Variability in the number of stems in Lotus tenuis seedlings growing at high density

Abstract

Successful establishment of Lotus tenuis, an important legume to improve grasslands in the Pampa Deprimida, might be limited by low seedling vigor. The number of crown stems is an important component of vigor. The objective of this work was to determine the variability in the number of crown stems on seedlings of 11 Lotus tenuis natural populations sown at high density under semi-controlled conditions. Seeds of all populations were collected in the Province of Buenos Aires, Argentina. They were sown in plastic pots and cultivated in a greenhouse. Eight weeks after seeding, seedlings of each population were grouped according to their number of stems per crown. Variability in the crown stem number was studied within and among populations. Number of seedlings with different stem crown numbers within each population, dry weight (PS) of the group of individuals and mean for each group, the predominant groups of crown stem numbers from the total number of seedlings within each population, and those that presented a greater grouped dry weight and average per individual of each group were also determined. Simple linear regression of the crown stem numbers versus dry weight was conducted. ANOVA and Tukey´s tests were used (p≤0.01). The relationships between crown stem numbers and number of seedlings within each population tended to bimodal in 10 out of 11 populations. The crown stem number presented differences among (p≤0.01) and within (variation coefficient=44 to 56%) populations. Classes of 1 to 3 stems per crown were dominant (p≤0.01). Groups of 3 or 5 stems per crown showed greater dry weight (p≤0.01) when they were grouped or taken as a mean per individual, respectively. The regression was significant (p≤0.01) for mean dry weight per individual. Using of high density allowed the expression of variability within and among populations in the number of stems per crown. This variability can be attributed to genetic causes, considering the semi-controlled conditions under which the experiment was conducted. This implies the possibility of improving such parameter and the seedling vigor indirectly.