Single-Site Root Inoculations on Eggplant with Microsclerotia of Verticillium dahliae

¿ For many soilborne plant pathogens, disease results from multiple root infections. Studying the infection dynamics of single or multiple propagules of these pathogens applied at one site of the root system may be the basis for understanding the development of disease caused by multiple root infections. The effect of single-site inoculations of roots of eggplant seedlings with microsclerotia of the wilt-causing fungus Verticillium dahliae, was studied. Experiments were conducted using specially designed pots which enabled the incorporation and removal of inoculum in the soil. Inoculations were carried out by placing microsclerotia, firmly embedded in small sections of polypropylene screen filter, directly below the growing tip of the main root of young eggplant seedlings. Three to 4 days after inoculation, the root had grown over the screen filter, and the filter was removed. Root platings showed high infection levels at the inoculation site, but also several (discrete) root infections were noted some distance above and below the site of inoculation. Exposure of the root to the lowest number of microsclerotia (26/inoculation site) was sufficient to lead to up to 65% root infections. Number of plants with root infections declined over time, ranging from a maximum of 65-100% 2-4 wk after inoculation, to 10-29% at 6-7 wk after inoculation. Apparently, V. dahliae died in nonsystemic infections after some time

Genotype, environment and their interaction on olive

Resumen del trabajo presentado en la 6th International Conference on the Olive Tree and Olive Products, celebrada en Sevilla (España) del 15 al 19 de octubre de 2018.The wide olive genetic patrimony has revealed high variability for most of the agronomic and oil quality traits of interest in olive growing. Few studies, however, have addressed the interaction of this variability with the environment, a subject of particular interest considering the natural high instability of the Mediterranean climate and the challenge of the predicted climate change. The current work presents results on the interaction between genotype and environment from multi-environment trials of olive cultivars and breeding selections, planted in different edaphoclimatic conditions of Andalusia, Southern Peninsular Spain and Canary Islands. For most of the agronomic and oil quality characters evaluated (flowering phenology, flower quality, pattern of oil accumulation, fatty acid composition and phenol content and composition), significant genotype and environment effects have been observed. For example, olive cultivars grown in Tenerife under much milder winter temperatures than in the Iberian Peninsula showed substantially earlierflowering and oil accumulation. Only in the case of flowering phenology was no significant genotype effect found. Furthermore, a strong genotype x environment effect was highly consistent in all characters considered. Regarding resistance to disease, such as Verticillium wilt, the variability of results from both natural and artificial inoculations also tends to indicate a considerable environmental effect and the need for careful testing of disease evolution. All this information strongly suggests the necessity of comparative trials of olive cultivars for both adequate choice of cultivar and final selection in breeding programs

Mejora de la sanidad y de la calidad en la propagación viverística del olivo

En: III Jornadas Técnicas del Aceite de Oliva, Madrid. Ed. INIA, Pp: 121-128.[ES] El uso de suelo y material de plantación libres de patógenos durante la propagación del olivo son medidas de lucha clave para prevenir las enfermedades causadas por patógenos de suelo transmisibles en material infectado y prevenir la dispersión de dichos patógenos. Por tanto, en este proyecto se ha investigado la detección molecular in planta de los patotipos defoliante y no defoliante de V. dahliae y se han estudiado diversas estrategias de desinfestación de sustratos viverísticos de olivo incluyendo la solarización de pilas cónicas de sustrato, enmiendas del sustrato con compost o la biofumigación con paja de sorgo. Además, se ha evaluado la eficacia de la termoterapia de plantones de olivo para controlar infecciones por nematodos fitoparásitos en el sistema radical de los cvs. Arbequina y Picual. Finalmente, también fue evaluado el efecto protector de las micorrizas arbusculares (Glomus intraradices, G. mossae, G. viscosum) contra infecciones por Meloidogyne spp. en plantones de olivo cvs. Arbequina y Picual. Se ha desarrollado un procedimiento basado en la nested-PCR para la detección in planta de los patotipos defoliante y no-defoliante de V. dahliae en plantones de olivo. Mediante el uso combinado de los iniciadores específicos de cada patotipo y diferentes protocolos de nested-PCR utilizando como molde ADN genómico total extraído de plantones de olivo, ha sido posible la detección consistente de ambos patotipos, tanto en raíces como en tallo de plantones infectados. La solarización durante 3 semanas de sustrato viverístico apilado (con una altura máxima de 40 cm) en Andalucía es apropiada para optimizar la producción de plantones de olivo libres de nematodos fitoparásitos. La enmienda del sustrato viverístico con residuos agroindustriales (p. ej. compost de corcho en proporción al 50%) puede ser una estrategia viable para minimizar las infestaciones de Meloidogyne spp. La biofumigación de sustratos conteniendo paja de sorgo (2% y 4% p/p) determinó una reducción significativa de la viabilidad e infectividad del inóculo de Meloidogyne incognita, independientemente de la concentración de sorgo y la cubierta con plástico. Los tratamientos de termoterapia (35-55º C) redujeron significativamente el crecimiento de los plantones en los cvs. Arbequina y Picual, independientemente de la edad de la planta (6-8 o 16-18 meses), y por tanto no son aconsejables para controlar infecciones de raíz por nematodos lesionadores. La inoculación de plantones con micorrizas arbusculares protegió a los plantones de olivo cvs. Arbequina y Picual de la patogénesis causada por Meloidogyne ssp. Este efecto de protección determinó un mayor crecimiento de las plantas micorrizadas e infectadas por el nematodo comparado con el de las plantas infectadas por el nematodo y no micorrizadas.[EN] The use of pathogen-free planting material and soil during olive plant propagation is essential for minimizing the effects of single or concomitant infections by soilborne pathogens during the early years of olive cultivation and for preventing pathogen spread. Consequently, in this project we have investigated the molecular in planta detection of defoliating and non-defoliating pathotypes of V. dahliae. Similarly, the potential of several soil disinfestation strategies as soil solarization of piled soil, amending of soil with compost or biofumigation with sorghum straw was studied. Similarly, the effectiveness of thermotherapy of olive planting stocks to control infections by plant-parasitic nematodes in root systems of cvs. Arbequina and Picual was also evaluated. Finally, the protective effect of arbuscular mycorrhizae (Glomus intraradices, G. mossae, G. viscosum) was also tested against infections of olive planting stocks by Meloidogyne spp. A PCR-based procedure has been developed for the early and consistent detection of defoliating and non-defoliating pathotypes of V. dahliae in infected olive planting stocks. By the combined use of specific external and internal primers and different nested-PCR protocols it was possible the detection of each of the two pathotypes of V. dahliae both in root and stem tissues of infected olive planting stocks. Solarization of piled soil (at a maximum depth of 40 cm) in nurseries in Andalucia is appropriate for optimizing production of plant-parasitic nematode-free olive plants. Amending olive soil nurseries with composted agro-industrial wastes (i.e. dry cork compost) may be a viable approach for minimizing soil infestations by Meloidogyne spp. Biofumigation of substrates used in nursery production by means of sorghum straw (2 % and 4 % w/w) as amendment determined a significant reduction of inoculum viability and infectivity of Meloidogyne incognita, and V. dahliae irrespective of straw concentration and plastic tarping. Hot-water treatments (35-55 ºC) significantly reduced plant growth in both olive cultivars Arbequina and Picual, irrespective of plant age (6-8 or 16-18 months), and therefore are not suitable for the control of root infections of olive planting stocks by root-lesion or root-knot nematodes. Inoculation of olive planting stocks with arbuscular mycorrhizal fungi protects ‘Picual’ and ‘Arbequina’ olives from pathogenesis caused by Meloidogyne spp. This protection effect determined higher growth rates in infected mycorrhized, plants compared with non mycorrhized infected controls.Peer reviewe

Genetic and virulence diversity in Verticillium dahliae populations infecting artichoke in Eastern-Central Spain

11 pages, 5 tablesSevere Verticillium dahliae attacks have occurred in artichoke crops in the Comunidad Valenciana region of eastern-central Spain since the late 1990s. Knowledge of genetic and virulence diversity in the pathogen population is a key factor for the management of the disease through disease risk assessment as well as development and use of resistant cultivars. V. dahliae isolates from artichoke (109 isolates) and cotton (three isolates) in that region were characterized by vegetative compatibility grouping (VCG), and specific polymerase chain reaction assays using three sets of primer pairs that differentiate the cotton-defoliating (D) and -nondefoliating (ND) V. dahliae pathotypes. In all, 35 and 39 V. dahliae isolates representative of the identified VCGs and geographic origins were tested for virulence to artichoke cvs. Nun 6374 and Nun 9444, and cotton cv. Acala SJ-2, respectively. Four VCGs were identified among 107 artichoke isolates, and 2 isolates were heterokaryon self-incompatible: VCG1A (one isolate), VCG2A (31 isolates), VCG2B (72 isolates), and VCG4B (three isolates). The three cotton isolates were VCG1A. Isolates in VCG2B were distributed across the region and were the most prevalent isolates in the northern part. Conversely, 83.9% of isolates in VCG2A were recovered from the southern part of the region. Two subgroups of isolates were identified in VCG2B based on heterokaryon compatibility with either international or local tester isolates, which further showed diversity in the amplification of 334- and 824-bp DNA fragments which are markers of the D and ND pathotypes, respectively. Virulence of isolates to artichoke and cotton correlated with VCG but the pattern of correlation varied with the host. VCG1A isolates from artichoke and cotton induced defoliation in cotton but not in artichoke. Collectively, isolates of VCG2B and VCG4B were the most virulent and isolates of VCG1A or HSI were the least virulent to artichoke; but isolates of VCG1A were more virulent to cotton than those of any other VCG. Also, molecular subgrouping in VCG2B determined by amplification of the 334- and 824-bp markers correlated with virulence of isolates to the two hosts tested.Grants AGL 2000-1444 from Comisión Interministerial de Ciencia y Tecnología (CICYT) and Grant GV-CAPA00-12 from Consellería de Agricultura, Pesca y Alimentación de Generalitat Valenciana. SpainPeer reviewe

Detection of the nondefoliating pathotype of Verticillium dahliae in infected olive plants by nested PCR

11 páginas, 4 figurasAn increasing incidence and distribution of verticillium wilt has occurred in the last few years in newly established olive orchards in southern Spain. This spread of the disease may result from use of Verticillium dahliae-infected planting material. The early in planta detection of the pathogen would aid the implementation of certification schemes for pathogen-free planting material. In this work, a nested polymerase chain reaction (PCR) method was developed for the in planta detection of the nondefoliating (ND) V. dahliae pathotype, aimed especially at nurseryproduced olive plants. For this purpose, specific primers were designed from the sequence of a 1958-bp random amplified polymorphic DNA (RAPD) marker of ND V. dahliae, and a procedure for the extraction of PCR-quality total genomic DNA from infected root and stem tissues of young olive plants was tested and further optimized. Nested PCR assays detected ND V. dahliae in 4- to 14-month-old artificially infected plants of three olive cultivars. The ND-specific PCR product was not amplified from total genomic DNA extracted from olive plants infected with the defoliating V. dahliae pathotype. Detection of the ND pathotype was effective from the very earliest moments following artificial inoculation of olive plants with a V. dahliae conidial suspension. Also, detection was achieved in inoculated, though symptomless, olive plants as well as in plants that were symptomatic but became symptomless by 217 days after inoculation.Comisión Interministerial de Ciencia y Tecnología (CICYT), España. 1FD97-0763-C03-01; Comunidad Europea, contrato no. QLK5-CT1999-01523.Peer reviewe