Caracterização de genótipos de alface (Lactuca sativa L.) em cultivo hidropônico sob diferentes valores de condutividade elétrica da solução nutritiva

Abstract

Lettuce (Lactuca sativa L.) is the most cultivated vegetable in hydroponic system. This work aims to evaluate and characterize genotypes of lettuce grown under two levels of electric conductivity of nutrient solution, as well the genetic variability of these genotypes through the molecular markers of the type ISSR (Inter Simple Sequence Repeat. Four experiments were carried out using nutrient solutions with electric conductivity of 2.0 or 2.5 dS.m-1. Seeds were sown in phenolic foam plates and the seedlings were transferred for the nursling, on which they grew for 10 days receiving diluted nutrient solution. Then, they were transferred to polypropylene hydroponics channels measuring 50 mm of diameter on a growth bench for the initial growth. After 15 days the plants were transferred to others hydroponics channels measuring 75 mm of diameter on which they received the experimental treatments for more 15 days. Plant fresh weight, leaves fresh weight, root and stem fresh weight, stem length, number of leaves and tip-burning index were evaluated. Comparing the reaction of the cvs to the nutrient solutions with electric conductivity of 2.0 and 2.5 dS.m-1, the results showed that the tip-burning index for Babá de Verão and Forest was lesser for those grown on the nutrient solution of 2.0 than 2.5 dS.m-1. The total plant fresh weight and leaves fresh weight were greater for the plants grown on de nutrient solution with electric conductivity of 2.5 than 2.0 dS.m-1. The cvs Tinto, P-76 and P-78 presented higher tip-burning index on the nutrient solution of 2.5 dS.m-1, comparing to 2.0 dS.m-1. There was no significant difference on total plant fresh weight neither leaves fresh weight of the cvs Regina 2000, Tinto, P-44, P-85 and P-89, comparing the two nutrient solutions. For the study of the genetic variability thirty primers of ISSR were used. The data were interpreted with the aid of a matrix of genetic similarity after the construction of a dendrogram. Regarding all genotypes of lettuce studied, ten primers were amplified of a total of 134 fragments of DNA. The average of 13.4 fragments per primer was amplified and the size of fragments varied from 400 (UBC 842) to 2000 bp (UBC 808 and 857). The results showed that ISSR markers can be useful in the studies of genetic diversity of lettuce germplasm.