Pollination is an essential process for fruit set, fruit growth, fruit quality, and seed set of most apple cultivars. The first step of successful apple pollination is the transfer of pollen to the stigmatic surface (typically vectored by bees) followed by an adhesion of pollen grains to the papilla cells of the stigmatic surface (Dresselhaus and Franklin-Tong, 2013; Selinski and Scheibe, 2014). The deposited pollen hydrates and germinates and then pollen tubes penetrate the stigma and grow down the style. Pollen recognition occurs both on the stigmatic surface and within the style (Dresselhaus and Franklin-Tong, 2013). Once pollen reaches the base of the style, one sperm nucleus enters the egg cell to produce the embryo (resulting in seed set), and the other fuses with the two polar nuclei to produce the endosperm.
Pollen source and temperature have a tremendous influence on the rate of pollen tube growth. Jackson (2003) and Petropoulou and Alston (1998) proposed that the proportion of the stigmatic surface covered by the germinated pollen of apples and pears depends on the pollen donor and environmental temperature at the time of pollination. They reported that ‘Spartan’ pollen had a higher germination percentage than that of ‘Cox’s Orange Pippin’ at 8 to 10 °C and ‘Idared’ at 14 to 16 °C. Linear correlations between pollen germination on the stigmatic surface and temperature were reported from 13 to 29 °C (Yoder et al., 2009) and from 6 to 33.5 °C (Jefferies and Brain, 1984).
Almost all apple cultivars are reported to be either self-incompatible or semicompatible and require cross-pollination to set fruit in marketable quantities (Garratt et al., 2013; Matsumoto, 2014). For commercial production, at least two cross-compatible cultivars with synchronous flowering are recommended (Garratt et al., 2013; Goldway et al., 2012). Matsumoto et al. (2008) reported a significant decline in fruit set with increasing distance between pollinizer and main cultivars, and suggested pollinizers should be planted not more than 10 m from the target cultivars (Matsumoto et al., 2008).
Pollen source is considered to be one of the most influential factors affecting the fruit set and therefore orchard design. Pollen density on the stigmatic surface is positively correlated with pollen tube growth and fruit growth rate (Zhang et al., 2010). Pollen tube growth down the style has been widely studied, but pollen source effects on pollen tube growth are not well understood. The objective of this study was to determine the impact of pollen source on the pollen tube growth and fruit set. The effects on the seed set, fruit quality, and subsequent return bloom will be reported in a subsequent manuscript.
Albuquerque, C.L.D. Jr, Denardi, F., Dantas, A.C.D.M. & Nodari, R.O. 2010 Number of anthers per flower, pollen grains per anther and pollen germination capacity of different cultivars of apple trees Rev. Bras. Frutic. 32 4 1255 1260
Bessho, H., Wada, M., Kudo, K., Inomata, Y., Iwanami, H., Abe, K. & Suzuki, A. 2009 Selection of crabapple pollinizers for ‘Fuji’ and ‘Tsugaru’ apple J. Amer. Pomol. Soc. 63 1 2 13
Das, B., Ahmad, N., Srivastava, K.K. & Ranjan, P. 2011 Top working method and bloom density of pollinizers as productive determinant for spur type apple (Malus×domestica Borkh.) cultivars Sci. Hort. 129 4 642 648
Delaplane, K.S., Mayer, D.R. & Mayer, D.F. 2000 Crop pollination by bees. CABI Publishing, New York, NY
Dresselhaus, T. & Franklin-Tong, N. 2013 Male–female crosstalk during pollen germination, tube growth and guidance, and double fertilization Mol. Plant 6 4 1018 1036
Garratt, M.P.D., Truslove, C.L., Coston, D.J., Evans, R.L., Moss, E.D., Dodson, C. & Potts, S.G. 2013 Pollination deficits in UK apple orchards J. Pollinat. Ecol. 11 1 6
Goldway, M., Stern, R., Zisovich, A., Raz, A., Sapir, G., Schnieder, D. & Nyska, R. 2012 The self-incompatibility fertilization system in Rosaceae: Agricultural and genetic aspects Acta Hort. 967 77
Jackson, J.E. 2003 The biology of apples and pears. Cambridge University Press, Cambridge, UK
Jahed, K.R. & Hirst, P.M. 2017 Pollen source effects on seed number, fruit quality and return bloom of apple J. Amer. Pom. Soc (in press)
Matsumoto, S. 2014 Apple pollination biology for stable and novel fruit production: Search system for apple cultivar combination showing incompatibility, semicompatibility, and full-compatibility based on the S-RNase allele database. Intl. J. Agron. Article ID 138271:9
Matsumoto, S., Eguchi, T., Maejima, T. & Komatsu, H. 2008 Effect of distance from early flowering pollinizers ‘Maypole’ and ‘Dolgo’ on ’Fuji’ fruit set Sci. Hort. 117 2 151 159
Midwest Fruit Workers Group 2013 Midwest tree fruit spray guide. Purdue Extension Publication ID-168
Petropoulou, S.P. & Alston, F.H. 1998 Selecting for improved pollination at low temperatures in apple J. Hortic. Sci. Biotechnol. 73 4 507 512
Williams, R.R., Luckwill, L.C. & Cutting, C.V. 1970 Factors affecting pollination in fruit trees, p. 193–207. In: L.C. Luckvill and L.V. Cutting (eds.). Physiology of tree crops. Academic Press, London, UK
Yoder, K., Yuan, R., Combs, L., Byers, R., McFerson, J. & Schmidt, T. 2009 Effects of temperature and the combination of liquid lime sulfur and fish oil on pollen germination, pollen tube growth, and fruit set in apples HortScience 44 5 1277 1283
Zhang, C., Tateishi, N. & Tanabe, K. 2010 Pollen density on the stigma affects endogenous gibberellin metabolism, seed and fruit set, and fruit quality in Pyrus pyrifolia J. Exp. Bot. 61 4291 4302