ABSTRACT
Resumen Para aumentar la resistencia de las plantas a los patógenos se requiere de un trabajointerdisciplinario de las ciencias biológicas y agrícolas. En este escenario, la fitopatología se habeneficiado del encuentro de disciplinas biológicas claves, como la ecología, la evolución y labiología molecular. Sin embargo, este encuentro no ha estado exento de controversia entre losacadémicos de estas disciplinas, quienes a menudo han otorgado diferentes significados a unmismo concepto. Este documento tiene como propósito ofrecer una visión abarcativa y modernade la resistencia de las plantas a los patógenos, enmarcada dentro del concepto clásico deresistencia vertical y horizontal propuesto por Van der Plank. Este concepto tiene implicacionesen áreas centrales para la agricultura, como el fitomejoramiento y la genética vegetal, loque justifica su uso como el marco conceptual indicado. Dentro de este contexto se explicanotros conceptos clásicos de la fitopatología en combinación con descripciones modernas de lainteracción entre plantas y patógenos, y se discute cómo estos conceptos están relacionadoscon la resistencia cuantitativa y de campo. Asimismo, esta revisión tiene un propósito adicionalcomo aporte a la ense˜nanza de la fitopatología en la América de habla hispana, dado que enesta región existe, además de la barrera interdisciplinaria, un factor adicional y persistenteque impide llevar la discusión a un terreno común: la baja competencia lingüística en el idiomainglés en todos los niveles educativos. Esta revisión pretende ser una herramienta de apoyopara los docentes de fitopatología de la región, interesados en explicar los conceptos modernosde resistencia a patógenos en plantas.
Abstract Understanding plant resistance requires an interdisciplinary effort between biolo-gical and agricultural sciences. In this setting, phytopathology has experienced an upsurge of interest from researchers and scholars in the disciplines of ecology, evolution and molecular biology. This encounter did neither avoid misunderstandings among scholars nor the use of similar concepts with different meanings. The purpose of this paper is to offer a modern comprehensive view of plant resistance against pathogens using a classical phytopathology concept as framework: Van der Plank s concept of horizontal and vertical resistance. This concept is used in other agricultural science disciplines (plant breeding and genetics), supporting why it is a proper framework for explaining plant resistance. Within this frame, other classical phytopathologycal concepts are explained in combination with modern model descriptions of plant-pathogen interactions and how all these concepts are related with quantitative and field resistance. This review is written in Spanish because it serves an additional purpose. In the Spanish-speaking America, besides interdisciplinarity, phytopathology as an academic discipline faces another challenge: the students' low-English language proficiency. In this regard, this review intends to become a companion guide for plant-pathology teachers in the region interested in providing an insight into the modern concepts of plant resistance.
ABSTRACT
Okra leaf curl disease (OLCD) is a major constraint on okra (Abelmoschus esculentus L. Moench) production in West Africa. The most effective way of managing this disease is through breeding and planting of resistant varieties. In order to identify sources of resistance and or tolerance, 21 okra genotypes were screened against OLCD in field trials which were conducted from May to October, 2015 (rainy season) and November 2015 to March 2016 (dry season). Field resistance was assessed at 2, 6 and 10 weeks after sowing (WAS) based on disease symptoms, and then confirmed by PCR amplification of viral coat protein gene. Populations of whitefly (Bemisia tabaci), the vector of begomoviruses associated with OLCD, as well as fruit yields were also assessed. Both PCR and field trials showed that all the okra genotypes were susceptible to the viral infection. The genotypes varied significantly (P<0.05) among them in terms of severity of OLCD, whitefly infestation, mean fruit yield (t ha-1), and the average fruit weight per plant. Higher cumulative average population of whitefly and mean fruit yield (t ha-1) were recorded in the dry season than in the rainy season. Genotypes GH5332 and GH6105 consistently showed mild symptoms of OLCD and also had very high fruit yields of 11.88 t ha-1 and 9.34 t ha-1 respectively in the rainy season, and 6.108 t ha-1and 4.05 t ha-1 respectively in the dry season, far above the overall mean yields for all the okra genotypes. Both genotypes GH5332 and GH6105 should be evaluated multi-locationally at farmers’ fields prior to their release as varieties or they should be incorporated into breeding lines.
ABSTRACT
Bacillus thuringiensis subsp. israelensis (Bti) is increasingly used worldwide for mosquito control and is the only larvicide used in the French Rhône-Alpes region since decades. The artificial selection of mosquitoes with field-persistent Bti collected in breeding sites from this region led to a moderate level of resistance to Bti, but to relatively high levels of resistance to individual Bti Cry toxins. Based on this observation, we developed a bioassay procedure using each Bti Cry toxin separately to detect cryptic Bti-resistance evolving in field mosquito populations. Although no resistance to Bti was detected in none of the three mosquito species tested (Aedes rusticus, Aedes sticticus and Aedes vexans), an increased tolerance to Cry4Aa (3.5-fold) and Cry11Aa toxins (8-fold) was found in one Ae. sticticus population compared to other populations of the same species, suggesting that resistance to Bti may be arising in this population. This study confirms previous works showing a lack of Bti resistance in field mosquito populations treated for decades with this bioinsecticide. It also provides a first panorama of their susceptibility status to individual Bti Cry toxins. In combination with bioassays with Bti, bioassays with separate Cry toxins allow a more sensitive monitoring of Bti-resistance in the field.