Biologia floral e reprodutiva do cajueiro-anão

Abstract

Abstract (Resumo em inglês ou outra língua de preferência do aluno): Information about floral and reproductive biology is essential for breeding programs, as floral characters are important for selection schemes since they are associated with production. However, little information related to this topic is available in the cashew literature, especially for the small-type, which has been acquiring more space among cashew farmers. Thus, the objective of this thesis was: (i) understand the floral development and sexual expression in dwarf cashew, and the influence of the evaluation period and harvest on the floral characters; (ii) to elucidate the influence of flower distribution on the plant crown and its implications for fruit production. The genetic material consisted of 10 genotypes (clones in preliminary evaluation phase), with four plants per plot, evaluated in two harvests (2018 and 2019). Thus, the data of two blooms for each harvest were obtained, processed, analyzed and the results separated into two chapters, according to the aforementioned objectives. In chapter I, three flowering seasons were analyzed at – 30, 45 and 60 days after the beginning of flowering, in the two seasons. To characterize the floral structures, the following were evaluated: number of male, hermaphrodite, and abnormal flowers; biomass; length and width, and panicle branches - primary and secondary branches. The evaluation period was significant for most floral characters, while the significance of the harvesting effect was observed only for the number of secondary branches. At 30 days, the production of hermaphrodite flowers was correlated by the characters: length and width of the panicle; at 45 days due to the presence of male flowers; and at 60 days for the structural characters of the panicle: length and primary branches. In conclusion, the flowering evaluation period brought about changes in the reproductive structure of the cashew tree, providing differences in the floral morphology of the panicles, affecting the production of hermaphrodite flowers. In chapter II, aspects of floral and reproductive biology, were evaluated in the two harvests and between the quadrants of the canopy. After the beginning of flowering, the following characters were evaluated: average number of emitted and accumulated flowers; average time for flower opening; estimated number of panicles, male flowers, hermaphrodite flowers and fruits/quadrant. Regardless of the type of flower, flowering and harvest, the cashew plants showed the same trends in relation to the average and accumulated number of flowers. The plants showed a high ratio between male and hermaphrodite flowers, around 10:1, reinforcing a common characteristic in allogamous species. Male flowers demanded more time before anthesis during the harvests. In addition, there was variation in the number of panicles and hermaphrodite flowers between the quadrants of the canopy, with a trend towards higher values in the northern quadrant. Otherwise, this same trend was not found for the number of fruits, indicating that the association between flowering and fruiting does not seem to be linked to flower distribution.