Fenologia, polinização e biologia reprodutiva da goiabeira (Psidium guajava var. ‘paluma’, Myrtaceae) em cultura irrigada no semiárido.

Abstract

Pollination is a fundamental process for fruit production and although Psidium guajava L. is self-compatible, it is inefficient in self-pollination. Thus, the presence of bees provides higher rates in the production of guavas. However, climatic seasonality can interfere with the abundance and / or activity of these pollinators. The aims of this work are to expand the knowledge on the reproductive biology of guava. We analyzed crucial aspects for a better understanding of fruit and seed production, such as reproductive phenology, floral and reproductive biology and interaction with floral visitors in an area of Caatinga. More specifically, we expected to contribute with useful information for increasing the productivity of guava in the Brazilian semi-arid region. We carried this study at Farm São Paulo dos Dantas (FASP), located at Northeast Brazil. We performed phenological observations over thirteen months, collecting data on flowering and fruiting of 20 randomly marked individuals. We tested the correlation of reproductive phenological events with climatic variables. We analyzed flowers in the field and laboratory, evaluating anthesis, floral morphometry, pollen viability, pollen-ovule ratio and stigma receptivity. We evaluated reproductive biology from

natural and controlled pollination tests (spontaneous self-pollination and manual self- pollination). We recorded the richness, abundance and behavior of floral visitors in the field

through daytime observations, totaling 24 hours in the dry season and 24 hours in the rainy season. Production of flowers and fruits was continuous in the population. We not found significant correlation between breeding phenology and precipitation and evapotranspiration, indicating that fruit pruning and irrigation are factors that interfere with these events. P. guajava flowers are melittophilous. The stigma was receptive from pre-anthesis to the last observation time (16:00) and pollen viability was 99.5%. The results of system breeding confirm that guava is self-compatible and natural pollination showed a higher number of fruits produced. There was no significant difference between the number of visits to flowers in the dry and rainy season (N=1117 and N=1346 visits, respectively). The potential pollinators of P. guajava are bees of the genus Centris and Xylocopa, although the most frequent visitor has been the exotic bee Apis mellifera, classified as inefficient pollinator, but which ensures pollination in the dry period.