Bloom Date Research Articles

Genotype, environment and their interaction effects on olive tree flowering phenology and flower quality

Flowering is one of the most critical processes in the reproductive phenology in fruit trees including olive. Under Mediterranean climate, olive flowering period normally occurs from early to late spring. Therefore, flowering time could be affected by environmental conditions such as water availability and temperature, thus influencing flower quality as well. Previous works have demonstrated the effect of genotype and environment on olive flowering, but those factors have never been compared in a single study nor their interaction evaluated. In the present work, we used a multi-environment trial established in four different agro-climatic conditions of Andalucia, Southern Spain, to test the genetic and environmental influences on flowering timing (flowering period, full bloom period, and full bloom date) and flower quality (flower number, perfect flower number and perfect flower percentage). Most of the variability found for flowering phenology parameters was due to environmental influence. On the contrary, for flowering quality parameters, most of the variability was of a genetic nature. In all cases, the genotype-environment interaction was significant. In this sense, the genotype by environment effects biplot model used to analyse the interaction showed that most of the genotypes evaluated have low stability for most of the parameters evaluated, except ‘Picual’ for flowering phenology parameters and ‘Koroneiki’ for quality. This emphasize the benefits of multi-environment trials on olive in order to select the best genotypes adapted to different environments and as a tool to face the future variability of environmental conditions caused by the climate-warming scenario. In conclusion, multi-environment trials allowed to efficiently quantify the effects of genetic and environmental factors and of their interaction on flowering phenology and on flower quality in olive.

Climate warming enhances flower formation, earliness of blooming and fruit size in plum (Prunus domestica L.) in the cool Nordic environment

The predicted and ongoing climate warming is expected to affect many aspects of plant development. We analysed data from a 31-year series of observations (1985–2016) on spring phenology and flowering and fruiting performance of three plum cultivars in an experimental orchard at Ås in southeast Norway (59° 40′N; 10° 50′E). Regression analyses revealed a trend of increasing March and April temperature during the study period that was highly significantly (P < 0.001) negatively correlated with the date of full bloom (FB). On average for all cultivars, blooming was advanced by 10 days over the study period. August and September temperature, which also increased significantly during the study period, was closely positively correlated with the amount of flowering in the subsequent spring and also interacted with early spring temperature in advancing blooming time. Investigation of the time of floral initiation in two of the studied plum cultivars revealed that the transition to reproductive development took place in early to mid-August. This finding strongly suggests that the close positive correlation between August-September temperature and the amount of flowering in plum observed in this and other studies, is causally linked to a specific physiological effect of elevated temperature on the flower bud formation process.Increasing March and April temperatures during the last 30 years has advanced blooming and spring phenology in plum and the resulting extension of the growing season has led to increasing fruit size at harvest. We conclude that so far, the ongoing climate warming appears to have been positive for plum production in the cool Nordic environment. However, an increasing risk of frost associated with earlier blooming will represent a potential negative effect of continued warming.

Determination of genetic loci in the control network of grapevine flowering

The study of grapevine phenological traits such as flowering and ripening time has become increasingly important in the past few years. With regard to climate change, cultivars with delayed flowering and ripening characteristics may be more advantageous in viticulture. However, genetic markers for these traits applicable for marker-assisted breeding are sparse. Even though homologs of genes that control flowering time have already been identified and characterized in model plants, our overall knowledge about which genetic factors are involved in the complex control of flowering time in Vitis remains very limited. A mapping population consisting of 150 F1 individuals derived from the cross of the early-flowering genotype 'Calardis Musque' and late-flowering cultivar 'Villard Blanc' was used for quantitative trait locus (QTL) detection of the flowering-time trait. For this purpose, vines were phenotyped in 11 seasons for the date of full bloom. QTL analysis led to the identification of several genomic regions, and epistatic effects between the identified loci were observed. The QTLs could be verified in a large extended population of 'Calardis Musque' × 'Villard Blanc'.

Predicting bloom dates by temperature mediated kinetics of carbohydrate metabolism in deciduous trees

Trees in seasonal climates gauge winter progression to assure vital and productive blooming. However, how dormant plants asses environmental conditions remains obscure. We postulated that it involves the energetic reserves required for bloom, and therefore studied winter carbohydrate metabolism in deciduous trees.We quantified non-structural carbohydrates throughout winter in almond, peach, and pistachio trees in California and Israel and characterized winter metabolism. We constructed a carbohydrate-temperature (C–T) model that projects changes in starch and soluble carbohydrate concentrations by temperature mediated kinetics. Then, we tested the C–T model projections of bloom times by 20 years of temperature and phenology records from California.The C–T model attributes winter carbohydrate regulation in dormant trees to continuous updates of metabolic pathways. The model projects a surge in starch synthesis at the end of winter, and critically low concentrations of soluble carbohydrates, that trigger bloom. This is supported by field measurements of starch accumulation at the end of winter (˜50 mg g−1 DW in almonds) that preceded bloom by ˜10 days.The C–T model provides a physiological framework for bloom forecasts in deciduous orchards. It integrates contrasting notions of chill and heat and elucidates why abnormal winter temperatures may compromise bloom in deciduous orchards.

Association of the phenylpropanoid pathway with dormancy and adaptive trait variation in apricot (Prunus armeniaca).

Trees use many mechanisms to adapt and respond to stressful conditions. The phenylpropanoid pathway in particular is known to be associated with a diverse suite of plant stress responses. In this study, we explored the relationship between the phenylpropanoid pathway metabolite production, gene expression and adaptive trait variation associated with floral bud reactivation during and following dormancy in Prunus armeniaca L. (apricot). Concentrations of eight phenylpropanoid metabolites were measured during chill accumulation and at developmental stages corresponding to the emergence of sepals and petals in floral buds of varieties that differ phenotypically in bloom date (BD). A significant interaction effect of chill hours and BD phenotype on the concentration of each of the compounds was observed (mixed analysis of variance, P<0.05), with the concentration of most phenylpropanoid metabolites dropping precipitously when sepals and petals emerged. While phenylpropanoid biosynthetic gene expression patterns were more variable in general, expression changed over time and was impacted, although to a lesser degree, by BD phenotype. Furthermore, separation of BD phenotypic groups was most pronounced when early and late BD varieties were at different developmental stages, i.e., 800 chill hours. Taken together, these results suggest that the phenylpropanoid pathway is associated with floral bud reactivation in apricot. Furthermore, we show that the phenylpropanoid pathway is also impacted by phenological trait variation associated with dormancy. A better understanding of how apricot and other perennial tree species respond and adapt to environmental perturbations will be critical for improvement programs aimed at identifying and breeding trees more suitable for rapidly changing environments.

Phenology, flowering and fruit-set performance of six recent pear cultivars of Nordic origin

ABSTRACT Flowering performance and phenology of six new pear cultivars of Nordic origin were examined during a 12 year period. The seasonal timing of shoot growth and flower initiation were monitored in three years. The morphological floral stages of the flower bud formation process were examined for the cultivar ‘Celina’. Seven floral stages were identified and described. The date of full bloom varied between years as a function of the currently accumulated heat sum in early spring. Still, the earliness ranking of the cultivars was consistent across years for both flower initiation and blooming. The cultivars ‘Anna’ and ‘Ingeborg’ consistently initiated floral primordia 2–3 weeks earlier than ‘Celina’, ‘Clara Frijs’, ‘Fritjof’ and ‘Kristina’, and this was accompanied with 4–5 days earlier blooming in the following spring. The early flower initiation cultivars ‘Anna’ and ‘Ingeborg’ also had richer flowering than the late-blooming cultivars. ‘Fritjof’ was identified as a suitable pollinator for ‘Celina’ in the Nordic climate. Comparison of the flowering phenology of pear and apple cultivars showed that while the pears, on average, flowered a week ahead of the apples, they initiated flower primordia almost two weeks later, thus rendering the intervening period approximately three weeks longer in pear than in apple.

Phenotypic, Biochemical and Molecular Characterization of New Egyptian Mango Genotypes

The first step towards improving mango production was started by the selection of eleven genotypes because of their superior horticultural characteristics and fruit quality parameters, from Suez Canal University orchard through 2016 to 2018 seasons. All studied mango genotypes (G) differed in dates of full bloom, maturity stage, bearing habit, floral malformation and fruit characteristics. All genotypes had commercially acceptable qualities and produced relatively high yield ranged from 298.7 - 394 Kg/tree. Generally, genotype No. 9 recorded the highest value (96.6%) in the general evaluation according to yield, Biennial bearing and fruit quality, followed by genotypes No. 7 and No. 5 which scored 94.0 and 91.8%, respectively. In general, these three genotypes possessed most of the desired commercial attributes of international standard. In addition, further understanding of the structure of genetic diversity was done using nine SSR markers based on their scorability, repeatability and capability to differentiate among studied genotypes. Also, analyze of DNA fingerprinting data to create molecular IDs was done to get an idea for the conservation and protection of studied genotypes. The nine SSR loci produced a total of 32 alleles with 97% polymorphism and observed alleles per locus diversified from 1 to 8 alleles with an average of 3.6 without zero alleles. The observed heterozygosity (Ho) within the loci ranged from 0.0 to 0.55 with an average value of 0.23, heterozygosity level within the genotypes varied from 0.11 to 0.44. The polymorphic information content (PIC) values ranged from 0.0 to 0.86 with an average value of 0.49, whereas the mean of discriminating power (DP) for all loci was 0.51. Regarding the probability of matching fingerprints, none of the genotypes were different or similar at all loci with any of the rest genotypes and this value ranged from low to medium with an average of 0.48. The similarity degree ranged from 0.18 to 0.90 with an average of 0.53, indicating that the genetic differences were moderate among mango genotypes under study. Whereas, seven of these genotypes produced 11 unique bands maybe accompanying to number of novel functional alleles, which can be used in mango improvement.

Cultural ecosystem services provided by flowering of cherry trees under climate change: a case study of the relationship between the periods of flowering and festivals.

In Japan, cherry blossoms are an important tourism resource and provide many cultural ecosystem service benefits. Under future warming conditions, we will require adaptions such as changing the timing of flower festivals to account for changes in the flowering phenology. In this study, we evaluated the coincidence between the flowering phenology of cherry blossoms and the associated festival periods in two Japanese cities under past, recent, and future climate conditions. We examined the situation in Shinhidaka, where the flower festival period changes every year, and Takayama, where the festival period is fixed to coincide with a shrine's annual spring festival. Currently, the average dates of beginning of flowering (more than four or five flowers open in an index tree; ~BBCH60) and full bloom (equal to or more than 80% of flowers open in an index tree; after BBCH65) in Shinhidaka (day of year (DOY) 126 and 130) are later than the long national holiday of Golden Week (DOY 119 to 125). The respective dates in Takayama (DOY 106 and 111, respectively) are later than the local a festival period (DOY 104 and 105). Under a scenario of 1.0 to 2.0°C warming, the full blooming dates in Shinhidaka will coincide with Golden Week, whereas under 1.0 to 1.5°C warming, the full blooming dates in Takayama will coincide with the spring festival period. Thus, moderate warming may increase the value of cherry blossoms to the tourism industry. Under more than 3.5°C warming in Shinhidaka and 2.5°C warming in Takayama, however, cherry blossoms will have already dropped by Golden Week and the spring festival period, respectively, suggesting that greater warming may decrease the value of this tourism resource.

Construction of a high-density SNP marker linkage map of ‘Vic’ × ‘Cristobalina’ in sweet cherry

The development of whole genome SNP arrays has allowed the construction of saturated linkage maps. These maps are a powerful tool for genetic studies such as QTL analysis. In this work, a SNP saturated linkage map was developed using a sweet cherry F(1) population of 161 individuals. This population was derived from the intra-specific cross of the sweet cherry cultivars 'Vic' and 'Cristobalina' (V×C). These parental cultivars were selected because their large differences in relevant agronomical characters such as bloom and maturity dates, fruit size and self-(in)compatibility. The parental and individual progeny genotypes were analyzed using the RosBREED whole genome cherry 6K Illumina Infinium® SNP array v1 and the consensus and parental maps were constructed using these data. The resulting maps were compared with other saturated linkage maps in the species.

Search for sweet cherry (Prunus avium L.) cultivars suitable for warm climate in the southwestern region of Japan

The cool climate of the northern part of Japan’s main island, Honsyu is suitable for the cultivation of sweet cherry (Prunus avium L.). In recent years, the warm southwestern region of Japan has also been proposed as a candidate region for cherry cultivation; cherry fruit set has, however, previously been reported to be significantly inhibited under warm climate conditions before flowering. We aimed to identify a suitable cherry cultivar for cultivation in the warm southwestern region by examining five cherry cultivars: ‘Summit’, ‘Benitemari’, ‘Kokanishiki’, ‘Benisyuho’, and ‘Saori’. Trees were grown in 2013 and 2014 in Matsue city, Shimane prefecture, Japan, (35°28’N; 133°03’E) with an annual mean temperature of 14.9°C, annual means of maximum and minimum temperature of 19.9 and 11.6°C, respectively (2013) and annual precipitation of 1787.2 mm. The data showed that the full bloom dates were around mid-April. These cultivars could all cross-pollinate one another. The fruit set of the cultivars was over 10% but that of ‘Summit’ was only 5.7% in 2013. Harvesting time was overlapping in June (June 1-20 in ‘Kokanishiki’ and ‘Benisyuho’, June 1-30 in ‘Benitemari’, June 4-16 in ‘Summit’, and June 6-20 in ‘Saori’). Harvesting time in Shimane prefecture could be two weeks earlier than those in the Yamagata prefecture, primary cherry producing prefecture in Japan. The soluble solid content of ‘Kokanishiki’ and ‘Benisyuho’ cherries was over 20 °Brix, and ‘Kokanishiki’ softened more rapidly. With juice extraction ratios of between 30 and 40%, the fruits of all cultivars were juicy. We recommend ‘Benisyuho’ which possessed the highest quality as being the most suitable cultivar for cultivation in the warm southwest region of Japan; the other three cultivars, excluding ‘Summit’, were also suitable for cultivation in this area.

Comparison between two methods of estimation of chilling and heat requirements for flowering in almond

A precise determination of thermic requirements (chilling and heat) for breaking dormancy is quite difficult under field conditions. However, quantification under laboratory conditions should be considered with caution and it is costly and time consuming when analyzing a large number of genotypes. For this reason, statistical models based on the analysis of historical blooming dates have been developed to fit the responses of tree species to local weather conditions. Chilling and heat requirements for breaking dormancy and flowering were studied in five local almond cultivars with a widespread time of full bloom (‘Pizzuta d’Avola’, the earliest, ‘Tribuzio’, ‘Tuono’, ‘Cristomorto’ and ‘Rana Gentile’, the latest) in Apulia region (southern Italy). The chilling portions (CP), determined by dynamic model, and the growing degree hours by Richardson model (GDH) were used to determine chilling and heat accumulations, respectively. Using both full bloom dates and temperatures of previous seasons for nine years, two methods for estimating thermic requirements were compared: the Ashcroft method (AM), and a new version (Ashcroft method modified, AMM) that takes into account in a higher extent the GDH accumulation in comparison with AM, and allows selecting the optimal requirements when alternative choices are possible. The two methods generally underestimated the blooming date, but with a difference from the real one within 5 days for most of the cases studied. AMM resulted more effective than the original method in Apulian semi-arid conditions. The estimation of thermic requirements using temperature data and full bloom dates seemed to be useful, easy and not too expensive to be implemented for a wide number of cultivars.

Spatial and Temporal Dynamics of Floating Algal Blooms in Lake Chaohu in 2016 and Their Environmental Drivers

Lake Chaohu has drawn increasing attention due to the occurrence of massive algal blooms. This study applied daily monitoring results from moderate-resolution imaging spectrum-radiometer (MODIS) satellite to extract algal blooms with a floating algal index algorithm and characterize surface floating algal bloom dynamics in 2016 with an algae pixel-growing algorithm. Combining water quality and meteorological data, environmental driving forces of algal blooms in 2016 were explored. The results showed that cyanobacterial blooms occurred throughout the lake from May to November, which is the same as in previous years. Compared with previous years, the initial bloom date was postponed to May, the duration was reduced to 204 days, and the average floating algal bloom area was reduced to 85.53 km2. By investigating the environmental driving forces affecting the algal bloom, it was found that a larger wind speed (△W=0.1 m·s-1), more precipitation (△P=0.8 mm), and a lower sunshine duration (△S=-1.3 h) in spring were the main reasons. When the temperature was suitable, precipitation was the main driving force affecting the monthly variation in algal blooms. The daily average wind speed was also negatively correlated with the algal bloom area (P<0.05). High wind speed can affect the area of algal blooms as well. These results will aid understanding of the situation of cyanobacterial blooms in Lake Chaohu and provide a theoretical basis for dealing with algal blooming and climate change.

Rootstock performance in the 2009 NC-140 peach trial across 11 states

From 14 to 18 Prunus rootstocks budded with ‘Redhaven’ peach were planted at 16 locations in North America in 2009. Seven-year performance from 12 remaining locations in 11 states showed that significant differences among rootstocks and sites were found for survival, root suckers, growth, bloom date, fruit maturity date, fruit size, cumulative yield, and yield efficiency. Survival was highest for peach seedling rootstocks at all locations. In contrast, survival of non-peach species and hybrid rootstocks was poor to fair in Missouri (winter cold, wet feet conditions) and Alabama, Georgia, North Carolina, and South Carolina due to bacterial canker. Krymsk®1, Krymsk®86, Penta, Controller(TM) 5 and Mirobac (a.k.a. Replantpac or Rootpac®R) were the most susceptible to tree death from Pseudomonas syringae canker in the four southeastern states. Overall, Imperial California had the lowest survival followed by Fortuna and Krymsk®1. Rootstock suckering was excessive on Prunus americana seedlings with lesser suckering noted on, Mirobac, Krymsk®1 and Penta. Largest trees were three Prunus × almond hybrids (Viking, Atlas, Brights Hybrid #5) and Guardian®. Fruit size varied with location and crop load (i.e., some rootstocks had few fruit). Atlas produced the largest fruit and Fortuna the smallest fruit across all sites. Cumulative yields were highest in the peach rootstocks such as Guardian®, Lovell and KV010127 and on Atlas. The lowest yields were from plum hybrids and plum species. Cumulative yield efficiency was higher on the non-peach rootstocks, but these rootstocks also produced trees much smaller than the peach and almond hybrid cultivars. The clonal P. persica rootstocks HBOK 10 (Controller(TM) 8) and HBOK 32 (Controller(TM) 7) appeared to be the most promising of the size-controlling rootstocks tested. These data suggest there was no demonstrated advantage to increase yield ha-1 by using clonal interspecific Prunus hybrids for peach production under current cultural practices. However, on higher pH soils in Colorado and Utah, peach seedlings were not the superior rootstocks for production so continuing evaluation of non-peach rootstocks is warranted.

Comparative transcriptome analysis identifies differentially expressed genes between normal and late-blooming Siberian apricot

Blooming date is an important trait in fruit tree species. Although several quantitative trait loci confirming blooming date were identified in Prunus spp., the molecular mechanism underlying it remains unclear. Arising from this, the transcriptomes of normal blooming and late-blooming Siberian apricot (P. sibirica L.) flower buds were analyzed using RNA-seq technology. A total of 68,855 unigenes were de novo assembled, among which 1204 were differentially expressed between normal and late blooming. Gene ontology enrichment analysis revealed that biological processes were enriched with metabolic processes. The catalytic-related gene transcripts between the two types of blooming were significantly changed in the molecular function. Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that 156 genes were successfully annotated and 75 pathways enriched. Genes for gibberellin biosynthesis were up-regulated in normal blooming, whereas abscisic acid degradation-related genes were also up-regulated in normal blooming. Moreover, circadian rhythms related genes including EARLY FLOWERING 4, LATE ELONGATED HYPOCOTYL and CIRCANDIAN CLOCK ASSOCIATED1 were all up-regulated in normal blooming, indicating that circadian rhythms have a very important role in controlling blooming date. Furthermore, zinc finger protein CONSTANS-LIKE 12 was blasted onto the quantitative trait loci region on linkage group 4 in peach. However, changes in the abundance of key flowering genes such as SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1, FLOWERING LOCU T, LEAFY and FLOWERING LOCUS C were not significantly different, indicating that further investigation should explore the function of these genes on blooming date. The outcomes of this study will provide a valuable platform for further research on the molecular mechanism of blooming date in Prunus.

Impact of decadal reversals of the north Ionian circulation on phytoplankton phenology

Abstract. In the north Ionian, water circulation is characterized by a decadal alternation of cyclonic and anticyclonic regime driven by the mechanism called BiOS (bimodal oscillating system). The circulation regimes affect both vertical dynamics and the nutrient distribution. The north Ionian is then a good study area to investigate how changes in circulation can affect phytoplankton dynamics in oligotrophic regions. From in situ observations, for each circulation regime the averaged distribution of isopycnals is provided, and a depth difference of about 80 m is estimated for the nitracline between the cyclonic and anticyclonic regime. Based on phytoplankton phenology metrics extracted from annual time series of satellite ocean color data for the period 1998–2012, the cyclonic and anticyclonic regimes are compared. Results show that the average chlorophyll in March, the date of bloom onset and the date of maximum chlorophyll were affected by circulation patterns in the north Ionian. In the center of the north Ionian gyre, the bloom started in December and chlorophyll was low in March when circulation was anticyclonic, whereas during the cyclonic circulation regime, a late chlorophyll peak, likely resulting from different phytoplankton dynamics, was commonly observed in March. An additional analysis shows that the winter buoyancy losses, which govern the mixed layer depth (MLD), also contribute to explaining the interannual variability in bloom onset and intensity. Two trophic regimes were then identified in the north Ionian gyre (NIG) and they could be explained with the relative position of the MLD and nitracline. The first one is characterized by an early winter bloom onset and the absence of a chlorophyll peak in March. It was observed when circulation was anticyclonic or when winter MLD was relatively shallow. Dominant regenerated production all year and an absence of significant nutrient supplies to surface waters are proposed to explain this trophic regime. Conversely, the second trophic regime is marked by a bloom onset in late winter (i.e., February) and a chlorophyll peak in March. The chlorophyll increase was interpreted as a direct response to the nutrient enrichment of surface waters. This winter–spring bloom was observed when circulation was cyclonic and when winter mixing was relatively strong.

Postharvest regulated deficit irrigation in early- and intermediate-maturing loquat trees

Postharvest deficit irrigation (DI) strategies have been proven to advance bloom, harvest dates and economic return in loquat ‘Algerie’ trees because an early harvest results in higher loquat fruit prices. This fact poses the question of whether postharvest DI strategies could have a similar effect on more precocious cultivars than cv. Algerie, providing thus a more profitable option to farmers. In this work, the response of an early- and intermediate-maturing loquat cultivars (cv. Cardona and Algerie, respectively) to a summer early (DIearly) and late (DIlate) DI strategy was assessed in two parallel studies during three consecutive years. The effects of the DIearly and DIlate strategies on bloom date, percentage of fruit picked at harvest per picking date and yield of both loquat varieties were studied. Moreover, fruit quality of cv. Cardona at harvest was also assessed. Plant water status was monitored by midday stem water potential (Ψstem) measurements. Results showed that DIearly and DIlate strategies advanced bloom in both cultivars although a higher effect was observed with the DIearly than with the DIlate treatment. Water restrictions did not increase the percentage of fruit picked at any of the picking dates and did not affect yield or fruit quality in the early-maturing cultivar. In ‘Algerie’ trees, a higher percentage of fruit was generally picked during the first picking dates in the DIearly and DIlate treatments than in the control although differences were only statistically significant during the last experimental season. Yield was significantly higher in ‘Algerie’ DIlate trees than in control or DIearly trees two out of the three experimental seasons. Overall, results showed that the DIearly and DIlate strategies tested here did advance bloom in the early-maturing cultivar but did not have an effect on the percentage of fruit picked per picking date at harvest. Nevertheless, the fact that substantial water savings (>30%) were obtained with no detrimental effect on yield presents the use of postharvest DI strategies as an interesting option to be followed in early-maturing cultivars for a more efficient crop production.

Evaluation of three modelling approaches for almond blooming in Mediterranean climate conditions

Abstract Chilling and heat requirements for breaking dormancy and flowering were studied in seven almond cultivars in Southern Italy. Chilling portions (CP), computed through the Dynamic model, and growing degree hours (GDH) were used to determine chill and heat accumulation, respectively. Then, using full bloom dates and temperature data from nine seasons (2003/2004-2007/2008 and 2009/2010-2012/2013), three sequential methods for the estimation of thermal requirements were compared: 1) the Ashcroft Method (AM), where chilling and heat requirements were selected considering the lowest variability of the GDH at several intervals of CP, and two variations: 2) modified Ashcroft Method (AMm) that took into consideration the lowest variability in both CP and GDH, and 3) reverse Ashcroft Method (AMr) opposite to AM. All methods were effective in predicting full bloom dates; however the modified Ashcroft method was the most accurate under Mediterranean conditions and allowed to classify almond cultivars for their thermal requirements. The results from AMm, showed chilling requirements ranging between 24–62 CP and heat requirements between 3263 and 6699 GDH, respectively.

Extreme phenophase delays and their relationship with natural forcings in Beijing over the past 260years.

By merging reconstructed phenological series from published articles and observations of China Phenology Observation Network (CPON), the first blooming date of Amygdalus davidiana (FBA) in Beijing between 1741 and 2000 is reconstructed. The Butterworth method is used to remove the multi-year variations for generating the phenological series of annual variations in the first blooming date of A. davidiana. The extreme delay years in the phenological series are identified using the percentage threshold method. The characteristics of the extreme delays and the correspondence of these events with natural forcings are analysed. The main results are as follows. In annual phenological series, the extreme delays appeared in single year as main feature, only A.D.1800-1801, 1816-1817 and 1983-1984 were the events of two consecutively extreme years. Approximately 85% of the extreme delays occurred during 1-2years after the large volcanic eruptions (VEI ≥ 4) in the eastern rim or the western rim of the Pacific Ocean, as the same proportion of the extreme delays followed El Niño events. About 73% years of the extreme delays fall in the valleys of sunspot cycles or the Dalton minimum period in the year or the previous year. According to the certainty factor (CF), the large eruptions have the greatest influence to the extreme delays; sunspot activity is the second, and ENSO is the last one. The extreme phenological delayed year is most likely to occur after a large eruption, which particularly occurs during El Niño year and its previous several years were in the descending portion or valley of sunspot phase.

Trends and Variability in Temperature Sensitivity of Lilac Flowering Phenology

AbstractThe responses of plant phenology to temperature variability have many consequences for ecological processes, agriculture, forestry, and human health. Temperature sensitivity (ST) of phenology could measure how and to what degree plant could phenologically track climate change. The long‐term trends and spatial patterns in ST have been well studied for vegetative phenology such as leaf unfolding, but trends to be expected for reproductive phenology in the future remain unknown. Here we investigate trends and factors driving the temporal variation of ST of first bloom date (FBD). Using the long‐term FBD records during 1963–2013 for common lilac (Syringa vulgaris) from 613 stations in Europe, we compared changes in ST from the beginning to the end of the study period. The Spearman partial correlations were used to assess the importance of four influencing factors. The results showed that the temporal changes in ST of FBD varied considerably among time scales. Mean ST decreased significantly by 0.92 days °C−1 from 1963–1972 to 2004–2013 (P &lt; 0.01), but remained stable from 1963–1987 to 1989–2013. The strength of FBD and temperature relationship, the spring temperature variance, and winter chill all impact ST in an expected way at most stations. No consistent responses of ST on photoperiod were found. Our results imply that the trends and variability in ST of flowering phenology are driving by multiple factors and impacted by time scales. Continued efforts are still needed to further examine the flowering‐temperature relationship for other plant species in other climates and environments using similar methods to our study.

Identification of bloom date QTLs and haplotype analysis in tetraploid sour cherry (Prunus cerasus)

Bloom date is an important production trait in sour cherry (Prunus cerasus L.) as the risk of crop loss to floral freeze injury increases with early bloom time. Knowledge of the major loci controlling bloom date would enable breeders to design crosses and select seedlings with late bloom date. As sour cherry is a segmental allotetraploid, quantitative trait locus (QTL) analysis for bloom date was performed based on haplotype reconstruction by identifying the parental origins of marker alleles in sour cherry. A total of 338 sour cherry individuals from five F1 populations were genotyped using the cherry 6K Illumina Infinium® SNP array and phenotyped for bloom date in 3 years. A total of four QTLs were identified on linkage group (G)1, G2, G4, and G5, respectively. For these QTLs, 14 haplotypes constructed for the QTL regions were significantly associated with bloom date, accounting for 10.1–27.9% of the bloom date variation within individual populations. The three most significant haplotypes, which were identified for the G4 (G4-k), G2 (G2-j), and G1 (G1-c) QTLs, were associated with 2.8, 1.8, and 1.0 days bloom delay, respectively. These three haplotypes were also demonstrated to have additive effects on delaying bloom date for both individual and multiple QTLs. These results demonstrate that bloom date is under polygenic control in sour cherry; yet, pyramiding late blooming haplotypes for single and multiple QTLs would be an effective strategy to obtain later blooming offspring.