Cassava Frogskin Disease: Current Knowledge on a Re-Emerging Disease in the Americas.

Cassava frogskin disease (CFSD) is a graft-transmissible disease of cassava reported for the first time in the 1970s, in Colombia. The disease is characterized by the formation of longitudinal lip-like fissures on the peel of the cassava storage roots and a progressive reduction in fresh weight and starch content. Since its first report, different pathogens have been identified in CFSD-affected plants and improved sequencing technologies have unraveled complex mixed infections building up in plants with severe root symptoms. The re-emergence of the disease in Colombia during 2019-2020 is again threatening the food security of low-income farmers and the growing local cassava starch industry. Here, we review some results obtained over several years of CFSD pathology research at CIAT, and provide insights on the biology of the disease coming from works on symptoms' characterization, associated pathogens, means of transmission, carbohydrate accumulation, and management. We expect this work will contribute to a better understanding of the disease, which will reflect on lowering its impact in the Americas and minimize the risk of its spread elsewhere.

Emerging pests and diseases of South-east Asian cassava: a comprehensive evaluation of geographic priorities, management options and research needs.

Cassava is a major staple, bio-energy and industrial crop in many parts of the developing world. In Southeast Asia, cassava is grown on >4 million ha by nearly 8 million (small-scale) farming households, under (climatic, biophysical) conditions that often prove unsuitable for many other crops. While SE Asian cassava has been virtually free of phytosanitary constraints for most of its history, a complex of invasive arthropod pests and plant diseases has recently come to affect local crops. We describe results from a region-wide monitoring effort in the 2014 dry season, covering 429 fields across five countries. We present geographic distribution and field-level incidence of the most prominent pest and disease invaders, introduce readily-available management options and research needs. Monitoring work reveals that several exotic mealybug and (red) mite species have effectively colonised SE Asia's main cassava-growing areas, occurring in respectively 70% and 54% of fields, at average field-level incidence of 27 ± 2% and 16 ± 2%. Cassava witches broom (CWB), a systemic phytoplasma disease, was reported from 64% of plots, at incidence levels of 32 ± 2%. Although all main pests and diseases are non-natives, we hypothesise that accelerating intensification of cropping systems, increased climate change and variability, and deficient crop husbandry are aggravating both organism activity and crop susceptibility. Future efforts need to consolidate local capacity to tackle current (and future) pest invaders, boost detection capacity, devise locally-appropriate integrated pest management (IPM) tactics, and transfer key concepts and technologies to SE Asia's cassava growers. Urgent action is needed to mobilise regional as well as international scientific support, to effectively tackle this phytosanitary emergency and thus safeguard the sustainability and profitability of one of Asia's key agricultural commodities. © 2016 Society of Chemical Industry.

Isolation of phytoplasmas associated to frogskin disease in cassava / Aislamiento de fitoplasmas asociados a cuero de sapo en yuca

ABSTRACT Frogskin is the most limiting disease of cassava crops in Colombia, causing losses in production up to 90%. Since this disease was associatated with 16SrIII phytoplasma presence, a study was carried out to isolate this phytoplasma using liquid and solid culture media. Root, petiol, stem, leaf and cutting tissues of cassava affected by frogsking were employed as source materials. Molecular and microscopy techniques were applied to verify the phytoplasma growth and to discard other microorganism´s presence. The results showed that the media consistently allow phytoplasma growth, and colonies in solid medium were obtained. PCR, qPCR and sequencing tests confirmed the presence of 16SrIII group phytoplasmas in both liquid and solid culture media. Additionally, the isolation of a pigeon pea witches' broom phytoplasma strain (group 16SrIX) was obtained from stems, petioles and flowers of symptomatic Catharanthus roseus confirming the effectiveness of the medium in the phytoplasma isolation and culture. This is the first isolation of field-collected phytoplasma strains in groups 16SrIII and 16SrIX in America that confirm and corroborate the previous results in phytoplasma cultivation achieved on micropropagated and field-collected phytoplasma infected samples.

RESUMEN En Colombia, el ''cuero de sapo'' es la enfermedad más limitante del cultivo de yuca, que ocasiona pérdidas en producción de raíces hasta del 90%. La presente investigación tuvo como objetivo, el aislamiento in vitro del fitoplasma asociado a cuero de sapo. Para ello, se emplearon medios de cultivo líquido y sólido, usando tejidos de raíces, peciolos, tallos, hojas y semillas de yuca, afectada por la enfermedad. Pruebas de PCR, qPCR, secuenciación, microscopia de luz y microscopia electrónica de transmisión fueron aplicadas, para verificar el crecimiento de fitoplasmas y descartar la presencia de otros microrganismos. Los resultados muestran que los medios permiten, consistentemente, el crecimiento de fitoplasmas, obteniendo colonias en medio sólido a partir de medio líquido. Las pruebas de PCR, qPCR y secuenciación confirmaron presencia de Cassava frogskin phytoplasma del grupo 16SrIII, en los dos medios de cultivo. Además, a partir de las colonias, se lograron fotografías de células con morfología y tamaño similares a las fitoplasmáticas. Es la primera vez, en el mundo, que se consolida información suficiente del aislamiento de fitoplasmas en medio artificial. Adicionalmente, se logró el aislamiento de Pigeon pea witches´ broom phytoplasma del grupo IX, a partir de tallos, peciolos y flores de vinca (Catharanthus roseus), con síntomas asociados a fitoplasmas. Este proceso permitió corroborar la efectividad del medio y la morfología de las células fitoplasmáticas, bajo microscopia electrónica.

Determining the pharmacological activity of Physalis peruviana fruit juice on rabbit eyes and fibroblast primary cultures.

PURPOSE: The pharmacologic activity of compounds isolated from Physalis peruviana has been demonstrated. The use of this fruit juice for treating pterygium has been reported in Colombian traditional medicine. However, studies demonstrating the fruit juice's pharmacologic activity when used in this disease have not been published to date. In the present study the anti-inflammatory and cytostatic activities of P. peruviana fruit juice in a rabbit eye inflammatory model were investigated. METHODS: A novel rabbit eye inflammation model was developed for studying the juice's anti-inflammatory activity (based on an adaptation of the Draize test). Cytostatic activity was evaluated by measuring and comparing growth rates of cultured fibroblasts exposed and not exposed to various fruit juice concentrations. RESULTS: P. peruviana fruit juice exhibited a mild anti-inflammatory activity compared with methylprednisolone, a known anti-inflammatory drug. An interesting dose-dependent cytostatic effect on cultured fibroblasts was also established. CONCLUSIONS: The data found suggest that the P. peruviana fruit juice anti-pterygium effect described in traditional medicine may be related to its inhibiting fibroblast growth. The present study contributes to the pharmacologic knowledge regarding a remedy commonly used in Colombian traditional medicine.