This news article was originally written in Spanish. It has been automatically translated for your convenience. Reasonable efforts have been made to provide an accurate translation, however, no automated translation is perfect nor is it intended to replace a human translator. The original article in Spanish can be viewed at Trabajos de selección de material vegetal de olivo resistente a la Verticilosis
The Centre 'Alameda of the Bishop' of the IFAPA in Córdoba develops a line of work that tackles the evaluation of all the possible new sources of resistance to this illness
Works of selection of vegetal material of olivo resistant to the Verticilosis
Lorenzo León, Rocío Arias-Calderón, José Bejarano-Fortress, Angjelina Belaj, Raúl Of Rosa, Dolores Rodríguez-Sworn (IFAPA - Centre 'Alameda of the Bishop')23/03/2012
The Verticilosis of the olivo, caused by the fungus of floor 'Verticillium dahliae' Kleb., it represents the phytosanitary ware problem more important of the olivar in the actuality, so much in Spain as in other producing countries (Bejarano Fortress, 2005to; López-Escudero et al., 2010; Moraño Dark et al., 2011). The importance of the illness has aggravated in the last years of parallel form to the increase of surface and intensification of the crop, ocasionando significant reductions in the production and even the death of the trees affected.
Several factors have influenced in the increase in the extension and gravity of the attacks of the Verticilosis of the olivo recently. Between them it fits to quote the dispersion of isolated of the fungus extremely virulentos, the establishment of new plantations of olivar with cultivated susceptible in floors infested by the pathogen, the utilisation of material of plantation asintomático but infected and the application of practices of crop (irrigation, vegetal covers based in rests of poda infected, etc.) that favour the illness (Photo 1).
Photo 1: Olivar showing characteristic symptoms of Verticilosis.
The Verticilosis of the olivo is an illness of complex nature been due to: the variability patogénica in the populations of the fungus, the high susceptibility to the Verticilosis of cultivated them of olivo of greater implantation in the actuality, the prolonged capacity of survival of the esclerocios of the fungus in the floor, the wide range of cultured and wild plants that are guests of 'V. dahliae', the location of the pathogen in the xylem of the plants infected during the phase parasítica of his cycle of life that does it inaccessible to determinate treatments, and the multiple means by means of which can disperse the inoculum of the fungus (Bejarano Fortress, 2005b; Rodríguez-Jury and Bejarano-Fortress, 2007; Jiménez Díaz et al., 2008). Thus, the control of the Verticilosis of the olivo is particularly complicated and the handle of the illness has to be posed under strategies of integrated cheese cheese control in which they combine measured of fight that can be applied before, during and/or after the plantation. Between them, the utilisation of resistant varieties represents an option of particular importance by his economy, efficiency and respect to the environingingment, and because it can combine with other methods of fight to improve the control.
The control of the Verticilosis of the olivo is particularly complicated and the handle of the illness has to be posed under strategies of integrated cheese cheese control
The works realised to date have considered the evaluation of the resistance of different varieties of olivo in function of the answer to the infection by 'V. dahliae' Observed in diverse experimental conditions. The resistance or susceptibility of many of the varieties represented in the World Bank of Germoplasma of Olivo of the Centre IFAPA 'Alameda of the Bishop' of Córdoba, has characterised in front of isolated highly virulentos pertaining to the patotipo defoliant (D) of 'V. dahliae' And/or isolated moderately virulentos of the patotipo no defoliant (ND) of the pathogen in conditions controlled (López-Escudero et al., 2005; Rodríguez Sworn, 1993; Trapero et al., 2010). These works have showed that the majority of the varieties evaluated, included the ones of greater diffusion in the actuality (like Arbequina, Cornicabra, Hojiblanca, Camomile of Seville and Picual), are extremely susceptible to the patotipo D, that is the most extended at present in the main zones of crop. Only a very reduced number of varieties (like ‘Changlot Real', ‘Dolce Agogia', ‘Empeltre', ‘Frantoio', ‘Grosal of Albocafer', ‘Kato Drys', ‘Camomile Picúa' and ‘Oblonga') have exhibited levels of moderated or considerable resistance to the development of symptoms caused by this patotipo. However, it does not know immunity to the infection by the pathogen, and the vascular infections occur with frequency even in absence of symptoms in varieties of olivo with high resistance to the patotipo D (Rodríguez Sworn, 1993). Likewise, in investigations realised in other countries the success in finding varieties of olivo more resistant that the previous has been limited. This situation and the scarce market of the few varieties with high level of resistance has carried to explore the utility of ‘Frantoio' like pattern for the control of the Verticilosis, having showed in some works his potential to control eficientemente the development of symptoms in susceptible varieties placed on said root (Sweeps Soriano et al., 2003).
One of the main strategies in the fight against the Verticilosis in different crops like algodonero, strawberry, tomato or potato, consists in the continuous obtaining of resistant varieties through programs of improvement. However, in spite of the importance of the Verticilosis of the olivo in the majority of countries olivareros, the greater part of the programs of improvement of olivo in course in the actuality do not consider like aim the improvement by resistance to the Verticilosis, by what do not know that it exist available information on the genetic control of the resistance to this illness in olivo.
Also the employment of wild relatives has used in the improvement of a lot of species to transfer different characteristic, mainly of resistance to plagues and illnesses including in some cases resistance to the Verticilosis. In olivo, recent works on the evaluation of wild material (Olea europaea var. sylvestris) Have put in evidence his possible employment like new source of resistance to the illness, signalling his potential use like pattern or genitor in programs of improvement (Colella et al., 2008).
Photo 2: Progenies of olivo pertinent of cruzamientos between some of the varieties that have showed to date greater level of resistance to the Verticilosis.
By all this, in the Centre 'Alameda of the Bishop' of the IFAPA in Córdoba is developing a line of work that tackles the evaluation of all these possible new sources of resistance to the Verticilosis, with the final aim to obtain to half new term varieties or patterns of olivo with high levels of resistance to this illness. On the one hand, They are evaluating new pertinent genotypes of cruzamientos. In the selection of genitores has taken into account the employment of some of the varieties that to date have showed the greater levels of resistance to the patotipo D of 'V. dahliae' Like ‘Changlot Real', ‘Dolce Agogia', ‘Empeltre' and ‘Frantoio', as well as other varieties that in previous works of improvement have showed to transfer good characteristic agronómicas to the descendants such as ‘Arbequina', ‘Arbosana' and ‘Koroneiki'. The previous works of cruzamiento, germination and crianza of the plants of seed develop following the already tuned procedures in the program of genetic improvement (León et al., 2005), until his final establishment in field (Photo 2). Later, the evaluation agronómica of the genotypes generated in base to the usually realised measures in the program of improvement (productivity, carry, performance graso, ...) It allows to select the most interesting genotypes. The genotypes selected multiply using the procedure of propagation of olivo in vivero by means of enraizamiento by estaquillado semileñoso (Photo 3), what allows to have of the saplings that will use in the following phase of evaluation of resistance to the Verticilosis.
Photo 3: Prospección of populations of olivo wild (acebuche).
they are evaluating Also genotypes of olivo wild recolectados of distinct zones of Spain, some of them located next to areas of high incidence of the illness. The works of prospección and study of the populations of olivo wild realised to date have allowed evidenciar the big genetic variability of said populations, his differentiation with the olivo cultured and the presence of forestrys of acebuches authentic in Andalucia and in other zones of Spain (Belaj et al., 2011) (Photo 4). Like result of these works, still in course, has of a bank of material of olivo wild. The genotypes chosen propagate of the same form that the pertinent material of cruzamiento for the back evaluation of his resistance.
Photo 4: Propagation of genotypes by estaquillado semileñoso.
The evaluation of the resistance of the genotypes of olivo selected, so much pertinent of cruzamiento as of wild origin, realises by means of experiments of artificial inoculation in camera of crop with environingingment controlled. In said experiments uses an isolated of 'V. dahliae' Pertinent of olivo conserved in the micoteca of the Laboratory of Vegetal Pathology. This isolated has been characterised, of consistent form, in previous investigations as highly virulento on olivo and pertaining to the patotipo D of the pathogen. The saplings inoculate by immersion of his roots in a suspension of conidias of the fungus following the procedures described in previous works (Photo 5) (Moraño Dark et al., 2011; Rodríguez Sworn et al., 1993; Rodríguez Sworn et al., 2007).
Photo 5: Inoculation of the plants by immersion of the radical system in a suspension of conidias of the fungus.
After the inoculation, the plants transplant to barren plant pots endowed of a mix of barren floor and have in a camera of crop with a fotoperiodo of 14 hours of light and temperature of 24/22 °C light/darkness (Photo 6).
Photo 6: Growth of the plants in camera of crop during the phase of evaluation of the resistance.
The severity of the symptoms of Verticilosis developed in the plants inoculated evaluates according to a scale 0-4 (0= absence of symptoms; 4= dead plant) based in the percentage of aerial part affected by symptoms of defoliation, marchitez, clorosis and/or necrosis (Rodríguez Sworn, 1993; Rodríguez Sworn et al., 2007) (Photo 7). The experiments include plant controls of two levels of different illness, the corresponding to the varieties Picual and Frantoio, and plants of the distinct genotypes no inoculated.
Photo 7: Scale of severity of symptoms of Verticilosis (0-4). To the left, one plants control no inoculated.
The values of incidence and severity of the symptoms observed use to calculate diverse descriptive variables of the development of the illness. At the end of the experiments, realise isolations of plants sintomáticas and asintomáticas to confirm the infection by 'V. dahliae' And the occurrence of possible infections in absence of symptoms, respectively (Photo 8).
Photo 8: Isolation of ‘V. dahliae' To confirm the infection of the plants.
The results obtained from the first experiments of inoculation realised to date have allowed to identify some new genotypes with levels of resistance to the development of symptoms of Verticilosis similar or slightly greater that the presented by one of the varieties with greater resistance known like ‘Frantoio' used like control in the experiments. In the actuality is completing the evaluation of new batches of genotypes selected so much in pertinent material of cruzamiento as of wild origin. Along the next years pretends finalise the evaluation of a high number of genotypes that allow to select those with greater level of resistance.
The resistance of the genotypes selected will confirm in new experiments for the definite selection of the most resistant. Likewise, it will check the resistance of the genotypes selected in conditions of natural infection in field. For this pretends explain in the future with the collaboration of companies and agriculturalists of the sector that are interested in checking the utility of these new materials in real conditions of field.
In summary, the works in course pretend to give answer to some of the urgent demands of the sector of the olivar in relation with the problematic of the Verticilosis of the olivo by means of the identification and selection of vegetal material with high levels of resistance. This will allow to half term the transfer of the results obtained to the sector by means of the register of new varieties or resistant patterns, once obtain the future confirmation of said results.
Gratitudes
These works are funding with the projects RTA2010-00036 and RF2009-00005 of the INIA and PEI.PEI2011.1 of the IFAPA, partially funded by pertinent resources of the European Bottom of Regional Development (FEDER).
Bibliography
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