Polimorfismo floral e sistema reprodutivo da erva-baleeira (Varronia curasavica Jacq.) em banco de germoplasma

Abstract

Varronia curassavica Jaqc., is a native shrub with medicinal use and characterized by the presence of a floral polymorphism. The objective of this study was to investigate floral biology, floral morphometry and the reproductive system of Varronia curassavica Jacq. in a germplasm bank in the north of Minas Gerais. The floral biology, inflorescence dynamics, calculated morphometric characterization, reciprocity index of flowers, quantification of the number of pollen grains by morphology and viability of these grains, and definition of the reproductive system. Pollination tests were carried out: natural pollination (control), spontaneous and manual self-pollination, apomixia, intermorfos cross-pollination (legitimate crossing) and intra-morphic cross-pollination (illegitimate crossing). The morphometric analysis demonstrated the presence of four distinct morphs, divided into two size categories: 1) Longistila Grande (LG), 2) Brevistila Grande (BG), 3) Longistila Pequena (LP) and 4) Brevistila Pequena (BP). Reciprocity was observed within the two size categories, confirming herostilia. The number of pollen grains was lower in the LG flowers (1627), which differed significantly from the others, whereas the lower pollen viability was observed in the LP flowers (82%), which distinguished themselves from the others. The floral opening begins in the morning with greater receptivity stigmatic until 11 o'clock. V. curassavica is non apomic, allogama obligatory and dependent on pollinators for fruiting for morphos LG, LP and BP, however the floral morph BG broke the barriers of autoincompatibility and heteromorphic incompatibility. The reproductive success of natural pollination was over 20% in flowers LG, BG, LP (21-27%), while BP presented an average fruit yield of 11%. In manual self-pollination only the BG morph (21%) presented fruiting. The legitimate pollinations formed fruits with longistil and brevistilo morphs acting as donor and recipient of pollen. An average fruiting of 23% was observed in small-sized morphs (LPxBP and BPxLP) and 53% in the large category (LGxBG and BGxLG). In the test of the illegitimate crosses between the categories fruit formation was observed only when the large category morphs acted as the female progenitor and the small ones as the male progenitor (LGxLP 14%) and BGxBP (23%). These results show that there is flexibility in the differentiated compatibility among morphs, allowing the proposition of different crosses between populations of interest.