Blueberry is a perennial evergreen or deciduous shrub that is native to North America (Wang et al., 2017). Northern highbush blueberry (Vaccinium corymbosum), rabbiteye blueberry, and southern highbush blueberry (V. corymbosum interspecific hybrids) are the three most commercially important species cultivated (Yu et al., 2016). As not all of these species are self-compatible, the need for cross-pollination between botanical varieties is widely acknowledged by commercial growers (Miller et al., 2011; Müller et al., 2013), and pollination by bees is required to improve yield and quality (Nicholson and Ricketts, 2019).
Blueberry is known to contain appreciable levels of phenolic compounds, which have high biological activity and may provide health benefits as dietary antioxidants (Castagnini et al., 2015; Lin et al., 2016; Shen et al., 2014). Blueberries are a rich source of flavonoids, phenolic acids, anthocyanins, stilbenes, and tannins, as well as nutritive compounds such as sugars, essential oils, carotenoids, vitamins, and minerals (Nile and Park, 2014). In addition, there has been a growing trend in the use of blueberry extracts as ingredients in functional foods and dietary supplements (Dróżdż et al., 2018). Blueberry fruit have thus become increasingly popular because of their high nutritional value and desirable flavor (Chu et al., 2017).
After nearly a decade of development, China recently became one of the leading countries in blueberry cultivation. In particular, the scale of cultivation has dramatically increased in south China because of its advantages of a longer growing season and high economic revenue (Yu et al., 2016). Rabbiteye blueberry has become an important economic crop in Guizhou Province (Zhang et al., 2015). However, extreme high-temperature events are becoming more frequent in south China as a result of increasing temperature and climatic variability, particularly during the flowering phenophase, thereby influencing cultivation (Yang et al., 2015b). In southeast Guizhou province, the daytime ground temperatures can remain at 35°C for more than 4 h on a typical spring day, and the difference in temperature can exceed 30 °C within 3 h (Yang et al., 2017). Abnormal temperature changes occurred frequently during the 2014 to 2018 period and were associated with erratic fruit set in blueberry. Production practice in recent years has shown that temperature stress constitutes the biggest obstacle to flowering and fruit setting in rabbiteye blueberry in south China.
In flowering plants, environmental factors play an important role in the regulation of plant growth and development, and the reproductive phase is typically highly sensitive to temperature stress (Gao et al., 2014; Ohnishi et al., 2010; Saini et al., 2017; Yang et al., 2015a). Complications can include abnormal meiosis (Bita et al., 2011; Draeger and Moore, 2017; Ohnishi et al., 2010; Yang et al., 2015a); accelerated pollen development and increased pollen abortion (Higuchi et al., 1998; Shen et al., 1999); accelerated flower bud development, resulting in a hastening of flowering time (Rodrigo and Herrero, 2002); reduced pollen germination for underdeveloped pistils (Hedhly et al., 2004; Koubouris et al., 2009; Pham et al., 2015); faster pollen tube growth in the style (Hedhly et al., 2004; Xu and Xu, 2014); inhibition of pollen tube elongation (Zhang et al., 2018); reduction in the number of pollen tubes (Radičević et al., 2016); and reduction in the percentage of the style traversed by the pollen tube (Gao et al., 2014; Koubouris et al., 2009; Pham et al., 2015; Song and Chen, 2018), all of which can result in low fruit set. The aforementioned phenotypic characteristics are closely related with the genotypes of the species and botanical varieties (Pham et al., 2015; Radičević et al., 2016; Sorkheh et al., 2011).
However, a limited number of studies have attempted to clarify the effects of temperature on pollination and fertilization in blueberry. Nesmith et al. (1999) found that the corollas were most sensitive to freeze damage, followed by the styles and then the ovaries. Pollen viability was extremely low or lacking following 3 d or more of rain, and the stigma was unreceptive under drip film irrigation (Yang et al., 2015b). In addition, pollen viability and stigma receptivity were significantly reduced with increases or decreases in optimum temperature (Yang et al., 2017). To date, no studies have determined whether temperature reduces pollen germination in situ in blueberry, inhibits pollen tube elongation, or reduces ovule viability, which would have consequences for fertilization and fruit setting.
Using the rabbiteye blueberry ‘Brightwell’ as the study material, field/greenhouse-based and controlled temperature experiments were carried out over two consecutive years in the present study to assess the influence of different temperatures during pollination on pollen germination, pollen tube growth, and ovule viability. This study aims to provide a basis for clarifying the mechanism of heat suppression in rabbiteye blueberry fruit production and seeks to determine the temperature conditions for improved production and decreased damage from temperature stress. In addition, the cardinal temperatures can inform breeding strategies for blueberry tolerance to heat stress, which is of great significance for breeding heat-tolerant germplasms.
AcarI.KakaniV.G.2010The effects of temperature on in vitro pollen germination and pollen tube growth of Pistacia sppScientia Hort.125569572
AustinP.T.HewettE.W.NoitonD.PlumerJ.A.1998Self-incompatibility and temperature affect pollen tube growth in ‘Sundrop’ apricot (Prunus armeniaca L.)J. Hort. Sci. Biotechnol.73375386
BitaC.E.ZenoniS.VriezenW.H.MarianiC.PezzottiM.GeratsT.2011Temperature stress differentially modulates transcription in meiotic anthers of heat-tolerant and heat-sensitive tomato plantsBMC Genomics12384401
CastagniniJ.M.BetoretN.BetoretE.FitoP.2015Vacuum impregnation and airdrying temperature effect on individual anthocyanins and antiradical capacity of blueberry juice included into an apple matrixLebensm. Wiss. Technol.6412891296
ChuW.J.GaoH.Y.CaoS.F.FangX.J.ChenH.J.XiaoS.Y.2017Composition and morphology of cuticular wax in blueberry (Vaccinium spp.) fruitsFood Chem.219436442
DraegerT.MooreG.2017Short periods of high temperature during meiosis prevent normal meiotic progression and reduce grain number in hexaploid wheat (Triticum Aestivum L.)Theor. Appl. Genet.13017851800
GaoY.B.WangC.L.WuJ.Y.ZhouH.S.JiangX.T.WuJ.ZhangS.L.2014Low temperature inhibits pollen tube growth by disruption of both tip-localized reactive oxygen species and endocytosis in Pyrus bretschneideri RehdPlant Physiol. Biochem.74255262
HedhlyA.HormazaJ.I.HerreroM.2003The effect of temperature on stigmatic receptivity in sweet cherry (Prunus avium L.)Plant Cell Environ.2616731680
HedhlyA.HormazaJ.I.HerreroM.2004Effect of temperature on pollen tube kinetics and dynamics in sweet cherry, Prunus avium (Rosaceae)Amer. J. Bot.91558564
HiguchiH.UtsunomiyaN.SakurataniT.1998High temperature effects on cherimoya fruit set, growth and development under greenhouse conditionsScientia Hort.772331
KoubourisG.C.MetzidakisI.T.VasilakakisM.D.2009Impact of temperature on olive (Olea europaea L.) pollen performance in relation to relative humidity and genotypeEnviron. Expt. Bot.67209214
MillerS.AlspachP.ScalzoJ.MeekingsJ.2011Pollination of ‘Hortblue Petite’ blueberry: Evidence of metaxia in a new ornamental home-garden cultivarHortScience4614681471
MüllerJ.L.SteynW.J.TheronK.I.2013The effect of cross-pollination of southern highbush blueberries on fruit set and fruit characteristicsActa Hort.1007571578
NesmithD.S.KrewerG.LindstromO.M.1999Fruit set of rabbiteye blueberry (Vaccinium ashei) after subfreezing temperaturesJ. Amer. Soc. Hort. Sci.124337340
OhnishiS.MiyoshiT.ShiraiS.2010Low temperature stress at different flower developmental stages affects pollen development, pollination, and pod set in soybeanEnviron. Expt. Bot.695662
PhamV.T.HerreroM.HormazaJ.I.2015Effect of temperature on pollen germination and pollen tube growth in longan (Dimocarpus longan Lour.)Scientia Hort.197470475
RadičevićS.CerovićR.NikolićD.ƉorđevicM.2016The effect of genotype and temperature on pollen tube growth and fertilization in sweet cherry (Prunus avium L.)Euphytica209121136
SainiR.SinghA.K.DhanapalS.SaeedT.H.HydeG.J.BaskarR.2017Brief temperature stress during reproductive stages alters meiotic recombination and somatic mutation rates in the progeny of ArabidopsisBMC Plant Biol.17103113
ShenX.SunX.H.XieQ.C.LiuH.Q.ZhaoY.PanY.J.HwangC.A.WuV.C.H.2014Antimicrobial effect of blueberry (Vaccinium corymbosum L.) extractsagainst the growth of Listeria monocytogenes and Salmonella enteritidisFood Control35159165
SongG.Q.ChenQ.X.2018Comparative transcriptome analysis of nonchilled, chilled, and late-pink bud reveals flowering pathway genes involved in chilling-mediated flowering in blueberryBMC Plant Biol.1898110
SorkhehK.ShiranB.RouhiV.KhodambashiM.2011Influence of temperature on the in vitro pollen germination and pollen tube growth of various native Iranian almonds (Prunus L. spp.) speciesTrees25809822
SukhvibulN.WhileyA.W.VithanageV.SmithM.K.DooganV.J.HetheringtonS.E.2000Effect of temperature on pollen germination and pollen tube growth of four cultivars of mango (Mangifera indica L.)J. Hort. Sci. Biotechnol.75214222
VasilakakisM.PorlingisI.C.1985Effect of temperature on pollen germination, pollen tube growth, effective pollination period, and fruit set of pearHortScience20733735
WangL.Y.LiY.D.SunH.Y.LiuH.G.TangX.D.WangQ.C.ZhangZ.D.2017An efficient droplet-vitrification cryopreservation for valuable blueberry germplasmScientia Hort.2196069
YangJ.ChenX.R.ZhuC.L.PengX.S.HeX.P.FuJ.R.OuyangL.J.BianJ.M.HuL.F.SunX.T.XuJ.HeH.H.2015aRna-seq reveals differentially expressed genes of rice (Oryza sativa) spikelet in response to temperature interacting with nitrogen at meiosis stageBMC Genomics16959976
YangQ.TangL.LiX.Y.ZhouJ.J.TianX.ZhangJ.YueY.WangX.Y.2015bEffect of rainy on stigma receptivity and pollen viability in blueberryNorthern Hort.394749
YangQ.WanX.Q.LiD.P.LiX.Y.ZhangT.T.PengS.2017Effect of temperature on pollen viability and stigma receptivity in ‘Premier’ rabbiteye blueberryNorthern Hort.413943
YangQ.FuY.WangY.Q.TaoL.DengQ.X.FanJ.X.DengR.J.2015cEffects of temperature on pollen tube growth and ovule longevity in loquat (Eriobotrya japonica)J. Fruit Sci.32646652
YangQ.WangY.Q.FuY.DengQ.X.TaoL.2012Effects of biological factors on fruit and seed set in loquat (Eriobotrya japonica Lindl.)Afr. J. Agr. Res.753035311
YuK.ZhuK.L.YeM.J.ZhaoY.P.ChenW.R.GuoW.D.2016Heat tolerance of highbush blueberry is related to the antioxidative enzymes and oxidative protein-repairing enzymesScientia Hort.1983643
ZhangC.X.LiG.G.ChenT.T.FengB.H.FuW.M.YanJ.X.IslamM.R.JinQ.Y.TaoL.X.FuG.F.2018Heat stress induces spikelet sterility in rice at anthesis through inhibition of pollen tube elongation interfering with auxin homeostasis in pollinated pistilsRice111425
ZhangS.S.LuY.H.LinD.R.WangP.P.2015Research on the development situation and counter measures of the blueberry industry in ChinaFor. Econ.56871