Effects of southern highbush blueberry cultivar and treatment threshold on flower thrips populations

In Florida, southern highbush (SHB) blueberries (Vaccinium corymbosum L. x Vaccinium darrowi Camp) are grown for a highly profitable early season fresh market. Flower thrips are the key pest of SHB blueberries, and Frankliniella bispinosa (Morgan) is the most common species found. Flower thrips injure blueberry flowers by feeding and ovipositing in all developing tissues. These injuries can lead to scarring of developing fruit. The objectives of this study were to determine the relationship between thrips and yield in different SHB blueberry cultivars and to determine an action threshold. Experiments were conducted during early spring 2007 and 2008 on four farms; a research farm in Citra, FL; and three commercial farms, two in Hernando Co., FL., and one in Lake Co., FL. At the Citra farm, 'Emerald', 'Jewel', 'Millennia', and 'Star' blueberries were compared in 2007, and all but Star were compared in 2008. On the Hernando and Lake Co. farms, two treatment thresholds (100 and 200 thrips per trap) and an untreated control and four cultivars (Emerald, Jewel, Millennia, and 'Windsor') were compared. Emerald consistently had more thrips per trap and per flower than the other cultivars on all four farms. However, this did not always lead to an increase in fruit injury. Thrips numbers exceeded the threshold on only one farm in 2007, and there was a significantly lower proportion of injured and malformed fruit in the 100 thrips per trap threshold treatment compared with the control on this farm.     

Adventitious shoot regeneration from leaf explants of southern highbush blueberry cultivars

Protocols were developed to optimize adventitious shoot regeneration from four southern highbush blueberry cultivars. Leaf explants from 6 week-old shoots of the four cultivars were excised and cultured on woody plant medium each containing thidiazuron (4.54 or 9.08 μM), zeatin (18.2 μM), or zeatin riboside (5.7 or 11.4 μM) either separately or in combination with α-naphthaleneacetic acid at 2.69 μM. Optimum medium for shoot regeneration was genotype-dependent. Efficient regeneration was obtained at frequencies of 88.9% for ‘Jewel’, 87.8% for ‘Emerald’, 53.3% for ‘Jubilee’ and 87.8% for ‘Biloxi’. Leaf explants of newly developed shoots from the cultures having undergone five subcultures had higher regeneration frequencies than those having undergone two subcultures. Regenerated shoots, 80–100% for each cultivar, rooted in 8 weeks after transplantation to soil. The regeneration systems described have potential use in genetic transformation of southern highbush blueberry cultivars.     

南方高丛蓝浆果‘南月’实生后代果实特性的变异分析

对南方高丛蓝浆果（Vaccinium corymbosum hybrids）品种‘南月’（‘Southmoon’）实生后代的单果质量、果实横径、可溶性固形物含量、单果种子数、果色、口感以及蒂痕类型等果实特征的变异进行了分析。结果表明,‘南月’实生后代的单果质量为0．64～2．15g,果实横径为10．0～16．4mm;果实可溶性固形物含量为9．1％-15．8％,其中有37％的单株果实可溶性固形物含量在12．0％以上;单果种子数为3～93粒,有18％的单株单果种子数小于25粒;果实颜色以蓝紫色和黑蓝紫色为主,比例分别为50％和42％;果实口感以中等和好2个等级为主,比例分别为50％和40％。在对果实的主要特征和经济性状进行评估的基础上,初步筛选出21个‘南月’实生后代优良单株。     

Epidemiological studies on the stunt disease of highbush blueberry

Population levels of Scaphytopius spp., possible sharpnosed leafhopper vectors of blueberry stunt disease (BBSD), were monitored during 1989,1990 and 1991, using yellow sticky traps and a D-Vac power aspirator. Scaphytopius magdalensis (Prov.), S. frontalis (Van D.) and 5. acutus (Say) had two population peaks, one after the petal fall stage and a larger second peak in late Summer to early Autumn. Healthy cv. Bluecrop highbush blueberry (Vaccinium corymbosum L.) plants were placed under stunt-diseased bushes in the field for 2-wk periods during 1989 and 1990. These plants and some of the leafhoppers trapped during 1990 and 1991 were tested for mycoplasma-like organism (MLO) infection with a DNA probe that detected BBSD-associated MLO. The percentage of plants and the number of Scaphytopius spp. that were MLO-positive tended to follow the same bimodal distribution found in the population studies. BBSD transmission tests were performed with Scaphytopius spp. collected from the field. Stunt-related MLO transmission was achieved with S. magdalensis, S. acutus and 5. frontalis.     

Ancient mtDNA haplogroups: a new insight into the genetic history of European populations

In the present work, DNA was extracted from 63 skeletal samples recovered at the Neolithic site of San Juan ante Portam Latinam (SJAPL) (Araba, Basque Country). These samples have proved useful as genetic material for the performance of population studies. To achieve this it was necessary to overcome the methodological problems arising when working with damaged DNA molecules. We succeeded in performing an amplification and restriction analysis of the polymorphisms present in the mtDNA. Ninety seven percent of the samples were classified as belonging to one of the nine mtDNA haplogroups described in Caucasians. This work shows that restriction analysis is a useful methodological tool to perform reliable population genetic analysis on archaeological remains. Tha analysis of ancient and modern haplogroup distribution can shed more light on the genetic evolution of human populations. Moreover, a more exhaustive data on prehistoric populations will allow to build stronger hypothesis on the genetic relationships among human populations.     

在不同pH值土壤中铵硝比对南方高丛蓝浆果生长的影响

以南方高丛蓝浆果(Vaccinium corymbosum hybrids)品种‘南月’(‘Southmoon’)优选系A47的1年生扦插苗为实验材料,采用盆栽实验方法,研究在pH 4.5和pH 6.0的土壤中按照摩尔比100∶0、75∶25、50∶50、25∶75和0∶100施用铵态氮与硝态氮,对扦插苗根、茎和叶干质量、茎基径和株高的影响。结果表明:在pH 4.5的土壤中,5个施肥处理组幼苗的根、茎和叶干质量均无显著差异(P>0.05);而多数处理组间幼苗的茎基径和株高也无显著差异。在pH 6.0的土壤中,铵硝摩尔比100∶0处理组幼苗的根、茎和叶干质量显著高于其他处理组(P<0.05),其余处理间均无显著差异;茎基径随铵态氮比例的提高而增大,其中铵硝摩尔比100∶0处理组幼苗的茎基径显著高于其他处理组;多数处理组间幼苗的株高无显著差异。与pH 4.5的土壤相比,在pH 6.0的土壤中各施肥处理组的根、茎和叶干质量均显著降低;除铵硝摩尔比100∶0处理组外,其他处理组的茎基径均显著降低;除铵硝摩尔比50∶50和0∶100处理组外,其他处理组的株高显著降低。综合分析结果表明:在pH 4.5的土壤中施用硝态氮和铵态氮对优选系A47生长的影响总体上无明显差异,但在pH 6.0的土壤中施用铵态氮肥较有利于植株生长;优选系A47适宜栽植于pH 4.5的酸性土壤中。     

Sucrose level influences micropropagation and gene delivery into leaves from in vitro propagated highbush blueberry shoots

In an effort to increase in vitro blueberry (Vaccinium corymbosum L.) shoot production without negatively impacting subsequent genetic engineering experiments, studies were conducted to examine the effects of sucrose concentration in the propagation medium on shoot proliferation and on the transfer of an intron-containing -glucuronidase (GUS) gene into leaf explants from the propagated shoots. Numbers of axillary shoots >0.5 cm in length did not significantly increase for `Bluecrop' when sucrose levels were increased from 15 mM to either 29, 44 or 58 mM. The number of axillary shoots increased significantly for Duke ' and `Georgiagem' when sucrose concentrations were increased from 15 to 44 mM, and from 15 to 58 mM, respectively. Four-days of cocultivation with Agrobacterium tumefaciens strain EHA105 yielded highest GUS-expressing leaf zones on leaf explants from shoots cultured on either 15 or 29 mM sucrose. The number of GUS-expressing leaf zones was significantly lower on leaf explants derived from shoots grown on 58 mM sucrose than from those grown on 15 mM sucrose for all three cultivars, and was significantly lower on 44 mM compared to 15 mM for cultivars Duke and Georgiagem. These studies indicate shoot pretreatment conditions for optimizing subsequent blueberry genetic engineering experiments. Thus, a blueberry shoot proliferation medium containing 15–29 mM sucrose is recommended for explants later used for genetic transformation.     

Effects of 24-epibrassinolide on in vitro micropropagation of highbush blueberry

In order to elucidate effects of 24-epibrassinolide (EB) on the efficiency of in vitro regeneration of highbush blueberry (Vaccinium corymbosum L., cv. Brigitta blue), we analyzed variability of seven bioproductive parameters in regenerant plants cultured on nutrient media differing in hormonal composition. The additive action of EB, cytokinin (2iP), and auxin (IAA) was discovered for several parameters, such as reproduction coefficient, weight of regenerant plants, and the content of anthocyanin pigments. The greatest reproduction coefficients were noted in regenerant plants cultured on the medium containing 0.25 mg/L EB, 7.25 mg/L 2iP, and 1.00 mg/L IAA, as well as on the medium with 0.05 mg/L EB, 2.00 mg/L 2iP, and 0.50 mg/L IAA. It is suggested that low concentrations of 2iP and EB, applied in certain combinations, can be used for the industrial in vitro propagation of regenerant plants of highbush blueberry varieties.     

Flooding, gas exchange and hydraulic root conductivity of highbush blueberry

Highbush blueberry plants ( Vaccinium corymbosum L. cv. Bluecrop) growing in containers were flooded in the laboratory for various durations to determine the effect of flooding on carbon assimilation, photosynthetic response to varying CO₂ and O₂ concentrations and apparent quantum yield as measured in an open flow gas analysis system. Hydraulic conductivity of the root was also measured using a pressure chamber. Root conductivity was lower and the effect of increasing CO₂ levels on carbon assimilation less for flooded than unflooded plants after short-(i-2 days), intermediate-(10–14 days) and long-term (35–40 days) flooding. A reduction in O₂ levels surrounding the leaves from 21 to 2% for unflooded plants increased carbon assimilation by 33% and carboxylation efficiency from 0.012 to 0.021 mol CO₂ fixed (mol CO₂)⁻¹. Carboxylation efficiency of flooded plants, however, was unaffected by a decrease in percentage O₂, averaging 0.005 mol CO₂ fixed (mol CO₂)⁻¹. Apparent quantum yield decreased from 2.2 × 10⁻¹ mol of CO₂ fixed (mol light)⁻¹ for unflooded plants to 2.0 × 10⁻³ and 9.0 × 10⁻⁴ for intermediate- and long-term flooding durations, respectively. Shortterm flooding reduced carbon assimilation via a decrease in stomatal conductance, while longer flooding durations also decreased the carboxylation efficiency of the leaf.     

Horizontal and vertical distribution of flower thrips in southern highbush and rabbiteye blueberry plantings, with notes on a new sampling method for thrips inside blueberry flowers

The dispersal behavior of flower thrips was studied during two field seasons within blueberry (Vaccinium spp.) plantings in Florida and southern Georgia. A "shake and rinse" technique used to extract thrips from inside the blueberry flowers was not significantly different from the conventional dissecting technique, but the time taken to complete the extraction of thrips was significantly shorter. Overall, the highest concentration of thrips was captured inside the canopy of blueberry bushes. Using a grid of traps to monitor the dispersal of thrips during the blueberry flowering season, we analyzed their dispersion with graphical and analytical methods to determine and describe their distribution within blueberry plantings. Thrips began to form "hot-spots" 5-7 d after bloom initiation. A hot-spot is defined as a large number of thrips concentrated in a small area of the field, whereas the rest of the field has a low population. The behavior of the population inside these hot-spots fit a Gaussian tendency and a regression was conducted to describe this tendency. Green's and Standardized Morisita's indices were used to determine thrips level of aggregation. Results showed significantly aggregated populations of thrips in both years. Formation of hot-spots in blueberry plantings seemed to be random. However, the formation of hot-spots was higher in places where more than seven thrips per day were captured on sticky traps, 5 to 7 d after the bloom begins. With these results, producers will be able to monitor thrips populations and locate and manage hot-spots before they become a more serious a problem on blueberry farms.     

不同基本培养基对南方高丛蓝浆果丛生枝增殖及生长的影响

比较了MWPM和WPM单一培养基以及MS-WPM、MS-MWPM、MWPM-WPM等体积混合培养基(均含2 mg·L-1 ZT、20 g·L-1蔗糖和7 g·L-1琼脂,pH 5.0)对南方高丛蓝浆果(Vaccinium corymbosum hybrids)品种‘南月’(‘Southmoon’)优选系A47和A167丛生枝增殖及生长的影响。实验结果显示:在MS-WPM和MS-MWPM混合培养基上,优选系A47和A167丛生枝的增殖倍数、总长度及叶片叶绿素含量均高于或显著高于MWPM和WPM单一培养基,丛生枝的鲜质量、干质量和含水量与MWPM和WPM单一培养基相当;而在MWPM-WPM混合培养基上,优选系A47和A167丛生枝的增殖倍数在5种培养基中虽然不是最低的,但丛生枝的各项生长指标均较低或最低。综合分析结果表明:MS-WPM和MS-MWPM混合培养基较目前常用的WPM和MWPM单一培养基更适宜于南方高丛蓝浆果品种‘南月’优选系A47和A167丛生枝的增殖培养。     

Settling behavior of the glassy‐winged sharpshooter,Homalodisca vitripennis,vector of Xylella fastidiosa,on southern highbush blueberry cultivars

The xylem‐limited bacterium Xylella fastidiosa Wells, Raju, Hung, Wiseberg, Mandelico‐Paul & Brenner causes bacterial leaf scorch, a new disease of southern highbush blueberry [Vaccinium corymbosum L. (Ericaceae) interspecific hybrids] in the southeastern USA. The bacterium is transmitted by sharpshooter leafhoppers (Hemiptera: Cicadellidae), with the glassy‐winged sharpshooter (GWSS), Homalodisca vitripennis (Germar), being the most common potential vector in blueberry plantings. Considerable differences are observed in disease intensity among blueberry cultivars in the field, but it remains unknown whether these differences are due to variations in cultivar susceptibility to the bacterium, differences in attractiveness to its vector(s), or both. The settling and feeding behavior of GWSS was evaluated on three southern highbush blueberry cultivars (FL 86‐19, Star, and Emerald) in the greenhouse; in previous field studies, these cultivars were found to be affected by bacterial leaf scorch at high, moderate, and low levels, respectively. Potted plants were caged together with field‐collected GWSS adults for a period of 5 days, with either all three cultivars caged simultaneously (choice test) or individually (no‐choice test). In the choice tests, no differences in cultivar attractiveness were observed during the first 2 days of study. However, from the 3rd day, significantly more adults settled on Emerald (52.7%) than on Star (25.5%) and FL 86‐19 (17.7%). In contrast, in no‐choice tests, the overall host plant acceptance for the three cultivars was similar, and 89.3–92.1% of adults settled on these plants. A significantly greater number of adults settled on the stems (79.3%) vs. the leaves (11.2%). Moreover, they preferred the middle portion of the shoot (56.9%) compared with the upper (7.8%) and the lower (14.7%) portions. In a separate study on FL 86‐19, greater numbers of GWSS nymphs settled on the upper (actively growing) portion of the shoot (82.3%), whereas only 15.8 and 1.5% settled on the middle and lower portions, respectively.     

Leaf anatomy of highbush blueberry grownin vitro and during acclimatization toex vitro conditions

Leaves of micropropagated highbush blueberry (Vaccinium corymbosum) cv. ‘Bluetta’ have been observed during the acclimatization phase. In vitro-developed leaf cells were circular and small, the spongy parenchyma was discontinuous and disorganized and formed by 1–2 layers of cells with large intercellular spaces and the palisade to spongy mesophyll thickness ratio was 1:1.5. After rooting ex vitro, the first leaves formed under natural conditions showed substantial changes in the anatomical characteristics. After 6 months, the plants produced leaves similar to those in field-grown plants. The palisade cells were rectangular, the spongy parenchyma was formed by 3–4 layers of cells and the intercellulars were around the stomata. Leaves from field-grown plants lost 24 % of water during 150 min after excision while leaves from in vitro shoots lost about 50 % of water in the same time. Leaves from in vitro shoots showed a higher number of smaller stomata (361 per mm²), with the guard cells forming a circular ring; the stomata frequency in field-grown leaves was 241 per mm² and the guard-cells were elliptical.     

Early-acting inbreeding depression and reproductive success in the highbush blueberry,Vaccinium corymbosum L.

Summary Tetraploid Vaccinium corymbosum genotypes exhibit wide variability in seed set following self- and cross-pollinations. In this paper, a post-zygotic mechanism (seed abortion) under polygenic control is proposed as the basis for fertility differences in this species. A pollen chase experiment indicated that self-pollen tubes fertilize ovules, but are also outcompeted by foreign male gametes in pollen mixtures. Matings among cultivars derived from a pedigree showed a linear decrease in seed number per fruit, and increase in seed abortion, with increasing relatedness among parents. Selfed (S₁) progeny from self-fertile parents were largely self-sterile. At zygotic levels of inbreeding of F>0.3 there was little or no fertility, suggesting that an inbreeding threshold regulates reproductive success in V. corymbosum matings. Individuals below the threshold are facultative selfers, while those above it are obligate outcrossers. Inbreeding also caused a decrease in pollen viability, and reduced female fertility more rapidly than male fertility. These phenomena are discussed in terms of two models of genetic load: (1) mutational load — homozygosity for recessive embryolethal or sub-lethal mutations and (2) segregational load — loss of allelic interactions essential for embryonic vigor. Self-infertility in highbush blueberries is placed in the context of late-acting self-incompatibility versus early-acting inbreeding depression in angiosperms.     

The effect of aluminium and media on the growth of mycorrhizal and nonmycorrhizal highbush blueberry plantlets

A factorial experiment was conducted to determine the effect of aluminium (0 and 600M) and media (sand, and 1:1 sand:soil) on mycorrhizal (M) and non-mycorrhizal (NM) highbush blueberry plantlets. There were no differences in nutrient uptake and total plant dry weight between M and NM plantlets. However, more root growth, as determined by dry weight, was observed in M than NM plantlets. The plantlets growing in sand had more dry weight than did those in the soil medium. Although the root growth and shoot growth were reduced by the 600M Al treatment, the direct effect of Al on plantlet growth was not clear due to Al and P interactions. Plant nutrient uptake was reduced by high concentrations of Al, suggesting that high Al concentration limited the ability of roots to acquire most of the nutrients. Mycorrhizal cortical cell infection levels of 15–20% wene maintained in the roots in soil medium but decreased to about 5% over the 6 weeks of the experiment in the sand medium. Although M plantlets accumulated more Al in their roots, Al was readily transported to the leaf tissues of M and NM plantlets.