Revista de Biología Tropical (Dec 1999)
Polimorfismo isoenzimático en cuatro razas y un híbrido de Bactris gasipaes (Palmae)
Abstract
Se estandarizó un sistema de electroforesis de isoenzimas con tejido de hojas que permitió la identificación del polimorfismo fenético entre cuatro razas y un híbrido de pejibaye Bactris gasipaes provenientes de Brasil, Perú, Bolivia, Panamá y Costa Rica. Las isoenzimas ensayadas fueron: PRX, EST, ACP, ME, DIA, MDH, G6PDH, PGI, SOD, PGM, ADH, GOT, de estas solamente las dos œltimas no mostraron actividad. El resto de isoenzimas mostraron polimorfismo fenético en diferentes grados, por esto se consideran marcadores polimórficos potenciales para estudios de variabilidad genética en pejibaye. Se encontró un locus único en el zimograma de la enzima PRX en las muestras de Utilis-Guápiles (CR), el cual podría usarse como un marcador discriminatorio para esta raza. Se establecieron relaciones de similitud isoenzimática entre las razas Utilis-Guápiles (CR) y Tuira-Darién (Pa); Tembé-Chapare (Bo) y Pará-Belem (Bra) respectivamente, mientras que el híbrido Yurimaguas (Pe) se ubicó aparte y ligeramente más cercano a Utilis y Tuira, por esto se considera que posiblemente desciende de padres aún no identificados.The study of genetic diversity in peach palm (Bactris gasipaes K.) is important for the breeding work on this palm and to corroborate the hypotheses on its origins. For that purpose it is necessary to use alternative techniques to complement the morphological studies traditionally made. One of the techniques that responds to that need is isozyme electrophoresis. The isozymes are biochemical markers of importance in the study of genetic variability in plants of economic importance, because they are the primary products of genetic expression. This work is an electrophoretic analysis on gels of polyacrilamide to study phenetic relations using twelve isozymes on four races and an spontaneous hybrid of peach palm. The biological material used came from the germplasm bank from Los Diamantes Experimental Station, Guápiles-Costa Rica. Four races and a hybrid were selected from that collection. They represented different procedences with morphological differences as well as having particular geographical distribution patterns; they were: Tembé-Chapare (Bolivia-Bo), Pará -Belem (Brasil-Bra), Utilis Guápiles (Costa Rica-CR), Tuira-Darién (Panamá-Pa) and Yurimaguas (Perú-Pe). Five trees of each race and the Yurimaguas hybrid were studied. Different tissues were tried: leaf, adventitious roots, spines, masculine flowers and ripe fruits. An standard native and discontinued method was established on a polyacrilamide matrix for the analysis of twelve isozymes: (PRX, EST, ACP, DIA, G6PDH, ME, MDH, GOT, ADH, PGI, PGM and SOD). The amount of tissue used was 1. 5 g, with 20 min clarification time at 15000 gravity value and a temperature of 4°C. The protocol proposed by Baaziz & Saaidi (1988) was followed with a modification of concentration of the phosphate buffer solution from 0,005 M to 0. 1M with a 50 to 200 volts gradient. The root, flower and spine tissue were difficult to homogenize because of their high fiber content. The fruit has too much oil and starch, which distort the banding. For those reasons they were discarted. The leaves were selected because they are easy to homogenize and are available all year round. The standardized electrophoretic method allowed the effective use of ten of the twelve isozymes in the leaf tissue. Those ten isozymes showed phenetic polymorphism and are considered useful polymorphic markers for genetic and phenetic diversity studies in Bactris gasipaes. A discriminant marker for the Utilis-Guápiles race was found with the PRX isozyme, which shows an additional locus only in material from that procedence. The conglomerate statistical analysis showed that the races and hybrid studies can be placed in three groups: one is formed by Par and Tembé, the second one by Utilis and Tuira, and the hybrid Yurimaguas is a class by itself and although it seems a bit closer to Utilis-Tuira, it is suspected that has its origin from unknown parents. These results fit previous morphological interpretations. A genetic analysis was not made because of the small sample size, but methodological procedures were established for future research projects using larger populations to study peach palm isozyme electrophoretic diversity.
