印度小圆胸小蠹的一种新寄主植物

自然条件下印度小圆胸小蠹Euwallacea fornicatus(Eichhoff,1868)在茶树枝条虫瘿内取食,是茶的重要害虫之一,以茶蛀虫著称.2010年5-8月,在印度Muga Eri研究中心3号农场(Lahdoigarh,Jorhat-Assam)的黄心树Persea bombycina Kost.(樟科)...     

Outbreak of Phytophthora cinnamomi causing severe decline of avocado trees in southern Turkey

Since the summer 2017, severe decline symptoms have been observed on 10- to 25-year-old avocado trees in almost all commercial orchards planted in the Mediterranean coastal region of Turkey. Young, newly planted trees in infected orchards were also affected by the disease. Affected trees showed wilting, leaf discoloration, defoliation and severe dieback. Some trees were completely desiccated. Although fine roots of symptomatic trees usually were decayed, reddish brown cankers also occurred on taproots and lateral roots of heavily infected trees. The pathogens were isolated from necrotic root and soil samples of symptomatic trees, using selective medium and soil baiting, and were identified based on morphological features and DNA sequences of the internal transcribed spacer (ITS) region. One isolate each of Phytophthora cryptogea and P. palmivora was identified, while all other isolates were P. cinnamomi. In addition, a subcortical fan-shaped mycelium, characteristic of Armillaria spp., was observed in the stem base of a symptomatic tree and identified as Armillaria gallica by DNA sequences of the internal transcribed spacer (ITS) and the translational elongation factor 1-α (EF 1-α) gene regions. Pathogenicity of Phytophthora isolates was tested by stem inoculation on one-year-old avocado seedlings. Two months after inoculation, canker lesions developed on stems of seedlings inoculated by any of the three Phytophthora spp. In contrast, collenchyma callus formed over the wound points on control plants over the same time period. This is the first report of P. cinnamomi, P. cryptogea, P. palmivora and A. gallica causing root rot of avocado trees in Turkey. In addition, P. cryptogea and A. gallica are reported for the first time associated with disease on this host. Due to the severe symptoms and widespread occurrence, P. cinnamomi should be considered a potential threat to avocado cultivation and natural ecosystems of this region of Turkey.     

Systemic Infection of Avocado,Persea americana,by Raffaelea lauricola,Does Not Progress Into Fruit Pulp or Seed

Avocado, Persea americana, is an important fruit crop in the tropics and warm subtropics. Laurel wilt, caused by Raffaelea lauricola, is a systemic vascular wilt of avocado that spread recently to Florida, an important producing state in the USA. As fruit and seed of avocado produced in Florida are sold in other states and countries where this crop is produced, there is concern that commerce in these commodities might spread this disease. Potted, fruit‐bearing trees were artificially inoculated with R. lauricola, and plants were systemically colonized by the fungus. In no instance did infection progress further than the hilum (87 total fruit), as determined by re‐isolation of R. lauricola on a semi‐selective medium or its detection, with qPCR and high fidelity PCR, of diagnostic small subunit (SSU) 18s rDNA. Thus, it would apparently be safe to propagate avocado with seed from trees affected by this disease. Pedicels/peduncles and hila associated with these fruit were colonized by the pathogen. The latter tissues would be associated with/attached to marketed fruit, but they do not harbour the pathogen’s ambrosia beetle vector, Xyleborus glabratus. Thus, commerce in avocado fruit appears to be a negligible risk for expanding the geographic range of laurel wilt.     

Bird-plant interactions and vulnerability to biological invasions

Aims Species interactions regulate the invasiveness of non-native species and as declines of native tree species escalate, exotic tree species that offer supplementary resources to animal seed-dispersers should expand their distributions as they fill ecological roles. Our primary objective was to forecast impacts from an imminent biological invasion (laurel wilt disease) by quantifying resources provided by native (threatened) and exotic fruits (disease-resistant) and associated bird foraging preferences.Methods In the southeastern USA, we tested for redundancy among the resources provided by native and exotic fruits to overwintering birds. Comparisons between abundant subcanopy species Persea borbonia (native) and Cinnamomum camphora (exotic) were paramount considering the widespread disease-induced decline of P. borbonia, and the biological and phylogenetic similarities between these species. Across two winter survey periods, we quantified fruit removal and documented bird species using motion-activated cameras in the field. Physical and chemical fruit characteristics were also quantified.Important findings Foraging bouts on both P. borbonia and C. camphora fruits were documented for four native bird species. There was no difference in selectivity between fruit types during Year 1 of our survey, but there was a significant preference for C. camphora fruit in Year 2; the change in preference was correlated with significantly lower temperatures in Year 2. While the pulp/seed ratio and moisture content differed, the nutritional content of fruit pulp (g/100g) was similar between fruit types. Given the apparent redundancy among these native and exotic fruit resources, we forecast increases in the consumption and dispersal of exotic propagules following the widespread laurel wilt disease-induced decline of P. borbonia and other native fruit bearing members of Lauraceae. This empirically based prediction is among the first to document exotic forest pathogens as indirect threats to native bird–plant interactions and potential facilitators of exotic plant invasion.     

Seventy microsatellite markers from Persea americana Miller (avocado) expressed sequence tags

Expressed sequence tags for Persea americana Mill. were investigated to expand upon the number of informative microsatellite markers available for avocado. Seventy informative loci were discovered using 24 P. americana var. americana Mill. accessions. The number of alleles detected ranged from two to 17 and averaged 7.1 alleles per locus. These primers successfully amplified products in different varieties of P. americana, hybrids and a related species, Persea schiedeana. These primers will be useful for characterizing germplasm, determining genetic relationships of cultivated accessions, and for marker‐assisted development of root rot‐tolerant P. americana var. americana rootstock material.     

Do cancer cells in human and meristematic cells in plant exhibit similar responses toward plant extracts with cytotoxic activities?

We examined the effect of water extracts of Persea americana fruit, and of the leaves of Tabernamontana divericata, Nerium oleander and Annona cherimolia (positive control) on Vicia faba root cells. We had confirmed in our previously published data the cytotoxicity of these plant extracts on four human cancer cell lines: liver (HepG-2), lung (A549), colon (HT-29) and breast (MCF-7). Vicia faba roots were soaked in plant extracts at dilutions of 100, 1,250, 2,500, 5,000, 10,000, 20,000 ppm for 4 and 24 h. All treatments resulted in a significant reduction in the mitotic index in a dose dependant manner. Root cells treated with T. divericata, N. oleander and A. cherimolia exhibited a decrease in prophase cell percentage, increase in micronuclei and chromosomal abnormalities as concentration increased. The P. americana treatment showed the highest cytotoxic effect on cancer cells, prophase cell percentage increased linearly with the applied concentration and no micronuclei were detected. This study shows that root tip assay of beans can be used in initial screening for new plant extracts to validate their use as candidates for containing active cytotoxic agents against malignant cells. This will greatly help in exploring new plant extracts as drugs for cancer treatment.     

Avocado shoot culture, plantlet development and net CO2 assimilation in an ambient and CO2 enhanced environment

Summary The proliferation and survival of avocado nodal cultures of juvenile origin were affected by the form and concentration of nitrogen. Optimum growth was achieved on modified Murashige and Skoog medium containing 67% KNO₃ and 33% NH₄NO₃ with total N of 40 mM supplemented with 100 mg l⁻¹ myo-inositol, 1 mg l⁻¹ thiamine HCl, 30 g l⁻¹ sucrose, and 4.44 μM BA with a 16-h photoperiod (120–150 μmol m⁻² s⁻¹). Proliferating shoots and plantlets were photosynthetically active. Better shoot growth and accumulation of higher biomass occurred in a CO₂-enriched environment than under ambient CO₂ conditions. CO₂ assimilation efficiency, however, was higher under the latter conditions than in a CO₂-enhanced environment, e.g., 31±7 and 17±2 μmol CO₂ m⁻² s⁻¹, respectively. The net CO₂ assimilation rates of in vitro grown plantlets were comparable to those of seedlings ex vitro.     

Effect of partial deglycosylation on catalytic characteristics and stability of an avocado peroxidase

An isoperoxidase (EC 1.11.1.7) purified from avocado ( Persea americana Mill. cv. Topa Topa) leaves, lost 35% of its glycosidic moiety after incubation with glycopeptidase F (EC 3.2.2.18). The partial removal of carbohydrate chains caused a decrease in the K_m for reductor substrates tguaiacol, syringaldazine and indole-3-acetic acid) and favoured the enzyme activation by Ca²⁺. A decrease in stability against temperature was also observed. Our results are consistent with the hypothesis that the carbohydrate moiety located on the surface of the peroxidase molecule acts as a molecular shield.     

牛油果果实发育过程中营养物质含量变化研究

为确定牛油果的最佳采收期,阐明牛油果生长发育过程中营养物质的累积变化规律。该文采用电感耦合等离子体发射光谱法、灼烧法、茚三酮柱后衍生离子交换色谱法、回流提取法和GC-MS联用技术,研究了‘HASS''‘V3''和‘V4'' 3个品种牛油果果实中粗脂肪、氨基酸、矿质元素以及灰分在6—12月间的含量变化。结果表明:(1)3个品种牛油果中油脂的主要成分均为油酸,其中‘HASS''和‘V4''果实中的粗脂肪含量在12月达到峰值,而‘V3''果实中的粗脂肪含量则在10月达到峰值,之后有所下降。(2)3个品种牛油果中均含有17种氨基酸,包括7种人体必需氨基酸、2种儿童必需氨基酸以及8种人体非必需氨基酸,其中‘HASS''和‘V3''果实中的17种氨基酸含量在11月达到峰值,而V4的则在10月达到峰值。(3)3个品种牛油果中均含有磷(P)、钾(K)、钙(Ca)、镁(Mg)、锌(Zn)、铁(Fe)、锰(Mn)、铜(Cu)、钠(Na)9种矿质元素,其中P、K、Zn、Fe、Na含量在10—12月累积至最大,其余4种矿质元素变化规律不明显。(4)灰分含量变化规律与粗脂肪相似。综上认为,3个品种牛油果的营养物质均在10月达到最佳值,可以根据需求进行采收。该研究结果为确定牛油果的最佳采收时间提供了科学依据。