Resumen Introducción. La cebolla de bulbo (Allium cepa L.) es una hortaliza que se caracteriza por sus escamas carnosas susceptibles al ataque de fitopatógenos que causan pérdidas económicas. Los síntomas de tizón foliar y la pudrición del bulbo, pueden ser causados por diferentes géneros y especies bacterianas que pueden coinfectar al hospedante, lo que dificulta la identificación del agente causal. Objetivo. Evaluar el efecto de coinfecciones bacterianas en el tizón foliar y la pudrición del bulbo en cebolla. Materiales y métodos. Las bacterias fueron aisladas de plantas de cebollas con síntomas de tizón foliar y pudrición de bulbos, provenientes de cultivos ubicados en Choachí Cundinamarca, Colombia, recolectadas en junio de 2018. Los aislamientos bacterianos se purificaron, identificaron e inocularon de manera individual y en mezcla en hojas y bulbos de cebolla sanos. Se evaluaron seis tratamientos por órgano: tres con infecciones individuales y tres con coinfección. El progreso de la lesión se midió en ambos órganos durante doce días después de la inoculación. Resultados. Se obtuvieron dos especies bacterianas identificadas como Pantoea ananatis y Rahnella aquatilis a partir de los síntomas foliares y del bulbo de cebolla. En las infecciones individuales, la cepa P. ananatis presentó la mayor virulencia con un 34,29 % de daño en el bulbo y un 100 % en hoja, mientras que R. aquatilis generó el menor porcentaje de pudrición en el bulbo (8,87 %) y no produjo tizón. En las coinfecciones, la combinación de P. ananatis y R. aquatilis produjo los menores porcentajes de daño en el bulbo (15 %) y en la hoja (10 %), asociada a una disminución de la expresión de los síntomas. Conclusiones. R. aquatilis actuó como organismo antagonista de P. ananatis y provocó un retraso en el desarrollo de los síntomas de tizón foliar y pudrición del bulbo en cebolla.

Abstract Introduction. The onion bulb (Allium cepa L.) is a cultivated vegetable characterized by its fleshy scales susceptible to phytopathogen attacks causing economic losses. The symptoms of foliar wilting, blighting, and rot of bulb can be caused by different genera and bacterial species that can co-infect the host, making it difficult to identify the causal agent. Objective. To evaluate the effect of bacterial co-infections on foliar wilt and bulb rot in onion. Materials and methods. The bacteria were isolated from onion plants with symptoms of leaf blight and bulb rot, from crops located in Choachí Cundinamarca, Colombia, collected in June 2018. Bacterial isolates were purified, identified, and inoculated individually and in a mixture on healthy onion leaves and bulbs. Six treatments per organ were evaluated: three with individual infections and three with co-infection. The lesion progress was measured in both organs for twelve days after inoculation. Results. Two bacterial species identified as Pantoea ananatis and Rahnella aquatilis were obtained from the foliar and bulb symptoms. In individual infections, the P. ananatis strain presented the highest virulence causing 34.29 % bulb damage, and 100 % leaf damage, while the R. aquatilis generated the lowest percentage of rotting in the bulb (8.87 %) and it did not produce wilt. In co-infections, the combination of P. ananatis and R. aquatilis produced the lowest percentages of bulb (15 %) and leaf (10 %) damage, associated with a decrease in the symptom’s expression. Conclusion. R. aquatilis acted as an antagonistic organism of P. ananatis and causes a delay in the development of foliar wilt and bulb rot symptoms in onion.

RESUMO Em feijoeiro, pouco se conhece sobre o papel dos alelos Co-52 e Co-42 na ativação precoce da imunidade da planta ao fungo Colletotrichum lindemuthianum. Utilizando-se a cultivar Sutagao suscetível à antracnose e o feijoeiro G2333 resistente à antracnose, objetivou-se avaliar a presença dos alelos Co-42 e Co-52 por meio de marcadores SCAR, bem como sua função nas respectivas respostas de defesa, por meio de testes histoquímicos e expressão gênica diferencial. Os resultados mostraram que o alelo Co-52 contribui para as respostas de defesa contra a antracnose, uma vez que os feijoeiros suscetíveis com o alelo Co-42 e sem o alelo Co-52 diminuíram tanto a quantidade de depósitos de calose quanto o acúmulo de espécies reativas de oxigênio nos locais de ataque do fungo. Ademais, para a cultivar Sutagao, houve resposta tardia de genes relacionados à defesa, como PR-1, PR-3 e Pv-POD. O alelo Co-52 contribui para induzir mecanismos de defesa na interação entre Phaseolus vulgaris e C. lindemuthianum.

ABSTRACT The role of the Co-52 and Co-42 alleles in the early activation of bean immunity against Colletotrichum lindemuthianum is poorly known. Thus, by using the anthracnose-susceptible Sutagao cultivar and the anthracnose-resistant bean G2333, this study aimed to evaluate the presence of the Co-42 and Co-52 alleles by SCAR markers, as well as their role in the respective defense responses, using histochemical tests and diferential gene expression. The results showed that the Co-52 allele contributes to defense responses against anthracnose, since susceptible beans with the Co-42 allele and without the Co-52 allele decreased both the number of callose deposits and the accumulation of reactive oxygen species at the fungus attack sites. Additionally, for the Sutagao cultivar, there was a late response of defense-related genes such as PR-1, PR-3 and Pv-POD. The Co-52 allele contributes to induce defense mechanisms in the Phaseolus vulgaris and C. lindemuthianum interaction.

RESUMO A alface é o vegetal folhoso para salada mais cultivado na Colômbia, sendo o município de Madrid, no Departamento de Cundinamarca, o segundo maior produtor. Nessa região, foram detectadas plantas com sintomas foliares caracterizados por manchas necróticas de coloração castanha formando uma extensa área necrótica, clorose, distorção foliar e atrofia das plantas, causados por infecção viral possivelmente associada ao gênero Orthotospovirus. Objetivou-se identificar as espécies de orthotospovirus associadas aos sintomas, contribuindo para a atualização do estatuto fitossanitário da alface nessa região. Foi constatada a presença de orthotospovirus pelo ensaio de imunoabsorção enzimática (DAS-ELISA), embora a sequência do gene nucleocapsid (N) tenha confirmado a presença de Alstroemeria necrotic streak orthotospovirus, desconsiderando-se o Tomato spotted wilt orthotospovirus e Impatiens necrotic spot orthotospovirus previamente relatados para essa cultura, sendo este o seu primeiro relato para o cultivo de alface na Colômbia.

ABSTRACT Lettuce is the most cultivated leafy salad vegetable in Colombia, being the municipality of Madrid, in the Department of Cundinamarca, the second largest producer. In this region, lettuce plants with foliar symptoms characterized by brown necrotic spots forming an extended necrotic area, chlorosis, leaf distortion and plant stunting have been detected, possibly caused by a viral infection associated with the Orthotospovirus genus. This study aimed to identify the orthotospovirus species associated with those symptoms, contributing to updating the lettuce phytosanitary status in this region. The presence of orthotospovirus was confirmed by the enzyme-linked immunosorbent assay (DAS-ELISA), although the sequence of the nucleocapsid (N) gene confirmed the presence of Alstroemeria necrotic streak orthotospovirus, disregarding the Tomato spotted wilt orthotospovirus and Impatiens necrotic spot orthotospovirus previously reported for this crop, being this its first report in lettuce crops in Colombia.