic dry rot postharvest; although further studies are needed to test the persistence of seed coating treatments after prolonged storage period, especially when the product is kept outside cold chambers.