Cherry Leaf Roll Virus in Juglans regia in the United Kingdom

Cherry leaf roll virus (CLRV) was detected in foliage, pollenor seeds of 43 of 113 mature/overmature Juglans regia L.; twohad foliar yellow-brown ring patterns whereas seven other infectedtrees had leaf necroses. Male catkins of a few infected treeswere malformed and blackened. Infection was rare (3/43) in the widely scattered J. regia ofnorthern England and Scotland, but commoner (40/70) in southernEngland. When J. regia seed was grown in methylbromide treated soil,six per cent (18/300) of the seedlings were symptomlessly infected.Four out of ten groups of imported seedlings were infected toa similar extent, CLRV being present in a total of 40 out of1146 trees aged five years or less. When 3 years old, CLRV infectedJ. regia were shorter and thinner than healthy seedlings. CLRV from walnut was serologically distinguishable from Betula,Prunus, Cornus and Sambucus isolates. One English walnut isolate(Ox) was distinguishable from two Italian walnut isolates. Anisolate (Sr) of CLRV obtained in Finland from Sambucus racemosaL. was antigenically distinct from S. ebulus and S. nigra isolates.     

Walnut demonstrates strong genetic variability for adaptive and wood quality traits in a network of juvenile field tests across Europe

Adaptive and wood quality trait data were collected and analyzed on commercially available Juglans regia and J. regia×J. nigra provenances and progenies planted across Europe in a multi-site network. A total of 19 seed sources, replicated 35 times per site, were planted at 13 sites from 5 European countries, encompassing the potential distribution area of timber production plantation sites. The following traits were evaluated: survival, height, diameter at breast height, stem form, apical dominance, vegetative budbreak, along with biotic and abiotic damage. Mean values were significantly different both among provenances/progenies and sites. Most common damage was late spring and early autumn frost. Bud break ranking was significantly correlated with provenance and progeny origin. Although J. regia is fast growing, southern European early budbreak plant material should not be planted under most middle European conditions where late spring frost can be expected, as it has a significant negative impact on architectural (and thus wood quality) traits. Hybrid J. regia×J. nigra progeny performed better than J. regia provenances/progenies for most traits measured. Differences were significantly in favor of hybrids at sites with medium to low fertility, although some locally selected seed sources tended to perform as well as hybrids on high fertility sites.     

Susceptibility of species of Juglans to pathovars of Xanthomonas campestris

Bacterial blight is considered one of the most serious diseases affecting the genus Juglans. Artificial inoculations with Xanthomonas campestris pv. Juglandis were performed in the field by spraying seedlings of Juglans cinerea, Juglans hindsii, Juglans mandshurica, Juglans nigra, Juglans regia and Juglans sieboldiana. Juglans nigra, J. cinerea ana J. sieboldiana proved to be the most resistant. The multiplication ability of Xanthomonas campestris pv. corylina, X. c. pv. juglandis, and X. c. pv. campestris was evaluated by injecting 2-year-old seedling leaves of J. mandshurica, J. nigra and J. regia. The bacterial growth was monitored in the infected tissue over 12 days. Xanthomonas c. pv. juglandis exhibited a high growth rate and induced black greasy spots in J. mandshurica and J. regia; X. c. pv. campestris grew in leaf tissues without inducing symptoms, X. c. pv. corylina showed a very low growth rate. None of the tested bacterial strains multiplied in the leaves of J. nigra. This confirms the results obtained in the field tests. Juglans regia was the most susceptible among the walnut species tested.     

Phytopbthora cactorum on walnut seedlings in Italian nurseries

Phytophthora cactorum was consistently isolated from basal stem tissues of walnut seedlings affected by collar and root rot. The isolates were identified on the basis of morphological and cultural characteristics and of electrophoretic patterns in polyacrylamide slab gels of total native mycelial proteins and isozymes (arylesterase, malate dehydrogenase, acid and alkaline phosphatase). The electrophoretic phenotypes of walnut isolates were identical or very similar to those of P. cactorum isolates from different hosts (apple, loquat, pineapple-guava and strawberry). In pathogenicity tests, P. cactorum isolates from walnut proved to be highly pathogenic for seedlings of English walnut (Juglans regia) and moderately pathogenic for seedlings of eastern black walnut (Juglans nigra); moreover, they did not rot apple seedlings, suggesting host-specificity. Poor soil drainage and excessive irrigation can be considered as predisposing factors to collar and root rot incited by P. cactorum.     

Variability in the Italian population of Gnomonia leptostyla,homothallism and resistance of Juglans species to anthracnose

Isolations of Gnomonia leptostyla were carried out in 13 plantations of Juglans regia distributed throughout Italy, including Sardinia and Sicily. Mean diameter of colonies grown in vitro at 22°C and sporulation of 191 isolates, grouped by site of collection, were compared. Four groups of isolates, from environmentally diverse sites, were more thoroughly investigated for the effect of temperature (from 10 to 30°C, 5°C increment) on growth and sporulation. Colony growth of isolates within groups correlated with temperature and environmental parameters at the site of collection, such as temperature, rainfall, number of rain days per month and per year, and altitude. Altitude and mean temperature in April correlated with colony growth. In general, the isolates that grew significantly more slowly were from sites with colder early springs and higher altitudes. More significant data were obtained comparing isolates from different sites obtained from the same walnut cultivar or population. The host source was more significantly correlated with colony growth within the same site of collection. Acervular conidiomata were abundantly produced by all isolates at 22°C in darkness after 21 days, while protoperithecia were produced within 2 months by most isolates, under the same conditions. Similarly, the four groups of isolates tested at different temperatures produced conidiomata at 20 and 25°C, but not at 10, 15 and 30°C. After 2 months, protoperithecia were present in most isolates at 20°C, very few at 25 and 15°C, and no production was recorded at 10 and 30°C. Fertile perithecia with asci and ascospores were produced, after 3 months at 10°C in darkness, by six homothallic isolates out of 38 tested. In general, perithecia were larger than protoperithecia both in ascocarp diameter and in neck length. Ascocarp diameter, width of asci and length of ascopores of in vitro-produced perithecia were larger than those of perithecia produced in nature. The latter showed a neck length longer than in vitro-produced perithecia. Virulence of isolates when inoculated on J. regia was correlated with colony growth rate, but rated independently for homothallic or heterothallic isolates. A preliminary screening for sources of resistance to anthracnose in the genus Juglans showed J. sieboldiana and J. cinerea to be highly resistant and both J. nigra and J. hindsii to be highly susceptible to the disease. Juglans regia showed an intermediate response of susceptibility to anthracnose.     

Evaluation of Juglans species for resistance to Phytophthora cinnamomi: differences in isolate virulence and response to fosetyl‐Al

Phytophthora is considered as an important pathogen on walnut, and severe losses are reported in European as well as in American walnut stands. Though several Phytophthora spp. are known to attack walnut, P. cinnamomi is considered the most virulent and widespread in southern Europe. Up to now, no walnut species or hybrid is known to have a high resistance level towards P. cinnamomi. Efforts are addressed in finding rootstock material graft compatible with English walnut and resistant/tolerant to P. cinnamomi. The extension of P. cinnamomi lesions on five Juglans species was studied to find out sources of resistance/tolerance to this pathogen. Walnut species clustered into two main groups, J. hindsii, J. nigra, and J. mandshurica were the less susceptible to the colonization of P. cinnamomi, while J. regia and J. sieboldiana were the most susceptible. On this account, J. mandshurica represents the best alternative as rootstock because its employment overcomes the risk of the occurrence of black line disease, it has good level of resistance to Agrobacterium temefaciens and Brenneria nigrifluens, and it is tolerant to Xanthomonas arboricola pv. juglandis. J. mandshurica is also compatible in cross‐pollinations with J. regia and J. nigra. Differences in virulence of P. cinnamomi isolates was assessed and a marked interaction between species and isolate emerged. Treatment with fosetyl‐Al by dipping was mainly efficient in reducing the length P. cinnamomi lesions, and an interaction between species and treatment was evident with the highest efficacy on J. regia and J. sieboldiana.     

Beneficial Effects of Intercropping on the Growth and Nitrogen Status of Young Wild Cherry and Hybrid Walnut Trees

Growing concern for economic and environmental issues emphasizes the potential value of intercropping systems in temperate regions. However, the selection of relevant tree species to be associated with crops has been little documented. The growth and the nitrogen nutrition of two economically valuable species, wild cherry (Prunus avium L.) and hybrid walnut (Juglans nigra L.×Juglans regia L.), were compared over six years after plantation. These two species were associated with non-irrigated cereal crops in the agroforestry treatment or grown separately (weeded control and fallow). Intercropping increased diameter growth as soon as year 2 in the two species. Leaf biomass assessment using allometric models showed an earlier and greater leaf biomass increase in hybrid walnut than in wild cherry tree. After six years, the relative growth increase of the agroforestry trees with respect to the control trees varied with the parameter considered (diameter at breast height from +26 to +65%, leaf biomass from +54 to +142%) and with the tree species (higher relative growth for hybrid walnut trees). The beneficial effect on tree growth can be accounted for in terms of enhanced nitrogen nutrition. The tree–crop association in intercropping systems, which improves tree growth, might thus allow the planting of more demanding trees on soils of lower fertility.     

凉山州核桃坚果表型多样性研究

[目的]以四川省凉山州核桃和泡核桃农家类型的坚果为样本,研究其表型丰富度和变异特点,为其资源挖掘和合理利用提供理论依据。[方法]以15个核桃和泡核桃居群的330棵实生单株为研究材料,利用18个坚果表型相关性状进行多样性和聚类分析。[结果]表明:(1)凉山州核桃和泡核桃实生居群坚果表型性状变异系数为8.46%59.47%,平均为35.26%,单果质量极大(20.0 g)和极小(5.0 g)的资源均占一定比例;该地区坚果资源在《植物新品种特异性、一致性和稳定性测试指南-核桃属》中所描述坚果表型性状的基础上,新增了3个垂直于缝合线纵切面形状和1个核仁皮色特征;居群遗传性状Simpson指数为0.201 0.855,Shannon-Wiener指数为0.649 2.873,说明凉山州核桃和泡核桃坚果表型多样性比较丰富。(2)18个坚果表型性状的居群内变异均大于居群间,居群间的表型分化系数为6.03%,说明居群内变异是凉山州坚果表型多样性的主要来源。(3)UPGMA聚类分析结果表明,凉山州坚果表型性状Manhattan距离表现出与地理距离或气候条件显著正相关的趋势。[结论]凉山州核桃和泡核桃资源坚果表型丰富度高,是重要的核桃资源多样性分布地区。     

The impact of climate on radial growth and nut production of Persian walnut (<Emphasis Type="Italic">Juglans regia</Emphasis> L.) in Southern Kyrgyzstan

This dendroecological study used time series of climate and radial growth and nut production of Juglans regia to investigate the relationships between these parameters. More than 200 trees growing at sites of different altitude, aspect, inclination and human impact intensity were sampled in walnut-fruit forests of the Jalal Abad region in Southern Kyrgyzstan. Tree rings were dated and ring widths measured. Wide and narrow tree rings, so called positive and negative pointer years, could be explained by climatic events. The mean annual increment differed significantly in different regions and altitudes. The highest values could be found in plantations and at higher altitudes (1,700–2,000 m a.s.l.). Analysing the relationships between nut crop yields and annual increment, we found a significantly positive correlation between nut crop of the current year (x) and ring width of the previous year (x − 1). This relationship is influenced by climatic conditions, and may change in the future if climatic conditions in the region will change. Our study shows that Persian walnut (Juglans regia L.) of South Kyrgyzstan can be used in dendrochronological studies, and illustrates the influence of site conditions and management practices on radial growth of this tree species.     

Silvicultural Characteristics of Abies equi-trojani Aschers-Sinten and Growth Relationships between Pinus nigra Arnold var. pallasiana Endl and Abies equi-trojani in Mixed Natural Forests of Turkey

Pinus nigra Arnold var. pallasiana Endl. and Abies equi-trojaniAschers-Sinten are indigenous species of Turkey. The area ofPinus nigra is very large (more than 2 million hectares) occurringin the west, south and north of Turkey. However, Abies equi-trojanioccurs only in the west of Turkey in the Ida Mountains (Kazdagi)and is of limited area (5500 ha).These two species naturallyform both mixed stands and pure stands in the Ida Mountains. When mixed stands of Pinus nigra and Abies equi-trojani areregenerated, if the seedlings of these two species regeneratesimultaneously, the Pinus nigra will be eliminated from thestand in 15 to 25 years because of the rapid growth of Abiesequi-trojani. In different site conditions, Abies equi-trojanireaches 22–30 m in height and 40–65 cm in diameterin 70 years, whereas Pinus nigra reaches 17–22 m in heightand 25–40cm in diameter in the same period in the sameforest sites.     

Seed source and vesicular-arbuscular mycorrhizal symbiont affects growth of Juglans nigra seedlings

Seedlings of Juglans nigra from three seed sources were grown in fumigated soil without vesicular-arbuscular mycorrhizal (VAM) fungi or inoculated with Gigaspora margarita, Glomus deserticola or Glomus etunicatum. Vesicular-arbuscular mycorrhizal development varied significantly between fungal symbionts within a black walnut source. Glomus deserticola and G. etunicatum produced the highest levels of root colonization in all sources. Significant differences in seedling shoot and root growth were attributed to root colonization by specific VAM fungi in each black walnut source. Glomus deserticola stimulated seedling leaf area and root weight 26 and 52%, respectively, in one seed source. Seedling leaf N, P and K concentrations were significantly improved by VAM in two seed sources. Juglans nigra seedlings respond favorably to VAM colonization. However, differences between seed sources suggest a strong host-symbiont interaction.     

16个早实核桃良种遗传多样性的FISH-AFLP分析

采用FISH-AFLP技术,筛选9对E+3和M+3引物组合,对我国首批16个早实核桃良种进行了基因组DNA水平上的检测,结果表明:共获得1 072条可统计的条带,其中946条呈多态性,平均的多态性带百分率达88.12%;经9对引物检测的16个品种基因型各不相同,均得到数目不等的特征带,并能将16个早实核桃良种完全区分开。研究分析了早实核桃良种的遗传多样性和亲缘关系并建立了它们的指纹图谱。     

Influence of alfalfa (Medicago sativa L.) intercropping and polyethylene mulching on early growth of walnut (Juglans spp.) in central Italy

Combined production of timber and forage species is considered to be a desirable land-use system to offset some of the current land management problems of Italy. This paper reports the early results of a study on intercropping young plants of walnut with alfalfa (Medicago sativa L.), with or without polyethylene mulching, in an experimental plantation in central Italy. Two genotypes of walnut were used:Juglans regia L. and the French hybrid NG23×RA. The seasonal changes of absolute and relative growth rates of walnut stem diameter and apical shoot length were investigated.During both growing seasons, alfalfa intercropping strongly decreased walnut growth, whereas polyethylene mulching promoted stem height and diameter growth. Stem growth of intercropped-and-mulched walnut was the same as that of sole walnut under clean cultivation management. The use of polyethylene mulching reduced or avoided the competitive effect of associated alfalfa on walnut growth. During both growing seasons, the intercropped-and-mulched walnut had higher relative growth rates than intercropped-unmulched walnut. The results show the effectiveness of polyethylene mulching in promoting early growth of walnut, even when intercropped with alfalfa during early stages of plantation establishment.     

Dothistroma pini Hulbary: A New Disease on Pine in Britain

Dothistroma pini Hulbary, not hitherto reported in Britain,is described. Since 1954, and possibly before this date, ithas caused serious defoliation of nursery pine stock, particularlyof Pinus nigra and P. ponderosa. It has been reported only fromtwo nurseries both in the Wareham area, Dorset, but the reasonfor this extremely limited distribution is unknown. Attacksare worst in wet summers. Spore inoculations on potted plantsgave severe infection.     

Transferring site information for black walnut from native woodlands in southeastern Kansas USA to identify sites for agroforestry practices

Black walnut (Juglans nigra) is an important tree species for temperate agroforestry in the United States for timber, nuts, wildlife, and abrasives. Predictions of forestland productivity are needed for proper species selection in tree planting. Potential productivity can be estimated for non-forested areas and agricultural croplands by relating site quality to site and soil characteristics. Our study measured the growth potential of black walnut in natural stands. We looked at over 210 stands on unglaciated soils in southeastern Kansas with the site index at 50 years ranging from 9.1 to 26.8 m. Numerous environmental factors were evaluated, including: site, soil chemical, and soil physical properties. These environmental factors were related to tree height at the standard age of 50 years. Simple correlation and multiple regression analyses were run with the site index using over 60 variables of soil and topographic characteristics. Understory competition had no effect on site index. Chemical characteristics had a slight effect on site index. We explained 73 % of the variation in site index with just two variables; depth to a restrictive layer (DRL) and soil type. DRL is a good predictor of walnut productivity.     

A review of suitable companion crops for black walnut

Black walnut (Juglans nigra L.) is a temperate tree grown for nuts and wood, but it is allelopathic to certain plants and animals. We compiled reports of valuable black walnut companion crops which may be grown in the short term (<15 years after planting walnut trees), medium term (15–30 years), and long term (>30 years). There are many black walnut companion cropping systems for the short and medium term, but there are few for the long term. Companion crops for black walnut serve multiple functions, including nitrogen fixation, added yields, the development of straight walnut stems, and added protection from forest pests such as deer. Black walnut polyculture is a viable alternative worthy of further development and implementation.     

Development of allometric leaf area models for intensively managed black walnut (Juglans nigra L.)

? Introduction

Intensive plantation management of high-value hardwoods, such as black walnut (Juglans nigra L.), is focused on maximizing both stem form and growth at the stand and tree level. While significant research has focused on genetic improvement in black walnut, little is known about the production ecology of this species in plantation settings.

? Objectives

The aim of this study is to assess the applicability of nondestructive projected leaf area (PLA) estimation based on the pipe model theory in three single-aged J. nigra plantations representing discrete age classes ranging from 3 to 27?years of age.

? Results

Branch-level PLA was modeled as a function of branch basal cross-sectional area (R ²?=?0.875). Six nondestructive tree-level PLA models were assessed, with four models yielding R ²?>?0.90. Tree-level models performed well across age classes, with model fits comparable to previous studies in coniferous species.

? Conclusion

This study demonstrates that allometric approaches to modeling leaf area distribution in hardwoods are feasible, but future efforts may need to use different sampling approaches and/or quantify variables that have not been significant in conifers. This study represents an important first step into more quantitative analysis of production ecology of deciduous species in the CHFR of the USA.     

An investigation of accelerated temperature-induced ageing of four wood species: colour and FTIR

The study investigated and compared the behaviour of four wood species, originating from Europe and China, in terms of temperature-induced artificial ageing. It was conducted at 100 °C for a total period of 288 h. Ageing effects were evaluated by colour measurements in the CIE Lab system and by FTIR analysis. Colour changes were then related to chemical changes in the wood. The investigated wood species were European ash (Fraxinus excelsior), European walnut (Juglans regia), Chinese ash (Fraxinus mandshurica) and Chinese walnut (Juglans mandshurica). Colour changes were maximum for European ash and minimum for Chinese ash, while European walnut and Chinese walnut evolved quite similarly. Main chemical changes due to temperature ageing were reduction of hydroxyl groups, increase of the unconjugated carbonyl groups and an apparent slight increase of lignin, more evident for European ash and delayed for European walnut. Formation of aromatic carbonyl conjugated groups as quinoid structures as a result of oxidative reactions was revealed especially for European ash. The different behaviour of the studied wood species may be explained by their different chemical composition, especially hemicelluloses, lignin and extractives content.     

间作绿豆对核桃苗光合特性及根系导水力的作用

[目的]为研究间作绿豆对核桃苗根系生长、根系水分运输和光合特性的影响,[方法]采用砂培方法,在温室内将1年生核桃嫁接苗和绿豆进行间作。[结果]显示:间作绿豆增加了土壤全氮含量(0.014%0.021%),不添加氮素间作绿豆,核桃苗根系总表面积、根系总长度、根系直径和根系总体积均显著增加,而正常供应氮素间作绿豆,核桃苗根系生长降低。核桃苗根系单位面积的导水率与土壤氮素含量显著相关,添加氮素与否间作绿豆后,根系单位面积导水率分别升高0.102×10^-5 mL·cm^-1·min^-1·MPa^-1和0.057 ×10^-5 mL·cm^-1·min^-1·MPa^-1;而不添加氮素间作绿豆整株根系导水率增加0.043 mL·cm^-1·min^-1·MPa^-1,正常供应氮素间作绿豆后,核桃苗整株根系导水率反而降低0.034 mL·cm^-1·min^-1·MPa^-1;核桃苗气孔导度对各处理响应和根系整株导水力有相同趋势,不添加氮素间作绿豆核桃光合能力升高至对照水平,光饱和点达1 567.17 μmol·m^-2·s^-1,最大净光合速率达12.84 μmol·m^-2·s^-1,光补偿点和暗呼吸速率降低;而正常供应氮素间作绿豆核桃苗光合能力降低。[结论]间作绿豆改善了核桃苗的生长环境,有益于增加核桃苗的根系吸收面积、水分运输以及光合代谢;但在氮素充足的土壤中,间作绿豆非但无益于核桃苗,反而降低核桃苗的水分供应,影响其气体交换和光合能力。     

Botryosphaeriaceae species causing canker and dieback of English walnut (Juglans regia) in Italy

English walnut (Juglans regia) is an important nut crop worldwide and is currently considered emerging in Italy. Botryosphaeriaceae fungi cause symptoms including cankers, discoloration and dieback, and several species are reported across the world on walnut. In this study, symptomatic trees from an orchard in Southern Italy showing branch dieback, cankers, wood discoloration and gummosis were surveyed. Three different fungi from the Botryosphaeriaceae were consistently isolated from symptomatic tissues. Representative isolates were characterized using morphological and molecular approaches based on conidial morphology, optimum growth temperature and the comparison of DNA sequence data from the ITS, tef1‐α and tub2 loci. Three species were identified: Botryosphaeria dothidea, Neofusicoccum mediterraneum and Neofusicoccum parvum. Pathogenicity tests on detached fruits and potted plants showed that all three species were pathogenic. To our knowledge, this is the first report of these Botryosphaeriaceae species causing canker and dieback on English walnut in Italy.