ABSTRACT Imazapyr (IM) treatment applied at early reproductive developmental stages have been associated with induced male sterility in sunflower (Helianthus annuus L.). The aim of this work was to determine the effects induced by two different doses of IM-treatment (1X and 2X; 80 and 160 g a.i.·ha-1) on pollen grain yield, pollen viability and on the exine surface, in an intermediate resistant (I) and a completely resistant (R) genotype. An anatomical analysis of some stages during the microsporogenesis and microgametogenesis was also achieved by confocal microscopy. Plants of both genotypes survived the herbicide treatments and showed no external injury symptoms. Differential response to different doses of IM was obtained in R and I genotypes. The pollen grains per flower and the viability in seeds were significantly reduced in the I genotype by the 2X treatment; however, the pollen viability of the remaining grains was not altered, and the diameter of the pollen grains was increased by the herbicide treatment. Anatomical and cytological observations of the sporogenous tissue development were made via confocal microscopy. IM treatment induced alterations in sporogenous cells during the initial phases of microsporogenesis in both genotypes, and the 2X dose accelerated the microgametogenesis process, particularly in the I genotype. These findings improved the understanding of the mechanism underlying the gametocide effects of the imidazolinones in sunflower.

ABSTRACT The first commercial herbicide-resistant trait in sunflower (Helianthus annuus L.) is known as ‘Imisun’. Imidazolinone resistance in Imisun cultivars has been reported to be genetically controlled by a major gene (known as Imr1 or Ahasl1-1) and modifier genes. Imr1 is an allelic variant of the Ahasl1 locus that codes for the acetohydroxyacid synthase, which is the target site of these herbicides. The mechanism of resistance endowed by modifier genes has not been characterized and it could be related to non-target-site resistance. The objective of this study was to evaluate the role of cytochrome P450 monooxygenases (P450s) in Imisun resistance. The response to imazapyr herbicide in combination with P450s inhibitor malathion was evaluated in 2 Imisun lines, IMI-1 and RHA426. Malathion reduced herbicide efficacy in both lines, but IMI-1 was affected in a greater extent. A significant reduction in plant growth in response to P450s inhibitors 1-aminobenzotriazole and piperonyl butoxide treatment was detected in the Imisun line HA425. The increased susceptibility to imazapyr after P450s-inhibitor treatment indicates that herbicide metabolism by P450s is a mechanism involved in Imisun resistance. These results also suggest the involvement of different P450s isozymes in endowing resistance to imazapyr in Imisun cultivars.

Several research projects are developed in animal genetics and plant breeding at Facultad Ciencias Agrarias UNR. A new ovine genotype has been obtained by crossing Ideal breed to Texel breed following by a breeding plan where the objectives were to improve female fertility and lamb growth rate. This new ovine genotype has the trade mark of Magrario and now this ovine new genotype is well known to produce lean meat and precocious lambs. Regarding Solanum lycopersicum species, 18 lines have been obtained introducing genes from a wild relative S. pimpinellifolium. This program included an agonistic-divergent selection to fruit weight and fruit shelf life. Molecular markers like as AFLP and SRAP to characterize these new tomato genotypes have been developed. Appropriate QTLs associated to fruit quality traits were found. Moreover, fruit protein profiles - associated to several fruit traits - were also detected. In sunflower the effort is focused on determining resistance to herbicides belonging to the family of imidazolinones (IMI) in early stages of the plants. A lot of experience was made through the development of several protocols in vivo and in vitro to detect the resistant, intermediate and susceptible genotypes. Root growth variables were useful parameters for the selection of sunflower genotypes differing in IMI resistance. This bioassay allowed the implementation of fast, reliable and low cost effective diagnosis method to assist breeding programs. Biochemical characterization of resistant process of the genotypes was also made through the quantification of ALS enzymatic activity.

En el ámbito de la Cátedra de Genética de la Facultad de Ciencias Agrarias de la UNR se desarrollan proyectos de genética y mejoramiento en ovinos, tomate y girasol. En ovinos se ha logrado un nuevo genotipo por retrocruzas de la raza Ideal hacia la Texel, seguido por un programa de mejora para la fertilidad femenina y la tasa de crecimiento en corderos. Este genotipo está registrado como Magrario y se lo reconoce como productor de carne magra. Con respecto al tomate (Solanum lycopersicum) se han obtenido 18 nuevos genotipos con la incorporación de genes de la especie silvestre S. pimpinellifolium en un cultivar a través de la selección antagónica-divergente para el peso y la vida poscosecha de los frutos. Se han identifcado marcadores de AFLP, SRAP, SSR y proteicos que permiten discriminar entre el genotipo cultivado y el silvestre para distintos atributos de calidad del fruto. En girasol se cuenta con una línea de investigación para la detección de genotipos resistentes a herbicidas de la familia de las imidazolinonas. Está basada en el desarrollo de protocolos in vivo e in vitro para detectar genotipos resistentes, medianamente resistentes y susceptibles, inspeccionando el desarrollo radicular de la planta. También se completó la caracterización bioquímica de la resistencia a través de la cuantificación de la actividad enzimática de ALS.

In species that show heterosis, information about combining ability with genetically divergent testers is useful to classify the germplasm in heterotic groups. The objective of this study was to evaluate 48 orange flint maize (Zea mays) lines for their combining ability with the testers: sB73 and sMo17 from the Reid x Lancaster pattern and with the flint testers HP3 and P5L2 from the local orange flint pattern during the 1991/92 season at four environments. Analyses of variance were computed for each environment separately and combined across environments for: seed yield, ear height, days to 50% silk, number of ear rows, ear length and diameter, 300 kernels weight, and test weight. Spearman correlation coefficients for grain yield of testcrosses with each tester were computed. Line x tester interactions were highly significant for the majority of the traits and there was no correlation between the merit order of lines based on testcrosses performance. These results suggest the importance of non-additive effects and the ability of the testers to rank the lines.

En las especies que exhiben heterosis, el conocimiento de la aptitud combinatoria del germoplasma en cruzamientos con probadores genéticamente divergentes permite su clasificación según grupos heteróticos. El objetivo del presente trabajo fue evaluar 48 líneas de maíz (Zea mays) flint colorado en base a su comportamiento en cruzamientos de prueba con los probadores dentados sB73 y sMo17 del patrón heterótico Reid x Lancaster y con los probadores flint HP3 y P5L2 del patrón heterótico local HP3 x P5L2 en cuatro ambientes durante la campaña 1991/92. Se realizaron los análisis de variancia por ambiente y en forma combinada a través de ambientes para: rendimiento en grano, altura de inserción de espiga, días a floración masculina, número de hileras de grano, largo y diámetro de espiga, peso de 300 granos y peso hectolítrico. Se estimaron los coeficientes de correlación de Spearman para el rendimiento de los cruzamientos de prueba con cada probador. Las interacciones línea por probador fueron altamente significativas para la mayoría de las variables y no hubo correlación entre el ordenamiento de mérito de las líneas basado en su comportamiento en cruzamientos de prueba. Ello refleja la importancia de efectos génicos no aditivos y la capacidad discriminatoria de estos probadores en cruzamientos con las líneas evaluadas.