Management of Plant Disease Epidemics with Irrigation Practices

Adequate water provision to roots is essential to warrant sustainable harvests of agricultural crops globally. However, water applied in excess or in deficit may result in the development of many fungal and bacterial plant diseases, which compromise produce yield and quality. Leaf wetness duration, soil water tension and related water variables impact several aspects of different plant disease cycles, such as the sporulation, survival of pathogen propagules, their dispersal to new hosts, germination and infection. Irrigation is thus arguably the most important cultural practice in the management of plant diseases, especially in the context of the quest of a more sustainable, less chemically dependent agriculture. The technology of water application and method of irrigation have been profusely studied as to their direct relation to plant diseases. Irrigation management has a strong impact on the disease severity and epidemic progress rates of many plant pathosystems, ranging from leaf blights to vascular wilts. In addition, plant virus vector population levels and vector dispersal are also affected by the method of irrigation. This chapter reviews experimental data on the effect of different irrigation configurations and management systems on some representative plant diseases

Acanthospermum australe is an alternate host of Thanatephorus cucumeris, the causal agent of web blight on dry beans

Em processament

Primer informe de Fusarium incarnatum (Desm.) Sacc. afectando al cultivo del garbanzo en Cuba

The objective of the work was to characterize isolates of Fusarium sp. from chickpea (Cicer arietinum L.) morphologically and molecularly. For this, the morphological characterization of the isolates of Fusarium sp. was conducted by using a taxonomic key and, for their molecular identification, DNA extraction, amplification of the translation and elongation factor 1α (tef-1α) gene, purification and sequencing of the amplified fragments were performed. The results allowed reporting the first identification of a new Fusarium species on chickpea in Cuba [Fusarium incarnatum (Desm.) Sacc.], a species belonging to the Fusarium incarnatum-equiseti species complex (FIESC). The Cuban strains were phylogenetically clustered with the FIESC 15 group. This is the first report of F. incarnatum associated with chickpea in Cuba.El trabajo tuvo como objetivo caracterizar morfológica y molecularmente aislamientos de Fusarium sp. procedentes de plantas de garbanzo (Cicer arietinum L.). Para ello, se realizó la caracterización morfológica de los aislados de Fusarium sp. mediante el uso de una clave taxonómica. Para la identificación molecular se realizó la extracción de ADN, amplificación del gen que codifica para el factor de elongación y traducción 1α (tef- 1α), purificación de los fragmentos amplificados y su secuenciación. Los resultados permitieron informar, por primera vez en Cuba, una nueva especie de Fusarium en el garbanzo [Fusarium incarnatum (Desm.) Sacc.], incluida en el clado Incarnatum, que pertenece al complejo de especies Fusarium incarnatum-equiseti (FIESC). Las cepas cubanas se agruparon filogenéticamente con el grupo FIESC 15. Este es el primer informe de F. incarnatum asociado al garbanzo en Cuba

Influência de práticas culturais e da resistência genética na intensidade do cancro da haste e produção de soja no Cerrado

Os efeitos de práticas culturais e resistência genética na intensidade ao cancro-da-haste da soja (Diaporthe phaseolorum f.sp. meridionalis - Dpm) foram examinados na safra 1995-96 em áreas de produção comercial, que haviam sido severamente atacadas na safra anterior (1994-95). Um experimento investigou os efeitos de cultivo mínimo (MT) e do plantio direto (NT) no desenvolvimento da doença e produtividade das cultivares FT-Cristalina e FT-Seriema. Em outro experimento, semeado em plantio direto, estudou-se o efeito da densidade de plantas (8, 15, 21 e 36 plantas/m) no desenvolvimento da doença e produtividade das cvs. FT-Cristalina (suscetivel), FT- 101 (moderadamente resistente) e FT-104 (resistente). Incidência e severidade da doença foram menores em NT do que em MT. A produtividade aumentou no sistema NT (23% para ‘FT-Cristalina’ e 14% para ‘FT-Seriema’), comparada com as produtividades em MT. As curvas de progresso da doença foram melhor descritas pelos mo- delos de Gompertz e logístico. A severidade do cancro aumentou pro- porcionalmente ao aumento das densidades de plantio nas cvs. suscetível e moderadamente resistente. No final do ciclo, 100% das plantas da cv. FT-Cristalina estavam infetadas por Dpm, em todas as densidades de plantio. Níveis intermediários de doença foram observa- dos na cv. FT-101, enquanto apenas níveis muito baixos de doença ocorreram na cv. FT-104. Estabeleceu-se uma correlação negativa entre severidade de cancro-da-haste e produção. Algumas das práticas estudadas demonstraram potential para aplicação direta no controle da doença, e poderiam ser combinadas considerando-se seus efeitos aditivos.Field experiments were conducted in the 1995-96 soybean (Glycine max) growing season to evaluate the effects of cultural practices and host genetic resistance on the intensity of soybean stem canker, caused by Diaporthe phaseolorum f.sp. meridionalis (Dpm). Experiments were conducted in a commercial field severely infected in the previous (1994-95) season. In one study, minimum tillage (MT) and no-tillage (NT) cropping systems were investigated for their effects on disease development and on plant yields in cvs. FT- Cristalina (susceptible) and FT-Seriema (moderately resistant). Another study evaluated the effects of plant densities (8, 15, 21 and 36 plants/m) on disease development in cvs. FT-Cristalina, FT-101 (moderately resistant) and FT-104 (resistant). Disease incidence and severity were consistently lower in NT than in MT, and plant yields were increased by 23% and 14% in the NT system for the susceptible and moderately resistant cultivars, respectively, compared to the yields in the MT system. The Gompertz and Logistic models described well the disease progress curves in all situations. For both susceptible and moderately resistant cultivars, disease severity increased proportionately to the increase in plant densities. At the end of the season, 100% of the plants of cv. FT-Cristalina were infected by Dpm, at all plant densities. Disease levels on cv. FT-101 were intermediate while only very low disease levels were recorded on cv. FT-104. There was a consistent negative correlation between stem canker severity and yield. Some practices demonstrated potential for direct application in disease control, and could be combined considering their additive effects

Efeito do espaçamento e da cultivar de feijoeiro sobre a intensidade do mofo-branco e a sanidade de sementes Effect of plant spacing and bean cultivar on white mold and seed sanity

Dois ensaios de campo foram realizados para avaliar o efeito do espaçamento entre linhas (30, 45 e 60 cm) e entre plantas de feijoeiro com hábitos de crescimento diferentes, sobre a intensidade do mofo-branco e a sanidade de sementes. No primeiro, foi mantida a mesma população de plantas por área, 27 plantas/m², reduzindo-se o espaçamento entre plantas. No segundo ensaio, manteve-se o mesmo espaçamento entre plantas, que resultou em populações de 40, 27 e 20 plantas/m². A porcentagem de plantas infectadas e a severidade da doença não diferiram estatisticamente quanto ao hábito de crescimento da cultivar, ao espaçamento ou à interação entre eles, mesmo a incidência tendo atingido valores de 98,4% em 1998 e de 2,7% em 1999. A porcentagem de sementes infectadas não foi afetada pelo espaçamento, mas diferiu erraticamente em relação às cultivares; em 1998, a cultivar Pérola não apresentou sementes infectadas, o mesmo acontecendo com a cultivar Diamante Negro em 1999.<br>The effect of spacing among rows and among bean plants, as well as two plant growth habits were evaluated on the intensity of white mold and seed health in two field trials in Brasilia, DF, Brazil. In the first trial, the same population of 27 plants/m² was maintained in rows of 30, 45 and 60 cm apart. In the second trial, the spacing among rows was maintained, which resulted in different plant populations of 40, 27 and 20 plants/m², respectively. Disease incidence and severity did not differ statistically within plants of different growth habits or different spacing, even with divergent disease incidences of 98.4% and 2.7% observed in 1998 and 1999, respectively. The percentage of infected seeds was not affected by spacing either, however the cultivar effect was erratic; in 1998, 'Perola' had no infected seeds and the same occurred with 'Diamante Negro' in 1999

Caracterización fisio-cultural y compatibilidad micelial de aislamientos de Sclerotium sp. procedentes de siete hospedantes

The objectives of the work were to culturally and physiologically characterize 15 isolates of Sclerotium sp. from beans (Phaseolus vulgaris L.), chickpea (Cicer arietinum L.), tomato (Solanum lycopersicum L.), taro [Colocasia esculenta (L.) Schott], garlic (Allium sativum L.), and ornamental plants [Neomarica caerulea (Ker Gawl.) Sprague and Hydrocotyle sp.], from Cuba and Brazil, under different lighting conditions and determine the presence of their Mycelial Compatibility Groups (GCM). For this, the inoculated Petri dishes containing Papa Dextrose Agar (PDA) culture medium were placed under three lighting regimes [constant darkness (OC), alternating light (LA), and constant light (LC)] at 28 ± 2°C. The mycelial growth diameter and the surface texture and color of the colonies were evaluated in each isolate, as well as the number, weight and diameter of sclerotia under each condition. Confrontation tests were used to determine the existence of GCM. The highest production of sclerotia was under LC, and the lowest under OC. Mycelial compatibility was observed between the colonies of isolates from the same host (No. 1 and 9 of C. arietinum and No. 5 and 6 of P. vulgaris) and between isolates from different hosts (P. vulgaris - S. lycopersicum and A. sativum - N. caerulea). Five GCM were obtained, GCM- I (No. 1 and 9), GCM-II (No. 5 and 6), GCM-III (No. 10 and 11), GCM-IV (No. 10 and 12), and GCM-V (No. 13 and 14).Los objetivos del trabajo fueron caracterizar cultural y fisiológicamente 15 aislamientos de Sclerotium sp. procedentes de frijol (Phaseolus vulgaris L.), garbanzo (Cicer arietinum L.), tomate (Solanum lycopersicum L.), malanga [Colocasia esculenta (L.) Schott], ajo (Allium sativum L.) y las plantas ornamentales Neomarica caerulea (Ker Gawl.) Sprague y Hydrocotyle sp. de Cuba y Brasil, bajo diferentes condiciones de iluminación, y determinar la presencia de los Grupos de Compatibilidad Micelial (GCM) de los mismos. Para ello se usaron placas Petri contentivas de medio de cultivo Papa Dextrosa Agar (PDA), bajo tres regímenes de luz: oscuridad constante (OC), luz alterna (LA) y luz constante (LC) a 28±2°C. Se evaluó el diámetro del crecimiento micelial, textura superficial y color de las colonias en cada aislamiento, así como el número, peso y diámetro de esclerocios en cada condición. Además, se realizaron pruebas de enfrentamiento para determinar la existencia de GCM. La mayor producción de esclerocios fue bajo LC, y la menor a OC. Se observó Compatibilidad Micelial entre las colonias de aislamientos procedentes de un mismo hospedante (No. 1 y 9 de C. arietinum; No. 5 y 6 de P. vulgaris) y entre aislamientos de hospedantes diferentes (P. vulgaris - S. lycopersicum y A. sativum - N. caerulea). Se lograron obtener cinco GCM: GCM- I (No. 1 y 9), GCM-II (No. 5 y 6), GCM-III (No. 10 y 11), GCM-IV (No. 10 y 12) y GCM-V (No. 13 y 14)

Caracterización fisio-cultural y compatibilidad micelial de aislamientos de Sclerotium sp. procedentes de siete hospedantes

The objectives of the work were to culturally and physiologically characterize 15 isolates of Sclerotium sp. from beans (Phaseolus vulgaris L.), chickpea (Cicer arietinum L.), tomato (Solanum lycopersicum L.), taro [Colocasia esculenta (L.) Schott], garlic (Allium sativum L.), and ornamental plants [Neomarica caerulea (Ker Gawl.) Sprague and Hydrocotyle sp.], from Cuba and Brazil, under different lighting conditions and determine the presence of their Mycelial Compatibility Groups (GCM). For this, the inoculated Petri dishes containing Papa Dextrose Agar (PDA) culture medium were placed under three lighting regimes [constant darkness (OC), alternating light (LA), and constant light (LC)] at 28 ± 2°C. The mycelial growth diameter and the surface texture and color of the colonies were evaluated in each isolate, as well as the number, weight and diameter of sclerotia under each condition. Confrontation tests were used to determine the existence of GCM. The highest production of sclerotia was under LC, and the lowest under OC. Mycelial compatibility was observed between the colonies of isolates from the same host (No. 1 and 9 of C. arietinum and No. 5 and 6 of P. vulgaris) and between isolates from different hosts (P. vulgaris - S. lycopersicum and A. sativum - N. caerulea). Five GCM were obtained, GCM- I (No. 1 and 9), GCM-II (No. 5 and 6), GCM-III (No. 10 and 11), GCM-IV (No. 10 and 12), and GCM-V (No. 13 and 14).Los objetivos del trabajo fueron caracterizar cultural y fisiológicamente 15 aislamientos de Sclerotium sp. procedentes de frijol (Phaseolus vulgaris L.), garbanzo (Cicer arietinum L.), tomate (Solanum lycopersicum L.), malanga [Colocasia esculenta (L.) Schott], ajo (Allium sativum L.) y las plantas ornamentales Neomarica caerulea (Ker Gawl.) Sprague y Hydrocotyle sp. de Cuba y Brasil, bajo diferentes condiciones de iluminación, y determinar la presencia de los Grupos de Compatibilidad Micelial (GCM) de los mismos. Para ello se usaron placas Petri contentivas de medio de cultivo Papa Dextrosa Agar (PDA), bajo tres regímenes de luz: oscuridad constante (OC), luz alterna (LA) y luz constante (LC) a 28±2°C. Se evaluó el diámetro del crecimiento micelial, textura superficial y color de las colonias en cada aislamiento, así como el número, peso y diámetro de esclerocios en cada condición. Además, se realizaron pruebas de enfrentamiento para determinar la existencia de GCM. La mayor producción de esclerocios fue bajo LC, y la menor a OC. Se observó Compatibilidad Micelial entre las colonias de aislamientos procedentes de un mismo hospedante (No. 1 y 9 de C. arietinum; No. 5 y 6 de P. vulgaris) y entre aislamientos de hospedantes diferentes (P. vulgaris - S. lycopersicum y A. sativum - N. caerulea). Se lograron obtener cinco GCM: GCM- I (No. 1 y 9), GCM-II (No. 5 y 6), GCM-III (No. 10 y 11), GCM-IV (No. 10 y 12) y GCM-V (No. 13 y 14)