Evaluación de semilla sexual hibrida de papa (Solanum tuberosum L.) provenientes del Centro Internacional de la Papa e India en la zona de Miraflor, Esteli

Con el objetivo de seleccionar progenies promisorias de semilla sexual de papa, procedentes del CIP (11) y Programa de la India (3) se estableció este ensayo el 21 de septiembre de 1994, utilizando un diseño de Bloques Completos al Azar (BCA) con cuatro repeticiones, en la estación experimental del Instituto Nicaragüense de Tecnología Agropecuaria (INTA-RB-3), ubicada a 1 350 msnm, humedad relativa del 91 por ciento, temperatura promedio mínima 15 °C/máx 26 °C, cuyos suelos son de textura franca bien drenada, medianamente profundo a profundo, con una precipitación durante el ensayo de 622 mm. Los resultados obtenidos muestran que todas las progenies híbridas enviadas por el CIP mostraron buena velocidad de emergencia en especial SERRANA x LT-7, con respecto a los lubridos de la India. En general el porcentaje de sobrevivencia fue mayor del 80 por ciento para la mayoría de las progenies el cual es un índice aceptable, a excepción de 104.12 LB x TS-4.En la altura final de la planta no hubieron diferencias significativas entre híbridos, solo fueron superiores a KATADIN x TS-10. En cuanto al rendimiento, la progenie HPS­ II/67 mostró ser superior a las demás con 6.2 kg/m2. El número total de tubérculos por metro cuadrado {740) y tubérculos por planta (7) fue superior en la progenie TS-6 x TPS-67. Las progenies de ambos programas mostraron rendimientos por metro cuadrado de más del 50 por ciento con tubérculos mayores de 5 gramos. No se presentó incidencia de virus para ambas progenies, las tres progenies provenientes del Programa de la India presentaron mayor resistencia a tizón tardío (Phytophthora infestans, Mont. D.bary).

Manejo de tizón tardío (Phytophthora infestant (Mont.) de Bary) en el cultivo de papa cv calwhite en época de apante en la zona de Tisey, Esteli. 2007

El objetivo principal de este estudio fue la evaluación de diferentes estrategias de alternancia de fungicidas de contacto con fungicidas sistémicos. Además, se alternó el fungicida biológico Serenade 1.34 SC ( Bacillus subtilis QST 713) con los fungicidas de contacto Mancozeb y Bravonil para determinar el efecto de ésta en el manejo de tizón tardío en época de apante. El trabajo experimental se llevó a cabo en la localidad Tisey (Reserva Natural), del departamento de Estelí en el periodo comprendido entre noviembre del 2006 a febrero del 2007. La variedad de papa evaluada fue CalWhite, la cual es susceptible a tizón tardío. El diseño utilizado fue bloques completamente al azar con cinco tratamientos y cuatro repeticiones. Los tratamientos evaluados en este estudio fueron (Mancozeb+Serenade) - Equation Pro (Bravonil+Serenade) - Ridomil, (Mancozeb+Serenade)- Curzate, (Bravonil+Serenade) - Verita y un testigo absoluto. El manejo agronómico fue el que utiliza el productor. Las variables evaluadas fueron severidad y rendimiento. Con los datos de severidad se calculó el área bajo la curva de progreso de la enfermedad (ABCPE). No se encontraron diferencias significativas entre bloques para la variable severidad de tizón tardío, ni en la interacción tratamiento - bloque, pero si se observó diferencias altamente significativas entre tratamientos. La media de severidad en el tratamiento testigo fue más alta en comparación con las medias de los otros cuatro tratamientos, lo cual explica la diferencia entre tratamientos. Sin embargo, no se encontraron diferencias significativas en las medias de severidad de los tratamientos diferentes del testigo. Cuando se analizó la severidad en los tratamientos de acuerdo a la variable días después de la siembra (dds) se observaron diferencias altamente significativas entre tratamientos, en la variable dds y en la interacción tratamientos*d ds. Se encontraron diferencias altamente significativas entre el testigo y los demás tratamientos y entre días después de la siembra (dds) para los valores de la variable área bajo la curva de progreso de la enfermedad (ABCPE), así como también en la interacción tratamientos*dds. La mezcla del fungicida biológico Serenade 1.34 SC ( Bacillus subtilis QST713) con los fungicidas de contacto Mancozeb y Bravonil al parecer tuvo un efecto sinergístico al inhibir el desarrollo de P. infestans sobre la superficie de las hojas de papa. Los rendimientos fueron bastantes bajos en comparación con otros resultados encontrados en América Latina con la variedad de papa CalWhite. Es posible reducir los porcentajes de severidad de tizón tardío en el cultivo de papa cuando se combinan estrategias de rotación de fungicidas de contacto y sistémicos con la época de siembra.

Efecto de la combinación fungicida protectante y variedad sobre el tizón tardío [Phythopthora Infestas (Montagne) De Bary] en el cultivo de papa (Solanum tuberosum L.) en época de primera localidad La Tejera, San Nicolás, Estelí, 2008

El objetivo principal de este estudio fue el de evaluar el efecto de tres intervalos de aplicación del fungicida clorotalonil y tres variedades de papa con diferentes niveles de resistencia sobre la epidemiología y manejo del tizón tardío [Phytophthora infestans (Montagne) De Bary] en el cultivo de papa (Solanum tuberosum L.) El trabajo experimental se realizó de Julio a Octubre 2008, en la localidad “La Tejera”, municipio de San Nicolás, departamento de Estelí, localizado en las coordenadas geográficas 12º58'23” latitud norte y 86º24'21” longitud oeste, a una altura de 1,328 metros sobre el nivel del mar. Se evaluaron doce epidemias de tizón tardío que resultaron de la combinación de tres variedades de papa (Cal White, Granola y Jacqueline Lee) y cuatro tratamientos (tres intervalos de aplicación del fungicida clorotalonil y un testigo en el cual no se aplicó fungicida). Los tratamientos fueron distribuidos en bloques completos al azar. El manejo experimental fue el mismo que realiza el productor convencionalmente. Las variables epidemiológicas evaluadas fueron: severidad, área bajo la curva de progreso de la enfermedad (ABCPE) y la tasa de infección aparente (r). Además, se midieron variables climáticas como temperatura, humedad relativa y precipitaciones y se determinó el rendimiento de las variedades incluidas en el estudio. Las doce epidemias analizadas en este estudio iniciaron con varios días de diferencia, en dependencia del nivel de resistencia de la variedad y del intervalo de aplicación del fungicida protectante clorotalonil. La severidad de la enfermedad alcanzó casi el 100% en las variedades susceptibles (Cal White y Granola) en las parcelas donde no se aplicó el fungicida clorotalonil, pero el porcentaje de severidad en las parcelas tratadas disminuyó conforme el intervalo de aplicación se fue acortando. En la variedad Jacqueline Lee los porcentajes de severidad fueron bajos, incluso en las parcelas que no fueron tratadas con el fungicida clorotalonil, lo cual demuestra que esta variedad es resistente a P. infestans. Ninguno de los intervalos de aplicación (cada 4, 7 y 14 días) del fungicida clorotalonil detuvo el avance de las epidemias de tizón tardío una vez que éstas iniciaron, principalmente, en las parcelas con variedades susceptibles. El rendimiento obtenido en cada una de las variedades evaluadas fue menor al compararlo con otro estudio de validación llevado a cabo en 2007 en tres localidades de Matagalpa y Jinotega. Los resultados de este estudio const ituyen una contribución muy importante para el desarrollo de futuras estrategias encaminadas, no a la erradicación total del tizón tardío de los campos de papa y/o tomate de Nicaragua, pero si para lograr mitigar su efecto devastador sobre tan importantes cultivos tanto desde el punto de vista nutritivo como económico.

Estudio comparativo de la producción orgánica y tradicional de Papa (Solanum tuberosum L.) en Miraflor, Estelí

Dos sistemas de producción de papa (Solanum tuberosum L.) fueron comparados en la comunidad de Miraflor, departamento de Estelí. El objetivo del estudio fue determinar la viabilidad y rentabilidad de los sistemas. Los sistemas comparados fueron: producción tradicional y producción orgánica. El experimento fue establecido en Febrero del año 2001, utilizando la metodología de parcelas pareadas, las cuales fueron establecidas en campos de productores. Se establecieron cuatro parcelas (una por productor) con cinco réplicas. Los datos fueron analizados con el programa estadistico SSPS utilizando el estadistico TStudent. Los resultados mostraron diferencias estadísticas entre las tecnologías en la producción de tubérculos de 35 -55 mm y cantidad total de tubérculos. Los máximos valores fueron registrados por el sistema de producción tradicional. Con relación a las variables peso de tubérculos de 35- 55 mm y peso total de tubérculos, las diferencias fueron altamente significativas, registrándose los máximos valores en el sistema de producción tradicional. En las variables altura final de plantas y numero de tallos por planta, no se observaron diferencias estadísticas entre tratamientos. El tizón tardío (Phytophthora infestans), enfermedad común en el cultivo, se presentó con mayor incidencia en sistema de producción orgánico. El análisis económico, no muestra diferencias entre los sistemas de producción, sin embrago, el sistema de producción tradicional mostró mayor taza de retorno marginal.

毛壳菌产抗真菌活性物质菌株筛选及种间原生质体融合研究

毛壳菌属很多种类具有重要生防价值，其生防机理包括对植物病原真菌的重寄生作用、诱导植物产生抗病性、产生抗真菌活性的次生代谢产物等。迄今，学界对毛壳菌的研究主要集中在毛壳菌的生防机理，毛壳菌活性次生代谢产物的分离等方面。本研究致力于产抗生素的毛壳菌的种间原生质体融合，从产抗生素毛壳菌菌株的筛选开始，进而对产抗生素的角毛壳菌进行诱变选育，最终用产不同抗生素的角毛壳菌与球毛壳菌进行种间原生质体融合。主要有以下五方面研究结果。 1、毛壳菌抗真菌活性物质产生菌株的筛选：不同毛壳菌菌株发酵液采用琼脂扩散法对植物病原真菌进行抑菌活性试验，结果显示，菌株CH08和CH23的发酵液对芒果炭疽、苹果炭疽和马铃薯晚疫菌具有抑制作用。菌株CH16和CH17的发酵液对芒果炭疽菌、苹果炭疽菌有抑制作用。菌株CH21发酵液对辣椒炭疽菌和西瓜枯萎菌有抑制作用。经形态学研究，菌株CH08、CH16、CH17和CH23鉴定为球毛壳菌，菌株CH21鉴定为角毛壳菌。对角毛壳菌与球毛壳菌菌株发酵液抑菌谱比较，发现角毛壳菌与球毛壳菌发酵液具有明显不同的抑菌谱，表明角毛壳菌与球毛壳菌产生不同的抗真菌活性物质。 2、角毛壳菌（CH21）和球毛壳菌（CH08）原生质体制备和再生条件研究：考察了菌龄、酶浓度、稳渗剂及其浓度、酶解温度、酶解时间及再生培养基对原生质体制备和再生的影响。用菌龄为生长54 h的角毛壳菌菌丝，以0.06 M磷酸缓冲液（pH6.0）配制成含蜗牛酶15 mg/ml、溶壁酶10 mg/ml、蔗糖0.6 mol/L的酶解液，30℃酶解1.5 h，原生质体释放量2.02×107个/g；以PDA为再生培养基，0.7 mol/L的蔗糖再生稳渗剂，再生率可达51.45%。用菌龄为生长48 h的球毛壳菌菌丝，以0.06 M磷酸缓冲液（pH6.0）配制成含蜗牛酶15 mg/ml、溶壁酶10 mg/ml、蔗糖0.6 mol/L的酶解液，30℃酶解1 h，原生质体释放量达1.57×108个/g；以PDA为再生培养基，0.7 mol/L的蔗糖为再生稳渗剂，再生率可达41.48%。 3、角毛壳菌（CH21）原生质体紫外诱变选育：以CH21为出发菌株，制备原生质体进行紫外诱变，诱变条件为：15 w紫外灯，距离30 cm，照射90 s，致死率80%~85%。建立了诱变菌株初筛的双层平板筛选模型。经平板初筛和摇瓶复筛，获得一株突变菌株CH21-I-402，其发酵液抑菌活性较出发菌株提高18.3%。 4、抗性标记菌株的获得：菌株CH21-I-402和CH08抗生素药敏试验表明， CH21-I-402菌株对潮霉素有抗性、对G418（Geneticin）敏感，菌株CH08对潮霉素和G418都敏感。根癌农杆菌EHA105介导的新霉素磷酸转移酶基因转化球毛壳菌，经PCR检测，新霉素磷酸转移酶基因成功转化进菌株CH08-GR70，CH08-GR120。转化子对G418抗性提高3～4倍，对潮霉素仍然比较敏感。 5、以G418和潮霉素抗性为筛选标记的原生质体融合与融合菌株AFLP分析：制备角毛壳菌CH21-I-402和球毛壳菌CH08-GR70原生质体，以35％的PEG6000为助融剂进行原生质体融合，以65 μg/ml的潮霉素和60 μg/ml G418为抗性筛选标记，获得46个再生菌株。再生菌株连续传代5代后，再生菌株表现出多种形态类型。利用AFLP技术对再生菌株及亲本菌株基因组DNA分析表明，再生菌株PF1、PF26为融合菌株。抑菌活性测试表明，融合菌株PF26发酵液对芒果炭疽菌和苹果轮纹菌有强的抑制作用，且抑菌活性比亲本球毛壳菌明显提高。 Chaetomium spp. have great potentials as biocontrol agents against a range of plant pathogens on the basis of its mycoparasitism, induced plant disease resistance, production of antifungal metabolites, and so on. Previous researches on C. spp. mostly focused on the mechanisms of its biocontrol and the isolation of secondary metabolites. In this study, screening antifungal C. spp., mutation breeding of C. cupreum and interspecies protoplast fusion between C. cupreum and C. globosum were carried out, respectively. The corresponding results are as follows: Firstly, among more than 40 C. spp., the strains produced anti-fungal antibiotics were screened by agar diffusion experiments. Results showed that both CH08 and CH23 had inhibition against Colletotrichum gloeosporioides, Cladosporium fulvum, and Phytophthora infestans. Both CH16 and CH17 had inhibition against Colletotrichum gloeosporioides and Cladosporium fulvum. In addition, CH21 exhibited anti-fungal activity against Fusarium oxysporum f. sp niveum and Colletotrichum capsici. Furthermore, CH08, CH16, CH17 and CH23 were identified as C. globosum, CH21 was proved to be C. cupreum based on morphology. The comparison of the anti-fungal spectrum between C. cupreum and C. globosum, showed they could produce different antibiotics. Secondly, specified protocols for preparing and regenerating protoplasts from mycelia of C. cupreum CH21 and C. globosum CH08 were studied. The effects of the age mycelia, the concentration of enzyme, digestion temperature and time, kinds of osmotic stabilizer and regeneration medium on protoplasts preparation and regeneration were all optimized, respectively. In one protocol, with 15 mg/mL snailase, 10 mg/mL lywallzyme, 0.6 M sucrose, in 0.06 M phosphate buffer (pH6.0), and digested for 1.5 h at 30 ºC, 2.02×107 protoplasts from each gram mycelia were obtained from cultures of C. cupreum CH21 grown in potato dextrose broth (PDB) medium for 54 h. And when 0.7 M sucrose was used as osmotic stabilizer in the regeneration medium OPDA (potato dextrose agar with osmotic stabilize), the regeneration efficiency of protoplasts was 51.45%. In another protocol, with 15 mg/mL snailase, 10 mg/mL lywallzyme, 0.6 M sucrose, in 0.06 M phosphate buffer (pH6.0), and digested for 1 h at 30 ºC, 1.57×108 protoplasts from each gram mycelia were obtained from cultures of C. globosum CH08 grown in PDB for 48 h. And when 0.7 M sucrose was used as osmotic stabilizer in the regeneration medium OPDA, the regeneration efficiency of protoplasts was 41.48%. Thirdly, the mutagenesis conditions and secondary screening model of C. cupreum CH21 were explored. An 80% to 85% death rate could be achieved when the protoplasts of C. cupreum CH21 were irradiated by 15 w UV lamp from 30 cm distance for 90 s. In addition, the doublelayer plate’s method for the primary screening of high-producing antibiotics strains was established. A high yielding antibiotic mutant CH21-I-402 was obtained through the primary screening on plate and the secondary selection in Erlenmeyer flask, compared to the original CH21 strain, the antifungal activity of the mutant CH21-I-402 was increased by 18.3%. Fourth, the sensitivity to antibiotics of both C. cupreum CH21-I-402 and C. globusm CH08 was detected. Results showed C. cupreum CH21-I-402 was sensitive to G418 (Geneticin) (Gs) and resistant to Hygromycin B(Hr), and C. globusm CH08 was sensitive to both G418 (Geneticin) (Gs) and Hygromycin B(Hs). At the same time, neomycin phosphotransferase II (npt II) gene was transformed into C. globusm CH08(Gs, Hs) mediated by Agrobacterium tumefaciens EHA105, and the npt II gene was verified by polymerase chain reaction in resistance to G418 strains CH08-GR70 and CH08-GR120. The transformants still showed sensitive to Hygromycin B(Hs). Finally, a selection system for hybrids was set up by interspecies protoplast fusion between C. cupreum and C. globusm using dominant selective drug resistance markers. At first, protoplasts of C. cupreum CH21-I-402 (Hr, Gs) and C. globusm CH08-GR70 (Hs, Gr) were prepared, then the protoplasts were fused in the presence of 35% polyethylene glycol 6000 and regenerated on OPDA medium with 65 μg/ml Hygromycin B and 60μg/ml G418, at last 46 colonies with Hr and Gr were obtained. Even after 5 generations’ subculture, most of the colonies displayed significant difference in taxonomic characteristics with their parental strains. Regenerated strains PF1 and PF26 were confirmed as fusants by amplified fragment length polymorphisms analysis with the genomic DNA as the model. PF26 showed higher inhibitory activity against Colletotrichum gloeosporioides and Macrophoma kuwatsukai than that of the parental strain C. globusm.

Phenotypical characterization in "Plasmopara halstedii" (sunflower downy mildew) isolates of several races

Phenotypic variation (morphological and pathogenic characters), and genetic variability were studied in 50 isolates of seven Plasmopara halstedii (sunflower downy mildew) races 100, 300, 304, 314, 710, 704 and 714. There were significant morphological, aggressiveness, and genetic differences for pathogen isolates. However, there was no relationship between morphology of zoosporangia and sporangiophores and pathogenic and genetic characteristics for the races used in our study. Also, our results provided evidence that no relation between pathogenic traits and multilocus haplotypes may be established in P. halstedii. The hypothesis explaining the absence of relationships among phenotypic and genetic characteristics is discussed.

Biocontrol agents promote growth of potato pathogens, depending on environmental conditions

There is a pressing need to understand and optimize biological control so as to avoid over-reliance on the synthetic chemical pesticides that can damage environmental and human health. This study focused on interactions between a novel biocontrol-strain, Bacillus sp. JC12GB43, and potato-pathogenic Phytophthora and Fusarium species. In assays carried out in vitro and on the potato tuber, the bacterium was capable of near-complete inhibition of pathogens. This Bacillus was sufficiently xerotolerant (water activity limit for growth = 0.928) to out-perform Phytophthora infestans (~0.960) and challenge Fusarium coeruleum (~0.847) and Fusarium sambucinum (~0.860) towards the lower limits of their growth windows. Under some conditions, however, strain JC12GB43 stimulated proliferation of the pathogens: for instance, Fusarium coeruleum growth-rate was increased under chaotropic conditions in vitro (132 mM urea) by >100% and on tubers (2-M glycerol) by up to 570%. Culture-based assays involving macromolecule-stabilizing (kosmotropic) compatible solutes provided proof-of-principle that the Bacillus may provide kosmotropic metabolites to the plant pathogen under conditions that destabilize macromolecular systems of the fungal cell. Whilst unprecedented, this finding is consistent with earlier reports that fungi can utilize metabolites derived from bacterial cells. Unless the antimicrobial activities of candidate biocontrol strains are assayed over a full range of field-relevant parameters, biocontrol agents may promote plant pathogen infections and thereby reduce crop yields. These findings indicate that biocontrol activity, therefore, ought to be regarded as a mode-of-behaviour (dependent on prevailing conditions) rather than an inherent property of a bacterial strain.

The Top 10 Oomycete Pathogens in Molecular Plant Pathology

Oomycetes form a deep lineage of eukaryotic organisms that includes a large number of plant pathogens that threaten natural and managed ecosystems. We undertook a survey to query the community for their ranking of plant pathogenic oomycete species based on scientific and economic importance. In total, we received 263 votes from 62 scientists in 15 countries for a total of 33 species. The Top 10 species and their ranking are: (1) Phytophthora infestans; (2, tied) Hyaloperonospora arabidopsidis; (2, tied) Phytophthora ramorum; (4) Phytophthora sojae; (5) Phytophthora capsici; (6) Plasmopara viticola; (7) Phytophthora cinnamomi; (8, tied) Phytophthora parasitica; (8, tied) Pythium ultimum; and (10) Albugo candida. The article provides an introduction to these 10 taxa and a snapshot of current research. We hope that the list will serve as a benchmark for future trends in oomycete research.

Organic potatoes for processing

Drei Feldversuche auf zwei Standorten (DFH: 51°4, 9°4’, BEL: 52°2’, 8°08’) wurden in den Jahren 2002 bis 2004 durchgeführt, um den Einfluss der Vorfrucht, des Vorkeimens, der N- und K-Düngung und der Sorte auf Nährstoffverfügbarkeit, Gesamt- und sortierte Knollenerträge sowie die Qualität von Kartoffeln und deren Eignung für die industrielle Verarbeitung zu Pommes frites und Chips zu untersuchen. Bestimmt wurden die N- und K-Verfügbarkeit im Boden, die N- und K-Aufnahme von Kraut und Knollen, gesamte Frisch- und Trockenmasseerträge, sortierte Frischmasseerträge für die Verarbeitung, sowie die Gehalte der Knollen an Trockensubstanz und reduzierenden Zuckern. In einer sensorischen Prüfung wurden Qualitätsparameter von Pommes frites (Aussehen/Farbe, Textur und Geschmack/Geruch) bewertet, die gewichtet in einen Qualitätsindex eingingen. Die Qualität der Chips wurde maschinell durch den L-Wert (Helligkeit) des Produktes quantifiziert. Der Gehalt des Bodens an mineralisiertem Nitrat-Stickstoff hing von der Vorfrucht und dem Jahr ab. Nach Erbsen wurden zum Auflaufen der Kartoffeln in den Versuchsjahren 2003 und 2004 (187 und 132 kg NO3-N ha-1) die höchsten NO3-N-Werte in 0-60 cm Boden gemessen verglichen mit Kleegras (169 bzw. 108 kg NO3-N ha-1 oder Getreide (112 kg bzw. 97 kg NO3-N ha-1), obgleich die Differenz nicht in allen Fällen signifikant war. Entsprechend wurden nach Erbsen die höchsten Knollen-Frischmasseerträge (414 und 308 dt ha-1) geerntet. Dasselbe galt für die Trockenmasserträge, was belegt, dass der Trockensubstanzgehalt der Knollen bei verbesserter N-Versorgung nicht im selben Maße sinkt, wie der Frischmasseertrag steigt. Das Vorkeimen der Pflanzknollen führte zu einer rascheren phänologischen Entwicklung im Jugendstadium der Pflanze, beschleunigter Trockenmassebildung des Krautes und einer früheren Einlagerung von Assimilaten vom Kraut in die Knollen. Obwohl die positive Wirkung des Vorkeimens auf den Gesamtertrag bis Ende Juli (+ 26 in 2003 bzw. 34 dt ha-1 in 2004) im Jahr ohne Krautfäuleepidemie von den nicht vorgekeimten Varianten bis zur Endernte im September kompensiert wurde, konnte in diesem Jahr durch Vorkeimen dennoch ein erhöhter Ertragsanteil (+ 12%) der besonders nachgefragten Übergrößen (>50 mm für Pommes frites) erzielt werden. Die durchschnittliche Knollenmasse reagierte positiv auf Vorkeimen (+ 5,4 g), Sortenwahl (Sorte Agria) und ein erhöhtes N-Angebot (Leguminosenvorfrucht). Generell wurde deutlich, dass die Knollengesamterträge unter den Bedingungen des Ökologischen Landbaus (geringe bis mittlere Nährstoffversorgung, verkürzte Vegetationsdauer) sehr stark vom Anbaujahr abhängen. Die Ergebnisse belegen jedoch, dass organisch-mineralische N-K-Düngung den sortierten Ertrag an Knollen für die Verarbeitung signifikant erhöht: Höchste Gesamt- und sortierte Knollenfrischmasseerträge wurden nach kombinierter N (Horngrieß) und mineralischer K- (Kaliumsulfat) Gabe erzielt (348 dt ha-1 im Durchschnitt von 2002-2004). Im Gegensatz dazu kann eine Wirkung von Stallmist auf den Ertrag im Jahr der Ausbringung nicht unbedingt erwartet werden. Steigende Erträge nach Stallmistdüngung wurden lediglich in einem von drei Versuchsjahren (+58 dt ha-1) festgestellt und ließen sich eher auf eine K- als eine N-Wirkung zurückführen. Die Ergebnisse belegen, dass die Sortenwahl eine entscheidende Rolle spielt, wenn die Kartoffeln für die industrielle Verarbeitung zu den oben genannten Produkten angebaut werden. Insgesamt kann festgestellt werden, dass Kartoffelknollen aus ökologischen Anbauverfahren ausreichend hohe Trockensubstanzgehalte aufweisen, um für die Verarbeitung zu Pommes frites (>19%) geeignet zu sein und ohne dass dadurch die Konsistenz des Endproduktes gefährdet würde. Der Trockensubstanzgehalt der Referenzsorte für Chips, „Marlen“, unterschritt das in der Literatur geforderte Minimum für Chips von 23% lediglich, wenn die kombinierte Horngrieß-Kaliumsulfatdüngung zur Anwendung kam. Die Trockensubstanzgehalte der Knollen konnten durch Vorkeimen signifikant gesteigert werden und der Effekt war besonders groß (+1.2% absolut) in dem Jahr mit frühem Auftreten der Krautfäule (Phytophthora infestans), d.h. verkürzter Vegetationszeit. Die Knollen-Trockensubstanzgehalte waren in zwei von drei Experimenten nach Lagerung höher (+0.4 und 0.5% absolut) als noch zur Ernte. Sorten der sehr frühen und frühen Reifegruppe wiesen den größten relativen Anstieg der Gehalte an reduzierenden Zuckern (Glukose und Fruktose) während der Lagerung auf. Den mittelfrühen Sorten „Agria“ und „Marena“ hingegen kann aufgrund des von ihnen erreichten höchsten Qualitätsstandards (Pommes frites) zur Ernte eine sehr gute Eignung für die Bedingungen des Ökologischen Landbaus unterstellt werden. Die durchgehend beste Chipseignung wies die mittelfrühe Referenzsorte „Marlen“ auf. Insgesamt konnte nachgewiesen werden, dass durch gezielte Sortenwahl der Trockensubstanzgehalt und die Konzentration reduzierender Zucker, sowie die Qualität der Endprodukte (Pommes frites und Chips) gezielt beeinflusst werden kann. Im Gegensatz dazu haben acker- und pflanzenbauliche Maßnahmen wie Düngung, Wahl der Vorfrucht und Vorkeimen der Pflanzknollen einen eher geringen Einfluss. Dementsprechend sollte der Landwirt versuchen, durch die Wahl der Sorte den hohen Anforderungen der Industrie an die Rohware gerecht zu werden.

Management approaches in organic potato and tomato production

The presented thesis considered three different system approach topics to ensure yield and plant health in organically grown potatoes and tomatoes. The first topic describes interactions between late blight (Phytophthora infestans) incidence and soil nitrogen supply on yield in organic potato farming focussing in detail on the yield loss relationship of late blight based on results of several field trials. The interactive effects of soil N-supply, climatic conditions and late blight on the yield were studied in the presence and absence of copper fungicides from 2002-2004 for the potato cultivar Nicola. Under conditions of central Germany the use of copper significantly reduced late blight in almost all cases (15-30 %). However, the reductions in disease through copper application did not result in statistically significant yield increases (+0 – +10 %). Subsequently, only 30 % of the variation in yield could be attributed to disease reductions. A multiple regression model (R²Max), however, including disease reduction, growth duration and temperature sum from planting until 60 % disease severity was reached and soil mineral N contents 10 days after emergence could explain 75 % of the observed variations in yield. The second topic describes the effect of some selected organic fertilisers and biostimulant products on nitrogen-mineralization and efficiency, yield and diseases in organic potato and tomato trials. The organic fertilisers Biofeed Basis (BFB, plant derived, AgroBioProducts, Wageningen, Netherlands) and BioIlsa 12,5 Export (physically hydrolysed leather shavings, hair and skin of animals; ILSA, Arizignano, Italy) and two biostimulant products BioFeed Quality (BFQ, multi-compound seaweed extract, AgroBioProducts) and AUSMA (aqueous pine and spruce needle extract, A/S BIOLAT, Latvia), were tested. Both fertilisers supplied considerable amounts of nitrogen during the main uptake phases of the crops and reached yields as high or higher as compared to the control with horn meal fertilisation. The N-efficiency of the tested fertilisers in potatoes ranged from 90 to 159 kg yield*kg-1 N – input. Most effective with tomatoes were the combined treatments of fertiliser BFB and the biostimulants AUSMA and BFQ. Both biostimulants significantly increased the share of healthy fruit and/or the number of fruits. BFQ significantly increased potato yields (+6 %) in one out of two years and reduced R. solani-infestation in the potatoes. This suggests that the biostimulants had effects on plant metabolism and resistance properties. However, no effects of biostimulants on potato late blight could be observed in the fields. The third topic focused on the effect of suppressive composts and seed tuber health on the saprophytic pathogen Rhizoctonia solani in organic potato systems. In the present study 5t ha-1 DM of a yard and bio-waste (60/40) compost produced in a 5 month composting process and a 15 month old 100 % yard waste compost were used to assess the effects on potato infection with R. solani when applying composts within the limits allowed. Across the differences in initial seed tuber infestation and 12 cultivars 5t DM ha-1 of high quality composts, applied in the seed tuber area, reduced the infestation of harvested potatoes with black scurf, tuber malformations and dry core tubers by 20 to 84 %, 20 to 49 % and 38 to 54 %, respectively, while marketable yields were increased by 5 to 25 % due to lower rates of wastes after sorting (marketable yield is gross yield minus malformed tubers, tubers with dry core, tubers with black scurf > 15% infested skin). The rate of initial black scurf infection of the seed tubers also affected tuber number, health and quality significantly. Compared to healthy seed tubers initial black scurf sclerotia infestation of 2-5 and >10 % of tuber surface led in untreated plots to a decrease in marketable yields by 14-19 and 44-66 %, a increase of black scurf severity by 8-40 and 34-86 % and also increased the amount of malformed and dry core tubers by 32-57 and 109-214 %.

Survey of Agricultural Practices and Alternatives to Pesticide Use to Conserve Water Resources in the Mojanda Watershed, Ecuador

Agriculture in the Mojanda Watershed is facing rainfall reductions caused by climate change. Reductions of water availability in the Watershed are also due to constant extension of the agricultural activities into the páramo ecosystem above 3000m a.s.l., with this ecosystem having immanently important functions in the local water balance. The application of pesticides threatens the quality of water and with less precipitation contaminations will further concentrate in the outflow. To analyze problems associated with agricultural practices in the area a questionnaire about agricultural practices (28) was conducted and fields (20) were surveyed for pests and diseases with a focus on potatoes (Solanum tuberosum L.), tree tomatoes (Solanum betaceum Cav.) and peas (Pisum sativum L.). Potatoes were infected to a low degree with Phytophthora infestans and according to the farmers the Andean potato weevil (Premnotrypes spec.) caused biggest losses. To combat the weevil the soils are disinfected with toxic Carbofuran (WHO Class 1B). Tree tomatoes showed symptoms of various fungal diseases. Most important was Fusarium solani causing the branches to rot and Anthracnosis (Colletotrichum gloeosporioides) causing the fruits to rot. Fungicide applications were correspondingly high. Peas were only minorly affected by Ascochyta blight (Mycosphaerella pinodes) and a root rot. Overall 19 active ingredients were applied of which fungicide Mancozeb (WHO class table 5) and insecticide Carbofuran (WHO Class 1B) were applied the most. Approved IPM methods are advised to reduce pesticide use. For tree tomatoes regular cutting of branches infected with F. solani and regular collection and disposal of infected fruits with Anthracnosis are advised. For potatoes plastic barriers around the fields prevent the Andean potato weevil from laying eggs thus reducing infestation with the larvae in the tubers. Local bioinsecticide “Biol” seems effective and without harm to the environment, although not used by many farmers. Organic fertilization promises to restore decreasing soil fertility, water holding capacity and reduce erosion. The here presented alternatives and strategies to reduce pesticide use pose an opportunity to preserve the water resources of the region.

Farmers’ knowledge and perceptions of potato pests and their management in Uganda

As we initiate entomological research on potato (Solanum tuberosum L.) in Uganda, there is need to understand farmers’ knowledge of existing insect pest problems and their management practices. Such information is important for designing a suitable intervention and successful integrated pest management (IPM) strategy. A farm household survey using a structured questionnaire was conducted among 204 potato farmers in six districts of Uganda (i.e., Kabale, Kisoro, Mbale, Kapchorwa, Mubende, and Kyegegwa) during August and September 2013. Diseases, insect pests, price fluctuations, and low market prices were the four highest ranked constraints in potato production, in order of decreasing importance. Cutworms (Agrotis spp.), aphids (Myzus persicae (Sulzer)), and potato tuber moth (Phthorimaea operculella (Zeller)) were the three most severe insect pests. Ants (Dorylis orantalis Westwood), whiteflies (Bemisia tabaci (Gennadius)), and leafminer flies (Liriomyza huidobrensis (Blanchard)) were pests of moderate importance. Major yield losses are predominantly due to late blight (Phytophthora infestans (Mont.) de Bary) and reached 100% without chemical control in the districts of Kabale, Kisoro, Mbale, and Kapchorwa. On average, farmers had little to moderate knowledge about pest characteristics. The predominant control methods were use of fungicides (72% of respondents) and insecticides (62% of respondents). On average, only 5% of the 204 farmers knew about insect pests and their natural enemies. This lack of knowledge calls for training of both farmers and extension workers in insect pest identification, their biology, and control. Empowering farmers with knowledge about insect pests is essential for the reduction of pesticide misuse and uptake of more environmentally friendly approaches like IPM. Field surveys would need follow-up in order to assess the actual field infestation rates and intensities of each insect pest and compare the results with the responses received from farmers.

Comparative phylogeography of Trypanosoma cruzi TCIIc: New hosts, association with terrestrial ecotopes, and spatial clustering

We characterized 28 new isolates of Trypanosoma cruzi IIc (TCIIc) of mammals and triatomines from Northern to Southern Brazil, confirming the widespread distribution of this lineage. Phylogenetic analyses using cytochrome b and SSU rDNA sequences clearly separated TCIIc from TCIIa according to terrestrial and arboreal ecotopes of their preferential mammalian hosts and vectors. TCIIc was more closely related to TCIId/e, followed by TCIIa, and separated by large distances from TCIIb and TCI. Despite being indistinguishable by traditional genotyping and generally being assigned to Z3, we provide evidence that TCIIa from South America and TCIIa from North America correspond to independent lineages that circulate in distinct hosts and ecological niches. Armadillos, terrestrial didelphids and rodents, and domestic dogs were found infected by TCIIc in Brazil. We believe that, in Brazil, this is the first description of TCIIc from rodents and domestic dogs. Terrestrial triatomines of genera Panstrongylus and Triatoma were confirmed as vectors of TCIIc. Together, habitat, mammalian host and vector association corroborated the link between TCIIc and terrestrial transmission cycles/ecological niches. Analysis of ITS1 rDNA sequences disclosed clusters of TCIIc isolates in accordance with their geographic origin, independent of their host species. (C) 2009 Elsevier B.V. All rights reserved.

Diverse eukaryotes have retained mitochondrial homologues of the bacterial division protein FtsZ

Mitochondrial fission requires the division of both the inner and outer mitochondrial membranes. Dynamin-related proteins operate in division of the outer membrane of probably all mitochondria, and also that of chloroplasts – organelles that have a bacterial origin like mitochondria. How the inner mitochondrial membrane divides is less well established. Homologues of the major bacterial division protein, FtsZ, are known to reside inside mitochondria of the chromophyte alga Mallomonas, a red alga, and the slime mould Dictyostelium discoideum, where these proteins are likely to act in division of the organelle. Mitochondrial FtsZ is, however, absent from the genomes of higher eukaryotes (animals, fungi, and plants), even though FtsZs are known to be essential for the division of probably all chloroplasts. To begin to understand why higher eukaryotes have lost mitochondrial FtsZ, we have sampled various diverse protists to determine which groups have retained the gene. Database searches and degenerate PCR uncovered genes for likely mitochondrial FtsZs from the glaucocystophyte Cyanophora paradoxa, the oomycete Phytophthora infestans, two haptophyte algae, and two diatoms – one being Thalassiosira pseudonana, the draft genome of which is now available. From Thalassiosira we also identified two chloroplast FtsZs, one of which appears to be undergoing a C-terminal shortening that may be common to many organellar FtsZs. Our data indicate that many protists still employ the FtsZ-based ancestral mitochondrial division mechanism, and that mitochondrial FtsZ has been lost numerous times in the evolution of eukaryotes.

The top 10 oomycete pathogens in molecular plant pathology

Oomycetes form a deep lineage of eukaryotic organisms that includes a large number of plant pathogens which threaten natural and managed ecosystems. We undertook a survey to query the community for their ranking of plant-pathogenic oomycete species based on scientific and economic importance. In total, we received 263 votes from 62 scientists in 15 countries for a total of 33 species. The Top 10 species and their ranking are: (1) Phytophthora infestans; (2, tied) Hyaloperonospora arabidopsidis; (2, tied) Phytophthora ramorum; (4) Phytophthora sojae; (5) Phytophthora capsici; (6) Plasmopara viticola; (7) Phytophthora cinnamomi; (8, tied) Phytophthora parasitica; (8, tied) Pythium ultimum; and (10) Albugo candida. This article provides an introduction to these 10 taxa and a snapshot of current research. We hope that the list will serve as a benchmark for future trends in oomycete research.