Bromus tectorum, an invasive winter annual, has displaced native vegetation throughout the western United States. Bromus tectorum litter influences nutrient cycling near the soil surface as well as plant establishment. Failed seed production of B. tectorum occasionally occurs in the field, with plants exhibiting weak flowering culms that turn straw-colored in spring when normal plants are green or purple in color. Because annual grasses transport most soluble carbon (C) and nitrogen (N) to reproductive organs, seed production failure results in significantly different fates for these nutrients compared with normal plants. As part of larger efforts to understand events leading to large-scale seedling emergence failure (termed die-offs), occasionally observed in near mono-cultures of B. tectorum, we here test the hypothesis that prematurely senesced litter associated with seed production failure has higher soluble C and N than normal litter. C and N concentrations of aboveground biomass were compared for normal and prematurely senesced B. tectorum plants. Two methods were used to cause premature senescence: fungal pathogen infection with Clarireedia capillus-albis and glyphosate herbicide application. In a related experiment, field sampling of normal and prematurely senesced plants under natural conditions was conducted to compare C and N levels in-situ. Herbicide-induced senescence resulted in 1.5 to 2 times greater soluble C concentrations, but fungal infection had no effect on soluble C under experiment conditions. Prematurely senesced litter had increased total N concentrations, resulting in lower C:N ratios. The C:N ratio for prematurely senesced plants (averaged across all studies) was 68:1, whereas mature normal plants averaged 243:1. These findings illustrate failed seed production associated with premature senescence results in B. tectorum litter with significantly higher N concentrations and can result in increased soluble C concentrations. Altered nutrient status may contribute to changes in soil microbial activity, including activity of soilborne pathogens found in die-offs.

Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Soilborne diseases of grapevines represent a complex problem with limited information available, both locally and internationally. Previous research in South Africa indicated that Phytophthora and Pythium spp. were the most widespread and devastating pathogens in grapevine nurseries and vineyards in the Western Cape province. The local grapevine industry is currently expanding; new cultivars, methods and agricultural chemicals are being used which can affect soilborne pathogens. It has therefore become necessary to reassess the status of soilborne pathogens in nurseries, since information in this regard is crucial for the development of disease management practices for the expanding local grapevine industry. Soilborne fungal genera associated with roots and crowns of declining nursery grapevines were assessed in surveys conducted at three different grapevine nurseries in the Western Cape province. Cylindrocarpon, Fusarium, Pythium, and Rhizoctonia spp. were consistently isolated from roots and crowns of declining nursery grapevines. Cylindrocladiella spp. and Phytophthora cinnamomi were infrequently isolated from diseased roots, crowns and soil whereas Pythium spp. were abundant in most of the soils. Results suggest that the status of soilborne fungal pathogens in grapevine nurseries in the Western Cape province has changed over the last 30 years. The DNA phylogeny and pathogenicity of the isolates of Cylindrocladiella were determined. Four species of Cylindrocladiella occur on grapevines in South Africa, namely C. lageniformis, C. parva, C. peruviana, as well as a new species, described in this study as C. viticola, which forms part of the C. infestans species complex. Pathogenicity trials were inconclusive. Ten Fusarium spp. were isolated from roots and crowns of declining nursery grapevines, namely F. acuminatum, F. anthophilum, F. chlamydosporum, F. equiseti, F. nygamai, F. oxysporum, F. proliferatum, F. scirpi, F. semitectum and F. solani. The dominant species was F. oxysporum, followed by F. proliferatum and F. solani. In pathogenicity trials F. oxysporum and F. solani significantly reduced root volume, root dry mass, length of new shoots, stem diameter and number of leaves, but increased the percentage of chlorotic leaves and root rot severity. Fusarium proliferatum also caused a significant reduction in new shoot growth, number of leaves and increased root rot severity compared to the controls. Fusarium so/ani seems to be more virulent than F. oxysporum, followed by F. pro/iferatum. This is the first report of F. oxysporum, F. pro/iferatum and F. so/ani as pathogens of grapevines in South Africa, and the first report of F. proliferatum as a pathogen of grapevines in the world. Phytophthora cinnamomi was isolated at low frequencies from declined grapevines, although present in the rhizosphere soil. It is possible that the extensive use of downy mildew chemicals in grapevine nurseries may protect grapevines from infection by P. cinnamomi. The effect of chemicals used to combat downy mildew on Phytophthora root rot of nursery grapevines was evaluated in a glasshouse. There was very little discernable effect of the chemicals tested relative to the control plants for the parameters measured and it was concluded that the inoculation technique needed refinement. However, plants treated with phosphorous acid tended to be taller and have more leaves, greater stem diameter and root volume than controls or plants treated with the other chemicals. The data obtained in this study are not conclusive, but indicated certain trends that more glasshouse trials and field trials would resolve. Results presented in this thesis indicate that a major shift has occurred in the status of soilborne fungi associated with roots and crowns of grapevines in nurseries in the Western Cape since the 1970s when Phytophthora and Pythium were predominant. The prevalence and role of soilborne fungi need to be determined so that new appropriate disease management strategies can be developed to limit losses in grapevine nurseries and ensure the sustainable production of healthy plants for the grapevine industry. / AFRIKAANSE OPSOMMING: 'N ONDERSOEK NA GRONDGEDRAAGDE SWAMME GEASSOSIEER MET WORTELS EN KRONE VAN WINGERD IN KWEKERYE Grondgedraagde siektes van wingerd is 'n komplekse probleem waaroor min inligting, beide plaaslik en internasionaal, beskikbaar is. Vorige navorsing in Suid-Afrika het aangedui dat swamme van die genera Phytophthora en Pythium die mees algemene en vernietigende grondgedraagde patogene in kwekerye en wingerde in die Wes-Kaap provinsie is. Die plaaslike wingerdbedryf brei huidiglik uit; nuwe kultivars, metodes en landbouchemikalieë word gebruik wat 'n invloed kan hê op grondgedraagde patogene. Gevolglik het dit noodsaaklik geword om die status van grondgedraagde patogene in wingerdkwekerye weer te bepaal, aangesien inligting in hierdie verband noodsaaklik is vir die ontwikkeling van siekte bestuurspraktyke vir die ontwikkelende plaaslike wingerdbedryf. Grondgedraagde swamgenera geassosieer met wortels en krone van terugsterwende wingerd in kwekerye is bepaal in opnames wat by drie verskillende wingerdkwekerye in die Wes-Kaap provinsie uitgevoer is. Cylindrocarpon, Fusarium, Pythium, en Rhizoctonia spp. is konstant vanuit wortels en krone van terugsterwende wingerdplante in kwekery geïsoleer, Cylindrocladiella spp. en Phytophthora cinnamomi is ongereeld vanuit siek wortels, krone en grond geïsoleer, terwyl Pythium spp. algemeen in meeste gronde voorgekom het. Resultate dui daarop dat die status van grondgedraagde swampatogene in wingerdkwekerye in die Wes- Kaap provinsie oor die laaste 30 jaar verander het. Die DNA filogenie en patogenisiteit van die isolate van Cylindrocladiella is bepaal. Vier spesies van Cylindrocladiella kom voor op wingerd in Suid-Afrika, naamlik C. lageniformis, C. parva, C. peruviana, sowel as 'n nuwe spesie, wat in hierdie studie as C. viticola aangedui is en wat deel is van die C. infestans spesie kompleks. Patogenisiteits proewe was onvoldoende om die patogeniese status van die swam me te bepaal. Tien Fusarium spp. is vanuit wortels en krone van terugsterwende wingerdplante in kwekery geïsoleer, naamlik F. acuminatum, F. anthophilum, F. chlamydosporum, F. equiseti, F. nygamai, F. oxysporum, F. proliferatum, F. scirpi, F. semitectum en F. solani. Die dominante spesies was F. oxysporum, gevolg deur F. proliferatum en F. solani. In pathogenisteitsproewe het F. oxysporum en F. solani gelei tot 'n betekenisvolle laer wortelvolume, droë massa van wortels, lengte en droë massa van nuwe groei en aantal blare, maar het die persentasie chlorotiese blare en graad van wortelvrot verhoog. Fusarium proliferatum het ook gelei tot 'n betekenisvolle afname in lengte en massa van nuwe groei, aantal blare en 'n verhoogde graad van wortelvrot in vergelyking met die kontrole behandelings. Dit wil voorkom asof Fusarium solani meer virulent is as F. oxysporum, gevolg deur F. proliferatum. Hierdie is die eerste aanmelding van F. oxysporum, F. proliferatum en F. solani as patogene van wingerd in Suid-Afrika, en die eerste aanmelding van F. proliferatum as 'n patogeen van wingerd in die wêreld. Phytophthora cinnamomi is konstant teen lae frekwensies vanuit terugsterwende wingerd in kwekerye geïsoleer, alhoewel dit in risosfeer gronde teenwoordig was. Dit is moontlik dat die ekstensiewe gebruik van chemikalieë teen donsskimmel in wingerdkwekerye die wingerdplante kan beskerm teen infeksie deur P. cinnamomi. Die effek van chemikalieë wat gebruik word teen donsskimmel op Phytophthora wortelverrotting van wingerd in kwekerye, is 'n glashuis geëvalueer. Die chemikalieë wat gestoets is, het vir die gemete parameters, tot baie min onderskeibare effek gelei relatief tot die kontrole plante, en daar is afgelei dat die inokulasie tegniek verbetering benodig. Plante wat met fosforiensuur behandel is, het egter geneig om langer te wees met meer blare, 'n groter stamdeursnee en wortelvolume as kontrole plante of plante behandel met ander chemikalieë. Data verkry vanuit die hierdie studie was onvoldoende, maar sekere neigings is aangedui wat deur verdere glashuis- en veldproewe verklaar sal word. Resultate wat in hierdie tesis weergegee is, het aangedui dat 'n algehele verskuiwing in die status van grondgedraagde swamme geassosieer met wortels en krone van wingerd in kwekerye vanaf die 1970s, toe Phytophthora en Pythium die dominante genera was, plaasgevind het. Die voorkoms en rol van grondgedraagde swamme moet bepaal word, sodat nuwe voldoende siektebestuurspraktyke ontwikkel kan word om verliese in wingerdkwekerye te beperk en sodoende die volhoubare produksie van gesonde plante vir die wingerdbedryf te verseker.

Submitted by (lucia.rodrigues@ufrpe.br) on 2017-03-10T14:20:09Z No. of bitstreams: 1 Eliane Mayumi Inokuti.pdf: 262975 bytes, checksum: 46e8a0576767e569d0817560c99aae40 (MD5) / Made available in DSpace on 2017-03-10T14:20:09Z (GMT). No. of bitstreams: 1 Eliane Mayumi Inokuti.pdf: 262975 bytes, checksum: 46e8a0576767e569d0817560c99aae40 (MD5) Previous issue date: 2012-07-30 / The fungi Rhizoctonia spp. is an important soilborne plant pathogen. The objective of this study was to evaluate the effectiveness of baits to quantify the saprophytic activity of Rhizoctonia in soil and determine the relationship between saprophytic and pathogenic activities in order to fit an equation of pathogenic activity risk in soils for cowpea and common bean planting. In the evaluation of baits, soils from three locations were packed in trays and infested with an isolate of R. solani (50 mg colonized substrate kg-1 soil). After seven days, soil samples were transferred to gerboxes and sown six baits: beet, cowpea, maize and sorghum seeds, cowpea segment stalks and toothpick segments. After 48 h at 25 ° C, the baits were transferred to the Ko & Hora modified medium. The wood toothpick bait led to the detection of higher levels of saprophytic activity in all soils. The bait toothpick was evaluated against eight isolates and six inoculum densities of R. solani, demonstrating highly effective in all situations. In the analysis of the relationship between saprophytic and pathogenic activities, were used 12 soils collected in areas for cowpea and common bean planting. The saprophytic activity was evaluated using toothpick baits and the pathogenic activity was assessed by the distribution of soils in trays, planting of cowpea seeds and assessment of Rhizoctonia canker severity. There was a significant (P≤0.05) positive correlation (r = 0.7698) between the saprophytic (ATS) and pathogenic (ATP) activities. The regression equation ATP = 1 / (0.5822 to 0.0056 ATS) was estimated with high precision (R2 = 0.9930, P≤0.05), indicating that the risk of pathogenic activity of Rhizoctonia in soils for cowpea and common bean planting can be estimated from the analysis of saprophytic activity. / O fungo Rhizoctonia spp. é um importante fitopatógeno habitante do solo. O objetivo deste trabalho foi avaliar a eficácia de iscas para quantificação da atividade saprofítica de Rhizoctonia no solo e determinar a relação entre atividade saprofítica e atividade patogênica, visando ajustar uma equação de risco de atividade patogênica em áreas destinadas ao plantio de feijão-caupi e feijão-comum. Na avaliação das iscas, solos de três localidades foram acondicionados em bandejas e infestados com um isolado de R. solani (50 mg de substrato colonizado kg-1 solo). Após sete dias, amostras dos solos foram transferidas para caixas gerbox e semeadas seis iscas: sementes de beterraba, feijão-caupi, milho e sorgo, segmentos de talos de feijão-caupi e segmentos de palito de dente. Após 48 h a 25 ºC, as iscas foram transferidas para o meio de Ko & Hora modificado. A isca de palito de dente de madeira propiciou a detecção dos maiores níveis de atividade saprofítica em todos os solos. A isca de palito de dente foi avaliada em relação a oito isolados e seis densidades de inóculo de R. solani, demonstrando elevada eficácia em todas as situações. Na análise da relação entre as atividades saprofítica e patogênica, foram utilizados 12 solos coletados em áreas destinadas ao cultivo de feijão-caupi e feijão-comum. A atividade saprofítica foi avaliada com iscas de palito de dente e a atividade patogênica foi avaliada pela distribuição dos solos em bandejas, plantio de sementes de feijão-caupi e avaliação da severidade da rizoctoniose. Houve correlação positiva (r = 0,7698) significativa (P≤0,05) entre as atividades saprofítica (ATS) e patogênica (ATP). A equação de regressão ATP=1/(0,5822-0,0056 ATS) foi estimada com elevada precisão (R2 = 0,9930; P≤0,05), indicando que o risco de atividade patogênica de Rhizoctonia nos solos destinados ao cultivo de feijão-caupi e feijão-comum pode ser estimado a partir da análise da atividade saprofítica.

Phytophthora cinnamomi is a soil-borne oomycete pathogen causing root rot in susceptible host species. P. cinnamomi is thought to have originated in Southeast Asia, but has since been introduced to many regions around the world, where it causes dramatic declines in many forest tree species. In the eastern US, the primary susceptible tree species of concern are American chestnut (Castanea dentata), white oak (Quercus alba), and shortleaf pine (Pinus echinata). American chestnut, functionally eliminated in the early 1900s by the rapidly acting chestnut blight (Cryphonectria parasitica), has been the subject of decades-long breeding efforts aimed at improving chestnut resistance to chestnut blight. To improve chestnut restoration success, and restoration of other susceptible species, the distribution patterns of P. cinnamomi on a landscape scale must be better understood. This project was initiated to develop an improved method for detecting P. cinnamomi to permit high-throughput screening of forest soils, and to implement the improved detection approach in characterizing the distribution patterns of P. cinnamomi in developing soils on reclaimed surface mines in eastern Kentucky, as well as mature forest soils within an undisturbed watershed in a reference-quality eastern Kentucky forest. We developed an improved detection method using a molecular DNA-amplification approach (PCR), which demonstrated similar sensitivity to traditional culture-based methods, but required less time and space than traditional methods. We used this detection approach to screen soils from a chronosequence of reclaimed surface mines (reclaimed at different points in time) to evaluate whether reclaimed surface mined sites become favorable for P. cinnamomi colonization over time. Our analysis detected P. cinnamomi at the two older sites (reclaimed in 1997 and 2003), but we did not detect P. cinnamomi at the two newer sites sampled (reclaimed in 2005 and 2007). These results suggest that surface mined sites become favorable for P. cinnamomi colonization over time, and should not be considered permanently “Phytophthora-free.” We also collected ~200 samples from a watershed in UK’s Robinson Forest, from plots representing a gradient of topographic position, slope, and aspect. This survey indicated that P. cinnamomi distribution in forests is complex and can be difficult to predict; however, P. cinnamomi was detected in both drier upslope sites and in moister drainage sites.

The increasing concerns about chemical pesticides that are environmentally hazardous and the continuous development of resistance by palhogens to chemical pesticides have led to this study. Many studies have shown that some Gram-negative bacteria, such as Pseudomonas flouresens, control plant diseases and promote plant growth. In this study Gram positive bacteria, Bacillus sp., were chosen because of their ability to produce endospores. Endospores can be used in stable, dry formulations. The advantage of using endospores is their ability to survive harsh conditions such as droughts and high temperatures, which give a long shelf life to the biological control agent. Bacillus isolates were recovered from the rhizosphere of 12 different crops, and were subsequently screened in vitro for their antimicrobial activity. Of 130 isolates, 87 exhibited antimicrobial activity against the test organisms: Rhizoctonia solani, Pythium sp., Phytophthora cinnamoni, Fusarium sp., and single representatives of Gram negative and Gram positive bacteria, namely, Erwinia carotovora and Staphylococcus aureus respectively. The Bacillus isolates B77, B81 and B69 inhibited all the test organisms investigated, which suggests that they produced broad spectrum antimicrobial compounds or more than one antimicrobial compound. Of the isolates that showed antimicrobial activity, 78 of them did not inhibit Trichoderma harzianum K D, which is a registered biological control agent; indicating their potential for combined application. Selected Bacillus isolates were tested for the biological control of R. solani under greenhouse conditions in wheat, cabbage, tomato, maize, and cucumber seedlings. Bacillus isolates were applied as seed treatments, and the inoculated seeds were planted in R. solani infested speedling trays. Shoot dry weight measurement of seedlings indicated that 12 out of 19 Bacillus isolates showed significantly different shoot dry weight in wheat whereas all the isolates tested in tomato and cucumber gave significantly different shoot dry weight. No significantly different shoot dry weight was obtained for maize or cabbage. Seed emergence findings indicated that none of the Bacillus isolates gave significantly different emergence percentage on wheat, cabbage, tomato, and maize but all of them showed significantly different emergence percentage on cucumber. The results indicate that both the pathogen and the biological control agents exhibited varying levels of specificity on each crop tested. The biological control potential of the best Bacillus isolates was tested on bean and maize crops in the field. Green bean and maize seeds were coated with the selected Bacillus isolates and then sown under field conditions. For each isolate, four replicate treatment plots were established, with and without a R. solani inoculum. Percentage emergence, plant survival levels to harvesting and yield of maize cobs and green beans pods were measured. For all parameters measured the positive and negative controls were not significantly different thereby rendering the results for the entire field study inconclusive. However, Bacillus isolates B77, BII, R5 and R7 improved green bean pod yield and Bacillus Isolate B8I increased maize yield, indicating their potentials as plant growth promoting rhizobacteria (PGPR). / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.

Various Trichoderma and Bacillus spp. have been documented as being antagonistic to a wide range of soilborne plant pathogens, as well as being plant growth stimulants. Successes in biological control and plant growth promotion research has led to the development of various Trichoderma and Bacillus products, which are available commercially. This study was conducted to evaluate the effect of six Trichoderma spp. and three Bacillus spp. and their respective combinations, for the biological control of Rhizoctonia solani damping-off of cucumber and plant growth promotion of dry bean (Phaseolus vulgaris L.). In vivo biological control and growth promotion studies were carried out under greenhouse and shadehouse conditions with the use of seed treatment as the method of application. In vitro and in vivo screening was undertaken to select the best Trichoderma isolates from 20 Trichoderma isolated from composted soil. For in vitro screening, dual culture bioassays were undertaken and assessed for antagonisms/antibiosis using the Bell test ratings and a proposed Invasive Ability rating based on a scale of 1-4 for possible mycoparasitic/hyperparasitic activity. The isolates were further screened in vivo under greenhouse conditions for antagonistic activity against R. solani damping-off of cucumber (Cucumis sativus L.) cv. Ashley seedlings. The data generated from the in vivo greenhouse screening with cucumber plants were analysed and grouped according to performance of isolates using Ward‟s Cluster Analysis based on a four cluster solution to select the best isolates in vivo. Isolates exhibiting marked mycoparasitism of R. solani (during ultrastructural studies) viz, T. atroviride SY3A and T. harzianum SYN, were found to be the best biological control agents in vivo with 62.50 and 60.06% control of R. solani damping-off of cucumber respectively. The in vitro mode of action of the commercial Trichoderma product, Eco-T®, and Bacillus B69 and B81 suggested the production of antimicrobial substances active against R. solani. In vitro interaction studies on V8 tomato juice medium showed that the Trichoderma and Bacillus isolates did not antagonise each other, indicating the possibility of using the two organisms together for biological control and plant growth promotion studies. Greenhouse studies indicated that combined inoculation of T. atroviride SYN6 and Bacillus B69 gave the greatest plant growth promotion (43.0% over the uninoculated control) of bean seedlings in terms of seedling dry biomass. This was confirmed during in vivo rhizotron studies. However, results obtained from two successive bean yield trials in the greenhouse did not correlate with the seedling trials. Moreover, no increase in protein or fat content of bean seed for selected treatments was observed. In the biological control trials with cucumber seedlings, none of the Trichoderma and Bacillus combinations was better than single inoculations of Eco-T®, T. atroviride SY3A and T. harzianum SYN. Under nutrient limiting conditions, dry bean plants treated with single and dual inoculations of Trichoderma and Bacillus isolates exhibited a greater photosynthetic efficiency that the unfertilized control plants. Bacillus B77, under nutrient limiting conditions, caused 126.0% increase in dry biomass of bean seedlings after a 35-day period. Nitrogen concentrations significantly increased in leaves of plants treated with Trichoderma-Bacillus isolates. However, no significant differences in potassium and calcium concentrations were found. Integrated control (i.e. combining chemical and biological treatments) of R. solani damping-off of cucumber seedlings proved successful. In vitro bioassays with three Rizolex® concentrations, viz., 0.01g.l-1, 0.1g.l-1 and 0.25g.l-1 indicated that the selected Trichoderma isolates were partly sensitive to these concentrations whereas the Bacillus isolates were not at all affected. In a greenhouse trial, up to 86% control was achieved by integrating 0.1g.l-1 Rizolex® with T. harzianum SYN, which was comparable to the full strength Rizolex® (1g.l-1) application. Irrespective of either a single or dual inoculations of Trichoderma and/or Bacillus isolates used, improved percentage seedling survival as achieved with the integrated system, indicating a synergistic effect. The results presented in this thesis further reinforce the concept of biological control by Trichoderma and Bacillus spp. as an alternative disease control strategy. Furthermore, this thesis forms a basis for Trichoderma-Bacillus interaction studies and proposes that the two organisms could be used together to enhance biological control and plant growth promotion. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

With an increasing realization that many agrochemicals are hazardous to animals and humans, came the desire to replace these chemical agents with biological approaches that are more friendly to the environment and human health. Microorganisms play an important role in plant disease control, as naturally occurring antagonists. Microorganisms may also have beneficial effects on plant development when applied to plant roots. Research efforts worldwide have recorded successes in biological control and growth stimulation on many crops, particularly when using members of the genera Bacillus and Trichoderma. Their use on citrus rootstock could be advantageous to nurserymen and growers in reducing the incidence of seedling mortality and increasing production. To achieve these objectives, laboratory and tunnel experiments were conducted to develop effective biocontrol agents for citrus seedlings and cuttings. Nineteen 0 ut 0 f 23 Trichoderma isolates tested in vitro against Phytophthora p arasitica sp showed antagonistic activity by hyperparasitism and four out of eight Bacillus isolates resulted in antagonism by forming inhibition zones. The positive in vitro activity of Trichoderma and Bacillus isolates on Phytophthora provided motivation step for further trials in the greenhouse to evaluate their biological control activity on citrus seedlings and cuttings. A greenhouse trial was carried out to evaluate the biological control potential of 23 Trichoderma isolates (drenched at 5 x 105 spores / rnI) and two Bacillus isolates (drenched at 1 X 106 or 1 X 108 colony forming units (CFU) / rnI) to suppress Phytophthora parasitica sp. of rough lemon (Citrus jambhirini Lush.) seedlings. Five isolates ofTrichoderma (AA12, AA5, Trichoderma harzianum (AA16), SY3F and Eco-T~ were highly effective in suppressing Phytophthora root rot, with AA12 providing the best control. The Bacillus isolates also suppressed the pathogen but were not as effective as the Trichoderma isolates. This trial was used to test for growth stimulation activity by some of the biocontrol agents. To verify these results, a further trial was carried out to evaluate growth stimulation capabilities in the absence of any pathogen. Trichoderma Isolates AA13 and AA17 caused no 111 change in seedling growth, while other Trichoderma and Bacillus isolates had an inhibitory effect on the seedling growth. This trial indicated that the biocontrol activity was affected by inoculum densities, and as a result in vitro sporulation capacity was evaluated. TrichodermaIsolate AA16 was the largest spore producer, followed by Eco-T®. Spore production was lowest from Trichoderma isolates AA4 and AA12. Growth stimulation responses of Trichoderma Isolates AA4, AA16, Eco-TID and SYN6 were further studied at four different doses (1 X 103, 1 X 104, 5 X 105 or 1 X 106 spores / ml) on rough lemon and trifoliate orange seedlings. Trifoliate oranges responded positively to 1 X 104 and 5 X 105 spores / ml of Eco-TID, but rough lemon responded negatively to all dosages of the Trichoderma isolates applied. This indicates that the inoculum density responses may be host specific. Higher population density of 1 X 106 spores / ml of all tested Trichoderma isolates had a stunting effect on seedling growth of both species. Based on t he positive results 0 f individual applications of some Trichoderma and Bacillus isolates, of the biological control agents on rough lemon seedlings against Phytophthora parasitica in an earlier greenhouse trial, their combined effect in the control of the pathogen was performed. Before carrying out a greenhouse trial, activities of the isolates to be combined were evaluated in vitro. This trial showed that Trichoderma Isolates AA16 and Eco-T®were compatible. Trichoderma isolates AA16 and Eco-T®were also found to be compatible with Bacillus Isolates B77, B81 and PHP. As a result, further in vivo trials were conducted. The tunnel trials were carried out as two separate experiments: In the first experiment, a combination of two Trichoderma Isolates A A 16 and Eco-T®was conducted assayed at 5 X 105 or 1 X 106 spores / ml, on rough lemon seedling, and cuttings and trifoliate orange and sour orange seedlings. A combination of Trichoderma isolate AA16 and Eco-T®at 5 X 105 spore / ml increased significantly the new flush biomass of rough lemon cuttings compared to AA16 alone, but was not different from Eco-TID alone. The combination of AA16 and Eco-T® achieved no change of biomass of rough lemon and trifoliate orange seedlings. The combination of AA16 and Eco-TID did not increase the root biomass of sour orange compared to AA16 or Eco-r® alone. The combination of AA16 and Eco-r® at higher doses (1 x 106 spores / ml) showed significantly better suppression of Phytophthora root rot of rough lemon cuttings but did not show disease suppression in all seedling species verities tested. In a second experiment, individual and combined effects of Trichoderma isolates (drenched at 5 X 105 spores / ml) with Bacillus isolate (drenched at 1 X 106 colony forming units (CFU) / ml) for suppression of Phytophthora root rot on rough lemon and trifoliate orange seedlings was performed. The combination of Trichoderma Isolate AA16 and Bacillus Isolate B81 increased root biomass on rough lemon seedlings compared to the combination of Trichoderma AAI6 or Bacillus PHP but was not significantly different to Trichoderma AA16 alone. Bacillus PHP combined with Trichoderma AA16 or singly had no effect on rough lemon seedlings. Combining Trichoderma Eco--r® and with Bacillus B8I or PHP did not increase biomass of rough lemon seedlings compared to Trichoderma Isolate Eco--r® alone. There was no statistically significant differences in the effects of the combinations of the Trichoderma and Bacillus isolates compared to their individual applications on the biomass of trifoliate oranges. This study established the antagonistic potential of several South African isolates of Trichoderma and Bacillus as a viable alternative to agrochemicals for controlling Phytophthora parasitica. The growth stimulation capabilities of Trichoderma isolates in terms of seedling development was also demonstrated. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

[Truncated abstract] Weeds are a major limitation to agricultural and horticultural production and the main method of control is the use of herbicides. In addition to the resulting chemical pollution of the environment, the wide spread and continues use of herbicides have resulted in many weeds developing resistance to commonly used herbicides. This study investigated the potential of using green manures as a cultural method of control of weed invasion in agricultural fields. To understand the general mechanisms involved in the suppression of seed germination in green manure amended soils, seeds of crop species with little or no dormancy requirements were used in certain studies. Lettuce (Lactuca sativa) and cress (Lepidium sativum) seeds were sown to a sandy soil amended with green manures of lupin (Lupinus angustifolius), Brassica juncea, or oats (Avena sativa) to determine if the amendments affected seed germination and/or decay. It was hypothesised that the addition of plant material would increase the microbial activity of the soil thereby increasing seed decay, under laboratory and greenhouse conditions. Initial experiments used lettuce, cress and lupin seeds. Lettuce and cress are commonly used as standard test species for seed viability studies. Subsequent experiments used seeds of annual ryegrass (Lolium rigidum), silver grass (Vulpia bromoides), wild radish (Raphanus raphanistrum) and wild oat (Avena fatua) as these weed species are commonly found throughout agricultural regions in Western Australia. Amending the soil with lupin or Brassica green manure was established as treatments capable of developing environments suppressive to seed germination. Lupin residues as green manure showed the strongest inhibition of seed germination and seed decay. The decay of certain seeds was enhanced with changes to soil microbial activity, dissolved organic carbon and carbon and nitrogen amounts in lupin amended soil. Seeds of weed species were decayed in lupin amended soil, but showed varied degree of decay. Annual ryegrass and silver grass were severely decayed and wild oat and wild radish were less decayed, in lupin amended soil.

Made available in DSpace on 2014-06-11T19:35:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-12-16Bitstream added on 2014-06-13T20:45:44Z : No. of bitstreams: 1 fortes_nlp_dr_botfca.pdf: 629205 bytes, checksum: 40d1e91cf18ab3678f66c246588008c7 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / O trabalho objetivou verificar os fatores químicos e microbiológicos do lodo de esgoto e do solo responsáveis pela incidência da podridão do colmo do milho, causada por Fusarium em solo fertilizado com lodo, e foi desenvolvido em condições de campo, numa área que vem sendo tratada com lodo e cultivada com milho desde 1999 em latossolo vermelho distróférrico (textura argilosa), localizada no município de Jaguariúna/SP. Os dois lodos utilizados foram obtidos nas Estações de Tratamento de Esgoto de Franca e de Barueri/SP. Os lodos foram incorporados ao solo nas concentrações de 0, 1, 2, 4 e 8 vezes a dose recomendada com base no teor de nitrogênio, em dois cultivos sucessivos de milho (Savana 133S) nas safras 2001/2002 e 2002/2003, em parcelas de 200 m2. As doses de lodo foram comparadas com a adubação mineral recomendada para a cultura do milho. Os tratamentos foram distribuídos em delineamento experimental casualizado em blocos e com três repetições. Foram verificadas, nas safras de 2001/2002 e 2002/2003, diferenças significativas entre as doses de lodo de esgoto, sobre a variação de Fusarium spp. no solo, na rizosfera, na raiz, no colmo e na semente, bem como sobre a incidência de plantas com podridão no colmo e nas espigas. As análises de regressão mostraram que a porcentagem de plantas doentes foi positivamente correlacionada com a concentração dos lodos incorporados ao solo. Os coeficientes de determinação para o cultivo de 2001/2002 foram de R2=0,61 e R2=0,32, enquanto para o cultivo de 2002/2003 foram de R2=0,76 e R2=0,45, para os lodos de Franca e Barueri, respectivamente. As concentrações de lodos também apresentaram correlação positiva com a comunidade de Fusarium do solo e da rizosfera e com a incidência de Fusarium na raiz, no colmo e na semente. As correlações entre a comunidade de Fusarium do solo e da rizosfera e o percentual de plantas... . / This work aimed at verifying the chemical and microbiological sewage sludge and soil factors re 0sponsible for the incidence of the corn stalk rot caused by Fusarium in soil fertilized with sludge and has been developed in field conditions, in an area that has been treated with sludge and cultivated with corn since 1999, in red dystroferric latosol (clayey texture), in Jaguariúna/SP. Both sludges used were obtained in the sewage sludge treatment stations of Franca and Barueri/SP. Sludges were incorporated into the soil in concentrations of 0, 1, 2, 4 and 8 times in relation to the recommended rate based on the nitrogen contents, in two successive corn cultures (Savana 133S), in 2001/2002 and 2002/2003, in plots of 200 m2. Sludge doses were compared to the mineral fertilization recommended to the corn culture. The treatments were distributed in a randomized design experimental drawing in blocks and with three repetitions. Significant differences were verified in both 2001/2002 and the 2002/2003 crops among the sewage sludge doses about the variation of Fusarium spp. in soil, root, stalk and seed, as well as about the incidence of plants with stalk and corn rot. The regression analyses have showed that the percentage of diseased plants was positively correlated to the concentration of the sludges incorporated to the soil. The determination coefficients to the 2001/2002 culture were R2=0.61 and R2=0.32, while the 2001/2003 culture showed R2=0.76 and R2=0.45, to Franca and Barueri sludges, respectively. The sludges concentrations also presented positive correlation with the Fusarium community of the soil and the rhizosphere, and with the incidence of Fusarium in the root, stalk and seed. The correlations between the Fusarium community of the soil and rhizosphere and the percentage of diseased plants with chemical soil attributes were significant and positive, for both kinds of sludges, in the level of 1 and 5%, to phosphorus and calcium contents.

Made available in DSpace on 2014-06-11T19:35:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-12-11Bitstream added on 2014-06-13T18:45:55Z : No. of bitstreams: 1 basseto_ma_dr_botfca.pdf: 601741 bytes, checksum: 682ae120d3b404d74fd6cd7839640f84 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A incorporação de culturas específicas associadas à solarização do solo tem sido apresentada como um avanço muito promissor para o controle de fungos fitopatogênicos habitantes do solo. Além das brássicaceas, comumente utilizadas, novos materiais vegetais como a mandioca e a mamona têm apresentado potencial para controle desses fitopatógenos. Vários fatores são apontados como responsáveis pelo controle, entre eles os voláteis oriundos da decomposição dos vegetais. Assim, este trabalho foi idealizado com dois objetivos divididos em duas etapas complementares: biológica - avaliar o efeito ocasionado pela incorporação e decomposição de parte aérea de brócolis, mamona e mandioca brava e mandioca mansa, associadas à simulação da solarização, sobre diferentes estruturas dos fungos Fusarium oxysporum f. sp. lycopersici Raça 2, Macrophomina phaseolina, Rhizoctonia solani AG-4 HGI e Sclerotium rolfsii; química - identificar e apontar dentro de cada material vegetal qual(is) é(são) o(s) volátil(eis) potencial(ais) pelo controle das estruturas dos fungos. Na primeira etapa, quatro ensaios idênticos foram instalados em conjuntos de microcosmos, com quatro períodos de exposição diferentes e independentes (7, 14, 21 e 28 dias), avaliando efeitos no crescimento micelial (inócuo, fungistático e fungicida) e na sobrevivência das estruturas de resistência dos fungos de solo. Verificou-se efeito fungistático e fungicida no crescimento micelial de F. oxysporum f. sp. lycopersici Raça 2, R. solani AG-4 HGI e de S. rolfsii. O efeito fungicida apenas ocorreu aos 21 dias de incubação para F. oxysporum e R. solani e aos 28 dias para S. rolfsii. Para M. phaseolina, observou-se apenas efeito inócuo. Os tratamentos solo+materiais vegetais, ao longo dos períodos testados, reduziram, significativamente, a sobrevivência das estruturas de resistência de todos os fungos... / The incorporation of specific cultures associated with solarization has been a highly promising advance to control phytopathogenic fungi inhabiting the soil. In addition to the commonly used Brassicaceae, new plant materials such as cassava and castor plants have shown potential to control these phytopathogens. Several factors are considered responsible for this control, including volatile compounds from plant decomposition. Thus, the present work was divided into two complementary steps according to its two major aims: biological step – to evaluate the effect of the incorporation and decomposition of broccoli, castor and cassava (bitter and sweet) shoot, associated with simulated solarization, on different structures of the fungi Fusarium oxysporum f. sp. lycopersici Race 2, Macrophomina phaseolina, Rhizoctonia solani AG-4 HGI and Sclerotium rolfsii; chemical step – to identify for each plant material which volatile compound(s) present(s) potential to control fungal structures. In the first step, four identical assays were established in groups of microcosms, with four different and independent exposure periods (7, 14, 21 and 28 days), to evaluate the effects on mycelial growth (innocuous, fungistatic and fungicide) and survival of resistance structures of soil fungi. Fungistatic and fungicide effects were detected on the mycelial growth of F. oxysporum f. sp. lycopersici Race 2, R. solani AG-4 HGI and S. rolfsii. Fungicidal effect occurred only at 21 days of incubation for F. oxysporum and R. solani and at 28 days for S. rolfsii. As regards M. phaseolina, only an innocuous effect was observed. The treatments soil+plant material, over the tested periods, significantly reduced the survival of resistance structures for all fungi. In general, broccoli and bitter and sweet cassava had expressive... (Complete abstract click electronic access below)