Abstract
Most apple trees (Malus domestica Borkh.) are self-incompatible and fruit yield depends on cross-pollination between genetically compatible cultivars with synchronous flowering. Flowering intensity can vary strongly among years due to the biennial bearing habit of the cultivars. The knowledge of the phenological stages and floral and pollen characteristics is essential to select suitable pollen donors. We evaluated the phenotypic variability of flowering-related traits (i.e., flowering phenology, flowering intensity, pollen production and pollen quality) in 45 apple cultivars over two successive flowering seasons. Large phenotypic variability was found among the studied cultivars indicating that the local germplasm collection provides a good source of genetic and phenotypic diversity. However, low correlations were observed between floral biology traits and, consequently, the improvement in one trait seems not to affect other traits. Some of the cultivars such as ‘Perurico’ and ‘Raxila Dulce’ regularly produced copious amounts of high-quality pollen which can improve the pollen load dispersion leading to a most effective pollination process. We did not identify statistically significant correlations between pollen attributes and the biennial bearing phenomenon. The large variation in bloom dates from year-to-year observed under a typical Oceanic climate makes it advisable to combine cultivars in new plantings.
Highlights
Published: 28 August 2021Pollination is a key event in plant reproduction which consists in the transfer of pollen grains from anthers to stigmas in order to fertilize the ovules and begin the development of seeds and fruits [1]
Large phenotypic variability in floral biology traits was found in the set of apple cultivars even though most of the cultivars were selected in the study region and have the same geographical origin
Our study covering two successive flowering seasons highlights some remarkable differences among apple cultivars in terms of flowering intensity and pollen biology attributes
Summary
Published: 28 August 2021Pollination is a key event in plant reproduction which consists in the transfer of pollen grains from anthers to stigmas in order to fertilize the ovules and begin the development of seeds and fruits [1]. Apple (Malus domestica Borkh.) is known as a gametophytic selfincompatible flowering tree [2] and yield relies on the successful cross-pollination between at least two cross-compatible cultivars which flower synchronously [3,4]. The quantity and quality of apple production is significantly affected by the effectiveness of the pollination process [5,6]. Apart from the fundamental requirement for fruit set and tree productivity, the presence of different pollen sources has a favorable impact on fruit quality parameters such as size, shape and organic matter [5,7,8,9,10]. Apple trees are heavily dependent on insect pollination and the contribution of pollinators is essential for obtaining consistent yields [3,5,6].
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