Barley yield losses due to defoliation of upper three leaves either healthy or infected at boot stage by <Emphasis Type="Italic">Pyrenophora teres</Emphasis> f. <Emphasis Type="Italic">teres</Emphasis>

This paper evaluates, in the greenhouse and under natural conditions, barley yield losses due to defoliation treatments of the upper three leaves either healthy or infected at the boot stage by Pyrenophora teres f. teres. Defoliation was assumed as a loss of a similar leaf area caused by net blotch disease severity of 100%. Contribution to grain yield was defined herein as a difference between defoliation treatments and a treatment where plants lost all their upper three leaves. In contrast, yield losses referred to differences in yield between defoliations and the control. In the greenhouse, removal of the antepenultimate leaf did not affect any yield component. For main stems, defoliating upper three leaves reduced grain yield by 30% and this was mainly due to flag leaf removal. These losses were similar to those induced by net blotch disease under natural conditions, but were of 42% for all tillers. Grain yield losses due to disease severity were not equivalent to the defoliation effect of a similar healthy leaf area. On the other hand and for a significant contribution to grain yield, flag leaf was dependent on the presence of the other two leaves. Inoculation and defoliation of 21 cultivars induced similar grain yield losses of 32%. However, biotic stress reduced by 40% the contribution of their upper three leaves. Under field conditions, yield losses were not significant until barley plants lost more than one upper leaf and flag leaf contribution was equivalent to that of the remaining leaves. Characteristic roots, defined as leaf coefficients for plant performance, were 0.13, 0.06 and 0.01 for the flag, penultimate and antepenultimate leaves, respectively. Because antepenultimate leaves become trivial at the boot stage, we propose that coefficients of the remaining leaves should be used when modelling yield losses due to barley foliar diseases.     

Fortuitous parasitoids of the invasive tomato leafminer Tuta absoluta in Tunisia

The South American tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is a major threat to tomato (Solanum lycopersicum L.) crops. After its first detection in Spain in 2006, it spread rapidly through the Western Palaearctic region, arriving in Tunisia 2 years later. The aim of this research was to assess whether generalist indigenous parasitoids are adapting to this exotic host in Tunisian tomato crops. For this, we conducted a survey in four Tunisian tomato-growing areas by sampling infested leaves of tomato and solanaceous weeds and exposing artificially infested sentinel plants. Two ectoparasitoid species were found attacking and developing on T. absoluta: Bracon sp. (Hymenoptera: Braconidae) and Necremnus sp. nr artynes (Hymenoptera: Eulophidae), whereas no egg or pupal parasitoids were found. The eulophid wasp was the most abundant with a peak of apparent parasitism rate of 25.5%. It emerged from parasitized T. absoluta young larvae in exposed sentinel plants and in sampled infested tomato leaves, both in greenhouse and open field cultivations. Bracon sp. showed a gregarious development on T. absoluta mature larvae and it was collected only on sentinel plants exposed in the Ragueda (Kiarouan) site, with 10.23% of estimated parasitism. Although further research is still needed to assess properly the ecological role of these parasitoids in the biological control of T. absoluta, this study represents the first step toward establishing the scientific basis for including these parasitoids in the Tunisian IPM and biological programs against this pest.     

Genetic variation analysis in the genus Lathyrus using RAPD markers

RAPD analysis was applied to five species belonging to the genusLathyrus (Fabaceae): L.sativus, L.cicera, L.ochrus, L.sylvestris and L.latifolius. All the species under study belong to thesection Lathyrus except L.ochrus which is in section Clymenum.Nine populations representing these species were used and ten random10-mer primers were sampled. A total of 129 amplification products,ranging in size from 0.3 to 3 Kb, were generated. Partitioning ofvariation was studied using the AMOVA technique. The genetic variation proved tobe nearly equally distributed among species and among populations withinspecies. A similar approach was carried out to distinguish populations, whichproved to be efficient. The between population dissimilarities were calculatedand a dendrogram of genetic relationships was drawn. The RAPDs obtained weresufficient to distinguish between the two accessions of a species and toseparate these accessions by clustering them according to species. A highgenetic similarity between the populations of L.sylvestris and L.latifolius was established. A similar result is also shownfor the populations of L. sativus andL. cicera.     

不同方法及材料检测大片吸虫感染的比较试验

为片形吸虫病诊断提供高效、简便的新技术,以大片吸虫分泌排泄抗原（ES抗原）,用于斑点酶联免疫吸附试验（Dot－ELISA）、琼脂扩散酶联免疫吸附试验（Dig－ELISA）、免疫胶体金滴渗法（DIGFA）检测动物体内的大片吸虫（Fasciolagigantica）感染。通过检测血清、血纸、牛奶等几种材料,多重试验比较,结果三种方法均具有敏感性高、特异性强、准确性可靠等优点,并各有特长,如操作简便快速、费用低廉,易于在基层推广应用等,同时证明用血纸和牛奶检测抗体效果同样可靠。本试验首次报道用Dot－ELISA、DIGFA在奶中检测片形吸虫抗体,为该寄生虫病普查提供一种新思路。     

Isolation of entomopathogenic Bacillus from a biodynamic olive farm and their pathogenicity to lepidopteran and coleopteran insect pests

The occurrence of Bacillus entomopathogenic bacteria on a Tunisian biodynamic farm was determined by examining 75 samples from olive tree (Olea europaea L.) habitats. A total of 40 Bacillus isolates were characterized according to their phenotypic, physiological and biochemical parameters. Isolates of the species Bacillus subtilis, Bacillus mycoides, Brevibacillus brevis, Paenibacillus polymyxa, Bacillus licheniformis, Bacillus sp. (1), Bacillus sp. (2) and a standard strain Btk HD-1 were used separately in feeding bioassays on fresh artificial diet against larvae of lepidopterans Prays oleae (Bernard) and Palpita unionalis (Hübner) and coleopterans Hylesinus oleiperda (F.) and Phloeotribus scarabaeoides (Bernard), which are olive tree pests. Larvae were successfully reared on an artificial diet with 25 g powdered olive tree leaves. Compared to the control data, only Btk and the isolates of B. licheniformis, P. polymyxa and B. brevis were entomopathogenic. Larval mortality assessed 7 days post-treatment showed high mortality rates with Btk to lepidopteran larvae (86.6% for P. oleae and 80.9% for P. unionalis) and low mortality against coleopteran pests. B. brevis isolates showed high mortality rates against P. oleae (up to 67.9%). B. licheniformis isolates caused up to 59.2% larval mortality for P. oleae and 43.6% for P. unionalis. Highest coleopteran mortality was achieved by P. polymyxa isolates (up to 55%). According to the 16S rDNA results, isolates of each of the three entomopathogenic strains were similar. Proteins in the strain supernatants were toxic to P. oleae larvae with LC50 values of 10.0 (B. brevis), 12.5 (B. licheniformis) and 37.6 μg/ml (P. polymyxa). Also, P. polymyxa showed an LC50 of 12.4 mg/l against P. scarabaeoides. Our results suggest that entomopathogenic Bacillus present locally in the biodynamic farm could be used in biological control programmes of olive tree pests.     

Changes in phytochemical, antimicrobial and free radical scavenging activities of the Peruvian pepper tree (Schinus molle L.) as influenced by fruit maturation

The effect of stage of maturity on total lipids, fatty acids, yields and essential oil composition and their antimicrobial and free radical scavenging activities of the Schinus molle fruits was investigated. The content of total lipids varied from 2.87 to 5.35% (w/w, dw) and were rich in unsaturated fatty acids particularly linoleic acid. As maturation progress, the essential oil yield dropped from 5.18% to 1.15%. Monoterpene hydrocarbons with α-phellandrene (35.15-40.38%), limonene + β-phellandrene (21.47-36.62%), β-myrcene (7.61-24.96%) and α-pinene (1.92-2.58%) were found to be the main components. At the same time, the essential oils were evaluated for their antimicrobial and free radical scavenging activities. They were found to be active against Bacillus subtilis, Bacillus cereus, Salmonella typhymurium and Escherichia coli but they do not inhibit the growth of Candida albicans. Conversely, they showed very weak activity against the DPPH radical. In both assay, the oil derived from the intermediate stage was reported as more efficient.     

Changes in essential oil and fatty acid composition in coriander (Coriandrum sativum L.) leaves under saline conditions

The influence of salinity on essential oil and fatty acid composition of Tunisian coriander (Coriandrum sativum L.) leaves grown in hydroponic culture was investigated. Volatile constituents and fatty acid of leaves were analyzed. The essential oil yield increased significantly up to 18 and 43% with 25 and 50 mM NaCl, respectively and decreased significantly under high salinity. The major volatile compound in leaves was (E)-2-decenal with 52% of total essential oil constituents, followed by decanal, dodecanal, (E)-2-tridecenal and (E)-2-dodecenal. Further, the content of these compounds was affected differently by the treatment level.Salinity decreased significantly the total fatty acid content of the upper and basal leaves. α-Linolenic (C18:3n3) was the main compound of both organs, followed by linoleic (C18:2n6), heptadecenoïc (C17:1n7) and palmitic (C16:0) acids. Raising NaCl concentrations lead to an important decrease in the unsaturated to saturated fatty acid ratio stimulating the formation of more rigid membrane.     

Detection of Ceratitis capitata Wiedemann (Diptera: Tephritidae) using trimedlure versus enriched ginger oil in citrus orchards

Abstract

Successful fruit fly control requires effective monitoring to make pest management decisions. Ceratitis capitata (Medfly) is typically monitored in Tunisia with parapheromone commercialised as trimedlure (TM). Chemical treatment is applied when the economic threshold (3 flies/trap/day) is reached. In this study, C. capitata populations in a commercial citrus orchard captured in McPhail traps baited with TM or enriched ginger oil (EGO) were compared over two seasons (2011 and 2012). Females of C. capitata were not attracted to TM or EGO. Trimedlure was significantly more attractive to C. capitata males than EGO under low and high population densities over sampling dates. The TM used in McPhail traps was adequate to attract male medflies in citrus orchards under a wide range of Medfly population levels. The use of the best attractant can help to make control decisions when population levels of flies are low, thus preventing unnecessary application of insecticides and/or other control methods.     

Genetic diversity and phylogenic relationships in date-palms (Phoenix dactylifera L.) as assessed by random amplified microsatellite polymorphism markers (RAMPOs)

Random amplified microsatellite polymorphisms (RAMPOs) were used to assess genetic diversity among 30 date-palm cultivars and 10 male trees. Using 18 primers combinations, 197 bands were scored and 186 were polymorphic suggesting the high level of polymorphism among studied cultivars. Moreover, taking into account the high percentage of polymorphic bands (ppb), the resolving power (R_p) together with the polymorphism information content (PIC) scored values, all the tested primer sets contribute strongly in the discrimination of date-palm genotypes. In addition, the topology of the derived UPGMA dendrogram exhibited cultivars’ clustering made independently both from the geographical origin and/or from the sex of trees. The present data support the Mesopotamian origin of the date-palm domestication. Thus we assume that the used method is efficient to assess genetic diversity within date-palm cultivars. Data are discussed in relation with the opportunity of the RAMPO method to provide additional molecular markers suitable in the improvement of the date-palms germplasm characterisation.     

Regional and maturational effects on essential oils yields and composition of coriander (Coriandrum sativum L.) fruits

The composition of volatile components of the essential oils extracted from fruits of coriander (Coriandrum sativum L.) growing in two different Tunisian regions in both Menzel Temime and Borj El Ifaa was studied by GC and GC–MS. The highest oil yields were observed at final stages of maturity: 0.324 ± 0.09% and 0.327 ± 0.08%, in Menzel Temime and Borj El Ifaa, respectively. Essential oil yields were highly (P < 0.001) affected by the growing region, stages of maturity and their interaction. Essential oil composition changed significantly (P < 0.05) among the different stages of maturity and growing region. Linalool and geranyl acetate were the main compounds at full fruit maturity in the two studied regions. Growing region, stages of maturity and their interaction had a strong effect (P < 0.001) on 35 compounds. α-Pinene, sabinene, limonene, γ-terpinene, cis-dihydrocarvone and geranial were insensible to the regional factor.