Estudo das causas da baixa produtividade de oliveiras no Rio Grande do Sul: aspectos morfológicos e genéticos relacionados ao sistema reprodutivo

Abstract

The olive tree has a great diversity of cultivars in the world, whose identification has been a problem. Genetic studies on the heritability of agronomic traits are scarce. Additionally, there is little information regarding the storage and viability of the species' pollen. The lack of information prevents advances in genetic improvement. Thus, the aim of this study was to generate information on the reproductive system; heritability in a broad sense of characters related to fruits and oil; and pollen viability after storage. In this work, the cultivars 'Arbequina', 'Arbosana', 'Frantoio', 'Koroneiki', 'Manzanilla de Sevilla' and 'Picual' were used in southern Brazil. Ultrastructural characters of pollen and pistil were analysed, which can be used to discriminate cultivars under local conditions in the south of the country. The results show that the measurements of the micromorphological characters of pollen grains and pistils are remarkably similar within each cultivar, but showing significant differences when comparing different cultivars, which may contribute to the establishment of studies on the classification of olive tree cultivars. A second study was carried out in order to observe the heritability in the broad sense (H2) of fruit traits of these same cultivars, in the same Brazilian region. From the results, it was observed that some cultivars such as 'Koroneiki' and 'Picual' had their characters mainly controlled by the genotype, while 'Arbequina' was more influenced by the environment. In the third study, the viability of pollen under long-term storage was analyzed, testing different temperatures, as well as the use of glycerin as a means of protection against damage caused by cold, in 'Arbequina' and 'Koroneiki' cultivars. The results showed suitable storage conditions for 82 days at -80°C, reaching the minimum limit of 30% germination, which can be used for crosses during the pollination period. However, the protocol did not show favorable results for keeping pollen stored in the long term, achieving only 122 and 136 days of viable pollen for 'Arbequina' and 'Koroneiki' cultivars, respectively. The results generated in this study can contribute to the identification and improvement of olive trees out of their original place of domestication. Despite the fact that different environmental conditions (temperature, humidity, radiation, among others) drastically influence some cultivars such as Arbequina, Arbosana or Manzanilla de Sevilla, affecting their reproduction, this study allowed us to demonstrate that there are cultivars such as Picual or Koroneiki that the genotype marks their development and, therefore, are little influenced by the surrounding environment, making them candidates for development and improvement in the southern region of Brazil.