BREEDING SYSTEM AND ESTIMATION OF THE POLLINATION EFFICIENCY ON TRICHOCEREUS PASACANA (CACTACEAE) IN TWO POPULATIONS FROM NORTHWEST ARGENTINA

Abstract

The objectives of this study were to analyse the breeding system and the pollination efficiency in Trichocereus pasacana and their effects on the reproductive fitness in two populations from Northwest Argentina. The first population is in a protected area (Tin Tin Valley), and the other is in a site with high human activity in agriculture and apiculture (Cachi Adentro). The breeding system was analysed by a pollination experiment considering hand self-pollination, hand cross-pollination, natural pollination and automatic self-pollination. The response variables were fruit production, seed production and seed germination. The fruit production permit suggests that the breeding system of T. pasacana is xenogamic and the pollination efficiency is greater in the protected area. However, the seeds from the population with human activity presented higher germination rates. These results permit the suggestion that the Cachi Adentro population presented lower fruit production, but with a higher resource allocation for the seeds. Instead, the Tin Tin population produced a higher number of fruits, but seeds of lower quality.