CIDEFI

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https://digital.cic.gba.gob.ar/handle/11746/33
El Centro de Investigaciones de FitopatologĆ­a realiza tareas de investigaciĆ³n cientĆ­fica bĆ”sica y aplicada, docencia de post-grado y servicios de extensiĆ³n para productores, empresas e instituciones, sobre PatologĆ­a Vegetal de los cultivos, con Ć©nfasis en las Ć”reas de MicologĆ­a, BacteriologĆ­a, VirologĆ­a, Manejo de Enfermedades y temas vinculados, que incluyen la Sanidad ApĆ­cola y el Control BiolĆ³gico de Plagas. El Centro es reconocido como un sitio de referencia en las Ć”reas de FitopatologĆ­a y Sanidad ApĆ­cola en todo el paĆ­s y es el Ćŗnico de estas caracterĆ­sticas en la Provincia de de Bs. Aires.

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  • Documento de conferencia
    Acceso Abierto
    Estudio sobre la septoriosis del trigo en la Republica Argentina
    (1978) Cordo, Cristina Alicia
    Se describe el procedimiento seguido para obtener cultivos esporulados de Septoria tritici, en medios artificiales y bajo condiciones controladas.Se propone un mĆ©todo practico de inoculacion para la determinaciĆ³n de lineas o cultivares de trigo bajo condiciones controladas mediante infecciones artificiales en estado temprano de crecimiento. Esto posibilita su empleo en las primeras generaciones segregadas del material, en proceso de mejoramiento, con un descarte temprano, de lineas suceptibles al parasito.
  • ArtĆ­culo
    Acceso Abierto
    Mancha de la hoja de trigo (Septoria tritici) en la RepĆŗblica Argentina
    (ComisiĆ³n de Investigaciones CientĆ­ficas de la Provincia de Buenos Aires, 1979) Cordo, Cristina Alicia
    Contiene: Cultivo del patĆ³geno en medios artificiales Efecto de la luz y los medios de cultivo en la esporulaciĆ³n de Septoria tritici
  • ArtĆ­culo
    Acceso Abierto
    AnƔlisis cualitativo de la variabilidad cultural de Septoria tritici
    (Sociedad Argentina de BotƔnica, 1987) Cordo, Cristina Alicia; Lindquist, Juan C.
    Septoria tritici (Rob. et Desm.), cause of leaf blotch of wheat (Triticum aestivum L. em. Thell.) exhibited cultural variability into the nine cultures isolated. The cultural variability was observed into the same generation and furthermore into members of different generations of cultures. Cultures from field collection of S. tritici were established from single spore transfers on C ZD Vā€™8 and APS. Produced stromatic and pycnidial colonies. Some cultures of pycnidial type show a marked tendency to produce mycelial type variants. Moreover, other cultures o f pycnidial type show stability. The variable cultural characters were: colour, area, mycelial structures, growth speed, sporulation. The saltation was very common into the cultures after some transfer generations. They dominated on C ZD V ā€™8, moreover, they were produced on all nutritive media. Only one culture was returned to original type with loss of sporulation.
  • ArtĆ­culo
    Acceso Abierto
    MĆ©todo simple para la obtenciĆ³n de inĆ³culo de Septoria tritici Rob. Ex Desm.
    (1988) PerellĆ³, AnalĆ­a; Cordo, Cristina Alicia; Wolcan, Silvia MarĆ­a; Sarandon, Santiago Javier
    La conducciĆ³n de estudios sobre grados de virulencia de Septoria tritici, asi como la detecciĆ³n de fuentes de resistencia varietal en el trigo, requieren el empleo de inoculaciones artificiales en ensayos conducidos ya sea en el campo o en un invernĆ”culo. En dichas inoculaciones se emplean tanto picnidiosporas (Cooke y Jones, 1970) (Hilu y Bever, 1957) (Lee y Jones, 1974) como conidios secundarios (Ballantyne, 1983) (Eyal, Amiri y Wahl, 1973) obtenidos mediante tĆ©cnicas engorrosas o poco prĆ”cticas para la producciĆ³n de inĆ³culo en gran escala.
  • Resumen
    Acceso Abierto
    Variation in virulencia in isolates of Septoria tritici Rob. Ex. Dem. on Wheat
    (1989) PerellĆ³, AnalĆ­a; Cordo, Cristina Alicia; Arriaga, H.O.; Alippi, H.E.
    Knowledge of the physiologic specialization of S. tritici on wheat is a necessary prerequĆ­site to any reliable breeding program for disease resistance (Eyal et al., 1983). All around the world many reports do not agree when referring to the identification of physiological races (Arjona et al., 1976; Arsenijevie, 1965; DĆ­az, 1983; Eyal et al., 1973; Prestes L Hendrix, 1977; Shipton et al., 1971). In Argentina, previous work revealed the existence of certain degree of specialization (Cordo y ArrĆ­agea, 1987; PerellĆ³ et al., 1987). Nevertheless, the insufficĆ­ent existence of judging eĆ­eaents does not allow isolates to be classified into physiological races, It is said that, for a particular pathogen (Buxtsn, 1960), the number of pathogenic races Ć­dentifiable by artificial inoculations on different wheats is related to the differential host that allows its differentiation. Thus, the present work attempts to identify physiologic races of S. tritici including a differential set already selected in Israel. Also it attempts to analyze the varĆ­etal reaction using two different variables to determine the significance of the evaluation method in the differentiation of the isolates. Nineteen wheat cultivars (Table 1) were used as host differentials to assay virulence variability in ten S. tritici isolates obained from various geographic areas of Buenos Aires (Argentina) (Figure 1). The isolates were obtaĆ­ned from leaves with typical lesions. Inoculations and 1987). The suspensiĆ³n concentration was aujusted co 1 x 10spure/mi. a randomized design with four replicates was used, with one pot considerad as a replicate. The experiment was carried out in a greenhouse under controlled conditions of temperature and relaive humidity. Syaptoms were evaluated 28 days after inoculation, on the third leaf of 20 plants from each isolate x variety coobination. Varietal reaction was measured through 2 variables: pycnidial leaf coverage percentage (PC) and necrotic lesiĆ³n percentage (NL) on the leaves, both in reference to the total leaf area. Riere were also observed qualitative differences within the type of lesiĆ³n developed. For the statistical analysis Friedman's test (Friedman, 1937) was applied to determine differences of isolates behavior in the varieties, and Page's test, to classify them according to the growth stages of the virulence (Page, 1963). Isolate x variety Ć­nteractions with similar levels of virulence-susceptibility were grouped into 3 classes with a cluster algorhytbm without supervisiĆ³n (Duda L Kart, 1973). Standard variance analysis was performed with main emphasis on the isolate x cultivar interaction. The isolates showed different behavior (P=0.005) on the different wheat cultivars. Both variables constituted good parameters to discriminate those isolates that act similarly from the ones that act differences (Table 2). Necrotic leaf area and pycnidial coverage percentage were different for each isolate x variety coabination; few cases showed coincidence between the two patterns. Only Bobwhite S , Iassul 20 and B. Puan presented as much NL as PC with the isolates assayed, The other varieties showed no coincidence in the order of the reactions induced by the two variables, In general, local isolates induced more PC than NL in the Argentina varieties. Two isolates (I.. and I .) behaved as the most virulent whereas other two (L. and I ) provoked the major percentage of resistant reactions on tne 17 cultivars tested, Isolate x variety interactions with similar levels of virulence-susceptibility were grouped in 3 classes for PC (Table 3) and in 2 for NL (Table 4), The fact that NL variable discriminates data in fewer classes than PC reflects that this variable provides less Information, Although NL is a good indicator of the degree of disease developed, the existence of aberrant lesions (with few of no pycnidia) complicates the interpretaciĆ³n. On the other hand, PC allowed a major differentiation within isolate behaviors, resulting a more sensible indicator of differences; in consequence, its use is more advisable. The results of variance analysis indicate that interaction variad according to the evaluation parameter considered. A significant valuĆ© (P=0.01) for PC (Table 5) can be considered as physiologic specialization index of the pathogen. However, a non-significant valuĆ© (P=0.01) for NL could indicate only differences between virulence or aggressiveness degree of the isolates. Moreover, the low specificity degree of the interactions and similar order in severity ranking of the disease in some cultivars, indicate that they are not true physiological races , The use of the International differential set did not contribute to a ciear and consistent differntiation of races. In the end, as several researchers apply different methodologies to study S. tritici physiological specialization, it is not possible to compare scientific Information on an International basis. This indicates, as has been aiready suggested (Shipton et al., 1971). the need to standardiza working co^ditions to obtain coparable results from the work on tritici-Triticum sp.
  • ArtĆ­culo
    Acceso Abierto
    Enzimas hidroliticas detectadas en cultivo filtrado de Septoria tritici (Teleomorfo, Mycosphaerella graminicola)
    (Universidade Estadual Paulista, 1989) Cordo, Cristina Alicia; Marechal, L. R.
    Una serie de tes fueron conducidos para verificar actividad de enzimas hidrolƭticas (pƩcticas y celulolƭticas) producidas por Septoria tritici como evaluar sus efectos en hojas de trigo. Por tanto fue cultivada en medio lƭquido y el cultivo filtrado fue parcialmente purificado. Una actividad enzimƔtica fue detectada a travƩs de mediciones regulares de viscosidad del sustrato. Las enzimas celulolƭticas y pƩcticas actuan en la mancha de la hoja del trigo.
  • ArtĆ­culo
    Acceso Abierto
    CaracterĆ­sticas morfolĆ³gĆ­cas y patogĆ©nicas de aislamientos de Septoria tritici Rob ex Desm
    (EDP Sciences, 1990) PerellĆ³, AnalĆ­a; Cordo, Cristina Alicia; Alippi, H. E.
    Se analizĆ³ el comportamiento cultural y patogĆ©nicos de 8 aislamientos de Septoria tritici obtenidos a partir de hojas de trigo colectadas en el campo e infectadas naturalmente. Los diversos aislamientos monospĆ³ricos pueden diferenciarse en cultivo artificial por su aspecto, la producciĆ³n de esporas, la presencia o ausencia de micelio, y el color y la frecuencia de saltaciones observadas en las colonias. Las cepas varĆ­an tanto en la abundancia como en el tipo de las esporas producidas bajo condiciones similares. AdemĆ”s de las picnidiosporas de forma y tamaƱos tĆ­picos de la especie, algunas cepas produjeron sĆ³lo esporas libres muy pequeƱas (microsporas), y otras, macro y mĆ­crosporas dentro des picnidios. Los tipos culturales predominantes de los aislamientos fueron 5: - estromĆ”tico (mayor frecuencia), - albino pulverulento, - levaduroide, - mixto y - miceliar. Estos tipos culturales, en algunos casos no se mantuvieron estables a travĆ©s de 3 generaciones de subcultivos. Las inoculaciones efectuadas sobre plantas de trigo en invernĆ”culo, revelaron diferencias altamente significativas en la patogenicidad de ciertas cepas. Se encontrĆ³ una relacĆ­Ć³n entre las caracterĆ­sticas culturales de los aislamientos y la severidad de la enfermedad: los aislamientos de tipo albino y levaduroide fueron los menos virulentos, tanto sobre variedades resistentes como susceptibles. La presente, constitutuye la primer cita de la presencia de esta clase de microsporas de S tritici.
  • ArtĆ­culo
    Acceso Abierto
    Presencia de Mycosphaerella graminicola (Fuckel) Schroeter teleomorfo de Septoria tritici Rob apud Desm. en trigos maduros de la Argentina
    (1991) Cordo, Cristina Alicia; PerellĆ³, AnalĆ­a; Alippi, HĆ©ctor E.; Arriaga, HĆ©ctor O.
    Este trabajo constituye la primera cita para el paĆ­s de la ocurrencia de Mycosphaerella graminlcola (Fuckel) Schroeter st. conidium: Septoria tritici Rob. apud Desm . Esta fase sexual del hongo mencionado fue hallado en lesiones foliares de plantas de trigo pan (Triticum aestivum L.) maduro del cultivar Buck Poncho. Para la identificaciĆ³n del patĆ³geno se realizaron observaciones con microscopio Ć³ptico y electrĆ³nico de barrido (SEM). El aislamiento fĆŗngico se obtuvo por la descarga de ascosporas en un medio de cultivo (agar-agua) y posterior transferencia a otro mĆ”s nutritivo (agar-malta). Se estudiĆ³ la morfologĆ­a, color y esporulaciĆ³n de las colonias y se observĆ³ y documentĆ³ el modo de germinaciĆ³n de las ascosporas. Los resultados del estudio realizado coinciden con la descripciĆ³n original para Mycosphaerella graminicola, como el estado ascĆ³geno de Septoria trltici. Se discute la probable incidencia del estado perfecto en la epidemiologĆ­a de la enfermedad bajo las condiciones de la regiĆ³n triguera argentina.
  • Comunicacion
    Acceso Abierto
    CaracterizaciĆ³n de las proteĆ­nas desnaturalizadas de Septoria tritici Rob. Ex Desm. por electroforesis en geles de poliacrilamida
    (1991) PerellĆ³, AnalĆ­a; Gianibelli, M. C.; Cordo, Cristina Alicia; Alippi, HĆ©ctor E.; Arriaga, HĆ©ctor O.
    La poblaciĆ³n de Septoria tritici de la Argentina presenta un alto nivel de variabilidad, reflejado en las diferencias culturales y la virulencia, expuestos en estudios anteriores (Cordo y Linquist, 1987; Cordo y Arriaga, 1987; Cordo et al., 1992a; PerellĆ³ et al., 1987, 1990a, 1990b, 1991). BasĆ”ndose en los patrones de palogenicidad producidos sobre lĆ­neas de hospedantes con diferente germoplasma, y segĆŗn los diferentes tipos morfoculturales ya caracterizados (Cordo et al, 1992a; PerellĆ³ et al., 1990a, 1991), la poblaciĆ³n de aislamientos de Septoria tritici puede subdividirse en subpoblaciones o tipos . Cada una de estas subpoblaciones estarĆ­an formadas, presumiblemente, por razas o biotipos relacionados entre sĆ­. La marcada diferencia en la estructura de la poblaciĆ³n de Septoria tritici en la Argentina, la hace de interĆ©s para examinarla electroforĆ©ticamente a nivel proteico.
  • ArtĆ­culo
    Acceso Abierto
    Una nueva especie de Phoma agente causal de la Mancha alquitranada del Fresno americano
    (1991) Cordo, Cristina Alicia; Merlo, P.A.
    De lesiones foliĆ”ceas encontradas en Fraxinus pensylvanica Marsh. se aislĆ³ una nueva especie de Phoma en APD donde produjo algunas conidias castaƱo-oscuro, irregulares, desarrolladas entre las nervaduras y desde el margen al centro de la lĆ”mina foliar. Estas lesiones se reprodujeron artificialmente sobre plantas de fresno americano de 1 aƱo. Para la identificaciĆ³n del patĆ³geno se enviaron muestras de hojas enfermas, con fructificaciones y cultivos de APD al Commonwealth Mycological Institute, Kew, U.K. Los caracteres de las colonias y el tipo de conidias no coincidieron con ninguna de las especies de Phoma descrptas en el mundo. Por ello se propuso a Ć©sta como una nueva especie, especĆ­fica del gĆ©nero Fraxinum. Esta enfermedad ha sido observada en plantas masculinas de fresno americano en las ciudades de La Plata, Ensenada y alrededores de Villa Elisa. Produce defoliaciĆ³n temprana en el verano, dando lugar al debilitamiento generalizado del arbol con detrimento de la calidad y cantidad de madera.
  • ArtĆ­culo
    Acceso Abierto
    Fusarium spp en trigo, capacidad toxicogenica y quimiotaxonomia de las cepas aisladas en la Argentina
    (EDP Sciences, 1992) Lori, Gladys Albina; Carranza, M. R.; Violante, A.; Rizzo, I.; Alippi, H. E.
    Se aislaron e identificaron 91 cepas de Fusarium spp (F graminearum, F equiseti, F moniliforme, F m var anthophilum, F acuminatum, F solani y F oxisporum) a partir de semillas de trigo pan procedentes de 17 localidades trigueras de la RepĆŗblica Argentina. Mediante el cultivo de las mismas en arroz pelado y pulido se evaluĆ³ la producciĆ³n de tricotecenos y zearalenona, a los efectos de revelar si existen diferencias regionales en cuanto a su presencia. Se detectaron cepas productoras de tricotecenos del grupo B y zearalenona, no habiĆ©ndose hallado productoras del grupo A. De las cepas evaluadas el 82,4% produjeron tricotecenos que se subdividieron en dos grupos: a) las cepas productoras de deoxinivalenol (DON) y su precursor 3 acetil-deoxinivalenol (AcDON) y b) las productoras de nivalenol (NIV) y su precursor 4 acetil-nivalenol o fusarenona-x (FUS-X). Los resultados demostraron que el 48,3% de las cepas fueron productoras de DON, el 7,7% de NIV y el 26,4% tuvieron la capacidad de producir simultaneamente DON y NIV en los cultivos. Al considerar exclusivamente las cepas de F graminearum el 89,4% fueron toxicogĆ©nicas, de ellas el 55,9% pertenecieron al quimiotipo DON, 10,3% al quimiotipo NIV y 33,8% produjeron DON y NIV. En cuanto a la zearalenona (ZEA) el 63,2% del total de las cepas fueron productoras de esta toxina, no existiendo ninguna relaciĆ³n entre los grupos DON y NIV con la producciĆ³n de ZEA. La distribuciĆ³n de las cepas toxicogĆ©nicas de Fusarium spp observada en las distintas localidades de la RepĆŗblica Argentina, permite inferir la existencia de diferencias regionales en el Ć”rea triguera.
  • ArtĆ­culo
    Acceso Abierto
    HistopatologĆ­a de hojas de tomate inoculadas con Xanthomonas campestris pv vesicatoria
    (EDP Sciences, 1992) Alippi, Adriana MĆ³nica
    Se estudiĆ³ la infecciĆ³n de Xanthomonas campestris pv vesicatoria en hojas de tomate por medio de microscopĆ­a Ć³ptica y electrĆ³nica de barrido. Se determinĆ³ que la bacteria penetra en el hospedante por los estomas y se localiza y multiplica en las cĆ”maras subestomĆ”ticas que sirven como sitios de supervivencia. Adicionalmente, tambiĆ©n penetrarĆ­a por las bases de los tricomas deteriorados. Luego, las bacterias colonizan los espacios intercelulares del parĆ©nquima esponjoso y, al alcanzar las cĆ”maras subestomĆ”ticas (no invadidas previamente), se multiplican abundantemente y son expulsadas, aglutinadas en un sustancia de naturaleza mucosa, dando origen a nuevas fuentes de inĆ³culo. Tras la inoculaciĆ³n, se notĆ³ una mayor concentraciĆ³n de cĆ©lulas bacterianas en la cara inferior de las hojas. Los estomas y las cĆ”maras subestomĆ”ticas fueron el nicho ecolĆ³gico preferido por el patĆ³geno para la posterior colonizaciĆ³n del hospedante.
  • ArtĆ­culo
    Acceso Abierto
    Characterization of Bacillus larvae White, the causative agent of American Foulbrood of honey bees
    (1992) Alippi, Adriana MĆ³nica
    American fouldbrood caused by Bacillus larvae white is recorded for the first time on brood combs of Argentinian hives. The identification of the causative agent was based on disease symptomatology, morphological characters, pathogenicity tests and physiological and biochemical reactions. Studies by scanning electron microscopy showed the occurrence of large flagellar bundles of Bacillus larvae strains growing in biphasic BL medium. An electron microscope survey of the surface configuration of bacterial spores was also made.
  • ArtĆ­culo
    Acceso Abierto
    A new disease of wheat caused by Alternaria triticimaculans in Argentina
    (EDP Sciences, 1996) PerellĆ³, AnalĆ­a; Cordo, Cristina Alicia; SimĆ³n, MarĆ­a Rosa
    Late maturity wheat plants (Triticum aestivum L) culivars Trigomax and Buck Poncho growing at the EstaciĆ³n Experimental Agropecuaria J Hirschhorn in Los Hornos (Provincia de Buenos Aires) were severely affected by a previously undescribed disease. The leaves initially showed necrotic, irregular brown/grey spots that progressed to general necrosis and death of the leaf. The pathogen was proposed as a new species: Alternaria triticimaculans Simmons and PerrolĆ³ in 1994. Disease symptomatology and characteristics of the causal agent on potato dextrose agar are described. Eight wheat cultivars exhibited significant differences in disease severity in the field under natural infection with A triticimaculans. Don Ernesto INTA was the most resistant and Pro INTA Isla Verde the most susceptible. Five greenhouse-grown wheat cultivars were inoculated by spraying young and adult plants with conidia of A triticimaculans. Lesions similar to those observed on naturally infected plants were observed. The fungus was reisolated from all inoculated plants and Kochā€™s postulates were fulfilled. Adult plants were more susceptible to the pathogen than younger ones. Inoculations made on disinfected wheat seeds indicated slightly reduced seedling emergence. This is the first reported ocurrence of A triticimaculans on a cultivated plant.
  • ArtĆ­culo
    Acceso Abierto
    Selective Effect of Wheat Germplasm upon Isolates of Mycosphaerella graminicola
    (1997) Cordo, Cristina Alicia; PerellĆ³, AnalĆ­a
    The selection of Septoria tritici biotypes by Bobwhiteā€™Sā€™ resistant wheat germplasm was studied. Seedlings of cultivars with Bobwhiteā€™Sā€™ germplasm and with dwarf-mexican germplasm were inoculated in the greenhouse. Two Septoria tritici isolates (atypical yeast-like variant coming from Bobwhiteā€™Sā€™ germplasm and stromatic from traditional argentine germplasm) were used. Isolates of S. triciti from each isolate x cultivar combination were analyzed, and the percentage of regular or variant colonies was registered. Significant pathogen population effect and cultivar effect were demonstrated. The regular isolate produced chlorotic and necrotic lesions with pycnidia in all the cultivar; the atypical variant had quite distinct reaction according to the cultivars, being predominant the non-pycnidial necrotic reaction. Pathogen population isolated from Bobwhiteā€™Sā€™ germplasm produced higher levels of variant colonies, than did population isolated from dwarf mexican cultivar. Inoculation with the variant produced a high number of variant colonies in cultivars with both germplasm, indicating that Bobwhiteā€™Sā€™ germplasm could induce the origin of less pathogenic variants from a heterogeneous pathogen population through a remarkable mechanism of selective effect and any genetic change.
  • ArtĆ­culo
    Acceso Abierto
    Evaluation of Trichoderma harzianum and Gliocladium roseum in controlling leaf blotch of wheat (Septoria tritici) under in vitro and greenhouse conditions
    (1997) PerellĆ³, AnalĆ­a; MĆ³naco, Cecilia InĆ©s; Cordo, Cristina Alicia
    The suitability of Trichoderma harzianum and Gliocladium roseum as biocontrol agents on the in vitro growing of Septoria tritici and their efficiency in reducing disease severity on wheat plants was evaluated under greenhouse conditions. For the in vitro tests, the micro-organisms were confronted through dual cultures on PDA. A histopathological clarification and staining technique was used in order to observe, if the penetration and development of the pathogen on wheat leaves was modified in the presence of the antagonistic agents. A highly significant effect of T. harzianum and G. roseum on the development of S'. tritici colonies was observed. Both antagonistic agents grew over the S. tritici colony and covered it completely. T. harzianum was more efficient than G. roseum in inhibiting the pathogen. The coiling of the hypha of T. harzianum on short sections of S. tritici colony was observed with the bioassay on wheat leaves. The spore germination and the superficial mycelial development of S. tritici was affected by T. harzianum and G. roseum. Although, the further stomatic penetration of S. tritici was not restrained. The in vivo inhibitory capacity of the two antagonists assayed were not expressed on the wheat plants tested. However, there has been a tendency to reduce the percentage of necrotic area with pycnidial coverage when compared with the control. Further studies are needed before unequivocal conclusions can be drawn. Greenhouse experiments are in progress.
  • ArtĆ­culo
    Acceso Abierto
    Morphocultural variants of Septoria tritici isolates
    (AsociaciĆ³n EspaƱola de MicologĆ­a, 1997) Cordo, Cristina Alicia; PerellĆ³, AnalĆ­a; Alippi, HĆ©ctor Eduardo; Arriaga, HĆ©ctor Oscar
    This is a morphocultural study under in vitro and in vivo condition on some Septoria tritici variants mainly originated from isolates collected from cultivars bearing Bobwhite 'S' and Kavkaz germplasm. The objective was to show the variability in cultural and morphobiometrical characters of atypical isolates (variants) derived from these germplasms and discuss the relationship with the pathogenā€™s adaptative process. The isolates were grown on potato dextrosa agar and studies with the optical and scanning electron microscope were performed. The thallus behaviour and the vegetative structures were described. It was confirmed that these atypical structures belong the S. tritici thallus. Under in vivo condition the isolates developed typical leaf blotch lesions with normal pycnidia. These contained cylindrical cells or pycnidiospores smaller than spores of the wild type . Possible reasons for the origin of these variants of S. tritici are considered.
  • ArtĆ­culo
    Acceso Abierto
    Inheritance of partial resistance to Septoria tritici in wheat (Triticum aestivum): limitation of pycnidia and spore production
    (EDP Sciences, 1997) SimĆ³n, MarĆ­a Rosa; Cordo, Cristina Alicia
    The aim of this work was to study the gene effects of two components of partial resistance (pycnidia.cm and spore production.mL-1) in a semi-diallel cross of four wheat cultivars differing in susceptibility to Septoria tritici. The F1 trials were carried out in two environments (greenhouse and field). The material was inoculated at the beginning of tillering (stage 21, Zadoks scale) and evaluations were performed on the fourth leaf. There was a significant interaction between crosses and environments for pycnidia.cm-.2 A separate ANOVA was performed for both traits. Crosses were significant for both traits in both environments. Griffing method 4, model 1 was used to test general and specific combining ability. General combining ability mean square was usually larger than the specific combining ability mean square. The presence of significant additive variance indicates the possibility of selecting for both traits in order to obtain partial resistant cultivars. However, it is necessary to consider that for pycnidia.cm the dominance variance was also large, indicating that selection for this trait should be delayed to advanced generations. The environmental influence is discussed.
  • ArtĆ­culo
    Embargado
    Diallel analysis of four resistance components to Septoria tritici in six crosses of wheat (Triticum aestivum)
    (1997) SimĆ³n, MarĆ­a Rosa; Cordo, Cristina Alicia
    Four resistance components, i.e. incubation period, latent period, maturation period and pycnidial coverage, were studied in a diallel cross of four wheat cultivars differing in susceptibihty to Septoria tritici. Inoculations and evaluations were carried out at the fourth leaf stage for two years. A combined ANOVA for both years exhibited a significant interaction between crosses and years for maturation period. A separate ANOVA for each year was done for this trait. The combined ANOVA showed that crosses were significantly different for incubation, latent period and pycnidial coverage. Cross effects were also significant for maturation period in each year for the separate ANOVA. Year effects were significant for latent period and maturation period. General combining ability (GCA) was significant and preponderant for incubation period, latent period and pycnidial coverage. For maturation period, the separated ANOVA showed the significance of the GCA for both years. Specific combining abihty (SCA) was significant for incubation and pycnidial coverage and for maturation in one year. The preponderance of the additive genetic variance for all traits indicates the possibility of selecting for them in order to obtain improved cultivars. Incubation period was inherited independently of maturation period and pycnidial coverage, indicating that combinations of some of those characters may lead to more effective and durable resistance.
  • ArtĆ­culo
    Embargado
    Response to selection in F2 populations of two wheat crosses for resistance to Septoria tritici
    (AkadĆ©miai KiadĆ³, 1998) SimĆ³n, MarĆ­a Rosa; PerellĆ³, AnalĆ­a; Cordo, Cristina Alicia
    Septoria tritici blotch is an important disease of wheat in many areas of the world that causes significant yield losses. Breeding for resistance to the disease is an important tool as a control measure. To efficiently breed wheat for resistance, an understanding of the inheritance of the resistance is required. This work is a part of a project to study the inheritance of the resistance to the disease. The aim was to determine the response to selection and realized heritability when selection for a reduction in percentage of pycnidial coverage was carried out in two wheat crosses. The response to selection and heri tabili ty showed moderate values. According to the results of these crosses, selection for resistance to the disease on a single plant basis could be successful but probably slow. Optimization of selection is discussed.