ISSN e:2007-4034 / ISSN print: 2007-4034

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     Vol. 23, issue 3 September - December 2017   Creative Commons License

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     Vol. 23, issue 3 September - December 2017  

 
  

Neoscytalidium dimidiatum: causal agent of dieback in Ficus benjamina L. in Mexico

Neoscytalidium dimidiatum agente causal de muerte descendente en Ficus benjamina L. en México

Ernesto Fernández-Herrera; Sergio F. Moreno-Salazar; María E. Rentería-Martínez; Alda A. Arratia-Castro; Edgar Villar-Luna

Keywords: branch necrosis, Botryosphaeriaceae, phylogenetic analysis, PCR.

10.5154/r.rchsh.2017.02.009

Received: 2017-02-14
Accepted: 2017-08-08
Available online: 2017-08-31
Pages:83-90

In Mexico, Ficus benjamina L. is mainly used as an ornamental and has been widely accepted because of its low production cost, rapid growth and abundant foliage. Ficus L. is a very broad genus that groups together diverse species native to tropical and subtropical regions. The aim of this research was to morphologically and molecularly identify the causal agent of “branch dieback” in F. benjamina plants. Dieback was observed in Ficus benjamina trees in urban areas and gardens in Sonora during the hottest season (June to September) in 2014. Fungal isolates were obtained from different symptomatic plants. The morphological characteristics of these isolates were similar to each other and their pathogenicity was confirmed by observing necrotic lesions caused by four of these isolates in F. benjamina plants 40 days after inoculation. Concatenated sequences from the internal transcribed spacer region (ITS; KU141333 and KU141334), large subunit (LSU; MF508739 and MF508740) and RNA polymerase II subunit (RPB2; MF508741 and MF508742) of the DNA from two representative isolates were analyzed phylogenetically, showing that the NDFB002 and NDFB003 isolates form a separate clade with several strains of Neoscytalidium dimidiatum. These isolates were previously reported in the National Center for Biotechnology Information (NCBI) GenBank. To our knowledge, this is the first report where N. dimidiatum is designated as a causal agent of branch dieback in F. benjamina plants in Mexico. 

In Mexico, Ficus benjamina L. is mainly used as an ornamental and has been widely accepted because of its low production cost, rapid growth and abundant foliage. Ficus L. is a very broad genus that groups together diverse species native to tropical and subtropical regions. The aim of this research was to morphologically and molecularly identify the causal agent of “branch dieback” in F. benjamina plants. Dieback was observed in Ficus benjamina trees in urban areas and gardens in Sonora during the hottest season (June to September) in 2014. Fungal isolates were obtained from different symptomatic plants. The morphological characteristics of these isolates were similar to each other and their pathogenicity was confirmed by observing necrotic lesions caused by four of these isolates in F. benjamina plants 40 days after inoculation. Concatenated sequences from the internal transcribed spacer region (ITS; KU141333 and KU141334), large subunit (LSU; MF508739 and MF508740) and RNA polymerase II subunit (RPB2; MF508741 and MF508742) of the DNA from two representative isolates were analyzed phylogenetically, showing that the NDFB002 and NDFB003 isolates form a separate clade with several strains of Neoscytalidium dimidiatum. These isolates were previously reported in the National Center for Biotechnology Information (NCBI) GenBank. To our knowledge, this is the first report where N. dimidiatum is designated as a causal agent of branch dieback in F. benjamina plants in Mexico. 

 

Potential for strengthening strawberry exports from Michoacán to the United States

Potencialidades para el fortalecimiento de exportación de fresa de Michoacán a Estados Unidos de América

María Eugenia Estrada-Chavira; Marcos Portillo-Vázquez; Guillermo Calderón-Zavala; Eduardo Segarra; Miguel Ángel Martínez-Damián; Sergio Ernesto Medina-Cuéllar

Keywords: growth rate, forecast, supply and demand, elasticity.

10.5154/r.rchsh.2017.02.007

Received: 2017-02-04
Accepted: 2017-05-25
Available online: 2017-08-31
Pages:135-146

The strawberry is Mexico’s thirteenth biggest export product and ranks third in value of exports, with the state of Michoacán being the leading exporter. The aim of this research was to analyze the potential for strengthening Michoacán strawberry exports to the United States, assuming the possibility of increasing exports from the state. The production growth rate, export forecast, and supply and demand for strawberry in Mexico and the U.S. were analyzed by means of logarithmic regression models processed in Statistical Analysis System (SAS) software. It was found that production grew more due to the increase in yield than to the increase in planted area; in addition, there is no evidence that strawberry exports are losing their upward growth trend. The price elasticity of the strawberry supply for Mexico and the US is inelastic, so there is still potential to increase strawberry exports.

The strawberry is Mexico’s thirteenth biggest export product and ranks third in value of exports, with the state of Michoacán being the leading exporter. The aim of this research was to analyze the potential for strengthening Michoacán strawberry exports to the United States, assuming the possibility of increasing exports from the state. The production growth rate, export forecast, and supply and demand for strawberry in Mexico and the U.S. were analyzed by means of logarithmic regression models processed in Statistical Analysis System (SAS) software. It was found that production grew more due to the increase in yield than to the increase in planted area; in addition, there is no evidence that strawberry exports are losing their upward growth trend. The price elasticity of the strawberry supply for Mexico and the US is inelastic, so there is still potential to increase strawberry exports.

 

Effect of plant row arrangement on yield components of bell pepper

Efecto de la disposición de hileras de plantas en los componentes de rendimiento de pimiento morrón

Felipe Sánchez-Del Castillo; Esaú del Carmen Moreno-Pérez; Felipe de Jesús Martínez-Gaspar; Ma. Teresa Colinas-León; José Armando Ramírez-Arias

Keywords: Capsicum annuum, planting arrangements, stepped canopy, greenhouse, hydroponics.

10.5154/r.rchsh.2017.02.008

Received: 2017-02-08
Accepted: 2017-06-29
Available online: 2017-08-31
Pages:147-161

An alternative to the production of bell pepper (Capsicum annuum L.) under greenhouse conditions is the management of plants in a high-density population, with blunting above the fourth branching to achieve short cycles and arrangement of plant rows at different heights to form a stair-like canopy (stepped canopy), a system that has not been studied in this species. The aim of this study was to compare four bell pepper production systems using two canopy arrangements (stair-like and uniform) and two planting densities (6 and 8 plants·m-2). The cultivar ‘Cannon’ was used. The experimental design used was plots split into randomized blocks with four replications. The plant row arrangements were located in the large plots and the densities in the subplots. With the stepped arrangement, the yield per unit area increased with respect to the control (uniform arrangement) by obtaining a higher fruit set per plant, without decreasing its weight. Under this plant arrangement, the density increase from 6 to 8 plants·m-2 did not boost yield. The highest yield obtained was 12 kg·m-2 with 6 plants·m-2 of greenhouse area in a period of four months, from transplant to final harvest. This suggests the possibility of establishing three crop cycles per year, with an annual yield higher than those achieved by current greenhouse production systems.

An alternative to the production of bell pepper (Capsicum annuum L.) under greenhouse conditions is the management of plants in a high-density population, with blunting above the fourth branching to achieve short cycles and arrangement of plant rows at different heights to form a stair-like canopy (stepped canopy), a system that has not been studied in this species. The aim of this study was to compare four bell pepper production systems using two canopy arrangements (stair-like and uniform) and two planting densities (6 and 8 plants·m-2). The cultivar ‘Cannon’ was used. The experimental design used was plots split into randomized blocks with four replications. The plant row arrangements were located in the large plots and the densities in the subplots. With the stepped arrangement, the yield per unit area increased with respect to the control (uniform arrangement) by obtaining a higher fruit set per plant, without decreasing its weight. Under this plant arrangement, the density increase from 6 to 8 plants·m-2 did not boost yield. The highest yield obtained was 12 kg·m-2 with 6 plants·m-2 of greenhouse area in a period of four months, from transplant to final harvest. This suggests the possibility of establishing three crop cycles per year, with an annual yield higher than those achieved by current greenhouse production systems.

 

Population densities and blunting levels for contrasting varieties of greenhouse tomatoes

Densidades de población y niveles de despunte para variedades contrastantes de jitomate en invernadero

Felipe Sánchez-Del Castillo; Esaú del Carmen Moreno-Pérez; José Cutberto Vázquez-Rodríguez; Miguel Ángel González-Núñez

Keywords: Solanum lycopersicum L., hydroponics, greenhouse, pruning, population density

10.5154/r.rchsh.2017.01.003

Received: 2017-01-18
Accepted: 2017-06-29
Available online: 2017-08-31
Pages:163-174

Due to population growth, scarce arable area and environmental problems, the need to increase agricultural production leads to the use of intensive production systems such as hydroponics and greenhouses. The aim of this study was to evaluate the behavior of agronomic management in varieties of tomato (Solanum lycopersicum L.), in particular the yield and its components in plants blunted or cut back to two and three clusters, established at different population densities. The varieties studied were: ‘Imperial’ (beef type), ‘Moctezuma’ (saladette type), ‘Pick ripe’ (beef type) and ‘Serengueti’ (saladette type). The first two show indeterminate growth and the other two determinate. Three population densities were established per blunting level (20, 16 and 12 plants∙m-2 for plants blunted above the second inflorescence, and 13, 10 and 7 plants∙m-2 for those blunted above the third inflorescence). A randomized complete block design was used with four replicates and a split-plot treatment arrangement with nested factors (densities within blunting levels). The beef varieties yielded 37 % more than the saladette ones. Among varieties with the same type of fruit, ‘Imperial’ yielded more than ‘Pick ripe’ and ‘Moctezuna’ surpassed ‘Serengueti’; that is, the indeterminate varieties yielded more than the determinate ones. The highest yield of ‘Imperial’ (38.16 kg∙m-2 of cultivated area, equivalent to 25 kg∙m-2 of greenhouse area) and ‘Moctezuma’ (28.16 kg∙m-2 of cultivated area, equivalent to 18.7 kg∙m-2 of greenhouse area) was achieved by establishing 13 plants∙m-2 and blunting above the third inflorescence.

Due to population growth, scarce arable area and environmental problems, the need to increase agricultural production leads to the use of intensive production systems such as hydroponics and greenhouses. The aim of this study was to evaluate the behavior of agronomic management in varieties of tomato (Solanum lycopersicum L.), in particular the yield and its components in plants blunted or cut back to two and three clusters, established at different population densities. The varieties studied were: ‘Imperial’ (beef type), ‘Moctezuma’ (saladette type), ‘Pick ripe’ (beef type) and ‘Serengueti’ (saladette type). The first two show indeterminate growth and the other two determinate. Three population densities were established per blunting level (20, 16 and 12 plants∙m-2 for plants blunted above the second inflorescence, and 13, 10 and 7 plants∙m-2 for those blunted above the third inflorescence). A randomized complete block design was used with four replicates and a split-plot treatment arrangement with nested factors (densities within blunting levels). The beef varieties yielded 37 % more than the saladette ones. Among varieties with the same type of fruit, ‘Imperial’ yielded more than ‘Pick ripe’ and ‘Moctezuna’ surpassed ‘Serengueti’; that is, the indeterminate varieties yielded more than the determinate ones. The highest yield of ‘Imperial’ (38.16 kg∙m-2 of cultivated area, equivalent to 25 kg∙m-2 of greenhouse area) and ‘Moctezuma’ (28.16 kg∙m-2 of cultivated area, equivalent to 18.7 kg∙m-2 of greenhouse area) was achieved by establishing 13 plants∙m-2 and blunting above the third inflorescence.

 

Sensitivity to fungicides of Phytophthora infestans (Mont.) de Bary in Chapingo, Mexico

Sensibilidad a fungicidas del Phytophthora infestans (Mont.) de Bary en Chapingo, México

Héctor Lozoya-Saldaña; Martha Nayeli Robledo-Esqueda; Patricia Rivas-Valencia; Sergio Sandoval-Islas; María Teresa Beryl Colinas y León; Cristian Nava-Díaz

Keywords: tizón tardío, papa, Solanum tuberosum, resistencia a fungicidas.

10.5154/r.rchsh.2017.01.004

Received: 2017-01-19
Accepted: 2017-07-16
Available online: 2017-08-31
Pages:175-186

  Chemical control of plant diseases exerts high selection pressure for the development of pathogen resistance to fungicides. The objectives of this study were to quantify the existence  of late blight in Solanum tuberosum L., detect the presence of variants of the oomycete resistant to agrochemicals and compare the different levels of resistance in the isolates from one cycle to another. Plots of the potato cv. Fianna, susceptible to late blight (Phytophthora infestans [Mont] de Bary), were exposed to natural infection of the pathogen to detect the presence of variants of the oomycete resistant to the agrochemicals from one cycle to another, and from in vivo with respect to in vitro conditions, by applying a half dose of fungicides. The disease reached 100 % final foliar infection in treatments with ciazofamid in 2011 and with fosetyl-Al in 2012. On the other hand, mandipropamid allowed only 21-22 % infection in both years in the field. However, 49 % of the P. infestans population was susceptible, 39 % was intermediate, and 19 % was resistant to this product in vitro. Plots treated with fosetyl-Al reached 80-100 % infection in the field, while in vitro 88 and 46 % of the P. infestans populations showed intermediate resistance when exposed to high dosages of the product, and 62 % were resistant at low dosage. Isolates from field plots with natural infection exposed to ciazofamid were all sensitive in vitro. The inconsistencies of the oomycete regarding fungicide resistance/sensitivity under in vivo/in vitro conditions, as well from one year to another, do not support behavior predictability. These results expose the great genetic plasticity of the oomycete in relation to its sensitivity to fungicides.

  Chemical control of plant diseases exerts high selection pressure for the development of pathogen resistance to fungicides. The objectives of this study were to quantify the existence  of late blight in Solanum tuberosum L., detect the presence of variants of the oomycete resistant to agrochemicals and compare the different levels of resistance in the isolates from one cycle to another. Plots of the potato cv. Fianna, susceptible to late blight (Phytophthora infestans [Mont] de Bary), were exposed to natural infection of the pathogen to detect the presence of variants of the oomycete resistant to the agrochemicals from one cycle to another, and from in vivo with respect to in vitro conditions, by applying a half dose of fungicides. The disease reached 100 % final foliar infection in treatments with ciazofamid in 2011 and with fosetyl-Al in 2012. On the other hand, mandipropamid allowed only 21-22 % infection in both years in the field. However, 49 % of the P. infestans population was susceptible, 39 % was intermediate, and 19 % was resistant to this product in vitro. Plots treated with fosetyl-Al reached 80-100 % infection in the field, while in vitro 88 and 46 % of the P. infestans populations showed intermediate resistance when exposed to high dosages of the product, and 62 % were resistant at low dosage. Isolates from field plots with natural infection exposed to ciazofamid were all sensitive in vitro. The inconsistencies of the oomycete regarding fungicide resistance/sensitivity under in vivo/in vitro conditions, as well from one year to another, do not support behavior predictability. These results expose the great genetic plasticity of the oomycete in relation to its sensitivity to fungicides.

 

Chronic infection of the citrus tristeza virus in Citrus sinensis / C. aurantium trees in a restrictive thermal regime in Yucatán

Infección crónica del virus de la tristeza de los cítricos en árboles de Citrus sinensis / C. aurantium en un régimen térmico restrictivo en Yucatán

Patricia Rivas-Valencia; Emiliano Loeza-Kuk; Santiago Domínguez-Monge; Claudia Tania Lomas-Barrié

Keywords: moderate isolate, epidemic, electrophoretic pattern, vigor, Toxoptera citricida.

10.5154/r.rchsh.2016.11.028

Received: 2016-11-16
Accepted: 2017-07-31
Available online: 2017-08-31
Pages:187-202

The citrus tristeza virus (CTV) is a pathogen present in almost all citrus areas. It reduces production in plantations with susceptible rootstocks, such as sour orange trees. The aim of this study was to temporally characterize the behavior of CTV considering its population structure (PS), vigor, concentration in tissues and availability of vectors, this on the basis of an analysis of the thermal conditions in Yucatán. In two sweet orange (C. sinensis) orchards in Yucatán, trees grafted onto sour orange (C. aurantium) were sampled and evaluated in terms of vigor for 12 years. Samples were analyzed by immunoprinting, single-strand conformation polymorphism (SSCP), and specific amplifications by real-time and conventional polymerase chain reaction (PCR). The incidence of CTV increased 40 % in four years. All samples analyzed (81) were negative for severe isolates; only T-30 isolates and minor changes in tree vigor were identified. The PS indicated changes with a tendency towards complexity (11 electrophoretic patterns in six haplotypes), a similarity coefficient of 0.80 and intrapopulation diversity of 65 %.The thermal regime (TR) was restrictive during 75 % of the year for CTV transmission and the optimum development of vector aphids. Pathogen PS and TR have contributed to the fact severe CTV epidemics have not been recorded; therefore, sour orange continues as a key element in the region’s citrus production despite the risk involved (commercializing propagating material that does not comply with NOM 079-FITO-2002).

The citrus tristeza virus (CTV) is a pathogen present in almost all citrus areas. It reduces production in plantations with susceptible rootstocks, such as sour orange trees. The aim of this study was to temporally characterize the behavior of CTV considering its population structure (PS), vigor, concentration in tissues and availability of vectors, this on the basis of an analysis of the thermal conditions in Yucatán. In two sweet orange (C. sinensis) orchards in Yucatán, trees grafted onto sour orange (C. aurantium) were sampled and evaluated in terms of vigor for 12 years. Samples were analyzed by immunoprinting, single-strand conformation polymorphism (SSCP), and specific amplifications by real-time and conventional polymerase chain reaction (PCR). The incidence of CTV increased 40 % in four years. All samples analyzed (81) were negative for severe isolates; only T-30 isolates and minor changes in tree vigor were identified. The PS indicated changes with a tendency towards complexity (11 electrophoretic patterns in six haplotypes), a similarity coefficient of 0.80 and intrapopulation diversity of 65 %.The thermal regime (TR) was restrictive during 75 % of the year for CTV transmission and the optimum development of vector aphids. Pathogen PS and TR have contributed to the fact severe CTV epidemics have not been recorded; therefore, sour orange continues as a key element in the region’s citrus production despite the risk involved (commercializing propagating material that does not comply with NOM 079-FITO-2002).