Liliana María Aragón-Caballero

Phytophthora capsici is an aggressive pathogen in escabeche pepper on the Peruvian coast. Root rot has a strong correlation with humidity and environment. Disease behavior was evaluated epidemiologically using spatiotemporal variables. Severity was evaluated according to the advance of the secondary symptom according to grades 1 to 5. Then, coordinates of each plant were established by photogrammetric survey of a field with 1705 escabeche pepper plants. For temporal analysis, severity was adjusted to an exponential model (R2 = 0.909) and incidence to a Gompertz model (R2 = 0.921) that detected an initial delay of the disease due to temperature. For the spatial analysis, the Global Moran Index (Ii) showed a high spatial dependence of the disease reaching a peak of 0.4 and 0.7 for severity and incidence, respectively. Also, heat maps related to the Local Ii were generated from which an initial source of infestation was determined where the furrow irrigation started in random infestations. Then, the infestation spots were settled in areas of surface water accumulation. Also, rhizosphere samples were collected per plant by degree of severity on V8 or CMA whit PARB and PDA-A selective medium. As a result, significant differences were obtained between grade 1, grade 2, 3, 4 and grade 5. In addition, the effect on yield was significant for plants with grade 4 and 5 with respect to fruit weight (22.3 and 18.5g/fruit) and weight per plant (509.5 and 371.8g/plant), respectively.

The production and export of avocado fruits, cultivar Hass, has grown exponentially in recent years in Peru, however, a high incidence of symptoms such as regressive death, cankers on plant branches, and fruit rot have been observed affecting optimal crop production and fruit quality. These symptoms are mainly generated by Lasiodiplodia theobromae fungus, whose control is limited to a few active ingredients that tend to generate pathogen resistance. The present investigation had as objective to evaluate the inducing effect of resistance in the control of Lasiodiplodia theobromae in avocado (Persea americana) cultivar Hass of five bioproducts: ProtecSea, Barrera, Timorex Gold, T 22, Vacun Q Pro and water as a control treatment, with a total of 6 treatments with 4 replications, 3 avocado trees per replication. One-year-old avocado trees cultivar Hass were used. Treatments were applied three times via drench at ten-day intervals. Five days after the last application L. theobromae was inoculated in the avocado trees cultivar ‘ Hass’ and 40 days after the inoculation, the parameters were evaluated: length of the disease lesion, percentage of dry matter of the roots and leaves, and length of the roots. It was observed that treatments, with the exception of treatment T1 (Control), reduced the length of the disease lesion infected by L. theobromae inside the stem. Treatment T6 (T.22) resulted in a higher percentage of root dry matter (46.52 %) compared to the control treatment (41.21 %). On the other hand, there were no significant differences in leaf dry matter content among treatments. Additionally, it was observed that treatment T2 (ProtecSea) reported a root length of 56.80 cm, followed by treatment T6 (T.22) with 54.90 cm. These results are important to continue with investigations into inducing systemic resistance in plants.

Botrytis cinérea Pers. (B.C.) es el fitopatógeno responsable de una amplia gama de síntomas en cultivos de gran importancia como el tomate. Su control principalmente se basa en la aplicación de fungicidas químicos; sin embargo, su uso excesivo conduce al desarrollo de cepas resistentes, contaminación ambiental y efectos perjudiciales para la salud humana. Por ello, el objetivo el estudio fue evaluar el efecto de dos fertilizantes foliares que contienen cobre, zinc y ácido cítrico en el control del moho gris B.C. en tomate cv. Huascarán. En condiciones de laboratorio se evaluó el efecto de los fertilizantes foliares en la inhibición del crecimiento micelial a los 6 DDI (días después de inoculación) con el método del medio envenenado en PDA (agar de papa y dextrosa); y en condiciones de campo se aplicaron los fertilizantes foliares por ocho semanas variando la frecuencia de aplicación en una y dos semanas. Los resultados mostraron que en condiciones de laboratorio el ácido cítrico incrementó la actividad antifúngica complementándose bien con las partículas de Cu y Zn presentando el T3 el mejor porcentaje de inhibición del crecimiento micelial. En condiciones de campo la mayoría de las aplicaciones tuvieron un control significativo de B.C. en el follaje, pero no en flores ni en frutos; destacando aquellos donde se aplicó los fertilizantes foliares semanalmente. Estos resultados son importantes para desarrollar estrategias dirigidas a mejorar el control de la enfermedad y disminuir el uso masivo de fungicidas.

Un sistema agroforestal (SAF) se caracteriza por tener una diversidad de componentes como especies forestales maderables y no maderables, así como cultivos, pastos o un sistema de producción ganadera. Esta diversidad de componentes en el sistema reduce la intensidad de las enfermedades, por ejemplo, las foliares. Los objetivos fueron detectar los microorganismos fúngicos asociados a las manchas foliares de las especies vegetales que forman parte de los sistemas de producción agroforestal de los agricultores de Yurimaguas (Loreto) que participaron en el SLA y determinar el nivel de incidencia de las manchas foliares en los sistemas de producción agroforestal. En estas fincas se implementaron diferentes sistemas de cultivo de la tierra, como la palma (Bactris gasipaes) para producir palmitos y cacao (Theobroma cacao), incluyendo el plátano (Mussa sp.). También, sistemas silvopastoriles con especies maderables de crecimiento rápido y lento y ganado con pastos para el pastoreo y la reforestación en áreas de bosques secundarios en estado de degradación. Se realizó la prospección, recolección y determinación de la incidencia de las enfermedades en cada finca, y posteriormente se identificaron con métodos moleculares utilizando los cebadores ITS 1 e ITS 4. Los síntomas que se observaron, predominantemente, fueron manchas foliares en cacao (patrón), palma y plátano. No se observaron síntomas de marchitamiento, decaimiento o podredumbre. La incidencia se evaluó en dos periodos de recolección (2018 y 2019). Los hongos aislados de las manchas foliares fueron Pestalotiopsis sydowiana y Colletotrichum siamense como agentes causantes de las manchas foliares en palma y cacao, y Mycosphaerella fijiensis en plátano. Al determinar la incidencia desde abril de 2018 hasta octubre de 2019, se observó una disminución de este parámetro para las fincas con palma, especialmente en aquellas donde la implementación consistió en mejorar el sistema de producción a través de la fertilización con base en los requerimientos del cultivo. Se concluyó que la mayor intensidad de enfermedades foliares se presentó en los sistemas agrícolas con monocultivo de palma con un 100 % al inicio de la evaluación, y para los sistemas agroforestales en el prototipo silvopastoril, solo se detectó en un rango de 0 % a 25 %.

Tomato susceptibility/resistance to stem canker disease caused by Alternaria alternata f. sp. lycopersici and its pathogenic factor AAL-toxin is determined by the presence of the Asc1 gene. Several cultivars of commercial tomato (Solanum lycopersicum var. lycopersicum, SLL) are reported to have a mutation in Asc1, resulting in their susceptibility to AAL-toxin. We evaluated 119 ancestral tomato accessions including S. pimpinellifolium (SP), S. lycopersicum var. cerasiforme (SLC) and S. lycopersicum var. lycopersicum “jitomate criollo” (SLJ) for AAL-toxin susceptibility. Three accessions, SP PER018805, SLC PER018894, and SLJ M5-3, were susceptible to AAL-toxin. SLC PER018894 and SLJ M5-3 had a two-nucleotide deletion (nt 854_855del) in Asc1 identical to that found in SLL cv. Aichi-first. Another mutation (nt 931_932insT) that may confer AAL-toxin susceptibility was identified in SP PER018805. In the phylogenetic tree based on the 18 COSII sequences, a clade (S3) is composed of SP, including the AAL-toxin susceptible PER018805, and SLC. AAL-toxin susceptible SLC PER018894 and SLJ M5-3 were in Clade S2 with SLL cultivars. As SLC is thought to be the ancestor of SLL, and SLJ is an intermediate tomato between SLC and SLL, Asc1s with/without the mutation seem to have been inherited throughout the history of tomato domestication and breeding.

T. minima is an heteroecious rust, included in the A1 list of quarantine pest for Perú; it can cause severe defoliation on Blueberry reducing the yields and can represent a limitation in the export...

Dentro de las enfermedades que se presentan en la producción de crisantemo a nivel mundial, una de las más importantes es la pudrición de raíz causada por Pythium sp. por lo anterior, se realizó una investigación cuyo objetivo fue evaluar la dosis óptima de biocontroladores y fungicidas químicos sobre Pythium sp. La aplicación de los tratamientos se llevó a cabo tanto en laboratorio como en el cultivo bajo invernadero. Se empleó un diseño completamente al azar con 10 tratamientos (testigo, metalaxil y clorotalonil, azoxystrobin, Trichoderma harzianum, Bacillus subtilis, aplicados en dos dosis 100% de la aplicación comercial y 150%). Los resultados obtenidos en la fase de laboratorio mostraron que el testigo inoculado con oosporas tuvo el mayor crecimiento micelial de Pythium sp., 36,43 cm en diámetro, así mismo los tratamientos con fungicidas químicos presentaron un control del 100% ya que no hubo crecimiento de Pythium sp. En el invernadero, las plantas de crisantemo mostraron los mejores resultados cuando se aplicó T. harzianum en dosis de 150%, ya que se presentó tan solo un 9,33% de incidencia, mientras que referente a la severidad, el tratamiento más eficaz fue con T. harzianum en dosis comercial con 4,9%. El mejor comportamiento de las características agronómicas de las plantas de crisantemo se presentó con la aplicación de T. harzianum con dosis de 150%, ya que las plantas mostraron mayor altura, masa radicular fresca y seca, masa aérea fresca y seca, número de botones, diámetro floral y masa floral.

Virus emergence is a complex phenomenon, which generally involves spread to a new host from a wild host, followed by adaptation to the new host. Although viruses account for the largest fraction of emerging crop pathogens, knowledge about their emergence is incomplete. We address here the question of whether Pepino Mosaic Virus (PepMV) emergence as a major tomato pathogen worldwide could have involved spread from wild to cultivated plant species and host adaptation. For this, we surveyed natural populations of wild tomatoes in southern Peru for PepMV infection. PepMV incidence, genetic variation, population structure, and accumulation in various hosts were analyzed. PepMV incidence in wild tomatoes was high, and a strain not yet reported in domestic tomato was characterized. This strain had a wide host range within the Solanaceae , multiplying efficiently in most assayed Solanum species and being adapted to wild tomato hosts. Conversely, PepMV isolates from tomato crops showed evidence of adaptation to domestic tomato, possibly traded against adaptation to wild tomatoes. Phylogenetic reconstructions indicated that the most probable ancestral sequence came from a wild Solanum species. A high incidence of PepMV in wild tomato relatives would favor virus spread to crops and its efficient multiplication in different Solanum species, including tomato, allowing its establishment as an epidemic pathogen. Later, adaptation to tomato, traded off against adaptation to other Solanum species, would isolate tomato populations from those in other hosts. IMPORTANCE Virus emergence is a complex phenomenon involving multiple ecological and genetic factors and is considered to involve three phases: virus encounter with the new host, virus adaptation to the new host, and changes in the epidemiological dynamics. We analyze here if this was the case in the recent emergence of Pepino Mosaic Virus (PepMV) in tomato crops worldwide. We characterized a new strain of PepMV infecting wild tomato populations in Peru. Comparison of this strain with PepMV isolates from tomato crops, plus phylogenetic reconstructions, supports a scenario in which PepMV would have spread to crops from wild tomato relatives, followed by adaptation to the new host and eventually leading to population isolation. Our data, which derive from the analysis of field isolates rather than from experimental evolution approaches, significantly contribute to understanding of plant virus emergence, which is necessary for its anticipation and prevention.