胜红蓟黄酮类物质对柑桔园主要病原菌的抑制作用

柑桔园引种杂草胜红蓟能有效地控制主要病害,研究发现,胜红蓟产生并释放到土壤中的黄桐类物质对疮痂病菌、炭疽病菌、白粉病菌和烟煤病菌等柑桔园主要病原真菌具有抑制活性,从胜红蓟植株中分离鉴定了10个黄酮物质,包括一个糖甙黄酮分子,但胜红蓟植株产生的大部分黄酮物质在土壤中会逐渐降解,只有3个黄酮分子能在柑梧园的土壤中累积并存在较长时间,而这3个黄酮物质对柑桔园主要病原真菌具有显著的抑制活性,其活性不仅超过胜红蓟释放的其化感物质,而且强于商业的杀菌剂多菌灵,表明胜红蓟产生和释放的黄酮物质在柑桔园病害控制中起着重要作用。     

Citrus replant problem in Iraq I. Possible role of soil fungi and nematodes

The role of soil fungi and nematodes in citrus replant problems was investigated. Several pathogenic and non-pathogenic fungi and the nematodeTylenchulus semipenetrans were isolated in about equal abundance from soils which displayed or did not display replant problems. However, in almost all trees showing evidence of decline, infection by the fungusPhytophthora citrophthora had advanced through the roots until it had reached the tree crown. Fumigation of old citrus soil with methyl bromide greatly increased the growth of sour organe. The application of Nemacure, Benomyl and Ridomil 5G confirmed the important role of pathogenic and non-pathogenic fungi and nematodes in the citrus replant problem. Inoculation of methyl bromide-treated soil with the pathogenic and non-pathogenic fungi separately or in combination further confirmed the previous experiments and also revealed an important role ofP. citrophthora andFusarium solani when replanting citrus in old citrus orchards.     

胜红蓟化感作用研究 Ⅸ.主要化感物质在土壤中的转化

在田间条件下,胜红蓟挥发油能抑制花生的出苗和生长发育,进一步用高效液相色谱（HPLC）研究证实;胜红蓟挥发油中的主要化感物质胜红蓟素在土壤中的转化与土壤的有机质和营养元素水平显著相关,在高有机质和营养元素水平的土壤中,胜红蓟素先聚合形成二聚体,26d后又解聚成胜红蓟素,然后逐步降解成苯甲酸类,2-甲基丙酸和乙酸等小分子,而在低有机质和营养元素水平的土壤中,胜红蓟素不经过二聚化过程,而是直接降解成小分子,经液质（LC/MS）和核磁共振（NMR）等技术分离鉴定了胜红蓟素二聚体的结构,生物测定表明：胜红蓟素二聚体对花生和黑牧草的生长没有抑制活性。     

Seasonal phenology and relative preference of Closterotomus (Calocoris) trivialis (Hemiptera: Miridae) on olive, citrus and associated host plants in the field

The seasonal appearance and population abundance of nymphs and adults of Closterotomus trivialis (Costa) were studied by weekly canopy shaking samplings in an olive and a citrus orchard in Chania, Greece, from January to May 2009. In addition, samples were taken from weeds referred to in the literature as alternative host plants for C. trivialis. Results showed that nymphal instars of C. trivialis were first recorded on weeds in mid-January. The first adult appearance was recorded on Mercurialis annua L. in early March in the citrus orchard, while in the olive orchard, it was recorded 13 days later. A significantly higher population of C. trivialis under field conditions was found on M. annua followed by Urtica sp., Parietaria officinalis L. and Sinapis alba L. Population density on olive (Olea europaea L.) and sweet orange (Citrus sinensis (L.) Osbeck) trees as well as on Sonchus oleraceus L. and Malva sylvestris L. was very low in general. Collected information on host plant preference of C. trivialis may be helpful for the prediction of its occurrence and movement among crop and non-crop host plants and therefore in the development of appropriate control strategies, thus avoiding unnecessary insecticidal treatments.     

胜红蓟化感作用研究 Ⅷ.植株对花生和相关杂草的田间化感效应

在田间条件下,胜红蓟化感效应与处理植株的方式和时间显相关。覆盖处理对花生出苗和生长不产生化感抑制效应,而是显示一定的促进效应,翻埋处理对花生出苗和生长都产生显的化感抑制效应,然而覆盖处理30d,翻埋处理10d后再播种花生,花生出苗均受显抑制,两种处理都能减少许多杂草的萌发,但对不同种属杂草萌发的抑制作用有差异。进一步用高效液相色谱（HPLC）技术研究证实;覆盖处理条件下,胜红蓟植株直到第14天才向土壤中缓慢释放化感物质胜红蓟素,第30天达到最大值后逐渐减少,而翻埋处理的第2天,植株就向土壤中释放胜红蓟素,第10天达到最大值后缓慢减少,但第26天后土壤中胜红蓟素含量又上升,然后再逐步下降。这些结果显示不同处理条件下,胜红蓟植株对花生和相关杂草的田间化感效应是与胜红蓟植株在不同时间释放的化感物质在土壤中的存在状态和有效作用浓度显相关的。     

Eupalopsellidae and Stigmaeidae (Acari: Prostigmata) within citrus orchards in Florida: species distribution,relative and seasonal abundance within trees,associated vines,and ground cover plants

Seven citrus orchards on reduced- to no-pesticide spray programs were sampled for predacious mites in the families Eupalopsellidae and Stigmaeidae (Acari: Prostigmata) in central and south central Florida. Inner and outer canopy leaves, fruit, twigs, and trunk scrapings were sampled monthly between August 1994 and January 1996. Open flowers were sampled in March from five of the sites. Two species of eupalopsellid mites (Exothorhis caudata Summers and Saniosulus harteni (van-Dis and Ueckermann)) were identified from 252 specimens collected within citrus tree canopies within the seven citrus orchards of which 249 were E. caudata. Only two E. caudata were collected from ground cover plants within five of the seven orchards. Eight species of Stigmaeidae were identified from 5,637 specimens: Agistemus floridanus Gonzalez, A. terminalis Gonzalez, Eustigmaeus arcuata (Chandhri), E. sp. near arcuata, E. segnis (Koch), Mediostigmaeus citri (Rakha and McCoy), Stigmaeus seminudus Wood, and Zetzellia languida Gonzalez were collected from within citrus tree canopies from seven orchard sites. Agistemus floridanus was the only species in either family that was abundant with 5,483 collected from within citrus tree canopies compared with only 39 from vine or ground cover plants. A total of 431 samples from one or more of 82 vines and ground cover plants were sampled monthly between September 1994 and January 1996 in five of these orchards and one or more eupalopsellids or stigmaeids were collected from 19 of these plants. Richardia brasiliensis (Meg.) Gomez had nine A. floridanus from 5 of 25 samples collected from this plant. Solanum sp. had five A. floridanus from three samples taken. Both eupalopsellid and stigmaeid species numbers represented <1 % of the total numbers of phytoseiid species taken from the same plants. The two remaining orchards were on full herbicide programs and ground cover plants were absent. Agistemus floridanus was more abundant in the citrus orchards with on-going or recent herbicide programs compared with orchards having well-developed ground cover plants. Agistemus floridanus was most abundant on inner leaves between January and April and again during September through November. Additional collection records of E. caudata, S. harteni, A. terminalis, M. citri, Z. languida, and Zetzellia sp. near silvicola within Florida citrus orchards between 1989 and 2004 are included. Four species of Eupalopsellidae and ten species of Stigmaeidae occur within Florida citrus orchards.     

柑橘园扩张对生态系统服务和景观格局的影响——以江西省信丰县为例

柑橘园扩张是我国柑橘主产区较典型的土地利用/覆盖变化过程之一。但柑橘园扩张对区域生态系统服务和景观格局的影响尚不清楚,探明柑橘园种植的生态效应对柑橘主产区实现生态-经济协同发展具有重要的理论和现实意义。以江西省信丰县为研究区,基于第二次、第三次全国国土调查数据,借助InVEST模型、景观格局指数、图谱分析等方法,结合地形梯度和相关性分析,对柑橘园扩张所致的生态系统服务和景观格局变化及其权衡与关联进行分析。结果表明：①2010-2019年,柑橘园扩张方向以占用林地和耕地为主,柑橘园面积从9961.29 hm²增至12633.84 hm²,其中新增柑橘园7504.72 hm²,退出柑橘园4832.16 hm²,区域内柑橘园转换频繁。②柑橘园扩张导致信丰县景观格局总体呈现破碎化趋势,景观连通性降低,并对土壤保持服务和碳储量服务产生负向影响,对柑橘供给服务产生正向影响,对产水服务几乎无影响。③不同类型柑橘园在不同地形梯度上的扩张对生态系统服务的影响方向和程度存在差异。④在权衡与协同分析中,供给服务与支持服务呈权衡关系,碳储量-产水、碳储量-土壤保持等支持服务之间呈协同关系;景观破碎化与生态系统服务显著关联。研究结果可为经济作物大规模种植区的园地合理开发利用和生境保护提供科学依据。     

Pseudomonas caspiana sp. nov., a citrus pathogen in the Pseudomonas syringae phylogenetic group

In a screening by multilocus sequence analysis of Pseudomonas strains isolated from diverse origins, 4 phylogenetically closely related strains (FBF58, FBF102^T, FBF103, and FBF122) formed a well-defined cluster in the Pseudomonas syringae phylogenetic group. The strains were isolated from citrus orchards in northern Iran with disease symptoms in the leaves and stems and its pathogenicity against citrus plants was demonstrated. The whole genome of the type strain of the proposed new species (FBF102^T = CECT 9164^T = CCUG 69273^T) was sequenced and characterized. Comparative genomics with the 14 known Pseudomonas species type strains of the P. syringae phylogenetic group demonstrated that this strain belonged to a new genomic species, different from the species described thus far. Genome analysis detected genes predicted to be involved in pathogenesis, such as an atypical type 3 secretion system and two type 6 secretion systems, together with effectors and virulence factors. A polyphasic taxonomic characterization demonstrated that the 4 plant pathogenic strains represented a new species, for which the name Pseudomonas caspiana sp. nov. is proposed.     

入侵植物藿香蓟与常见伴生杂草的生态位特征

基于传统生态位理论的生物入侵机制假说认为外来种和土著种生态位的差异是决定入侵成功与否和危害程度的关键。藿香蓟(Ageratum conyzoides L.)是一种在我国南方快速蔓延的恶性入侵种。为了了解藿香蓟与其他杂草在群落中的生态关系,探究造成藿香蓟成功入侵的可能机制及危害,在浙西南的丽水市开展了杂草群落调查,计算了藿香蓟和16种常见本地杂草的生态位宽度、生态位重叠和种间相关系数,并对主要物种进行典范对应分析(CCA)排序。结果表明(1)藿香蓟与常见本地杂草间的生态位重叠度显著高于本地杂草间的生态位重叠度,这与藿香蓟具有最大的生态位宽度有关;(2)藿香蓟与常见本地杂草的Pianka生态位重叠指数介于0.04-0.296之间,重叠度处于中下水平;(3)常见本地杂草对于藿香蓟的n-维超体积生态位重叠值显著高于藿香蓟对于常见本地杂草的n-维超体积生态位重叠值;(4)藿香蓟在CCA排序图上处于较中心的位置,说明其具有较高的中生性;不仅如此,外来杂草和本地杂草在排序图上充分混杂,说明外来种相对于本地种并无明显特化;(5)群落中大多数常见杂草间未出现显著种间负相关,仅7个种对显著正相关,大多数种对不相关。总的来说,丽水农村的杂草群落稳定较差,资源相对充足,种间生态位重叠较低,本地植物对于藿香蓟的竞争阻抗较小,加上藿香蓟本身较大的生态位宽度,导致了藿香蓟在本地区广泛而严重的入侵。     

Role of root-mediated interactions in phytotoxic interference of Ageratum conyzoides with rice (Oryza sativa)

Ageratum conyzoides L. (billy goat weed; Asteraceae) is an annual invasive weed native of tropical America and has now naturalized worldwide, particularly in Southeast Asia. The present study investigated the nature and potential of root-mediated allelopathic interference of A. conyzoides against rice (Oryza sativa). Root and shoot length and biomass accumulation of rice were significantly reduced (by 18–30%) when grown in the rhizosphere soil of the weed indicating the release of putative allelochemicals from the weed into the soil. The growth of rice was also progressively reduced in the soil amended with increasing amounts of root residues (5, 10 and 20 g kg⁻¹ soil) of A. conyzoides. The addition of activated charcoal, an inert material with high affinity for organic biomolecules, partly ameliorated the negative effects of root residues amended in the soil. Further, there was no negative effect on the availability of soil nutrients in the root-amended soils. These were rather nutrient rich with greater electrical conductivity, and higher amount of organic matter, thus indicating no role in observed growth reduction. The reduction in allelopathic effects of root residue upon charcoal addition further indicated that putative phytotoxins released from the weed roots are water-soluble phenolic compounds. A significant amount of water-soluble phenolics were present in rhizosphere (∼6-times higher) and root-amended soils (∼5–10-fold higher) and their content was reduced (to ∼3.6–7.0-fold higher) when charcoal was added. The observed growth reduction in Ageratum rhizospheric or root-amended soils was concomitant with the amount of phenolic compounds. Upon HPLC analyses, these were identified as p-coumaric acid, gallic acid, ferulic acid, p-hydroxybenzoic acid and anisic acid. Under laboratory conditions, these phenolic acids reduced the root length and seedling weight of rice individually as well as in equimolar mixture, though no synergistic effect was noticed. The study concludes that root exudates and residues of A. conyzoides suppress the growth of rice by releasing phenolic allelochemicals into the soil rhizosphere and not through alteration of soil nutrients, and allelopathy plays a significant role in root-mediated negative interference of A. conyzoides.     

Native soil fungi associated with compostable plastics in three contrasting agricultural settings

Plastics are used widely as agricultural mulches to suppress weeds and retain soil moisture. Disposal of conventional plastic mulches requires physical removal for disposal in a landfill or incineration. Biodegradable plastic mulches that could be tilled into the soil at the end of a growing season represent an attractive alternative to conventional plastic mulches. In this study, three commercially available mulches labeled as “biodegradable” and one experimental, potentially biodegradable mulch were used during a tomato growing season, and then buried in field soil at three locations for approximately 6 months, as would occur typically in an agricultural setting. Degradation after 6 months in soil was minimal for all but the cellulosic mulch. After removal of mulches from soil, fungi were isolated from the mulch surfaces and tested for their ability to colonize and degrade the same mulches in pure culture. The majority of culturable soil fungi that colonized biodegradable mulches were within the family Trichocomaceae (which includes beneficial, pathogenic, and mycotoxigenic species of Aspergillus and Penicillium). These isolates were phylogenetically similar to fungi previously reported to degrade both conventional and biodegradable plastics. Under pure culture conditions, only a subset of fungal isolates achieved detectable mulch degradation. No isolate substantially degraded any mulch. Additionally, DNA was extracted from bulk soil surrounding buried mulches and ribosomal DNA was used to assess the soil microbial community. Soil microbial community structure was significantly affected by geographical location, but not by mulch treatments.     

Amendment with biocontrol strains increases Trichoderma numbers in mature kiwifruit (Actinidia chinensis) orchard soils for up to six months after application

A Trichoderma mixture was applied to kiwifruit plants in a pot experiment and to mature orchard vines to determine its effect on numbers of root-associated fungi and compare application methods into kiwifruit orchards in New Zealand. Trichoderma and other fungal numbers were recorded using a root plating technique. In the pot experiment, a significantly greater number of Trichoderma was isolated from treated compared to untreated plants 6 and 10 weeks after inoculation. Six months after application, greater numbers of Trichoderma were recovered in the orchards from Trichoderma treated vines and the increase was comparable for all application methods with over 50% of isolated fungi identified as Trichoderma compared to 33% in the water-only control. Different viable methods are available that can easily be integrated into everyday orchard management in order to introduce Trichoderma into mature kiwifruit stands. A six-monthly or more frequent application schedule seems advisable.     

Spatial Patterns of Belonolaimus spp. Among and Within Citrus Orchards on Florida's Central Ridge

A survey was initiated to determine the incidence of Belonolaimus spp. (sting nematodes) in citrus orchards in the central ridge region of Florida, following widespread damage by these nematodes to young trees replanted after freezing weather in 1989-90. Sting nematodes were detected in 50% of 210 samples and in 64% of 84 orchards surveyed. More orchards in Polk County were infested with sting nematodes (82%) than in counties to the north (36%) or south (48%). Principal component analysis of morphometric data separated six of seven sting nematode populations in northeastern Polk County from six populations in adjacent regions. Stylet:tail ratio for nematodes in northeastern Polk County tend to be > 1.0 and were ≪ 1.0 for all other populations. Patchiness of nematodes within an orchard was associated with stunted trees (23% smaller), reduced root mass density (25% lower), and low fruit yield (57% reduction). Soil texture did not vary among trees of different size in the orchard, but soil water potential between irrigation events was highest beneath small trees with low root mass density. Results of the survey indicate that the incidence of sting nematodes in orchards on the central ridge is much higher than previously estimated and that sting nematodes can cause substantial damage in replanted orchards. Further research is needed to evaluate the significance of sting nematode population variability and its relationship to citrus crop loss in Florida.     

Comparative toxicity of an acetogenin-based extract and commercial pesticides against citrus red mite

Acetogenins, a class of natural compounds produced by some Annonaceae species, are potent inhibitors of mitochondrial electron transport systems. Although the cellular respiration processes are an important biochemical site for the acaricidal action of compounds, few studies have been performed to assess the bioactivity of acetogenin-based biopesticides on spider mites, mainly against species that occur in orchards. Using residual contact bioassays, this study aimed to evaluate the bioactivity of an ethanolic extract from Annona mucosa seeds (ESAM) (Annonaceae) against the citrus red mite Panonychus citri (McGregor) (Acari: Tetranychidae), an important pest of the Brazilian citriculture. ESAM is a homemade biopesticide which was previously characterized by its high concentration of acetogenins. It caused both high mortality of P. citri females (LC₅₀ = 7,295, 4,662, 3,463, and 2,608 mg l^?1, after 48, 72, 96, and 120 h of exposure, respectively) and significant oviposition deterrence (EC₅₀ = 3.194,80 mg l^?1). However, there was no effect on P. citri female fertility (hatching rate). In addition, the ESAM efficacy (in terms of its LC₉₀) was compared with commercial acaricides/insecticides (at its recommended rate) of both natural [Anosom^® 1 EC (annonin), Derisom^® 2 EC (karanjin), and Azamax^® 1.2 EC (azadirachtin + 3-tigloylazadirachtol)] and synthetic origin [Envidor^® 24 SC (spirodiclofen)]. Based on all of the analyzed variables, the ESAM exhibited levels of activity superior to other botanical commercial acaricides and similar to spirodiclofen. Thus, our results indicate that ESAM may constitute a biorational acaricide for citrus red mite integrated pest management in Brazilian citrus orchards, particularly for local use.     

The ground beetle Pseudophonus rufipes revealed as predator of Ceratitis capitata in citrus orchards

The Mediterranean fruit fly Ceratitis capitata (Wiedemann) is a major citrus pest in Spain. Although medfly is being controlled chemically, alternative biorational strategies should be developed, like those based on conservation biological control of polyphagous predators. The ground beetle Pseudophonus rufipes (De Geer) is the most abundant carabid inhabiting the ground of citrus orchards in eastern Spain. However, little is known about its activity–density and predatory role against C. capitata in the citrus agroecosystem. Here, we report on its predatory potential on the medfly’s developmental stages that take place in the citrus ground. This carabid species preyed efficiently on C. capitata third instar larvae and especially on pupae but not on teneral adults. Moreover, predation under field conditions was evaluated by detecting C. capitata DNA remains using PCR-based gut-content analysis. Half-life DNA detectability of C. capitata was of 32.33 h. Pseudophonus rufipes specimens were field-collected after C. capitata sterilized pupae were deployed in a commercial citrus orchard. Thereafter, the carabids captured by pitfall traps were analyzed, being DNA-remains of C. capitata detected in 22.2% of them. Data reported here clearly suggest that P. rufipes could play an important role in regulating medfly populations in citrus orchards. This information is particularly useful when biological control conservation strategies are being considered to control this pest.     

Influence of ground beetles (Carabidae) as biological agent to control of the Mediterranean fruit fly pupae,Ceratitis capitata,in Iranian citrus orchards

Damage by Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) in the northern Iranian citrus orchards has been led to spray by different chemical pesticides. The present study was conducted in the citrus orchard in Mazandaran province of Iran where with the exception of mineral oil treatments for scale insects, had not been sprayed with synthetic insecticides for six years. The purpose of this study was initially to investigate faun and seasonal activity of predaceous ground carabid beetles in the citrus orchards. Additionally, their role as predators of Ceratitis capitata (Wiedemann) pupae was evaluated under laboratory and field conditions. Predation in laboratory was evaluated by no choice feeding experiments while predation under field conditions was evaluated by molecular detection of the pest DNA in the gut contents of field-collected Carabids. A total of 3437 beetles of ten carabid species were collected from a non-chemical treatment citrus orchard. The results of the seasonal density fluctuation indicated increasing population in spring reaching the highest in September, simultaneously with the peak of fruit fly damage, and thereafter decreasing during winter when the pest was overwintering. However, three species, Harpalus rufipes, Broscus karelinii and Brachinus brevicollis were most abundant in the field collection but the results of no-choice experiments in the laboratory indicated H. rufipes, B. karelinii and Pterostichus macer were the most voracious predators on pupae. Results of gut content analysis of the voracious species indicated the positive testing for pest DNA in 79.16 % of H. rufipes, 76.92 % of B. karelinii and 75 % of P. macer of analyzed beetles. The results of the study strongly indicated that in citrus orchards where intensive spraying is eliminated, natural enemies such as Carabid beetles could play an important role in reducing pests such as medfly.     

Control of Tylenchulus semipenetrans on Citrus With Aldicarb,Oxamyl, and DBCP

Soil application of DBCP (l,2-dibromo-3-chloropropane) and foliar applications of oxamyl (methyl N'',N''-dimethyl-N-[(methylcarbamoyl)oxy]-l-thiooxamimidate) were compared for control of Tylenchulus semipenetrans in a grapefruit (Citrus paradisi) orchard, DBCP reduced nematode populations and increased fruit growth rate, fruit size at harvest, and yield compared to the untreated controls in the 2 years following treatments. Foliar applications of oxamyl reduced nematode populations and increased fruit growth rate slightly the first year, but not in the second. Foliar applications of oxamyl did not improve control attained by DBCP alone. Soil application of aldicarb [2-methyl-2-(methylthio)propionaldehyde-O-(methylcarbamoyl)oxime] or DBCP to an orange (C. sinensis) orchard reduced T. semipenetrans populations in the 3 years tested and increased yield in 1 of 3 years. Aldicarb treatment reduced fruit damage caused by the citrus rust mite, Phyllocoptruta oleivora. Aldicarb, applied at 5.7 or 11.4 kg/ha, by disk incorporation or chisel injection, was equally effective in controlling nematodes, improving yields, fruit size, and external quality. In a grapefruit orchard, chisel-applied aldicarb reduced nematode populations and rust mite damage and increased yields in both years and increased fruit size in one year. The 11.4-kg/ha rate was slightly more effective than the 5.7-kg/ha rate. Aldicarb appears to be an adequate substitute for DBCP for nematode control in Texas citrus orchards and well-suited to an overall pest management system for Texas citrus.     

Intercropping Cover Crops with Pineapple for the Management of Rotylenchulus reniformis

Effect of cover crops intercropped with pineapple (Ananas comosus) on Rotylenchulus reniformis population densities and activity of nematode-trapping fungi (NTF) were evaluated in two cycles of cover crop and pineapple. Sunn hemp (Crotalaria juncea), rapeseed (Brassica napus), African marigold (Tagetes erecta), or weeds were intercropped with pineapples. Beds planted with sunn hemp or rapeseed had lower population densities of R. reniformis than African marigold, weeds, or pineapple plots during cover crop growth, and the subsequent pineapple-growing periods. Rapeseed was a good host to Meloidogyne javanica and resulted in high population densities of M. javanica in the subsequent pineapple crop. Fireweed (Erigeron canadensis) occurred commonly and was a good host to R. reniformis. Bacterivorous nematode population densities increased (P ≤ 0.05) most in sunn hemp, especially early after planting. Nematode-trapping fungi required a long period to develop measurable population densities. Population densities of NTF were higher in cover crops than weeds or pineapples during the first crop cycle (P < 0.05). Although pineapple produced heavier fruits following sunn hemp than in the other treatments (P < 0.05), commercial yields were not different among rapeseed, weed, and sunn hemp treatments.     

Cultivation of Mediterranean species of Tuber (Tuberaceae) in British Columbia,Canada

Based on an assessment of soil and climatic conditions in British Columbia (BC), the Truffle Association of British Columbia (TABC) determined that the cultivation of Mediterranean Tuber melanosporum and Tuber aestivum might be possible in the warmer parts of the province. With the cooperation of independent truffle growers, TABC assessed the colonization of host tree roots collected from eight truffle orchards planted 2–7 years earlier using morphological and molecular criteria. Both Tuber species persisted on the roots of inoculated trees in six of the eight truffle orchards studied. The identity of Tuber ectomycorrhizas that had been characterized morphologically as differing from those of T. melanosporum and T. aestivum were determined using DNA sequence analysis to belong to three species of truffles native to the Pacific Northwest. One of those species, Tuber anniae, had been previously reported from BC, but the other two, Tuber menseri nom. prov. and Tuber beyerlei, are reported here from BC for the first time. Recently, production of three Périgord black truffles in one truffle orchard and one Burgundy truffle in another orchard demonstrates that these truffles are able to fruit in BC.     

A comparison of the effect of genetic improvement, seed source and seedling seed orchard variables on progeny growth in Eucalyptus nitens in South Africa

Eucalyptus nitens is an important forestry species grown for pulp and paper production in the temperate, summer-rainfall regions of South Africa. A tree improvement programme has been ongoing at the Institute for Commercial Forestry Research for two decades, but genetic improvement in the species has been slow due to delayed and infrequent flowering and seed production. Three trials were established, firstly, to quantify the gains that have been made in the first generation of improvement in the breeding programme and, secondly, to establish whether a number of seed source and orchard variables influence the performance of the progeny. These variables were the amount of flowering trees in the seed orchard, year of seed collection, seed orchard origin and composition of seed orchard bulks. Diameter at breast height and tree heights were measured in the trials at between 87 and 97 months after establishment, and timber volumes and survival were calculated. Improved seed orchard bulks performed significantly better (p?<?0.01) than unimproved controls in the field trials. Genetic gains ranging from 23.2 to 164.8 m³?ha^?1 were observed over the unimproved commercial seed. There were significant differences (p?<?0.01) in progeny growth between the levels of seed orchard flowering, with higher levels of flowering (≥40 %) producing substantially greater progeny growth than lower flowering levels (≤20 %). The seed orchard had no effect on progeny growth in this trial series. This suggests that seed collected from any of the four seed orchards tested will produce trees with significant improvement in growth.