Efficacy of a micro‐encapsulated formulation compared with a sticky barrier for excluding ants from citrus canopies

Inesfly IGR FITO^® is an insecticidal paint containing chlorpyrifos and pyriproxyfen incorporated in a micro‐encapsulated formulation that confers the advantage of releasing active ingredients slowly. In this study, a 15‐cm band of Inesfly IGR FITO^® was painted around citrus trunks. The efficacy of this paint and a sticky barrier to exclude ants from foraging in citrus trees was evaluated in two citrus orchards during the season in two different ant communities, one dominated by Lasius grandis and the other by Linepithema humile. Field results demonstrated that a single application of Inesfly IGR FITO^® at the beginning of the season was highly effective in excluding ants from canopies throughout the season. Inesfly IGR FITO^® provides an efficient and more economical alternative than current ant exclusion strategies used in many perennial crops. Further studies should be performed to determine the effects of this strategy on other pests and on beneficial arthropods in citrus.     

化州柚查尔酮合成酶基因克隆与序列分析

利用CTAB-LiCl法提取高质量的化州柚总RNA,采用RT-PCR技术克隆查尔酮合成酶基因,获得广东道地药材化橘红资源化州柚的查尔酮合成酶基因。该基因编码区全长1176bp,编码391个氨基酸残基,与同样来源于柑橘属的查尔酮合成酶基因同源性高达98%。CTAB-LiCl法能提取高质量的化州柚总RNA,可以用于后续基因克隆和分析;克隆获得的查尔酮合成酶具有编码区,与同属植物相同基因具有高度序列同源性。     

A method for determining the apoplastic water volume of conifer needles

A method for direct estimation of percentage apoplastic water volume (% APO) in conifer needles is described. The method presented here, and designated the pressure-needle (P-N) method, measures the relative water content of the needles to develop a curve similar to the pressure-volume (P-V) curve. P-V and P-N curves were developed for Picea pungens Engelm. cv. Hoopsi, Pinus sylvestris L., Abies gradis (Dougl.) L., and Pseudotsuga menziesii (Mirb) Franco. The % APO estimated by the two procedures varied as much as 2-fold, while other parameters were similar. The P-V method generated consistently higher and more variable % APO than the P-N method, due to the inclusion of the apoplastic water of the stem in the P-V method. For conifers, the P-N method offers a more accurate and precise method for determining % APO.     

13C-NMR study of the ruthenium(II)-catalyzed degradation of labeled G-factor endoperoxides: proposal of a likely biogenetic pathway and evidence for CO2 release

G-factor endoperoxides are natural products acting as phytohormones and contribute to root inhibition and frost resistance in Eucalyptus grandis and other Myrtaceae. Several (Z)- and (E)-configured cyclopentane-1,3-dione metabolites of G-factors have been found in some Eucalyptus extracts. Interestingly, these probable metabolites are identical to the products obtained by Ru(II)-catalyzed reduction of G-factors. In the present work, we, thus, studied the mechanism involved in the formation of these compounds by means of in-depth NMR distribution analysis of two differently 13C-labeled G3-factors. The observed CO2 release is underlined, and a comparison with the corresponding Fe(II)-induced degradation of G-factor endoperoxides is made. Also, the type of electron transfer proposed in the two processes is discussed and, tentatively, connected to the role of endoperoxides in plants.     

Examining the genetic diversity of Stipa grandis under various grazing pressures

The Stipa grandis steppe in the Inner Mongolia Autonomous Region occupies an area of 2798081 hm2. On the basis of the genetic variation, it was found that its adaptability to the environmental conditions under grazing pressure was significant. Using the Inter-Simple Sequence Repeat (ISSR) procedure, the changes to the genetic diversity of the Stipa grandis population under different grazing pressures were observed. Plant samples were collected from a series of grazing gradients of the Stipa grandis steppe in Dalinuoer National Nature Reserve in the Inner Mongolia (located at 116°38′–116°41′E and 43°25′–43°27′N.), which has the following vegetation types in abundance: Leymus chinensis is the constructive species; the dominant species include Stipa grandis, Cleistogenes squarrosa, and Artemisia frigida; the companion species is Potentilla acaulis and others. According to the grazing pressure, the following four grazing gradients were identified from the dwellings of the herdsmen to the enclosure site: (1) no grazing (CK enclosure site); (2) light grazing (LG); (3) moderate grazing (MG); (4) heavy grazing (HG). Young leaves of each Stipa grandis were collected during the growing season. The results showed that the Stipa grandis showed abundant genetic diversity despite the fact that certain polymorphic loci were lost; at the same time, new polymorphic loci emerged when grazing pressure increased; a total of 10 primers were used, and 74 bands were produced in total, of which 65 bands were polymorphic; the total percentage of polymorphism was 89%; the percentage of polymorphic loci of the Stipa grandis population decreased with the increase of grazing pressure; the percentage of polymorphic loci was 62.2% in the no-grazing (CK) population, 64.9% in the light-grazing (LG) population, 58.1% in the moderate-grazing (MG) population, and 56.8% in the heavy-grazing (HG) population; the genetic diversity of the population in the descending order using the Shannon's information index is as follows: (1) light grazing (0.3486); (2) no grazing (0.3339); (3) moderate grazing (0.3249); (4) heavy grazing (0.2735) with the same distributional pattern as the Nei's genetic diversity index. The test showed the following: As the grazing pressures increased, the change of genetic diversity decreased; the genetic differentiation coefficient among the population (Gst) was 0.1984, which showed the presence of small partial genetic diversity (19.8%) among populations; gene flow (Nm*) between primers varied from 0.9806 to 3.4463, and the mean gene flow (Nm*) was 2.0202; the UPGMA cluster figure that was constructed on the basis of the genetic distance matrix showed four populations that became genetically closer at each step: (1) The first group was the moderate-grazing (MG) population and the heavy- grazing (HG) population; (2) The second group consisted of the no-grazing (CK) population and the light-grazing (LG) population; (3) The two groups gathered together.     

Construction and Characterization of a cDNA Library from the Pulp of Cara Cara Navel Orange （Citrus sinensis Osbeck）

A cDNA library was constructed end characterized from the pulp of Cera Care navel orange （Citrus sinensis Osbeck） at different stages of ripening. Tittering results revealed that approximately 5.086×10^5 independent clones were included in this library. Electrophoresls gel results of 15 randomly selected clones revealed that the size of the insertion fragments ranged from 400 bp to 2 kb, with an average size of 900 bp. Sequencing results of 150 randomly picked clones showed that the recombination rate was 94%. During subsequent sequence analysis, 41 of 139 clones failed to be identified end the amino sequence of 71 clones shared less than 30% identity with related plants in GenBank. Of 27 clones whose amino sequences shared more than 60% identity with other related plants in GenBenk, 17 clones showed an 80% identity with the corresponding candidate genes of citrus. The clone recognized as the type Ⅲ metallothlonein-llke （MT） gene was observed to occur 13 tlmes, Indlcatlng that the protein may play an important role In frult development and rlpenlng.     

‘沙田’柚果生长期套袋对果实品质的影响

‘沙田’柚果生长期进行套袋,是提高果实品质的有效措施之一。在田间生长条件下,研究了套袋对‘沙田’柚果实品质的影响。结果表明,套袋促进了柚果生长发育,提高了商品率,降低了含酸量,较明显地提高其糖酸比,并增加了维生素C的含量,从而提高了柚果品质。     

Characterization of electrical penetration graphs of the Asian citrus psyllid, Diaphorina citri, in sweet orange seedlings

Detailed information on probing behavior of the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is critical for understanding the transmission process of phloem‐limited bacteria (Candidatus Liberibacter spp.) associated with citrus ‘huanglongbing’ by this vector. In this study, we investigated stylet penetration activities of D. citri on seedlings of Citrus sinensis (L.) Osbeck cv. Pêra (Rutaceae) by using the electrical penetration graph (EPG‐DC system) technique. EPG waveforms were described based on amplitude, frequency, voltage level, and electrical origin of the observed traces during stylet penetration into plant tissues. The main waveforms were correlated with histological observations of salivary sheath termini in plant tissues, to determine the putative location of stylet tips. The behavioral activities were also inferred based on waveform similarities in relation to other Sternorrhyncha, particularly aphids and whiteflies. In addition, we correlated the occurrence of specific waveforms with the acquisition of the phloem‐limited bacterium Ca. Liberibacter asiaticus by D. citri. The occurrence of a G‐like xylem sap ingestion waveform in starved and unstarved psyllids was also compared. By analyzing 8‐h EPGs of adult females, five waveforms were described: (C) salivary sheath secretion and other stylet pathway activities; (D) first contact with phloem (distinct from other waveforms reported for Sternorrhyncha); (E1) putative salivation in phloem sieve tubes; (E2) phloem sap ingestion; and (G) probably xylem sap ingestion. Diaphorina citri initiates a probe with stylet pathway through epidermis and parenchyma (C). Interestingly, no potential drops were observed during the stylet pathway phase, as are usually recorded in aphids and other Sternorrhyncha. Once in C, D. citri shows a higher propensity to return to non‐probing than to start a phloem or xylem phase. Several probes are usually observed before the phloem phase; waveform D is observed upon phloem contact, always immediately followed by E1. After E1, D. citri either returns to pathway activity (C) or starts phloem sap ingestion, which was the longest activity observed.     

High-light stress does not impair biomass accumulation of sun-acclimated tropical tree seedlings (Calophyllum longifolium Willd. and Tectona grandis L. f.)

Studies with seedlings of tropical rainforest trees ( Calophyllum longifolium Willd.; Tectona grandis L. f.) were designed to test whether high-light stress affects photosynthetic performance and growth. Seedlings were cultivated in pots at a field site in Central Panama (9 degrees N) and separated into two groups: (1) plants exposed to full solar radiation; (2) plants subjected to automatic neutral shading (48 %) whenever visible irradiance surpassed 1000, 1200, or 1600 micromol photons m-2 s-1. After 2-4 months, chlorophyll fluorescence (Fv/Fm ratio), photosynthetic net CO2 uptake, pigment composition, alpha-tocopherol content of leaves, and plant biomass accumulation were measured. Fully sun-exposed, compared to periodically shaded plants, experienced substantial high-light stress around midday, indicated by photoinhibition of photosystem II and depressed net CO2 uptake. Higher contents of xanthophyll cycle pigments, lutein, and alpha-tocopherol showed an enhancement of photoprotection in fully sun-exposed plants. However, in all experiments, the maximum capacity of net CO2 uptake and plant dry mass did not differ significantly between the two treatments. Thus, in these experiments, high-light stress did not impair productivity of the seedlings studied. Obviously, the continuously sun-exposed plants were capable of fully compensating for any potential costs associated with photoinhibition and repair of photosystem II, reduced CO2 assimilation, and processes of high-light acclimation.