Abstract
Gibberellins (GAs) are involved in internode elongation and other important processes such as seed germination, flowering, maturation, tuberization, and tuber dormancy. The discovery of GA-deficient mutants enabled further study of the role of these hormones in many plant processes. GA-deficient mutants lack the ability to produce adequate amounts of gibberellin for normal growth, resulting in a rosette type growth and short internodes. Thega 1 mutant allele was introduced into various genetic backgrounds including differentSolanum species and ploidies. Diploid GA-deficient genotypes were obtained by crossing haploidSolanum tuberosum ssp.andigena withSolanum chacoense. The progeny was then bulked and intermated to produce F2 individuals. Tetraploid GA-deficient genotypes were obtained by crossingS. tuberosum ssp.andigena withSolanum sucrense and withSolanum gourlayi. The two resulting progenies were then bulked and intermated. Diploid and tetraploid GA-deficient genotypes were grown on MS media containing different levels of gibberellin (GA3). Plant height and visual observations were made as a way to assess the response of these genotypes to GA3. Concentration of 0.1 µM GA3 and lower failed to restore normal plant height in both diploid and tetraploid genotypes. Normal plant height was restored in most of the GA-deficient genotypes when concentrations between 0.8 and 1.2 µM GA3 were used. We found some important differences between these genotypes: (1) the level of GA3 to restore normal plant height varies among the GA-deficient genotypes, some needed more GA3 than others to grow normally; (2) the time to respond to the presence of GA3 in the media differs between the GA-deficient genotypes, (3) tetraploid genotypes exhibited normal growth and internode length in response to GA3, while diploid genotypes tended to show a rosette-type growth at the apical end. These results suggest thatga 1 mutants can be affected by a series of modifier genes and/or iso-alleles. The importance of variable response to GA among dwarf individuals is two fold: (1) experiments measuring GA response should choose and clonally multiply one genotype to ensure uniform optimal response to GA application; and (2) variation betweenga 1 mutant phenotypes could be used to characterize GA-response modifier genes.
Resumen
Las giberelinas (GAs) están involucradas en el crecimiento internodal y en otros procesos importantes como germinación de semillas, florecimiento, maduración, tuberización y dormancia del tubérculo. El descubrimiento de mutantes deficientes en GA ha permitido estudiar el rol de estas hormonas en muchos procesos en la planta. Los mutantes deficientes en GA carecen de la habilidad de producir cantidades adecuadas de giberelina para tener un crecimiento normal, resultando en un crecimiento tipo roseta y espacio internodal corto. El alelo mutantega 1 fue introducido en varios materiales genéticos, incluyendo diferentes especies deSolanum y diferentes ploidías. Genotipos diploides deficientes en GA fueron obtenidos cruzando haploides deS. tuberosum ssp.andigena conS. chacoense. La progenie fue después combinada y entrecruzada para producer individuos F2. Genotipos tetraploides deficientes en GA fueron obtenidos cruzandoS. tuberosum ssp.andigena conS. sucrense y conS. gourlayi. Las dos progenies resultantes fueron combinadas y entrecruzadas. Los genotipos diploides y tetraploides deficientes en GA fueron cultivadosin vitro en medio de cultivo MS conteniendo diferentes niveles de giberelina (GA3). La altura de la planta y observaciones visuales fueron utilizadas como parámetros para evaluar la respuesta de los genotipos a GA3. Concentraciones de 0.1 µM GA3 y menores no restauraron la altura normal de la planta en los dos tipos de genotipos, diploide y tetraploide. La altura normal de la planta fue restaurada en la mayoría de los genotipos deficientes en GA cuando las concentraciones utilizadas fueron entre 0.8 y 1.2 µM GA3. Este estudio encontró diferencias importantes entre estos genotipos: (1) el nivel de GA3 necesario para restaurar la altura normal de la planta varía entre los diferentes genotipos deficientes en GA, algunos necesitan más GA3 que otros para crecer normalmente; (2) el tiempo en el cual la planta responde a la presencia de GA3 en el medio es diferente entre los genotipos deficientes de GA; (3) los genotipos tetraploides exhibieron crecimiento y espacio inter-nodal normal en respuesta al GA3 presente en el medio de cultivo, mientras que los diploides tendieron a mostrar un crecimiento tipo roseta en el extremo apical de la planta. Estos resultados sugieren que los mutantesga 1 pueden estar afectados por una serie de modificadores genéticos y/o iso-alelos. La importancia de la presencia de modificadores y/o isoalelos son dos: (1) experimentos que miden la respuesta a GA deben elegir y multiplicar clonalmente un solo genotipo para asegurar una respuesta óptima y uniforme a la aplicación de GA; y (2) la variación fenotípica entre los mutantesga 1 puede ser utilizada para caracterizar los modificadores genéticos que pueden estar involucrados en la respuesta a GA.
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Abbreviations
- GA:
-
gibberellin
- GC-MS:
-
gas chromatography-mass spectrometry
- MS:
-
Murashige-Skoog
- PAR:
-
photosynthetically active radiation
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Vega, S.E., Bamberg, J.B. & Palta, J.P. Gibberellin-deficient dwarfs in potato vary in exogenous GA3 response when thega 1 allele is in different genetic backgrounds. Am. J. Pot Res 83, 357–363 (2006). https://doi.org/10.1007/BF02872012
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DOI: https://doi.org/10.1007/BF02872012