Polinização entomófila do híbrido interespecífico (Elaeis oleifera (Kunth) Cortés, 1897 x Elaeis guíneensís Jacquin, 1763) (Arecaceae) e Ciclo Evolutivo de um Derelomini (Coleoptera: Curculionidae) na Amazônia Central, Brasil

Abstract

Actually the palm tree Elaeis guineensis Jacquin, 1763, is the oleaginous more productive in the world. It is a monoicous palm tree with flowers grouped into masculine and feminine inflorescences that usually needs pollination for the formation of the seeds. The genetic improvement of this palm tree in America has been addressed for the selection of highly profitable crossings, resistant to the disease of the 'Fatal Yellowing', producing the hybrid (E. guineensis x E. oleifera) - EmbrapaICirad. The pollinating agents of these palm trees are small beetles that belong to the Derelomini group (Curculionidae), which help the optimization of the productivity of the plantings. This way, the objectives of this work were: to esteem the Capacity to Carry Pollen (CCP); the Charge of Pollen calculated (CPc) and the Pollinating Force (PF) of four pollinating species of the hybrid (Elaeidobius kamerunicus, E. subvittatus, Grasidius n. sp. and morfospecie Ml) and CCP and CPc of two pollinating species of the 'caiaué' (Grasiúius n. sp. and morfospecie MI), as well as to determine the Evolutionary Cycle of the morfospecie M1. The study was accomplished in Urubu River Experimental Station, Embrapa - Western Amazonia. To quantify CCP, the insects were collected rnanually in the masculine inflorescences of the hybrid and the 'caiaué' (E, oleifera). The number of pollen grains adhered to the body of the insects was quantified under microscope. The Charge of Pollen was calculated (CPc) considering the CCP and the PF was measured quantifying the number of insects in the feminine inflorescences. To determine the Evolutionary Cycle of the morfospecie Ml, the insects were created into entomologic cages in the masculine spike of the hybrid. The cephalic capsule of the worms was measured under stereoscopic magnifying glass, to differentiate the larval stadiums. Of the four pollinating species studied in the hybrid, Grasidius n. sp. presented the highest values of CCP, CPc and PF. Therefore, this specie had a CP = 5626 and CPc = 2293; E. kamerunicus CCP = 5247 and CPc = 2138; the morfospecie Ml CCP = 3591 and CPc = 1463 and E. subvittatus CCP = 1943 and CPc = 792 grains of pollenlinsect, respectively. PF of Grasidius n. sp was of 15,6; the one of E. kamerunicus was of 6; the one of E. subviffatus and rnorfospecie M1 was of 0,4 feminine individuaI/inflorescences of hybrid, respectively. The values of CCP and CPc in the 'caiaué' were inferior than the same species in the hybrid, so that for Grasidius n. sp. the CCP = 962 and CPc = 392 and for morfospecie Ml the CCP = 1403 and the CPc = 572. The morfospecie M1 completed its Evolutionary Cycle in I 9 - 20 days, the worms emerged of the eggs in two days and passed through four larva1 stadiums (p<0.05). The pupa period lasted approximately nine days. These results indicated that Grasidius n. sp. has a larger pollinating capacity in the hybrid than the other studied species. Therefore, Grasidius n. sp has potential to be included in the Programs of Liberation of Pollinating agents in hybrid plantings.