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Mycosphaerella graminicola (anamorph Septoria tritici) causes Septoria tritici blotch, a globally important disease of winter wheat. Resistance and pathogenicity generally vary quantitatively. The pathogen reproduces both sexually and asexually, and the pathogen population is highly genetically variable. Several unresolved questions about the epidemiology of this pathosystem are addressed by this research. Among them are whether cultivar-isolate specificity exists, how partial host resistance affects pathogen aggressiveness and sexual reproduction, and how host genotype mixtures influence epidemic progression and pathogenicity. At its release in 1992, the cultivar Gene was highly resistant to M. graminicola, but that resistance had substantially dissolved by 1995. Six of seven isolates collected in 1997 from field plots of Gene were virulent to Gene seedlings in the greenhouse, while 14 of 15 isolates collected from two other cultivars were avirulent to Gene. Gene apparently selected for strains of M. graminicola with specific virulence to it. In a two-year experiment, isolates were collected early and late in the growing season from field plots of three moderately resistant and three susceptible cultivars, and tested on seedlings of the same cultivars in the greenhouse. Isolates were also collected from plots of two susceptible cultivars sprayed with a fungicide to suppress epidemic development. Isolate populations were more aggressive when derived from moderately resistant than from susceptible cultivars, and more aggressive from fungicide-sprayed plots than from unsprayed plots of the same cultivars. Over 5,000 fruiting bodies were collected in three years from replicated field plots of eight cultivars with different levels of resistance. The fruiting bodies were identified as M. graminicola ascocarps or pycnidia, or other. In all three years, the frequency of ascocarps was positively correlated with cultivar susceptibility, as measured by area under the disease progress curve, and was also positively associated with epidemic intensity. For three years, four 1:1 mixtures of a moderately resistant and a susceptible wheat cultivar were planted in replicated field plots. Isolates from the plots were inoculated as bulked populations on greenhouse-grown seedlings of the same four cultivars. Mixture effects on disease progression varied among the years, and were moderately correlated with mixture effects on pathogenicity. / Graduation date: 2002

The number of lesions increased with increasing temperatures over the range of wet periods except at 30$ sp circ$C, where their number decreased with increasing wetness duration. Cultivars were evaluated for partial resistance under field and greenhouse conditions. In the field ranking was based on cluster analysis of the standard area under the disease progress curve (SAUDPC) for intervals between sampling dates. In the greenhouse, the cultivars were evaluated on the basis of their response relative to five components of partial resistance: the SAUDPC, mean lesion area (MLA), pycnidial density (PCD), spore density (SPD), and the latency period defined as the time from inoculation to 50% and 75% disease (T$ sb{50}$ and T$ sb{75}$). In the greenhouse, overall ranking was based on cluster and principal component analysis of responses to SAUDPC, MLA, PCD and SPD. T$ sb{50}$ and T$ sb{75}$ were not significant. Three cultivars, Golden Plume, Superdora and Summit, were rated as moderately resistant in both field and greenhouse trials. The others ranged from moderately susceptible to very susceptible. (Abstract shortened by UMI.)

Kentucky reported a solid 13.1% growth in certified organic land from 1997 to 2002. The relative lack of research on disease management practices in Kentucky consistent with organic regulations is an issue that needs to be addressed to provide more reliable information to local farmers. Thus, the first objective of this research was to investigate the potential disease control obtained with natural, organically certifiable spray materials against Colletotrichum orbiculare in vitro and in vivo. The second objective was to test certifiable spray materials in combinations to identify synergistic interactions. The third objective was to evaluate Organic Material Review Institute (OMRI)-certified materials for managing Septoria leaf spot and early blight in tomato under field conditions. The fourth objective was to evaluate chitosan-based products against C. orbiculare in vitro and in vivo. Essential oils, Trilogy®, and Actinovate®, failed to suppress C. orbiculare in vitro as well as cucurbit anthracnose. Bicarbonate salts, Regalia®SC, Sonata®, copper based-products, lime sulfur and water-soluble chitosan showed high antifungal activity in vitro. Bicarbonate salts, Sonata®, Serenade Max®, Soil Gard 12G®, copper based-products and lime sulfur reduced anthracnose disease severity in vivo. In the synergism experiments only a limited number of mixtures showed synergistic interactions, but even in those cases, the effect was not consistent between experiments. The main response obtained was antagonism. In field experiments the most effective fungicides for managing Septoria leaf spot and early blight of tomato were copper-based fungicides. None of the biological-based products (Sonata® and Serenade Max®)), plant-based extracts (Trilogy® and Regalia® SC), chitosan, ammonium bicarbonate nor horticultural lime sulfur provided a significant reduction in disease severity. For the fourth objective, water-soluble chitosan with a molecular weight between 3 to 10 kDa (80 and 85% deacetylated) showed the highest antifungal activity among all chitosan-based products evaluated in vitro. Also, combining the in vitro and in vivo results suggest that the antifungal activity of chitosan-based products is molecular weight- and concentration-dependent. These results provide a significant advance in the evaluation of the efficacy of OMRI-certified materials and natural materials to help organic farmers in Kentucky and the USA to manage diseases.

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Orientador: Antonio Goes / Coorientador: Fernanda Dias Pereira / Banca: Rita de Cássia Panizzi / Banca: Juliana Stracieri / Resumo: O presente trabalho teve como objetivo avaliar fungicidas de diversos grupos, isoladamente ou em mistura, no controle de Septoria lycopersici em tomateiro híbrido H-9553. Os tratamentos foram avaliados em três anos consecutivos, e constituíram nos seguintes: T1 - azoxistrobina + difenoconazol + clorotalonil; T2 - azoxistrobina + difenoconazol; T3 - clorotalonil; T4 - azoxistrobina; T5 - difenoconazol; T6 - fluazinam + clorotalonil; T7 - fluazinam; T8 - metiram + piraclostrobina + metconazol; T9 - metiram + piraclostrobina; T10 - metconazol; T11 - piraclostrobina; T12 - mancozebe; T13 - tetraconazole + tionafato metilico; T14 - tetraconazole; T15 - tiofanato metilico; T16 - ciprodinil; T17 - ciprodinil + difenoconazol; T18 - testemunha (sem fungicida). O delineamento experimental adotado foi o de blocos ao acaso, com quatro repetições. Cada unidade amostral foi representada por área de 31,25 m2 . As pulverizações, em número de 18, foram realizadas mediante pulverizador pressurizado a CO2, a 50 lb pol2, em intervalos de 7 dias e volume de 400 L ha-1 . Foram realizadas 17 avaliações, em intervalo semanal, nas três linhas centrais, em área de 18,75 m2 . Nas avaliações determinou-se a severidade dos sintomas, mediante escala de notas que variaram de 0 (ausência de sintomas) a 5 (severidade máxima). A partir do conjunto de dados foi determinada a área abaixo da curva de progresso da doença (AACPD). Adicionalmente, foram avaliadas a produtividade, em kg ha-1,... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The present study aim to evaluate various groups fungicides, alone or in combination, working on the control of Septoria lycopersici in hybrid tomato plant H-9553. The treatments were evaluated during three consecutive years, and was consisted in the following: T1 - azoxystrobin + difenoconazol + clorotalonil; T2 - azoxystrobin + difenoconazol; T3 - clorotalonil; T4 - azoxystrobin; T5) difenoconazol; T6) fluazinam + clorotalonil; T7 - fluazinam; T8 - metiram + piraclostrobina + metconazol; T9 - metiram + piraclostrobina; T10 - metconazol; T11 - piraclostrobina; T12 - mancozeb; T13 - tetraconazole + tionafato metilico; T14 - tetraconazole; T15 - tiofanato metilico; T16 - ciprodinil; T17 - ciprodinil + difenoconazol; T18 - witness (with no fungicide). The experimental adopted model was a randomized block with four replications. Each sample unit represented by the area of 31.25 m2 . The 18 spraying were made by spray pressurized CO2, at 50 lb pol2 at 7 day intervals and volume of 400 L ha-1 . Were realized 17 evaluations in weekly intervals, in three central lines in area of 18,75 m2 . The evaluations measured the severity of symptoms, a note scale ranging from 0 (no symptoms) to 5 (maximum severity). From the data set was determined the area under the disease progress curve (AACPD). In addition they were evaluated productivity in kg ha-1 and fruit standart. All treatments were statistically different from the witness as AACPD, productivity, % of green fruits and % of rotten fruit. Five treatments highlighted positively: T1 - azoxystrobin + difenoconazol + clorotalonil; T3 - clorotalonil; T4 - azoxystrobin; T8 - metiram + piraclostrobina + metconazol e T11 - piraclostrobina / Mestre

Master of Science / Department of Horticulture, Forestry, and Recreation Resources / Edward E. Carey / With acceptance and utilization of chemical pesticides declining, some vegetable producers are turning to alternative methods to manage plant health issues. Compost tea (CT) has provided control of some foliar pathogens and may provide benefits beyond disease suppression. Despite an increasing body of popular and scientific literature focusing on CT as a biological control option for growers, information on the efficacy of CT is still lacking for many pathosystems. In this study, field trials were conducted to evaluate the efficacy of CT on Septoria lycopersici, causal agent of Septoria leaf spot on tomato, in Kansas, in 2006 and 2007. Previous research done at KSU with a similar CT showed adequate control of this pathogen in field and greenhouse studies conducted. Additional work to develop a rapid screening method for efficacy of CT formulations was carried out in the greenhouse at Manhattan, KS. CT sprayed weekly on tomato plants prior to and after disease onset led to no significant difference in control of the pathogen compared to untreated controls. A contact fungicide (chlorothalonil) provided significant control of the pathogen in 2007, but not in 2006. These results contrast with those obtained in previous K-State research. It is difficult to assess why such striking differences were obtained, but the variation in these results point to the need to identify optimal recipes of CT for this pathosystem. Preliminary investigations standardized plant age, inoculum concentration, incubation conditions, and incubation interval for measurable Septoria leaf spot disease development on young tomato plants in the greenhouse. Ingredients of the field-tested CT were used to make a variety of CTs to test using the greenhouse-screening assay. Further work on identifying effective CT recipes is needed to substantiate the validity of this screening protocol and to evaluate the correlation of this method with disease suppression in the field.

La septoriose (pathogène Zymoseptoria tritici) est la plus importante maladie foliaire des cultures de blé en Europe. Les méthodes de lutte comprennent la résistance variétale, les stratégies d’évitement de la maladie et le recours aux fongicides. Cependant, ces stratégies n’assurent pas une protection complète des cultures de blé. La tolérance à la septoriose est une approche complémentaire qui vise justement à maintenir le rendement en présence de symptômes. La tolérance à la septoriose dépend de traits physiologiques de la plante et d’équilibres source/puits : la demande des puits (croissance des grains) doit être satisfaite malgré une disponibilité réduite des sources (capacité photosynthétique réduite par les symptômes foliaires). La surface verte du couvert, la sénescence et les composantes du rendement sont des traits potentiels de tolérance intéressants qui ont été étudiés lors de ce projet. Une étude de datamining, une expérience en serre et deux expériences au champ ont été menées pour fournir des informations complémentaires sur les mécanismes de tolérance à la septoriose. Les effets des interactions génotype × environnement sur les traits de tolérance ont été étudiés pour deux saisons × cinq localisations × neuf cultivars. La nutrition azotée et le métabolisme de quatre lignées double-haploïdes (DH, contrastées du point de vue de leur tolérance à la septoriose) ont été examinés dans une expérience en conditions contrôlées à l'UMR ECOSYS (INRA, AgroParisTech Grignon, France). Les bilans source/puits de six lignées DH contrastant pour la tolérance ont également été examinés en fonction de leurs réponses à un traitement d'égrainage, appliqué dans une expérience au champ à Hereford (Royaume-Uni). Enfin, une expérience au champ avec deux stratégies fongicides (contrôle total des maladies / lutte contre les maladies non-ciblées) a permis d’étudier la tolérance à la septoriose de six cultivars modernes (Leicestershire, Royaume-Uni). L'objectif principal était de vérifier les traits potentiels de tolérance à la septoriose sur des cultivars actuellement commercialisés. Des traits potentiels de tolérance à la septoriose ont été identifiés tels que la date d’épiaison, le faible degré de limitation des puits par les sources lors de la phase de remplissage du grain des couverts sains, la distribution verticale des surfaces foliaires favorisant des feuilles supérieures relativement grandes. Les résultats ont montré que ces caractères pourraient être sélectionnables, sans compromis avec le rendement potentiel. Enfin, le projet a également discuté du besoin de méthodes alternatives de quantification de la tolérance du blé à la septoriose, ainsi que de l'importance des variations environnementales qui doivent être prises en compte pour étudier les variations génétiques de la tolérance, mais qui pourraient également être utilisées pour identifier des environnements tolérants. / The Septoria tritici blotch disease (STB, pathogen Zymoseptoria tritici) is the most damaging foliar infection of wheat crops in Europe. Disease management strategies include cultivar resistance, disease escape strategy and fungicides. However, these strategies have failed to provide a complete protection of wheat crops. The STB tolerance is a complementary approach which aims to maintain yield in the presence of the symptoms. The tolerance of STB relies on plant physiology and source/sink balance: the sink demand (the grain growth) must be satisfied in spite of reduced source availability (photosynthetic capacity as affected by the STB symptoms on the leaves). The green canopy area, the senescence timing and the grain yield components are interesting potential sources of tolerance that were studied in this project. A data-mining study, one glasshouse experiment and two field experiments were carried out providing complementary insights on STB tolerance mechanisms. The genotype × environment interaction effects on tolerance traits were investigated for two seasons × five locations × nine cultivars datasets. The nitrogen nutrition and metabolism of four doubled-haploid (DH) lines contrasting for STB tolerance were examined in a controlled-glasshouse experiment at UMR ECOSYS (INRA,AgroParisTech) Grignon, France. The source/sink balance of six DH lines contrasting for STB tolerance was also examined according to their responses to a spikelet removal treatment, applied in a field experiment in Hereford, UK. Finally, a field experiment with two fungicide regimes (full disease control and non-target (STB) disease control) probed the STB tolerance of six modern UK winter wheat cultivars in Leicestershire, UK. The main objective was to verify identified potential STB tolerance traits in commercial cultivars. Putative STB tolerance traits have been identified such as the early heading date, the low degree of grain-source limitation of healthy crops during the grain filling phase, the vertical canopy distribution favouring a relatively larger flag-leaf. Results showed these traits might be selectable in wheat breeding without a trade-off with the potential yield. Finally, the project also discussed the need for alternative STB tolerance quantification methods, as well as the importance of environmental variations which have to be taken into account to study genetic variation in tolerance, but which could also be used to discriminate tolerant environment.

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