Abstract

ESPINOZA, Y  and  GUTIERREZ, R. Intra-specific variability in Azolla filiculoides collected in the west-center of Venezuela. Rev. Fac. Agron. [online]. 2003, vol.20, n.2, pp.156-167. ISSN 0378-7818.

Azolla filiculoides have been reported as native plant in Venezuela, but there is no taxonomic or agronomic information about this species in the country. The objective of this study was to determine the differences among the Azolla filiculoides species collected in the west-central area of Venezuela. The variability of the environment where Azolla was collected was studied through chemical analysis (pH, CE, P, K, Ca, Mg y Fe) of the soil and water where the samples was found to live. The relative growing rate, nitrogen fixing rate, and the biomass doubling time Also the nutrient content ( N, P, K, Ca, Mg, Mn, Fe, Cu, Zn, Na) concentrations in the A. filiculoide leaf were determined by growing 0.5 g of Azolla in Hogland´s solution under greenhouse condition. According to principal component analysis the variables Cu, Fe, and Zn determined in the leaf and the concentration of P, Ca and K in soil and Ca in water caused greater variability among the Azolla samples. Cluster analysis based on these variables, and including nitrogen fixation rate, double time, and potential growth rate revealed 3 ecotypes of A. filiculoides that showed more than 65% similarity. The two dominant groups contained 68% of the samples taken. These two group will be more successful in areas with high natural soil fertility, or where phosphate fertilizers with high potassium rates are used. Under this condition samples # 28, 29, 31 y 35 are recommended as nitrogen bio-fertilizers in rice fields because of their high nitrogen fixation ability.

Keywords : Azolla filiculoides; accessions; symbiotic nitrogen fixation; growth rate; doubling time; nutrients.