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Analysis of the early expression characters for the cultivars differentiation of Lotus glaber Mill. (= Lotus tenius Waldst. et Kit.).

M. Colares *, M.M. Mujica **, and C.P. Rumi***

*Area de Botánica
**Area de Genética y Mejoramiento Animal y Vegetal
***Instituto de Fisiología Vegetal
Facultad de Ciencias Agrarias y Forestales
UNLP, CC 31 (1900)
La Plata, Argentina
infive@isis.unlp.edu.ar

Objective: Identify characters of early expression, useful for the differentiation of the cultivars of L. glaber.

Materials and Methods

Four improved populations were evaluated: the cv. Tresur Chajá, the experimental synthetic varieties LH1 and LH2, and an improved population for seedling vigor by the recurrent selection method (SR1).

Sowing was made in May, in individual pots with previously homogenized soil. The experiment was carried out outdoors. Watering was as needed according to environmental conditions. A sample of n= 50 individuals was evaluated for each population. After emergence, a sparsely was made until one plant per pot could be guaranteed. One week before the final evaluation (September), the central terminal leaflet next to the last unfolded leaf of each plant was collected. They were conditioned arranging them between two self adhesive plastic films, following a matrix arrangement that allowed the identification. A magnified photocopy at 150% was made and afterwards they were measured using a 0.5 mm-graduation ruler. The length, medium and maximum latitude were determined for each leaflet and the latitude/longitude ratios were calculated.

For the final evaluation the substrate of each plant was separated by flooding followed by washing of the radical system in a flow of water on a mesh. The following determinations were made: main stem length, number of unfolded leaves on the main stem, number of crown stems, root length, number of secondary ramifications and degree of root dominance; dry weight of main stem, crown stems and root. Aerial dry weight was calculated both, in total and aerial dry weight/root dry weight ratio. In order to analyze the root dominance characteristic, three categories were established according to the main root length in relation to the secondary roots length: with no dominance (not exceeding), semi-dominant (up to 50% longer) and with dominance (> 50% longer), which were assigned arbitrary values of 0, 1 and 2, respectively. These values, the unfolded leaves number and the crown stems number were transformed by Ö (Y+ ½). The crown was separated from each plant and was fixed in FAA for later observation and measurement of the maximum diameter by means a 0.5 mm-graduation ruler, under an stereoscopic microscope.

A statistical analysis was made and the following parameters were determined for each character: mean (X) and coefficient of variability (CV (%)). The t-test (a = 0.05 and a = 0.01) was applied to analyze mean differences among populations.

Results

The characters evaluated in the 4 populations showed a CV of similar magnitude among populations, but with major differences among characters (Table 1). The higher ones (CV ³ 40%) were present in the total dry weight and in all of its components, while the lower ones (CV£ 20%) were present in the number of unfolded leaves, the number of crown stems, aerial dry weight/root dry weight, maximum latitude/central leaflet length, medium latitude/central leaflet length. Data transformation had no effect on the statistical analysis used for means comparison, except for the degree of the root dominance character.

The dry weight of the different components, the medium latitude of the central leaflet and the maximum diameter of the crown showed greater differences and thus a more effective discrimination among the populations evaluated (Table 2). The comparison of the experimental populations against the commercial cultivars showed that there were highly significant differences for many of the characters, specially total dry weight and weight of all its components, main stem length and crown maximum diameter. The greatest inter-population similarity was reported between the two experimental synthetic varieties LH1 and LH2, as expected, as LH2 resulted from the second selection cycle from LH1. Moreover, it is worth mentioning that according to these results, this second selection cycle increased the differences compared to the commercial cultivar.

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