Morphological development of Alfagraze cultivar and Crioula alfalfa populations selected at the seedling stage

Abstract

-The objective of this study was to compare two populations of Crioula alfalfa cultivars, selected by the length of the seedling second internode (Crioula-LI, long internode = 2.5 cm; Crioula-SI, short internode = 1.5 cm) with Alfagraze cultivar in order to verify the seedling morphology value for the selection of more prostrate plants. The plants were grown individually in pots in a semi-protected environment and harvested at 74, 104, 134, 164, 194 and 224 days. Crioula populations varied in terms of height, leaf area, root volume, dry matter yield, and the Crioula-LI population outnumbered that of Crioula-SI. For height, length of internode and primary stem, Alfagraze (45.1 cm, 2.1 cm and 16.7 cm) was similar to Crioula-SI (37.6 cm, 2.3 cm and 18.2 cm); however, the leaf area (2.028 cm 2 ) and dry matter yield (20.3 g) did not differ from those of Crioula-LI (2.021 cm 2 , 21 g). The Alfagraze cultivar surpassed the Crioula population in terms of procumbency, crown diameter and crown stem number. At the flowering stage, the Crioula-LI cultivar had total stem number (61/plant) higher than Alfagraze (47/plant) and Crioula-SI (41/plant) cultivars. The length of the seedling internode is a promising marker for the selection of alfalfa, being a predictive factor for plant height, stem number, root volume and leaf area, and can be useful in the alfalfa breeding.

Grazing resistance mechanisms in alfalfas of different aptitude in the juvenile stage

“…Alfagraze showed, from 60 days of age, some avoidance mechanisms (Briske, 1991), such as smaller height, internodes, apical bud accessibility and leaf size than the upright cultivars ( Figure 1). Some studies performed in Brazil showed that it is possible to select alfalfa populations with small height through the internode length at seedling stage (Favero et al, 2009), which could indirectly indicate a higher grazing persistence. Favero et al (2008) observed higher survival for severe cut (weekly and 2-cm stubble) of a Crioula alfalfa population selected by short internode (50% survival) in relation to that of long internode (25% survival).…”

“…Favero et al (2008) selected alfalfa populations with variability in dry matter yield and survival variability based in this trait. The seedling internode was shown as a predictive factor for plant height, stem number, root volume and leaf area and persistence to severe cutting in alfalfa (Favero et al, 2009). …”