Although cultivated SHB are typically capable of setting fruit when self-pollinated, growers commonly plant multiple cultivars to enhance cross-pollination (Williamson et al., 2015). This recommendation is based on previous research describing the benefits of cross-pollination among cultivated blueberry species. Cross-pollination has typically been associated with improved fruit set in northern highbush blueberry [V. corymbosum (Bailey, 1938; Coville, 1921; Dogterom et al., 2000; Ehlenfeldt, 2001; MacKenzie, 1997; Meader and Darrow, 1947; Miller et al., 2011; Morrow, 1943)], rabbiteye blueberry [Vaccinium virgatum (Darnell and Lyrene, 1989; El-Agamy et al., 1981; Gupton and Spiers, 1994; Meader and Darrow, 1944; Payne et al., 1989)], lowbush (Vaccinium angustifolium) and half-high blueberry (V. corymbosum × V. angustifolium hybrids) (Aalders and Hall, 1961; Harrison et al., 1994; Rabaey and Luby, 1988; Wood, 1968), and SHB (Chavez and Lyrene, 2009; El-Agamy et al., 1981; Gupton and Spiers, 1994; Lyrene, 1989). In contrast, greater fruit set in a cultivar after self-pollination compared with cross-pollination has been observed infrequently and has often been attributed to reduced compatibility with the pollen source used for cross-pollination (Ehlenfeldt, 2001; Gupton, 1984; Lang and Danka, 1991; White and Clark, 1939).
Greater fruit size and/or a shorter fruit development period with cross-pollination compared with self-pollination has been documented in northern highbush, rabbiteye, lowbush, half-high, and SHB cultivars (Chavez and Lyrene, 2009; Ehlenfeldt, 2001; Gupton, 1984; Gupton and Spiers, 1994; Lang and Danka, 1991; Lyrene, 1989; MacKenzie, 1997; Meader and Darrow, 1944, 1947; Morrow, 1943; Payne et al., 1989; Rabaey and Luby, 1988; Wood, 1968). In these studies, an increase in the number of fully developed seeds was associated with the increase in fruit size and shorter fruit development period. Supporting this association between seed number and fruit size and development period are cases where interspecific crosses have been compared with crosses that were either self- or cross-pollinated. Aalders and Hall (1961) found reduced seed set in lowbush × velvetleaf blueberry (Vaccinium myrtilloides) crosses that resulted in smaller fruit size and later ripening compared with intraspecific lowbush crosses. Similarly, Gupton and Spiers (1994) found that SHB cultivars pollinated with rabbiteye pollen had reduced fruit weight, but no significant difference in fruit development period compared with intraspecific SHB crosses. Among intraspecific northern highbush crosses, Ehlenfeldt (2001) regressed fruit size and ripening time measurements on total seed number and found the weight of ‘Rubel’ was not impacted by seed number.
The degree to which earliness and yield are improved by cross-pollination is an important consideration when forming planting recommendations for SHB. Early fruit maturity is a critical factor for the SHB industry, as growers rely on the high-value marketing period between the conclusion of southern hemisphere fresh blueberry imports and onset of harvest in traditional U.S. production regions. Therefore, current recommendations suggest including multiple cultivars for cross-pollination in all new SHB plantings. However, larger single-cultivar fields are easier to manage, particularly for some of the common cultural practices necessary for production in subtropical regions (e.g., timing and rate of hydrogen cyanamide application), and would be desirable for mechanical harvest.
The objective of this study was to compare the effects of cross- and self-pollination on fruit set, fruit size, seed number, and time to reach berry maturity among new and traditional SHB cultivars.
Brewer, J.W. & Dobson, R.C. 1969 Seed count and berry size in relation to pollinator level and harvest date for the highbush blueberry, Vaccinium corymbosum J. Econ. Entomol. 62 1353 1356
Chavez, D.J. & Lyrene, P.M. 2009 Effects of self-pollination and cross-pollination of Vaccinium darrowii (Ericaceae) and other low-chill blueberries HortScience 44 1538 1541
Coville, F.V. 1921 Directions for blueberry culture. U.S. Dept. Agr. Bul. 974
Dogterom, M.H., Winston, M.L. & Mukai, A. 2000 Effect of pollen load size and source (self, outcross) on seed and fruit production in highbush blueberry cv. ‘Bluecrop’ (Vaccinium corymbosum; Ericaceae) Amer. J. Bot. 87 1584 1591
El-Agamy, S.Z.A., Sherman, W.B. & Lyrene, P.M. 1981 Fruit set and seed number from self- and cross-pollinated highbush (4x) and rabbiteye (6x) blueberries J. Amer. Soc. Hort. Sci. 106 443 445
Gupton, C.L. & Spiers, J.M. 1994 Interspecific and intraspecific pollination effects in rabbiteye and southern highbush blueberry HortScience 29 324 326
Harrison, R.C., Luby, J.J. & Ascher, P.D. 1994 Fruit and seed set of half-high blueberry cultivars following repeated pollinations at varying time intervals Fruit Var. J. 48 176 182
Knight, R.J. Jr & Scott, D.H. 1964 Effects of temperatures on self- and cross-pollination and fruiting of four highbush blueberry varieties Proc. Amer. Soc. Hort. Sci. 85 302 306
Lang, G.A. & Danka, R.G. 1991 Honey-bee-mediated cross- versus self-pollination of ‘Sharpblue’ blueberry increases fruit size and hastens ripening J. Amer. Soc. Hort. Sci. 116 770 773
Lyrene, P.M. & Goldy, R.G. 1983 Cultivar variation in fruit set and number of flowers per cluster in rabbiteye blueberry HortScience 18 228 229
MacKenzie, K.E. 1997 Pollination requirements of three highbush blueberry (Vaccinium corymbosum L.) cultivars J. Amer. Soc. Hort. Sci. 122 891 896
Miller, S., Alspach, P., Scalzo, J. & Meekings, J. 2011 Pollination of ‘Hortblue Petite’ blueberry: Evidence of metaxenia in a new ornamental home-garden cultivar HortScience 46 1468 1471
Moore, J.N., Reynolds, B.D. & Brown, G.R. 1972 Effects of seed number, size, and development on fruit size of cultivated blueberries HortScience 7 268 269
Payne, J.A., Amis, A.A., Cane, J.H. & Lyrene, P.M. 1989 Fruit size, seed size, seed viability and pollination of rabbiteye blueberries (Vaccinium ashei Reade) Acta Hort. 241 38 43
White, E. & Clark, J.H. 1939 Some results of self-pollination of the highbush blueberry at Whitesbog, New Jersey Proc. Amer. Soc. Hort. Sci. 36 305 309
Williamson, J.G., Olmstead, J.W. & Lyrene, P.M. 2015 Reproductive Growth and Development of Blueberry. 30 June 2015. <https://edis.ifas.ufl.edu/hs220>