Abstract
The insufficiency of morphological descriptors reveals the importance of studies related to this topic for the genetic improvement of soybean, with attention to the possible descriptors measured in early stages of plant development which allows obtaining fast results. The aim of this work was to estimate the coefficient of repeatability of some morphological descriptors in the early stages of development of soybean and the minimum number of evaluations necessary to predict the real value of genotypes. Five (5) experiments were carried out with 124, 93, 90, 16 and 16 genotypes of soybean for the first, second, third, fourth, and fifth experiment, respectively, with characteristics combined at the stage V3. It was concluded that the length of the first internode requires fewer measurements compared to other measured characteristics. With six measurements, it was possible to obtain 95% and 90% reliability for plant height in V3 and first internode length, respectively, by the methods ANOVA, CP (correl), CP(cov) and AE(correl). With seven measurements, it was obtained 90% reliability for the epicotyl length for all methods used; 85% for the petiole length of unifoliate leaf by method of CP(cov) and 90% by methods ANOVA, CP(correl), AE(correl). With 15 measurements, it was possible to obtain 90% reliability for the hypocotyl length, petiole length of trifoliate leaf and the angle formed by the insertion of the petioles of the unifoliate leaf for all methods used; and, for the rachis length of the first trifoliate leaf, 37 measurements would be necessary for reliability of 90% by methods of ANOVA, CP(correl), CP(cov) and AE(correl). Key words: Glycine max (L.), soybean breeding, number of evaluation, stability.
Highlights
One of the major components of the global financial market are the agricultural Commodities, within the soybean (Glycine max (L.) Merrill) stands out, in relation to the volume sold
With 15 measurements, it was possible to obtain 90% reliability for the hypocotyl length, petiole length of trifoliate leaf and the angle formed by the insertion of the petioles of the unifoliate leaf for all methods used; and, for the rachis length of the first trifoliate leaf, 37 measurements would be necessary for reliability of 90% by methods of ANOVA, CP(correl), CP(cov) and AE(correl)
The results indicate the need for further studies with the aim of better understanding about the effect of genotypes, the influence of environmental conditions and genotype x environment interaction for the additional descriptors, aiming to estimate repeatability and determination coefficients and the number of evaluations needed in order to estimate the difference between the evaluated materials
Summary
One of the major components of the global financial market are the agricultural Commodities, within the soybean (Glycine max (L.) Merrill) stands out, in relation to the volume sold. The genetic improvement programs of the oleaginous have been intensively acted in the development of new cultivars in Brazil, mainly after 1,997, when it was sanctioned the Law of Protection of Plant Varieties (LPC). The distinctiveness of a cultivar refers to a clear difference from any other variety whose existence on the date of the period of protection is recognized (Grilli, 2005). The differentiation of cultivars is performed by a minimum margin of descriptors that are specific to each species (Neto et al, 2005). About 38 descriptors are used between the mandatory and the additional to differentiate genotypes of soybean, they are still insufficient to distinguish cultivars (Nogueira et al, 2008).
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