Ten naturalized populations of tall wheatgrass (Thinopyrum ponticum) were evaluated in a completely randomized block design with three replicates. Each plant was analyzed for morphological and reproductive characters, and statistical and genetic characters were estimated. Signifi cant differences (p < 0.001) were obtained for the means of all ten populations, indicating great variability between tall wheatgrass populations. The results show that the environmental coeffi cients of variation were high for total seed production (69.24%), number of tillers (54.93%), number of spikes (48.50%), and dry matter production (49.01%). Coeffi cients of variation were rather low for spike length (19.11%) and the 1000-seed weight (18.44%). Heritability was high for seed weight (0.86), dry matter production (0.55), and the number of tillers (0.55). Intermediate heritability was found for total seed production (0.30), and low heritability for the number (0.19) and length (0.09) of spikes. Even though the number of spikes showed an intermediate heritability, it was highly and positively correlated with seed production (r=0.603), and a little less so with seed weight (r=0.177). Seed weight showed a high heritability and was positively correlated with seed production (r=0.285). The wide variability observed between populations for almost all the studied characters will allow them to be integrated into a single germoplasm or into a genetic pool that could be used in programs aimed at the genetic improvement of tall wheatgrass.

No abstract

Trece genotipos de Bromus catharticus se evaluaron, durante 3 años, utilizando un diseño experimental completamente aleatorizado con seis repeticiones. Porplanta individual se analizaron el número de panojas, el número de semillas y el peso de 1000 semillas. La interacción genotipo x ambiente fue estadísticamente significativa e indica un comportamiento diferencial de los genotipos evaluados a través de los años. Una vez comprobada la interacción, se aplicaron tres metodologías para evaluar la estabilidad y adaptabilidad de los genotipos: la ecovalencia de Wricke, el índice de Lin & Binns y el modelo de Eberhart & Russell. Estas dos últimas metodologías coinciden en identificar como estables y adaptables a los mismos genotipos para los caracteres estudiados, mientras que la coincidencia con Wricke fue parcial. Considerando las tres metodologías usadas, la de Lin & Binns es fácil de aplicar e interpretar, ya que siempre asocia mayor productividad con mayor estabilidad, y no presenta las restricciones de uso de la regresión. Sin embargo, es necesario acumular más resultados antes de proceder a la generalización de su uso.

IntroducciónLa cebadilla criolla (Bromus catharticus ( ( Vahl.) es uno de los pastos nativos más cultivado en Argentina y es una de las pocas especies forrajeras autóctonas que se cultiva en Bolivia, Brasil, Chile, Ecuador, Perú y Uruguay e inclusive en el Sur de los Estados Unidos.Se caracteriza por poseer numerosas ramifi caciones basales (macollos) algunas de las cuales producen cañas fl oríferas en cuyo extremo está la infl orescencia. Las infl orescencias corresponden a panojas laxas con espiguillas achatadas, cada una de las cuales contiene de seis a doce semillas grandes. Posee dos tipos de fl oración, cleistógama y chasmógama. No obstante, se considera una especie autógama facultativa debido a su baja tasa de alogamia (Cladera and Pahlen 1984;Naranjo 1985; Pahlen 1986;Morant 1990; Aulicino y Arturi, 2002).Es una especie anual o bianual de ciclo otoño-invierno-primaveral con alta capacidad de implantación y buen crecimiento inicial. Se consocia muy bien con otras especies, formando pasturas de óptima calidad en las cuales perdura por muchos años a causa de su gran producción de semillas y su destacado comportamiento en la resiembra natural (Wolff et al., 1996 Over a two-year period, 13 genotypes of rescue grass were evaluated in a completely randomized design with six replications. The correlation coeffi cients and the path coeffi cient were analysed over nine characters related to seed production. Genotypic variability was signifi cant for total seeds per panicle in the second year (p = 0.019), fl ag leaf length was signifi cant in both years (p = 0.039 and 0.045, respectively), and the number of tillers per plant was signifi cant in the fi rst year (p = 0.003). For the rest of the characters, variability was highly signifi cant (p ≤ 0.001). The relationship between genotype and the environment interaction was signifi cant for the following characteristics: the number of tillers per plant (p = 0.003), the number of panicles per plant (p = 0.010), the width of the fl ag leaf (p = 0.010) and the 1000 seeds weight (p = 0.047). For the remaining characters, the interaction was not signifi cant. Path coeffi cient analyses demonstrated that the total number of seeds per panicle and the number of spikelets per panicle were the main components that determined seed yield. The contribution of these components was infl uenced by other characters, such as panicle and fl ag leaf lengths. Therefore, these can be considered to be secondary yield components. The following four components: the number of total seeds per panicle, the number of spikelets per panicle, the panicle length and the fl ag leaf length rendered a total determination for this system that explained 83.36 % and 81.61 % of the phenotypic variation for the number of fully developed seeds per panicle each year.

L. Abbott, S. Filippini, H. Delfino and S. Pistorale. 2012. Stability analysis of forage production in Bromus catharticus (prairie grass) using three methodologies. Cien. Inv. Agr. 39(2): 331-338. Thirteen genotypes of Bromus catharticus (prairie grass) were evaluated for forage production over three years using completely randomized trials with six replicates. The genotype x environment interaction was statistically significant and indicates that the behavior of genotypes differs over time. Once this interaction was detected, we used three methodologies to assess the stability of genotypes: Wricke's ecovalence, the Lin and Binns index, and the Eberhart and Russell model. The methods of Lin and Binns and Eberhart and Russell indicate that genotypes 11, 9, 3 and 4 are stable. They also rule out possible selection of genotypes 2, 10, 1 and 12 for lack of stability or poor adaptation. The correlation among these indices was statistically significant (r=0.61). When using Wricke's ecovalence, there is agreement among the indices for the selection of genotypes 9 and 4, which show good stability. There is no agreement with the other two methods for ruling out unstable genotypes. Considering the three methodologies used, the Lin and Binns index is easiest to apply and interpret because higher productivity always correlates with greater stability, and there are no restrictions on the use of regression. However, it is necessary to accumulate more data prior to the widespread use of these methods.