Identificación morfológica y comprobación de patogenicidad de agentes biológicos asociados Tabebuia rosea (Bertol) en etapa de vivero en Morelia (Risaralda) / Morphological identification of pathogenic agents associated with Tabebuia rosea (Bignoniaceae) in nursery stage in morelia (Risaralda)

Introducción. Las susceptibilidades de las plantaciones al ataque de organismos dañinos pueden ocasionar efectos nocivos para su desarrollo, cuando se considera que el nivel de daños ocasionado no se puede tolerar, es indispensable determinar acertadamente la naturaleza del agente causal, sea éste tipo biótico o abiótico; la acertada determinación del agente de un problema fitosanitario en un vivero o plantaciones forestale, se fundamenta en un análisis detallado de los factores que la pueden estar afectando. Tabebuia rosea o Guayacán rosado es una especie forestal nativa de amplia aceptación en el mercado, que presenta durante su etapa de vivero, limitantes en las fases de germinación, emergencia y sobrevivencia, por lo anterior el objetivo de esta investigación era la de Identificar morfológicamente los posibles agentes patógenos asociados a Tabebuia rosea en etapa de vivero y comprobar su patogenicidad. Metodología. Se tomaron plántulas de vivero, las cuales se les realizo un análisis de los signos y los síntomas para el aislamiento y siembra de zonas afectadas en agar papa dextrosa. En el cultivo mixto se identificó los posibles agentes patógenos, los cuales fueron sembrados para obtener cultivos puros, y utilizados en la prueba de patogenicidad, para la inoculación de las estructuras sanas (hojas, peciolos y tallos) y su respectivo control. Resultados. Se identificaron tres géneros de hongos Colletotrichum, Mucor, y Candida, y un género de nematodo denominado Meloidogyne. La prueba de patogenicidad para Colletotrichum y Candida mostraron relaciones significativas en el proceso de infección principalmente en estructuras foliares. Se concluye en este trabajo dos nuevos posibles géneros patógenos para Tabebuia rosea evidenciados en la prueba de patogenicidad. Y se corrobora que el género Meloidogyne es un patógeno severo en el guayacán rosado que ocasiona anomalías morfológicas en la raíz; cabe resaltar que es el primer reporte para el departamento de Risaralda

Introduction. The susceptibilities of plantations to attack by harmful organisms can cause harmful effects for their development, when it is considered that the level of damage caused cannot be tolerated, it is essential to correctly determine the nature of the causal agent, be it biotic or abiotic; The correct determination of the agent of a phytosanitary problem in a nursery or forest plantations is based on a detailed analysis of the factors that may be affecting it. Tabebuia rosea or pink Guayacán is a native forest species widely accepted in the market, which presents, during its nursery stage, limitations in the germination, emergence and survival phases, therefore the objective of this research was to morphologically identify the possible pathogens associated with Tabebuia rosea in the nursery stage and check its pathogenicity. Methodology. Nursery seedlings were taken, which were analyzed for signs and symptoms for the isolation and sowing of affected areas on potato dextrose agar. In the mixed culture, possible pathogens were identified, which were sown to obtain pure cultures, and used in the pathogenicity test, for the inoculation of healthy structures (leaves, petioles and stems) and their respective control. Results. Three fungal genera Colletotrichum, Mucor, and Candida, and a nematode genus named Meloidogyne were identified. The pathogenicity test for Colletotrichum and Candida showed significant relationships in the infection process mainly in leaf structures. Two new possible pathogenic genera for Tabebuia rosea evidenced in the pathogenicity test are concluded in this work. And it is corroborated that the genus Meloidogyne is a severe pathogen in the pink guayacán that causes morphological anomalies in the root; It should be noted that it is the first report for the department of Risaralda

Molecular identification, in vitro copper resistance and antibiotics susceptibility of the causal agent of the olive knot disease in Morocco

Aims@#This study aimed to i) identify Pseudomonas savastanoi pv. savastanoi (Pss) as a causal agent of the olive knot on the basis of biochemical, pathogenicity and PCR technique ii) investigate in vitro bacterial resistance toward copper-based compounds and efficiency of some antibiotics on pathogen suppression. @*Methodology and results@#Biochemical, pathogenicity and molecular identification based on alkaline method for the DNA extraction were performed to identify possible causal agent of the olive knot. Copper resistance for Pss strains was evaluated by inoculation of bacterial suspensions into YPG medium, containing the cupric sulfate at 0, 100, 250 and 500 ppm. The efficiency of eight antibiotics on Pss strain was evaluated at different concentrations. Fifty-nine isolates caused typical knots at the site of inoculation with bacterial suspensions. All isolates have been identified as Pss using specific primers. No resistance to copper was detected with concentration of 500 ppm. In contrast, copper resistance was found during 48 h with lower concentration (100 or 250 ppm). The maximal inhibition of Pss 2102-4M was observed with the highest concentration (20 μg/mL) of the Aureomycin, Streptomycin and Novobiocin with inhibition diameters of 30, 24 and 10 mm, respectively. Whereas, Colchicine, Bacitracin, Cephalex, Ampicillin and Cycloserine have no inhibitory effect on the Pss 2102-4M strain. @*Conclusion, significance and impact of study@#The alkaline method for the DNA extraction from pure culture was reliable and rapid and can be recommended for molecular detection the causal agent of the olive knot. This is the first report determined copper resistance levels of Moroccan strains of Pss and in vitro evaluated for the susceptibility towards the antibiotics.

Pathogenicity Tests and Evaluation of Efficacy of Fungicides Against Rhizoctonia Bataticola, the Causal Agent of Dry Root Rot of Chickpea.

The pathogen was identified based on its mycelial and sclerotial characters and pathogenicity test was proved by soil inoculation method. Efficacy of two non systemic fungicides (copper oxychloride and captan), two systemic fungicides (hexaconazole and tebuconazole) and one antifungal antibiotic validamycin each at different concentrations were tested against Rhizoctonia bataticola, incitant of dry root rot of chickpea under in vitro conditions. The fungicides copper oxychloride, captan, hexaconazole and tebuconazole were found to be highly effective (100%) in inhibiting the mycelial growth of the highly virulent pathogen at all the concentrations tested.

Optimization of Cultural Conditions for Cochliobolus heterostrophus Isolates from Infected Maize Plants from Different Agricultural Zones of Pakistan.

Southern corn leaf blight caused by Cochliobolus heterostrophus is a major foliar disease of maize crop in Pakistan. The disease affects leaves, leaf sheaths, ears and maize grains. Suitable physiological conditions which include different nutrient media, temperature, pH, carbon and nitrogen sources were determined for growth and reproduction of the pathogen. Among all media used viz, the best supporting medium was found to be Richard’s agar for the growth of pathogen after 7 days of incubation. Different temperatures (20, 25, 30 and 35ºC) were selected for mycelia growth of the pathogen, among which maximum growth was found to be at 30ºC (80 mm colony size) and minimum at 35ºC (35 mm). Maximum radial colony growth of the pathogen was observed at neutral pH (80 mm). Sucrose and potassium nitrate (KNO3) were found to be the most appropriate sources of carbon and nitrogen respectively.

Métodos de inoculação de Phakopsora euvitis Ono em Vitis labrusca L / Inoculation methods of Phakopsora euvitis Ono in Vitis labrusca L

A ferrugem é uma das principais doenças da videira, com ocorrência registrada em diversas regiões produtoras. Neste trabalho, foram avaliados três métodos de inoculação de Phakopsora euvitis em mudas de videira 'Isabel' com o objetivo de selecionar um método para determinação da patogenicidade. Mudas oriundas de bacelos de videira foram inoculadas com esporos de P. euvitis e mantidas sob temperatura entre 25±4°C e UR 85±10 por cento durante 13 dias. O delineamento experimental foi inteiramente casualizado, com 10 repetições. Os tratamentos foram compostos por: T1 - pincelamento de esporos; T2 - pulverização com suspensão de esporos com 2,7x10³ esporos mL-1; T3 - discos de folhas de videira com sintomas afixados em cinco folhas por planta; e T4 - Testemunha. O método do pincelamento de esporos foi o mais eficiente, com início dos sintomas a partir do quinto dia e, após 13 dias, 100 por cento das folhas apresentavam sinais do patógeno.

Rust is one of the most important diseases in grapevine, with occurrence recorded in many production areas. In this research it was evaluated three methods of Phakopsora euvitis inoculation on grapevine seedlings cv. 'Isabel' with the objective of selecting an inoculation method for rapid pathogenicity determination. Grapevine seedlings were inoculated with P. euvitis and maintained under conditions of 25±4C and UR 85±10 percent for 13 days. The experimental design was completely randomized, with 10 replications. The treatments were: T1 - brush of pathogen spores; T2 - spores suspension spraying (2.7x10³ spores mL-1); T3 - disks of grapevine leaves with symptoms stuck in five leaves per plant and T4 - control. The spore brushing method was the most efficient, showing early symptoms at five days, and 100 percent of the leaves showing pathogen symptoms 13 days after treatment.