3 results
Effect of three environments on the efficiency of indirect selection in Eragrostis curvula (lovegrass) genotypes
- M. A. DI RENZO, M. A. IBAÑEZ, N. C. BONAMICO, M. E. FARICELLI, M. M. POVERENE, C. V. ECHENIQUE
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- Journal:
- The Journal of Agricultural Science / Volume 140 / Issue 4 / June 2003
- Published online by Cambridge University Press:
- 07 October 2003, pp. 427-433
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A significant genotype–environment interaction can limit gains in selecting superior genotypes since the best genotype in one locality may not be the best one in another locality. The efficiency of indirect selection is related to the heritability of the trait and to the genetic correlation between localities. Since a major objective of Eragrostis curvula (lovegrass) breeding programmes in Argentina is to select superior genotypes from new cultivar introductions, research on the relative effectiveness of direct and indirect selection is necessary in order to identify localities under which the efficiency of indirect selection could be maximized. To do this, experiments using a set of 18 hybrids were carried out in three localities from the semi-arid region of Argentina. Aerial biomass yield, leaf length, crown diameter, panicle number and panicle length were measured and an analysis of variance and covariance were performed. The high genetic correlation obtained suggests that the genetic mechanisms involved in the expression of these traits would be the same, or at least very similar, in Río Cuarto, Villa Mercedes and Bahía Blanca environments where the hybrids showed a stable performance. In general, the heritability obtained was higher in Villa Mercedes and Bahía Blanca than in Río Cuarto. For a given selection intensity the expected correlated response in Villa Mercedes and Bahía Blanca to indirect selection was compared with the expected gain with direct response to selection in Río Cuarto. For dry matter yield, indirect selection in Bahía Blanca did not differ from selection done in Río Cuarto (−3%). However, for performance in Villa Mercedes indirect selection was shown to be less efficient (−29%). For the other traits considered, indirect selection was variable and less efficient, ranging from −18 to −34%. The estimated decrease in efficiency of selection for all the traits considered in the locality of Río Cuarto was higher than in the other localities, suggesting that this place was not a good choice for carrying out indirect selection. Conversely, genetic progress would be faster if selection was carried out in Villa Mercedes, because the evaluations provide higher and more accurate estimates of the heritabilities than in the other localities.
Genotype–environment interaction of lovegrass forage yield in the semi-arid region of Argentina
- M. A. IBAÑEZ, M. A. DI RENZO, S. S. SAMAME, N. C. BONAMICO, M. M. POVERENE
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- Journal:
- The Journal of Agricultural Science / Volume 137 / Issue 3 / November 2001
- Published online by Cambridge University Press:
- 23 January 2002, pp. 329-336
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Genotype–environment interaction and yield stability were evaluated for 19 genotypes of lovegrass (Eragrostis curvula). The study was conducted in the central semi-arid region of Argentina. Three locations and two growing seasons in combination generated six environments. Genotypic responses and stability of yield under variable environments were investigated. The genotype–environment interaction was analysed by three methods: regression analysis, AMMI and principal coordinates analysis (PCO). Analysis of variance showed that effects of genotype, environment and genotype–environment interaction were highly significant (P < 0·01). The genotypes accounted for 20% of the treatment sum of squares, with environment responsible for 65% and interaction for 14·5%. The biplot indicated that there was partial agreement between the AMMI and regression model. However the scatter point diagrams obtained from PCO analysis revealed only limited agreement with the results obtained by the regression analysis and the AMMI model. The results show that the AMMI model as a whole explained twice as much of the interaction sum of squares as did regression analysis and was more adequate than PCO analysis in quantifying environment and genotype effects for forage yield. AMMI analysis of the genotype–environment interaction effects showed that there were responses characteristic of a particular location. This type of association implies some predictability of genotype–environment interaction effects on forage yield production when differential responses across genotypes are associated with locations. Environmental factors may contribute to the interpretations of genotype–environment interaction. However in the semi-arid region, where fluctuations in growing conditions are unpredictable, additional research is required to obtain an integration of interaction analysis with external environmental (or genotypic) variables.
Estimation of repeatability and phenotypic correlations in Eragrostis curvula
- M. A. DI RENZO, M. A. IBAÑEZ, N. C. BONAMICO, M. M. POVERENE
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- Journal:
- The Journal of Agricultural Science / Volume 134 / Issue 2 / March 2000
- Published online by Cambridge University Press:
- 01 March 2000, pp. 207-212
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Eragrostis curvula (Schrad.) Nees s. lat., a highly polymorphic polyploid complex, can be considered as one of the most important warm season perennial grasses for the semi-arid regions of central Argentina. In apomictically propagated and perennial plants such as weeping lovegrass, where successive measurements can be done across time, repeatability estimates provide an indication of the degree of influence of permanent effects on the phenotypic variation and allow prediction of future performance from past records. Analysis of variance of the experiment showed highly significant variation (P < 0·01) for the main factors in all four traits. Although there was very high variability between cuts, hybrids of E. curvula exhibited considerable inter-entry variability, in particular for those traits determining forage yield. Repeatability calculated in this experiment was highest for the crown diameter (0·86), leaf length (0·84) and dry matter (0·84), while in panicle number (0·66) it was lowest. Repeatability estimates for the vegetative characteristics indicate small effects of temporal environment. The four traits studied, including panicle number with their moderate repeatability, do not require an essentially different number of observations to obtain measures at the same level of accuracy. For vegetative characters two harvests provided 98% of the accuracy of the total obtained with four cuts, and for panicle number the same percentage was obtained for three harvests. This stability of performance is a desirable characteristic for grass cultivars. Patterns of trait associations were also described. Because leaf length is closely associated with dry matter and has high repeatability, to use leaf length as an indirect evaluation criterion should be almost as efficient as direct evaluation for aerial biomass yield. Reliable estimates of parameters such as repeatability and phenotypic correlation are needed for prediction of production values and for the design of efficient improvement programmes. For genotype evaluation additional research is required to quantify the extent of genotype × environment interaction across years and localities of semi-arid regions.