Estudo da biologia floral e reprodutiva dos gêneros opuntia e nopalea: suporte ao programa de melhoramento genético

Abstract

The cactus pear forage (Cactaceae) has physiological adaptations that make it tolerant to high temperature and low water availability, representing an important source of food and water in dry regions, such as the semi-arid region. Given its relevance, gaining knowledge about its floral biology is fundamental to understand the functioning of your reproductive system and to know the processes involved in the development of its cycle. This information is essential, especially for areas such as genetic improvement that use techniques such as hybridization, performed through interspecific crossing aiming at the selection of genotypes potentially useful for the selection of characteristics of agronomic interest. In this context, this study aimed to evaluate the development of the floral structure of forage palm species of the genera Opuntia and Nopalea and its relationship with the fertilization of the ovaries. Three palm accesses were analyzed under conditions without irrigation, which were: Miúda (IPA 100004) and F21 melhorada (IPA 200021) (Nopalea cochenillifera) and F8 (IPA-200008) (Opuntia atropes, Rose), aiming to expand the knowledge about its floral reproduction, in order to support breeding programs of this cacti. For this, fruit abortion rates, stigma receptivity experiments and pollen grain viability analysis were evaluated by means of staining and in vitro germination tests. The result obtained in the abortion rate of floral buds revealed an index of 84.4% in the cultivar IPA - Miuda, 98% in improved IPA - F21 melhorada and 100% in IPA - F8. The receptivity of the stigma was 100% in the 3 accesses evaluated. In the verification of pollen viability, the staining test expressed an average of 64.4% of viable grains in Miúda, 84.6% in IPA - F21 melhorada and 97% in IPA - F8. In vitro germination, an average of 5% was observed in IPA - F21 melhorada, 21% in Miúda and 36% in IPA - F8, demonstrating a significantly low germination power. These results indicate that, in the case of fruit abortion, the failure of fertilization may be related to low ability to develop the polynic tube. However, due to the early trim of floral buds, further studies and research are necessary to identify other possible adverse factors.