Interference at several temporal and spatial scales between two chestnut insects

Detection of interspecific competition between insects is often sensitive to scaling. We give an example of scale-dependent interference between the weevil Curculio elephas and the moth Cydia splendana, which both have larvae that develop in the fruits of chestnut Castanea sativa. Measures at three scales were considered: chestnut, husk (with one to three fertile fruits) and tree. Data come from observations in the field over 14 years, complemented by experiments done directly in trees. Data on individual chestnut fruits revealed a marked statistical interference between the two insects. Experiments demonstrated that presence of a moth larva in a fruit usually inhibits weevil egg-laying. Conversely, weevil presence does not strongly modify moth larval behavior. Cases of double infestation often correspond to fruits first attacked by the weevil. With measures on husks, interference between the two insects was observed only in some trees; its intensity was always weaker than in the chestnuts themselves. At the scale of entire trees, rates of infestation by each insect are not correlated. Interference in chestnut fruits is interpreted by assuming that the weevil female either is sensitive to a repellent molecule originating from a moth larva or its frass, or can detect moth larval sounds. Mechanisms governing infestation rates from data per tree are discussed in relation to those found at fruit scale and to plant-insect interactions. The need to estimate available resources both from quantitative and qualitative points of view is emphasized.     

Role of genomics in the potential restoration of the American chestnut

The development of genomic tools will enhance traditional tree breeding technologies leading to more certain and timely recovery of the American chestnut, a keystone heritage tree of the eastern United States. Major efforts are being made in gene discovery, genetic marker development, construction of a BAC-based physical map, and DNA transformation technology. A strategy of map-based cloning, association genetics, and genetic engineering, combined with traditional and marker-assisted backcross breeding is proposed for the long-term genetic restoration of this iconic tree species.     

Cloning of two classes of PR genes and the development of SNAP markers for powdery mildew resistance loci in chestnut rose (<Emphasis Type="Italic">Rosa roxburghii</Emphasis> Tratt)

Pathogenesis-related (PR) genes were isolated from chestnut rose (Rosa roxburghii Tratt) using a PCR approach with degenerate primers designed for the conserved regions of two PR gene families: class 2 (β-1,3-glucanase) and class 5 (osmotin). Thirteen PR2 and ten PR5 genes were obtained, with a nucleotide identity that ranged from 40.1 to 99.7% and from 99.2 to 99.8%, respectively. Sequence comparison revealed the presence of single nucleotide polymorphisms (SNPs) in these sequences with, on an average, one SNP in every 64-bp fragment for the PR2 genes and one in every 68-bp fragment for the PR5 genes. A total of 23 primers were used to genotype these SNPs for use in developing single nucleotide-amplified polymorphisms (SNAP) markers. One marker (Glu7) was found to be linked to powdery mildew resistance loci. Based on genetic mapping of a segregating F₁ population, we determined that 16 of the 23 SNAP markers formed one group and subsequently detected a quantitative trait locus that accounted for 12% of the variation in the powdery mildew resistance phenotype. The results of this study provide a first insight into the genomic structure of PR genes and show that the candidate gene approach in combination with SNAP markers is an attractive strategy to search for powdery mildew resistance loci in chestnut rose.     

Development and characterization of microsatellite markers in <Emphasis Type="Italic">Castanea sativa</Emphasis> (Mill.)

Thirty-three simple sequence repeat (SSR) markers were isolated andcharacterized in Castanea sativa (Mill.) from the cultivarGarrone Nero. For the identification of SSR loci, primers were designed on eachside flanking the repeat region and they were initially tested on 5 chestnutsamples using chemiluminescence detection. Twenty four loci where shown to bepolymorphic and the number of alleles detected per locus varied from 2 to 7.Fourteen loci were chosen for the analysis of 20 cultivars grown in North Italyusing the semi-automatic system ABI PRISM 377. These 14 markers showed a highlevel of genetic polymorphism with a total of 90 alleles; the number of allelesranged from 4 to 10 per locus, with an average level of 6.4. The mean expectedand observed heterozygosity were 0.724 (range: 0.649–0.835) and 0.793(range: 0.350–0.950) respectively. The estimated frequency of nullallelesshowed a positive value for 3 loci, but except for 1 locus, the values wereverylow. The total value for the probability of identity was 7.04 ×10^–11. Paternity exclusion probability was very high (0.999),sufficiently high to study pollen flow.     

Histological investigation on gall development induced by a worldwide invasive pest,Dryocosmus kuriphilus,on Castanea sativa

The Asian chestnut gall wasp Dryocosmus kuriphilus (Hymenoptera: Cynipidae) is one of the most serious pests of chestnut trees worldwide. Wasps lay eggs into chestnut buds from mid Jane to late July, depending on latitude, and galls develop the following spring on new vegetation, reducing photosynthesis and nut production. We observed that modification of tissues surrounding D. kuriphilus eggs, which differentiate to form the larval chamber, started approximately 1 month after oviposition, shortly after eggs hatch. The larval chambers continued to increase slightly in size throughout the autumn months until January. After that, a period of stagnation, which corresponds to the plant's dormancy, occurred, followed by rapid growth from March to May, during the period from bud swelling to bud break. Galls continued to grow during the leaf expansion after bud break and stopped when plant organs achieved their final size. Our results have implications for the management of the pest, providing a better understanding of the critical time periods for the effective control.     

The cultivation of<Emphasis Type="Italic"> Castanea sativa</Emphasis> (Mill.) in Europe,from its origin to its diffusion on a continental scale

The history of Castanea sativa (sweet chestnut) cultivation since medieval times has been well described on the basis of the very rich documentation available. Far fewer attempts have been made to give a historical synthesis of the events that led to the cultivation of sweet chestnut in much earlier times. In this article we attempt to reconstruct this part of the European history of chestnut cultivation and its early diffusion by use of different sources of information, such as pollen studies, archaeology, history and literature. Using this multidisciplinary approach, we have tried to identify the roles of the Greek and Roman civilizations in the dissemination of chestnut cultivation on a European scale. In particular, we show that use of the chestnut for food was not the primary driving force behind the introduction of the tree into Europe by the Romans. Apart from the Insubrian Region in the north of the Italian peninsula, no other centre of chestnut cultivation existed in Europe during the Roman period. The Romans may have introduced the idea of systematically cultivating and using chestnut. In certain cases they introduced the species itself; however no evidence of systematic planting of chestnut exists. The greatest interest in the management of chestnut for fruit production most probably developed after the Roman period and can be associated with the socio-economic structures of medieval times. It was then that self-sufficient cultures based on the cultivation of chestnut as a source of subsistence were formed.Electronic Supplementary Material Supplementary material is available in the online version of this article at . A link in the frame on the left on that page takes you directly to the supplementary material.     

中国东部栗疫病菌群体的遗传分化*

本实验采用RFLP技术,对中国东部栗疫病菌(Cryphonectria parasitica)进行了群体遗传结构的研究。313个参试菌株来自10个省(市)的16个群体(子群体),样本分布在北纬24°N—41°N。各菌株的DNA分别用限制性内切酶Pst Ⅰ和EcoR Ⅰ酶切,先后以10个低拷贝DNA探针和1个DNA指纹图谱探针进行了杂交和检测。结果表明,两个探针(pCB29和pMS29.1)的杂交图谱呈单态性;探针pCB19的杂交图谱显示,菌株DNA以PstⅠ酶切的为单态性,以EcoR Ⅰ酶切的则呈多态性;其他7个低拷贝探针的杂交图谱都呈多态性(Pst Ⅰ酶切)、指纹图谱探针的检测结果显示,辽宁凤城群体的菌株与中国东部其他群体的菌株相比,具有更多的限制性杂交片段,菌株间的遗传变异性也更大。     

Origin and relationships of New Zealand chestnut (Castanea sp.Fagaceae) selections reflect patterns of graft failure

Graft failure that occurs in the clonal propagation of chestnuts is a practical problem which has arisen in recent years. Several hypotheses have been put forward to explain reasons for the failure but none have focused on origin and relationships of cultivars. This study was carried out to determine whether relationships of New Zealand chestnut selections and their origin reflect patterns of graft failure within the selections. Two different character data sets, random amplified polymorphic DNA (RAPD) and morpho-nut, were employed for the analyses of the relationships between the chestnut selections. Four different analyses were done to generate trees depicting the relationships of the selections. These were: morpho-nut character, RAPD character, taxonomic congruence (combination of morpho-nut and RAPD trees), and character congruence (combination of morpho-nut and RAPD data sets). When graft failure data were mapped onto the majority rule consensus tree constructed from character congruence analysis, it was found that self graft incompatibility was reflected in the origin and relationships of the chestnut selections. Information on the affinities of the chestnut selections to introduced chestnut species showed that the selections that were mostly implicated in graft failure which are from the North Island had affinities with theCastanea crenata species. But the selections (from the South Island) that were placed withCastanea sativa as well as hybrids (1002 and 1007 from the North Island) ofCastanea mollissima andC. crenata had no failed grafts. This finding indicates that graft failure in New Zealand chestnut selections does not occur by chance but is dependent on the origin and/or evolutionary history of the selections.