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Farmers in Cuba sow high doses of seeds to guarantee rice populations and therefore obtain better yields, however, this trend is counterproductive since production becomes more expensive due to seed costs, fertilizers, fungicides, insecticides and they are not always achieved the expected yields due to the inadequate development of plants and the high incidence of pests. Based on this problem, the objective of this work was to evaluate the interaction between four doses of cultivar LP-5 seed and the incidence and severity of fungal diseases on rice yield. For this, plots were made and sown with four doses of seeds (100, 120, 140, 160 kg ha-1). A randomized block design with five repetitions was carried out. In each of the variants, the incidence and severity of the main rice diseases were evaluated, and the theoretical yield and its components were also evaluated. Highest incidences and severity of diseases were observed when the highest doses of seeds were applied (160 and 140 kg ha-1), regardless of the disease and the evaluation time. It was found that it is not always that high planting densities lead to higher yields. As the seed dose increased, the distribution and incidence of diseases increased, fundamentally affecting the number of filled grains per panicle and the weight of one thousand grains. Highest yields were obtained at doses of 120 and 140 kg ha-1. [ABSTRACT FROM AUTHOR]

Farmers in Cuba sow high doses of seeds to guarantee rice populations and therefore obtain better yields, however, this trend is counterproductive since production becomes more expensive due to seed costs, fertilizers, fungicides, insecticides and they are not always achieved the expected yields due to the inadequate development of plants and the high incidence of pests. Based on this problem, the objective of this work was to evaluate the interaction between four doses of cultivar LP-5 seed and the incidence and severity of fungal diseases on rice yield. For this, plots were made and sown with four doses of seeds (100, 120, 140, 160 kg ha-1). A randomized block design with five repetitions was carried out. In each of the variants, the incidence and severity of the main rice diseases were evaluated, and the theoretical yield and its components were also evaluated. Highest incidences and severity of diseases were observed when the highest doses of seeds were applied (160 and 140 kg ha-1), regardless of the disease and the evaluation time. It was found that it is not always that high planting densities lead to higher yields. As the seed dose increased, the distribution and incidence of diseases increased, fundamentally affecting the number of filled grains per panicle and the weight of one thousand grains. Highest yields were obtained at doses of 120 and 140 kg ha-1. [ABSTRACT FROM AUTHOR]

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Fungal diseases in rice crop (Oryza sativa Lin.) are considered among the main causes of low cereal yields. In this sense, numerous studies indicate that the applications of Trichoderma asperellum Samuels, Lieckfeldt & Nirenberg strains to the soil in fields destined to the cultivation of rice, are promising for the control of numerous phytopathogenic fungi. The objective of the work was to evaluate the effect of the Ta 78 strain of T. asperellum against the most important diseases of rice cultivation under field conditions. For this, the strain of T. asperellum was sprayed in a terrace system during soil preparation, and a terrace was used as a production control. The severity and incidence of the main diseases caused by fungi were evaluated at various times and the number of plants, tillers and panicles per m2 was evaluated. R. solani, Helminthosporium sp. and Cercospora sp. were the fungi that most affected rice crop. The incidence and severity of the diseases evaluated in the treatment with T. asperellum, decreased significantly with respect to the control treatment, regardless of the time of the evaluation. On the other hand, the number of tillers and spikes was significantly higher in the plot treated with biological control. [ABSTRACT FROM AUTHOR]

Copyright of Investigación Agraria is the property of Investigacion Agraria and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Nova Acta Científica Compostelana is the property of Universidad de Santiago de Compostela, Servicio de Publicaciones and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The objective of this study was to evaluate in vitro the endophytic bacteria resistance to different lead concentrations. The sampling was undertaken in the first half of 2013, when tissue samples of commercial varieties of rice at tillering stage were collected in Montería, Cordoba, Colombia. Each tissue was subjected to surface cleaning. Endophytic bacteria in agar R2A medium were isolated. Population density (CFU/g tissue) was determined from each tissue, by direct counting of R2A medium surface. morphotypes were classified by shape, color, size, and appearance. A total of 168 morphotypes were isolated from root, tillers, and leaf of different commercial varieties of rice. The lead resistance test was performed in vitro, to do that, suspensions of endophytic bacteria in log phase were prepared and inoculated in minimal medium with five concentrations of lead as Pb(NO3) 2. The experiment was incubated at 32 °C and agitated at 150 rpm, for five days. Every hour afterstarting the test, turbidimetry measuring at 600 nm was conducted. Results showed the ability of endophytic bacteria to grow at concentrations of 100% of Pb as Pb(NO3) 2. The results of the identification with kit API20E confirmed the presence of Burkholderia cepacia and Pseudomonas putida, which showed resistance to different lead concentrations. [ABSTRACT FROM AUTHOR]

The chitosan is widely used in agriculture for having a strong fungistatic effect, also it has other properties such as extending the post harvest life of fruits and vegetables and stimulating the plant growth, among others. However, the use of this biopolymer for inducing salinity tolerance has been few studied, so the objective of this work was to check if chitosan-treated seeds are able to reverse the effects caused by salinity in the rice seedling growth and some biochemical indicators associated to this response. To do this, rice (Oryza sativa L.) seeds variety INCA LP-5 were treated for 24 hours with different concentrations of chitosan (0, 100 and 500 mg L-1). The germinated seeds were transferred to pots containing diluted Hoagland nutritive solution supplemented or not with NaCl 100 mmol L-1 and they were placed in a growth chamber with controlled conditions. The growth and biochemical indicators were evaluated eleven days after stress treatment. Seeds treated with chitosan 100 mg L-1 stimulated shoot length and dry matter in saline medium grown seedlings and lowered malondialdehyde and increased proline levels. Both chitosan concentrations enhanced the activities of catalase and peroxidase enzymes, although a higher effect was obtained with chitosan 500 mg L-1. [ABSTRACT FROM AUTHOR]

El artículo discurre sobre el desarrollo de un tipo de arroz cultivado para resistir la infección del hongo Pyricularia grisea. Los autores comentan sobre el impacto de las enfermedades en la producción agrícola y examina la Pyricularia, la cual es una enfermedad criptogámica compleja que produce la toxina pericularina.

The objective of this study was to determine the presence of B. glumae in the rice crop in Costa Rica. The bacterium Burkholderia glumae is associated with the cultivation of rice, causing the disease known as bacterial blight. Under favorable weather conditions, the bacterial density increases, thus causing the expression, under a system called quorum sensing regulation, of its virulence mechanisms, by activating genes responsible for toxoflavine synthesis, which blocks the flow of nutrients for flagellum biogenesis and the chemostatic response, and the production of the enzyme catalase. Plants develop symptoms that eventually lead to empty hulls, causing significant economic losses. The current level of contamination of rice seeds with this bacteria in Costa Rica was studied during 2009 and 2010, through an agreement between the National Rice Corporation, the Plant Pathology Laboratory of the Crop Protection Research Center at the University of Costa Rica. The Endpoint PCR methodology recommended by researchers at the International Center for Tropical Agriculture in Colombia, the identification was reinforced with conventional microbiology. Results indicating the presence of the bacteria in Costa Rica were obtained, providing the first information on the prevalence of a bacterial plant pathogen of great importance for the rice sector. [ABSTRACT FROM AUTHOR]

Obtaining eggs of Oebalus insularis Stal., for the multiplication of Telenomus podisi Ashmead depends on the quality of the food provided by diverse host plants. Therefore, the biological and reproductive performance of O. insularis on Oryza sativa L. and Echinochloa colona (L.) was determined at 28±2°C, 80 ± 5% of relative humidity and 12 hours photophase. The duration of the period of nymph eclosion until the emergence of the adult of O. insularis varied between 20,9 and 21,2 days, for O. sativa and E. colona, respectively. The longevity of the female and male of O. insularis was statistically similar on both host plants. The female longevity was higher than that shown by the male, varying between 15 and 12 days, respectively. The O. insularis female fed with E. colona presented a high number of eggs per batch, total number of eggs per female and the eclosion rate of nymphs was higher. The biological and reproductive parameters of this insect confirmed their adaptation to the alternative host E. colona, optimizing the production of eggs subjected to T. podisi parasitism. [ABSTRACT FROM AUTHOR]

This study was aimed to determine the in vitro antifungal activity of four essential oils on three pathogens causing spotted grains in rice Curvularia lunata (Wakker) Boedijn, Sarocladium oryzae (Sawada) W. Gams & D. Hawksworth and Bipolaris oryzae (Breda de Haan) Shoemaker. The bioassay was performed as a completely randomized design; the method used consisted of filter paper disks soaked with the oils and placed in direct contact with the phytopathogenic fungi. The radial growth was evaluated daily for 96 hours. The oils of Piper auritum Kunth (Caisimón anise) and Piper aduncum subsp. Ossanum (C. DC.) Saralegui (Platanilllo of Cuba) produced complete growth inhibition of the three isolates. Similarly, the oil of Melaleuca quinquenervia (Cav) ST Blake (melaleuca) affected the growth of S. oryzae and B. oryzae, while that of Citrus sinensis (L.) Osbeck (sweet orange) inhibited only B. oryzae growth. The oils of P. aduncum and P. auritum were the most prominent; further research on their use as fungicides is suggested. [ABSTRACT FROM AUTHOR]

Bipolaris oryzae and Sarocladium oryzae are the principal causal agents of rice disease in Cuba. The aim of this work, was to determine antagonic activity of Trichoderma harzianum against B. oryzae and S. oryzae isolated from Camagüey. Exposition time and interactions amongs T. harzianum and the fungal causal agents. Also antagonic mechanisms (micoparasitism, competence and antibiosis) were evaluated. At 48 hours hyphal interaction between B. oryzae and T. harzianum were determined. Hyphal Coiling, penetration, lysis and vacuolization on parasited B. oryzae were observed. At 240 hours, hiperparasite activity of antagonist showed total colonization of mycelial of B. oryzae with 67.10% growth inhibition. In the case of S. oryzae, growth inhibition was 64.4% with 75% of colonozation of total surface of Petri dish. Antibiosis was observed in both fungal causal agents at 24 hours. Non differences were determined in the competence and antibiosis mechanism among antagonist-fungal causal agents interactions. fúngicas del arroz. Evaluation of “in vitro" antagonism of Trichoderma harzianum against B. oryzae and S. oryzae could be a promising alternative for a sustainable management of the principal causal agents of rice disease in production areas of Cuba. [ABSTRACT FROM AUTHOR]

The objective pursued with this study was to isolate Bacillus bacteria from rice (Oryza sativa L.) and determine its potential for phosphate solubilization. Isolates were obtained using the Microcosm model from Iacuba 30 and Perla cultivar, established by Bauta (2008) in La Habana, Cuba. Fifty eight isolates were obtained from the rice rhizosphere and inside of the roots and leaves with characteristics typical of Bacillus, such as Gram positive, rod cells and endospore formation. The qualitative capacity of these isolates for phosphate solubilization was assayed in solid NBRIP medium; the results revealed that only 19 strains solubilized inorganic phosphate and some of them changed the medium color from blue to yellow, presumably due to acid excretion. Positives were selected for assay in liquid medium, and they showed different responses in terms of time and maximum phosphate solubilization. [ABSTRACT FROM AUTHOR]

The apple snail is affecting rice crops in the lower Daule river basin, Ecuador. There is an estimated production loss of 40 to 60%. To avoid substantial losses the farmers applied agrochemicals in high doses, therefore unbalancing native fauna and micro fauna, and aggravating the problem. The pathogenicity of H. bacteriophora on apple snails was evaluated using a completely randomized design (DCA) with four treatments and five repetitions, the results show 100% mortality from sepsis at 96 hours after inoculation, in comparison with the control group. [ABSTRACT FROM AUTHOR]

In the months of March until July (rainy season) of the year 2003, in areas of the «Blas Roca» farm belonging to «Los Palacios» Rice agroindustrial enterprise, on a «Gley Nodular Concretionary soil, the behavior of six lines (3981, 8748, 8738, 4482, 8554, 8741) and three varieties (INCA LP-7, IACUBA-25 and the commercial variety J-104 as comparison control of rice, seven of them obtained in the breeding program for tolerance to salinity, was studied. The quantitative characters (final plant height, full grains per panicle, panicle per square meter, 1000 grain weight, empty grains per panicle, cycle in days and the agricultural and industrial yields), as well as the qualitative characters (resistance to lodging, shattering, blast and discoloured grain diseases and to the mite Steneotarsonemus spinki Smiley) were evaluated. Some differences among studied genotypes were observed. The highest agricultural and industrial yield and the best behavior to the main plagues and illnesses were obtained for the lines 3981, 8748 and 8554, and the variety INCA LP-7. [ABSTRACT FROM AUTHOR]

Rice is one of the main food crops having a higher demand in the market today, due to the large number of peoples who consume it. One alternative to eliminate fungal origin diseases is the use of plant-growth-promoting-rhizobacteria for the biological control. These microorganisms can inhibit phytopathogenic fungi growth due to their ability to produce many metabolites with antifungic activity. Bacillus genus isolates are one of the most used because their members produce a wide variety of these metabolites. In the present work, seven isolates identified as Bacillus sp. were used. The antagonistic effect against two phytopathogenic fungi of rice Curvularia sp. (Boed.) and Pyricularia grisea (Sacc.) was determined. Such effect was studied at seven and eleven days of the dual culture incubation. High percentages of inhibition against the two fungi were obtained; and the seven day was the best incubation time under the laboratory conditions tested. [ABSTRACT FROM AUTHOR]

For the introduction of new varieties into the production system, it is recommendable to characterize their behavior in the presence of the common key pests of this crop; therefore the objective of this experiment was to know the response of eight IDIAP varieties and the cultivar Vioal to the presence of populations of the mite Steneotarsonemus spinki. Mite populations were counted every eight days from the 27th day after germination. Five stems per treatment were randomly selected for each of three replications. The weights of whole, vain and chalky grains and the yields were determined. The response to diseases and the agronomic characteristics were evaluated. S. spinki density was compared by simple variance analysis, the influence of the climatic factors was evidenced by main component analysis; a cluster analysis permitted the grouping of varieties according to their full grain weights, and the polynomial regressions evidenced the population tendencies. All the varieties were resistant or moderately resistant to common diseases of the crop. The minima relative humidity changed by the action of rainfall and influenced in the mite dynamic markedly. The highest yields were spowntobe by the varieties with the highest weights of whole grains. The varietal response may be in function of the occurrence of high populations of the mite in stages near flowering, which may directly influence on the decrease or increase of whole grain weights and agricultural yields. [ABSTRACT FROM AUTHOR]

Presently work deal on the incidence of pest and diseases on 21 varieties of rice in the Garden of Cumanayagua, in the year 2006. Surveys were made at 60, 75 and 90 days after planting. The pests with more incidences were the insect Tagosodes orizicolus Muir, in early stages, and the mite Steneotarsonemus spinki Smiley in almost all the varieties from the beginning of the crop, but with low level. Among the diseases the most important were the spotted of the leaf caused by Pyricularia grisae Cooke and the spotted of the grain caused by Sarocladium oryzae Sawada. The varieties to IR 69, V 4554, V4499, INCA 6, INCA 3, IA Cuba 33, IA Cuba 28, IA Cuba 26 and IA Cuba 23 showed susceptibility to P. oryzae while the varieties Collection 1 and Collection 2 reached grade 1 as maximum. The varieties Caribbean, INCA 10, INCA 6, IA Cuba 28, IA Cuba 26, IA Cuba 23 and IA Cuba 19 manifested a bigger level of spotted of the grain, while the varieties Bolito Media Luna and J 104 only reached grade 2 as maximum. The varieties LP 5 and Bolito Media Luna were the favourite ones for the producers that participated in the biodiversity fair, since they manifested good agricultural behaviour and low incidence of pests and diseases. [ABSTRACT FROM AUTHOR]

El artículo presenta un estudio sobre el crecimiento de poblaciones de géneros de nematodos parasíticos de arroz. Se examinaron áreas en el norte y en la región atlántica de Costa Rica para realizar el estudio. Se proveen modelos matemáticos para describir las dinámicas poblacionales de los géneros diversos, especialmente Pratylenchus.

The study was carried out from 2000 to 2006, in the areas of 'Los Palacios' Rice Agroindustrial Complex (CAI), Pinar del Río, with the objective of studying the monthly behavior of leaf blast (Pyricularia grisea Sacc.) occurrence, which is the most important rice disease worldwide and its relationship with temperatures: maximum (Tmax), minimum (Tmin) and mid (Tmid), relative humidity (Hr) and rainy days (Dcll). Thus, data were subjected to variance analysis, tendency and correlation; besides, a study of temporary series was made by using the additive seasonal decomposition method. Results showed that monthly disease occurrence was not correlated with Hr but with Tmax, Tmin and Tmid, as well as Dcll. Meanwhile Hr kept a slightly growing tendency of its mid monthly values, Tmax, Tmin, Tmid and Dcll as well as P. grisea occurrence had an increasing-decreasing tendency, which constitutes a year-on-year variability example of these variables. The resulting seasonal decomposition indexes enabled a better understanding of the studied variable behaviour patterns that make this variability evident, besides keeping with the tendencies and variations observed in the current climate of Cuba. [ABSTRACT FROM AUTHOR]

Aerobiological studies are important to understand distribution, ecology and possible affectation of rice pathogenic fungi. Wind is one of the most important factors in the dispersion of these fungi. That is the reason why some different samplers have been designed to collect airborne fungi in order to identify them. Some of rice phytopathogenic fungi are Pyricularia grisea, Bipolaris oryzae, Gerlachia oryzae, Sarocladium oryzae, Gaeumannomyces graminis, Cercospora oryzae, Alternaria padwickii and some species of Phyllosticta and Curvularia genus. The majority of these fungi has been reported in several aerobiological studies done in outdoor environments around the world. A good sampling method could bring information of the air distribution of phytopathogenic fungal spores affecting rice crop. This information together with the meteorological data could help to understand the ecology of these fungi and the rice disease epidemiology, as well as to apply predictive models. [ABSTRACT FROM AUTHOR]

The sheath blight or blot easterly is considered the second important disease on rice in Cuba and worldwide. The methods used to control this disease have not been effective and, at present, there is a tendency to use the biological control. Trichoderma is recognized as a potential antagonist of soil pathogens, with positive results as an antagonist to Rhizoctonia. The objective of this work was to select promising strains of Trichoderma spp. according to their in vitro antagonism and effectiveness to control Rhizoctonia sp. under semicontrolled conditions. Antagonism was evaluated using the dual culture method, where the competition for the substrate, mycoparasitism and antibiosis could be observed. The colony radial growth was measured with a graduated ruler and the inhibition percentage was calculated after 96 hours. Micoparasitism was also observed using an optic microscope with 400x magnification, where the interaction between strains was evaluated. Strains showing a radial growth inhibition higher than 50 % and at least two types of hyphae interaction were selected to be tested under semicontrolled conditions for evaluating the technical effectiveness on the pathogen in stainless steel trays of 0,30cm². The 100 % of the strains had high antagonism capabilities with different types of hyphal interactions, lysis, vacuolization, rolling, and penetration. Five strains were selected, three of them showing a technical effectiveness of 50% under semicontrolled conditions. Strains 39, 56 and 78 resulted promising to control the disease under field conditions. [ABSTRACT FROM AUTHOR]

Sheath blight, caused by Rhizoctonia solani Kühn is considered the second important disease on rice in Cuba and the world. Trichoderma potentiality as antagonist of soil pathogen is recognized with positive results on R. solani. The present work had as objective to select the best Trichoderma isolates according to their in vitro antagonism and efficacy in the control of Rhizoctonia sp. in greenhouse and in the field. Antagonism was evaluated by the dual culture method, where the competition by the substrate, mycoparasitism and antibiosis were observed. The inhibition percentage of radial growth (IPRG) was calculated at 72 hours. The isolates with more than 60 PICR and at least two types of hyphal interaction were selected for being tested under greenhouse conditions, where the selection criterion was the technical efficacy (TE) under these conditions. Isolates with a TE higher than 80% were selected for field screening. The results showed that the 98,31% of the isolates had high antagonist capacity. They presented several hyphal interaction types such as lyses, vacuolization, coiling and penetration. Eleven Trichoderma isolates were selected in vitro. Of them, seven showed a TE higher than 80% in greenhouse. As promissories for the disease control in the field, isolates: 17, 75 and 78 with a TE higher than 90% were those highlighted under these conditions. [ABSTRACT FROM AUTHOR]

The morphological disorders of rice (Oryza sativa) seedling rootlets affected by salinity were studied in INCA-LP-10 cv., which has a certain salt-tolerance degree. Seeds were germinated in two saline concentrations, besides a separate control treatment just with water. After five days, rootlets were sampled, fixed to formaldehyde at 4 % and later processed until they were included in Epon resin. The semithin cuts were stained with blue toluidine. Longitudinal rootlet sections showed that salinity provoked morphological changes, according to NaCl concentrations employed, which mainly consisted of rootlet morphological changes and disorganized tissues, then opening large cavities among cell lines. [ABSTRACT FROM AUTHOR]

The in vitro effect of different concentrations (300, 500, 700 and 1000 mg/L) of K1 (INCA) and SIGMA chitosans on mycelial growth and sporulation of the rice grain pathogen fungus Fusarium subglutinans was studied. The colony diameter was measured after 3, 4, 5, 6 and 7 days, and the inhibition percentage of fungal mycelial growth compared with the non-treated control was determined. Conidia concentration was evaluated after 7 days. The fungicide effect of the product was determined for the treatments that totally inhibited the fungus. The results indicated that both products had an inhibitory effect on growth and sporulation at all evaluated concentrations. SIGMA chitosan showed a total inhibition at 1000 mg/L. Both substances had a fungistatic effect on F. subglutinans. [ABSTRACT FROM AUTHOR]

Eight produts or crop rests available in the zone were evaluated at the pest biological control laboratory of the Technological University of Huasteca from Hidalgo (UTHH), Mexico in order to know those of higher efficiency for being used as substrates in the production of biopesticides by entomopathogenous fungi (Paecilomyces fumosoroseus) and as plant disease antagonist (Trichoderna viride). Significant difference (p<0,05) among the treatments evaluated were observed for both fungi. In the case of T. viride, corn for consumption and the rest of corn crop showed the highest titers (conidia/g) in mass reduction, followed by coffee thin shell, enriched with corn. Rice and corn were very effective in P. fumosoroseus mass production. [ABSTRACT FROM AUTHOR]

Starting from Taylor indexes, Steneotarsonemus spinki Smiley (Acari: Tarsonemidae) aggregation pattern on rice (Oryza sativa L.) in Perla variety from Cuba, is shown. A modified Lotka - Volterra model that allows estimating population density is presented for the first time in the country. The correlation among estimated and observed values was of 0.967. [ABSTRACT FROM AUTHOR]

El artículo discurre sobre la gestión de la cultivación de Steneotarsonemus spinki por la evaluación de cultivares de arroz in Panamá. La autora comenta sobre la importancia de la cultivación de arroz porque es una fuente principal de comida para la población mundial. También se consideran los métodos para el manejo de las plagas que afectan el crecimiento de arroz, incluyendo la peste S. spinki.

El artículo presenta un resumen de un tesis del autor sobre los aislamientos de Trichoderma promisorios para el control biológico del tizón de la vaina (Rhizoctonia solani) en arroz. Discurre sobre su eficacia en condiciones semicontroladas. También se consideran los aspectos económicos de su implementación.

Se presenta el resumen de una tesis presentada por el autor para el título académico de Master en Sanidad Vegetal. La tesis describe una investigación sobre la identificación y el control de los agentes fungosos causantes del manchado de los granos de arroz. La investigación fue realizada in vitro y consideró el potencial de la quitosana y cepas de Trichoderma spp. para controlar la enfermedad.

Se presenta el resumen de una tesis presentada por el autor para el título académico de Master en Sanidad Vegetal. La tesis analiza la resistencia al hongo Sarocladium oryzae de varios genotipos de arroz en diversas etapas de crecimiento. El estudio también evalúa la fitotoxicidad del hongo para otros cultivos como sorgo y pata de gallina.