Seasonal parasitism of cereal aphids in a Mediterranean arable crop system

We monitored winter cereal fields in a Mediterranean arable crop system to obtain information about the aphid parasitoid species composition and the aphid–parasitoid interactions through the whole cropping cycle. Nine species of aphid primary parasitoids (Hymenoptera, Braconidae, Aphidiinae) were identified. The most abundant species were Aphidius rhopalosiphi, Aphidius matricariae, Aphidius ervi and Lysiphlebus testaceipes. The genus Aphelinus sp. (Hym., Aphelinidae) was also identified. We determined seasonal host–parasitoid associations over the entire cereal crop cycle. A number of new such associations were recorded, which were previously unknown in Spain and Europe. Our results indicated broad associations of L. testaceipes and A. matricariae with cereal aphids; furthermore, the association of Aphelinus sp. with several cereal aphid species was also substantial. In the NE of the Iberian Peninsula, the cereal aphid parasitoids that we identified are able to develop throughout the crop season on one or more host species. Thus, the main aphid species can be parasitized effectively throughout the entire cereal crop cycle. We discuss the role of cereal aphid parasitoids in the region in the context of our experimental results.     

Expansion of the aphid Myzocallis (Lineomyzocallis) walshii (Monell) on the red oak Quercus rubra, and adaptation of local parasitoids in the northeastern Iberian Peninsula (Hom., Aphididae, Calaphidinae; Hym., Braconidae, Aphidiinae)

An ongoing expansion of Myzocallis (L.) walshii (Monell) in the NE Iberian Peninsula was detected. The aphid species was recorded in Catalonia, Andorra and Navarra. Adaptation of local native parasitoids (at least Trioxys pallidus Haliday and T. tenuicaudus Stary) to the new immigrant was documented, together with background information on their host range in the native environments. The detection of parasitoids of M. walshii is the first published evidence in Europe. The new evidence for M. walshii in the NE Iberian Peninsula also supports the warning of the expansion of the aphid as a pest of Quercus rubra over Europe.     

Parasitoid complex (Hymenoptera, Braconidae, Aphidiinae) of Aphis craccivora Koch (Hemiptera: Aphidoidea) in Iran

The parasitoids (Hymenoptera, Braconidae, Aphidiinae) of the cowpea aphid, Aphis craccivora Koch, were investigated throughout two far distant provinces, Tehran and Sistan-Baluchestan. Colonies of the cowpea aphid were collected from different host plants and reared under laboratory conditions until the parasitoids emerged. The aphids were parasitized by an expected range of parasitoids. The species were Aphidius colemani Viereck, Lysiphlebus fabarum (Marshall), Lysiphlebus confusus Tremblay and Eady, Lysiphlebus testaceipes (Cresson), Binodoxys acalephae (Marshall), Binodoxys angelicae (Haliday), Praon volucre (Haliday) and Ephedrus persicae Froggatt. L. testaceipes is reported here for the first time in Iran. The most common species was L. fabarum followed by B. acalephae and L. confusus. A key is provided for identification and host plant associations are considered.     

Spring aphid-parasitoid (Hom., Aphididae,Hym., Braconidae) associations and interactions in a Mediterranean arable crop ecosystem,including <Emphasis Type="Italic">Bt</Emphasis> maize

Conspecific and heterospecific associations of aphid parasitoids (Hymenoptera, Braconidae, Aphidiinae) were used to determine the interactions between crops forming the main arable crop ecosystem (wheat, alfalfa, isogenic and [Bt Bacillus thuringiensis] transgenic maize) in an irrigated area in Catalonia, Spain. Species composition and instars of parasitized aphids (mummies) were used to detect the parasitoid population movements between the crops and proved interactions (alternation) between the crops, including transgenic maize. Parasitoid interactions were species-dependent, appearing in the movements between alfalfa-wheat-maize in the individual species. Aphidius ervi Hal., A. rhopalosiphi DeSt.-Perez, A. uzbekistanicus Luzh., Lysiphlebus testaceipes (Cress.) and Praon volucre (Hal.) were classified as key-stone species in the target agroecosystems in the area. No differences were found in aphid-parasitoid associations on Bt transgenic maize and isogenic maize for aphid species composition and associated parasitoid guild.     

New parasitoids of<Emphasis Type="Italic"> Saperda populnea</Emphasis> (L.) (Col. Cerambycidae) in Bulgaria

The parasitoid complex of Saperda populnea (L.) (Col., Cerambycidae) was studied during the period 2002–2003 at different sites in Bulgaria. Galls containing cerambycid larvae were collected on branches of aspen (Populus tremula L.), goat willow (Salix caprea L.) and hybrid poplars and were studied under laboratory conditions. As a result, four new species for the parasitoid complex of S. populnea in Bulgaria were recorded: Dolichomitus tuberculatus (Geoffroy), Xylophrurus lancifer (Gravenhorst), Gelis ornatulus (Thomson) (Hym., Ichneumonidae) and Dendrocerus serricornis (Boheman) (Hym., Megaspilidae). D. serricornis and G. ornatulus are new species for Bulgarian fauna. D. tuberculatus and X. lancifer were found as primary parasitoids, and G. ornatulus and D. serricornis as hyperparasitoids. The primary parasitoids developed solitarily in the host larvae. D. serricornis was reared gregariously from a puparium of Billaea irrorata (Meig.) (Dipt., Tachinidae). The host of G. ornatulus was not identified, but the hyperparasitid could be connected with Iphiaulax impostor (Scop.) (Hym., Braconidae). The mortality of S. populnea caused by the parasitoids was 2.0–6.3%.     

Parasitoid complex of alfalfa aphids in an IPM intensive crop system in northern Catalonia

Alfalfa aphids were monitored and aphid parasitism was determined in three crop-growing seasons (2007–2009) in commercial alfalfa fields in valleys close to the Pyrenees, where an intensive arable crop rotation is practised under non-tillage and an integrated pest management system. Acyrthosiphon pisum, Therioaphis trifolii, and Aphis craccivora were the aphid species colonizing alfalfa fields but their occurrence varied between years. Thirteen Aphidiinae parasitoid species and four Aphelinidae from the genus Aphelinus sp. were recorded. Aphidius ervi was the prevalent parasitoid species associated with A. pisum but Praon barbatum was also noticeable, especially during the first year. Trioxys complanatus and P. exsoletum were the only species associated with T. trifolii. Lysiphlebus fabarum was the prevalent parasitoid species associated with A. craccivora. The occurrence of Lysiphlebus testaceipes parasitizing A. craccivora on alfalfa is a new record for the study region because this parasitoid species had only been previously found on weeds. Only A. pisum and A. craccivora were parasitized by Aphelinus sp. Whereas A. abdominalis and A. semiflavus were associated with A. pisum, A. chaonia, and Aphelinus sp. nr. albipodus were associated with A. craccivora. Associations between aphid species and Aphidiinae or Aphelinidae parasitoid species emphasize that individual aphid species also possess individual parasitoid complexes (guilds) which do not interfere with each other in alfalfa. Alloxysta victrix, A. macrophadna, Alloxysta spp., Asaphes suspensus, A. vulgaris, Dendrocerus aphidum, Pachyneuron aphidis and Syrphophagus aphidivorus were the hyperparasitoids associated with aphid–parasitoid complexes. Our study showed A. ervi, T. complanatus, P. exsoletum, and L. fabarum as potential candidate species which could provide biological control of their respectively aphid hosts in alfalfa.     

Reconstructing forest history from archaeological data: A case study in the Duero basin assessing the origin of controversial forests and the loss of tree populations of great biogeographical interest

The study of more than 700 charcoals from the Vaccaean settlement of Pintia (Padilla del Duero, Valladolid) provides new local and detailed data about the Iron Age II forest composition in Continental-Mediterranean inland Spain. Pinus gr. sylvestris/nigra (from which an unexpectedly high number of charcoals were identified), together with Mediterranean pines (also highly represented), Juniperus L. and evergreen and deciduous Quercus, were the main taxa living in the area, revealing two different marked biogeographical elements in the late-Holocene landscapes of the Duero basin: Mediterranean and Eurosiberian. On one hand, the results shed new light on the assessment of the origin of Mediterranean pinewoods in the area. On the other hand, the charcoal assemblage of Pintia reveals a more important presence of the current Mediterranean highland pines in the lowlands of the Central Iberian Peninsula in the late-Holocene suggesting the existence of interglacial refugia. Finally, this work highlights palaeoecological studies as valuable tools to support decisions on forest management related to conservation and restoration of our natural heritage.     

Phenotypic plasticity and climatic adaptation in an Atlantic maritime pine breeding population

Context

Pinus pinaster Ait. is found in the Iberian Peninsula under Mediterranean and Atlantic conditions. Both climates encounter each other in Galicia (NW Spain), where two bioclimatic regions can be differentiated: coastal and inland. A breeding program was launched in the coastal area, with two breeding and deployment areas delimited.

Aims

We analyse plasticity patterns across regions in a coastal breeding population to assess the suitability of current breeding areas and how genetic material will likely respond to future climate.

Methods

Total height at ages 3 and 8?years was assessed in 16 trials established along the coast and in inner Galicia. Clustering of environments with similar genotypic performance, family sensitivities to climatic factors and stability analyses were performed.

Results

Sizeable genetic variation in plasticity was found among families, and crossover genotype-by-environment interactions were detected within and between regions. It was unfeasible to regionalize Galicia into alternative areas of stable genotypic performance. Only the cold regime was found to noticeably underlie the array of phenotypic responses to changing environmental conditions.

Conclusions

Results suggest that previous delimitation in two breeding areas is pointless and indicate reduced effects of a changing climate towards Mediterranean conditions on decreasing population fitness.     

Studies on <Emphasis Type="Italic">Aleurothrixus floccosus</Emphasis> (Maskell) (Homoptera,Aleyrodidae) and its parasitoid, <Emphasis Type="Italic">Cales noacki</Emphasis> Howard (Hymenoptera,Aphelinidae) in the East Mediterranean Region of Turkey

Survey studies of Aleurothrixus floccosus (Maskell) (Homoptera, Aleyrodidae) and its parasitoid Cales noacki Howard (Hymenoptera, Aphelinidae) were made in 4 provinces; namely Adana, Mersin, Hatay and Osmaniye, which are the main citrus growing areas of the East Mediterranean region of Turkey. Inoculative parasitoid releases were made in regions where no or low natural parasitism occurred after obtaining preliminary results on presence of the parasitoid. The population dynamics of A. floccosus and C. noacki were examined in Silifke (Mersin), Dörtyol (Hatay) and Yüreir (Adana), where the A. floccosus population was remarkably high at the beginning of the study in 1999. However, after parasitoid release, the pest population declined in all the sites and did not attain the same high levels again. Five predators, three parasitoids and one entomopathogen species were determined as natural enemies of A. floccosus. In addition, seven plant species, six of them belong to Rutaceae, were found as host plants for A. floccosus.     

Laboratory rearing of the solitary egg-larval parasitoid, Chelonus oculator Panzer (Hymenoptera: Braconidae) on a newly recorded factitious host Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) is recorded as a new factitious host for the solitary egg-larval parasitoid, Chelonus oculator Panzer (Hymenoptera: Braconidae). A short biology and rearing method of the parasitoid on the new host were studied at 30±1°C, 60–70% relative humidity, with a photoperiod of 16:8 (L: D). Chelonus eclosed from 74.60% of parasitized hosts. No significant difference was found between development times of male and female parasitoids. Development of the parasitoid was completed in 28.14±0.47 days in male, and 28.87±0.58 days in female. However, a significant difference was found between adult sizes of male and female parasitoids. Adult dry mass was found 0.88±0.04 mg in male, and 1.99±0.11 mg in female. In addition, C. oculator was successfully reared from P. interpunctella in twenty generations with the explained method. Significant knowledge about biology of C. oculator is still lacking. However, the parasitoid can be candidate for future research as a biological control agent against some important lepidopteran pests, and P. interpunctella may be suitable factitious host for mass rearing of C. oculator.     

Parasitism of canola aphids in France in autumn

In light of a recent increase in the aphid populations on young canola (Brassica napus) in autumn in Northwestern Europe, we carried out a survey of their parasitoid species during this season. The study was done in France from 1998 to 2001 using different sampling methods. Results highlighted the presence of two main species of Aphidiinae, Aphidius matricariae and Diaeretiella rapae (and to a lesser extent Aphidius ervi) on Myzus persicae, and of D. rapae on Brevicoryne brassicae. Nine other Aphidiinae species were found occasionally as well as some Aphelinidae parasitoids and hyperparasitoids. There was no difference in parasitoid species pattern between fields in Northern and Southern France. The principal parasitoid species found in the fields were reared in the laboratory to confirm their ability to develop on the canola aphids. Aphidius matricariae and D. rapae were reared successfully on M. persicae, but a low parasitism rate was obtained for A. ervi on this aphid. This study showed that A. matricariae and D. rapae could develop on aphids on canola and that they are present naturally in canola in autumn. However, the parasitism rate is low in autumn, so the options could be the use of these parasitoids in augmentative release biological control programs or in an IPM project on canola fields during this time of the year.     

寄主树木、寄主和环境因子对松褐天牛深沟茧蜂寄生率的影响研究

[目的]松材线虫病是我国对森林危害和威胁最严重的病害,控制其传播媒介昆虫松褐天牛是防治松材线虫病的主要手段。作者发现的松褐天牛深沟茧蜂(Iphiaulax monochamusi Yang)是寄生松褐天牛中老龄幼虫的重要天敌。为明确松褐天牛深沟茧蜂的寄生率与寄主树木、寄主和环境因子的关系,开展了本研究。[方法]通过解剖46株松褐天牛危害致死的马尾松,调查了松褐天牛深沟茧蜂寄生率与马尾松、松褐天牛和环境因子之间的关系。[结果]调查研究表明:寄主树木的高度、胸径和树龄对松褐天牛深沟茧蜂寄生率没有显著影响,松褐天牛的数量对松褐天牛深沟茧蜂寄生率亦没有显著影响,而松褐天牛幼虫龄期和松褐天牛幼虫在树干上的位置显著影响松褐天牛深沟茧蜂寄生率。松褐天牛深沟茧蜂寄生率与松褐天牛龄期呈显著正相关,其偏好寄生3~5龄幼虫;就天牛在其危害寄主树木上的位置而言,松褐天牛深沟茧蜂偏好寄生马尾松主干上部和在韧皮部危害的松褐天牛幼虫,其对位于马尾松树干上部的寄主幼虫寄生率最高,达27.38%,对在韧皮部生活、危害的寄主幼虫寄生率为20.18%,显著高于位于木质部生活的寄主幼虫寄生率(5.46%)。逐步回归分析表明:影响松褐天牛深沟茧蜂寄生率的关键环境因子是寄主树木的坡位和其它天敌寄生率,其中,坡位与松褐天牛深沟茧蜂呈显著正相关,其它天敌寄生率与松褐天牛深沟茧蜂寄生率呈显著负相关。[结论]以上研究初步明确了松褐天牛深沟茧蜂的寄生率与寄主树木、寄主害虫和天敌之间的关系,为今后利用该重要天敌控制松褐天牛打下了基础。     

Regional patterns of fire recurrence effects on calcareous soils of Mediterranean Pinus halepensis communities

The effects of fire recurrence on soils were studied on calcareous sites of Mediterranean Pinus halepensis-dominated communities in Catalonia (NE Iberian Peninsula). Soil organic horizons and mineral soils of 15 sites consisting in two adjacent areas, one burnt only once (in 1994) and the other burnt twice (in the same 1994 fire but also once before, from 1975 to 1993) were surveyed 9 years after the last fire. Fire recurrence decreased the occurrence and dry mass of soil organic horizons. Total nitrogen concentration in L organic horizon was higher in less recurrently burnt areas. No other significant difference between once- and twice-burnt areas was found for any studied chemical parameter either in organic L and FH horizons or in mineral soils. The present study underlines the fact that fire effects on soil organic horizons are accumulated through consecutive fires.     

Efficacy assessment of some<Emphasis Type="Italic"> Trichogramma</Emphasis> species (Hymenoptera: Trichogrammatidae) in controlling the potato tuber moth<Emphasis Type="Italic"> Phthorimaea operculella</Emphasis> Zell. (Lepidoptera: Gelechiidae)

Laboratory studies were conducted to assess several life-history characteristics of three Trichogramma species—T. cacoeciae, T. evanescens, and T. principium—reared on potato tuber moth eggs. The effects of host age, parasitoid age, and different temperatures on the mean number of parasitized eggs and the percentage of emerged progeny were determined. The age of both Trichogramma and host eggs significantly affected the number of eggs parasitized by the wasps, but did not affect the percentage of parasitoids emerging from parasitized eggs. No intraspecific differences for potato tuber moth eggs were found among the tested Trichogramma species. However, T. principium proved to be more effective than T. cacoeciae and T. evanescens in parasitizing host eggs at high temperatures (>33 °C). Trichogramma significantly decreased the number of potato tuber moth F₁ emerged progeny when they were released with moths in small cages either over potatoes or potato seedlings.     

Bioecological characteristics of Bracon intercessor Nees (Hymenoptera: Braconidae) as a parasitoid of the poplar clearwing moth, Paranthrene tabaniformis (Rott.) (Lepidoptera: Sesiidae) in Bulgaria

The major bioecological characteristics of Bracon intercessor Nees (Hymenoptera: Braconidae), a parasitoid of the poplar clearwing moth, Paranthrene tabaniformis (Rott.) (Lepidoptera: Sesiidae), were studied from 1987 to 2003. Poplar shoots infested with P. tabaniformis larvae were collected in 11 localities in Bulgaria and examined in the laboratory, and infestations were also studied in the field. B. intercessor was recorded in seven localities and was found to be a gregarious external larval parasitoid of P. tabaniformis. Two generations of the parasitoid developed on the host. The first (summer) generation was associated with early and mid-stage (up to third instar) host larvae, and the second (overwintering) generation with third- to fifth-instar larvae. The average number of parasitoid individuals feeding on a host was 4.5 and 12.4 in summer and overwintering generations, respectively. The maximum number recorded was 25 individuals per host in the overwintering generation. B. intercessor overwintered as a mature larva on the host and completed its development in early spring. The adults from the overwintering generation appeared in April, about 1 month prior to emergence of P. tabaniformis. The life cycle of B. intercessor was not in close synchrony with the development of P. tabaniformis in the spring, but the parasitoid adults which fed on honey-sugar solution lived for up to 31 days (males) and 86 days (females), respectively. This suggests that, in the field, B. intercessor females eclosing in the spring could survive until the host larvae appear if nectar is available. Adults of the summer generation emerge from July to September when sufficient suitable host larvae are available. B. intercessor was responsible for 1.5% of the average mortality of the P. tabaniformis overwintering larvae. The host mortality caused by the summer generation of the parasitoid ranged from 3.2% to 5.8%.     

A review on <Emphasis Type="Italic">Trioza erytreae</Emphasis> (African citrus psyllid), now in mainland Europe,and its potential risk as vector of huanglongbing (HLB) in citrus

The African citrus psyllid (AfCP), Trioza erytreae (Del Guercio) (Hemiptera, Triozidae), recently has been found in northwestern Iberian Peninsula (Spain and Portugal). The insect is an important citrus pest because it transmits the phloem-limited bacteria Candidatus liberibacter spp., the causal agents of huanglongbing (HLB), the most devastating disease affecting citrus. The bacteria can be acquired by both AfCP nymphs and adults, but only adults can spread the pathogen. HLB has been detected neither in the Iberian Peninsula nor in Madeira and the Canary Islands, where the psyllid was recorded more than a decade ago. In the latter European islands, the eradication programmes of AfCP failed. Chemical-based control strategies are costly, could trigger increases of other pests and may have negative impact on the environment. The adoption of rigorous quarantine measures is extremely important for areas free of the psyllid. These measures likely represent the most effective prevention strategies for psyllid containment, because the geographic expansion of psyllids in citrus is mainly due to human activities, especially by the transport of plants and freshly harvested fruits from infested to uninfested areas. Many natural enemies may contribute to the reduction of its populations and consequent spread; hence, conservation biological control should be emphasised, especially in areas where the psyllid is not abundant. Classical biological control programmes should also be implemented in HLB-free areas by introducing effective AfCP parasitoids. In areas where HLB is detected, biological control is difficult to apply, and a rigorous chemical control program targeting the psyllid could complement this strategy. This report is an updated review of AfCP and strategies for its control in anticipation of its possible further spread in Europe and the Mediterranean Basin.     

Studies on the parasitoid complex of Choristoneura murinana (Hbn.) (Lep.: Tortricidae) in Turkey

The parasitoid complex of Choristoneura murinana (Hbn.), a pest of Abies cilicica Carr., was studied in Isparta, Turkey. Shoots and needles of A. cilicica with C. murinana larvae and pupae were collected and examined under laboratory conditions in 2002 and 2003. As a result of this study, 14 parasitoid species of C. murinana were determined: Apanteles obscurus Nees. (Hym.: Braconidae), Brachymeria intermedia Nees (Hym.: Chalcididae), Mesopolobus mediterraneus Mayr, Mesopolobus dubius Walker, Pteromalus chrysos Walker, Pteromalus sp. (Hym.: Pteromalidae), Monodontomerus aereus Walker (Hym.: Torymidae), Itoplectis maculator (Fabricius), Apophua bipunctoria Thunberg, Triclistus globulipes Desvignes, Dirophanes maculicornis Stephens, Hyposoter sp., Dusona sp. (Hym.: Ichneumonidae) and Aprostocetus sp. (Hym.: Eulophidae). In the studied parasitoid complex, A. obscurus, B. intermedia and I. maculator were the most important in reducing pest numbers. The level of total parasitism of the C. murinana was 19.4% in 2002 and 22.3% in 2003.     

两种接种方式下角倍蚜虫瘿对寄主盐肤木枝叶生长的影响

[目的]明确两种接种方式(自然迁飞和人工挂袋)下角倍蚜虫瘿的数量和分布及其对寄主盐肤木枝叶生长的影响。[方法]在自然迁飞和人工挂袋形成虫瘿的盐肤木林内,按随机区组设计设置样地,在样地内随机选取有虫瘿树和无虫瘿树,分别测量和统计盐肤木及虫瘿的生长指标,采用方差分析虫瘿对盐肤木生长的影响。[结果]在自然迁飞和人工挂袋两种接种方式下,盐肤木单株虫瘿数没有显著差异。但人工挂袋时,单片复叶的平均虫瘿总体积为170.92±14.85 cm~3、小叶总面积为616.26±32.73 cm~2,显著高于自然迁飞形成虫瘿的总体积85.82±9.40cm~3和小叶总面积482.81±28.51 cm~2。表明人工挂袋接种可以增加虫瘿的总体积,从而提高角倍产量;同时,较大体积的虫瘿还促进了盐肤木小叶的生长,使小叶面积增大。[结论]角倍蚜虫瘿对寄主盐肤木的枝叶生长具有促进作用,且这种生长促进与虫瘿的体积呈正相关。与自然迁飞接种相比,人工挂袋接种更能发挥盐肤木的生长和结倍潜力,提高角倍产量。     

角倍蚜及其寄主植物盐肤木游离氨基酸研究

[目的]明确角倍蚜、角倍与寄主盐肤木协同生长过程中游离氨基酸变化的营养关系。[方法]用全自动氨基酸分析仪Biochrom30+检测角倍发育初、中、后期的角倍蚜、角倍、有倍叶、无倍叶及无角倍盐肤木叶片(CK)的游离氨基酸含量,分析不同时期各试样游离氨基酸总量(FAA)、昆虫必需氨基酸总量(EAA)、昆虫必需氨基酸总量与检出物质总量比值(EAA/TAA)及几种游离氨基酸含量的变化。[结果]表明:不同时期各试样均检出32种游离氨基酸(包括17种蛋白氨基酸和15种非蛋白氨基酸),2种其他组分(不含氨),其中,游离氨基酸含量从大到小依次为角倍蚜(5.569)角倍(2.122)有倍叶(0.560)无倍叶(0.537)CK(-0.114)。从角倍生长初期至后期,角倍蚜体内必需氨基酸总量呈递增变化,而其他材料EAA/TAA变化幅度从大到小依次为CK(1.73%)有倍叶(0.52%)=无倍叶(0.52%)角倍(0.43%)角倍蚜(0.02%),但角倍蚜EAA/TAA稳定为(27.91±0.01)%,角倍蚜对寄主盐肤木叶片EAA/TAA的变化幅度有显著减缓影响。在角倍生长发育期间,角倍蚜体内精氨酸和苯丙氨酸含量均增加2.93倍;而寄主植物组织中脯氨酸含量发生变化,增幅大小为角倍(0.028)有倍叶(0.003)无倍叶(-0.001)CK(-0.018)。[结论]角倍蚜取食盐肤木不会改变寄主盐肤木叶片中游离氨基酸组分,但可使其游离氨基酸含量增加;在角倍生长过程中,盐肤木植株游离氨基酸总量与角倍蚜个体数量和角倍体积的增加趋势基本一致,反映了角倍蚜取食与盐肤木防御之间的平衡。     

Variation in pinewood nematode susceptibility among <Emphasis Type="Italic">Pinus pinaster</Emphasis> Ait. provenances from the Iberian Peninsula and France

Key message

Pinus pinaster Ait. susceptibility to pinewood nematode significantly differed among provenances, and the two Atlantic provenances of the Iberian Peninsula being the most affected. However, significant provenance × environment interaction was found. Provenance susceptibility was related to basal diameter, number of branches and oleoresin flow, and some climatic parameters.

Context

The pinewood nematode Bursaphelenchus xylophilus, native to North America, is an important pest affecting pine forests throughout Eurasia. In Europe, it has been detected in Portugal and Spain and is primarily associated with Pinus pinaster, an important Mediterranean tree species.

Aims

We have investigated the differences in susceptibility among several P. pinaster provenances in the Iberian Peninsula and France, as well as their relationship to certain growth traits and physiological parameters.

Methods

Three independent inoculation tests were performed on 3 to 4-year-old trees, followed by assessment of growth traits and physiological variables, along with time course destructive sampling for nematode quantification.

Results

The results showed significant differences among provenances for almost all growth traits, wilting, and mortality, though a significant provenance × environment interaction was also detected. Two Atlantic provenances, Noroeste-Litoral and Leiria, displayed the largest susceptibility to pinewood nematode. Changes in susceptibility to B. xylophilus between experiments were influenced by temperature and seasonality. Autumn precipitation and mean maximum temperature during summer at the original provenance sites could be related to provenance susceptibility.

Conclusion

Noroeste-Litoral and Leiria were the most disease-affected provenances. This study emphasizes the need for further research on how tree growth stage influences susceptibility and on the possibility of cross-breeding among provenances.