Ethylene and jasmonate as stimulants of latex yield in rubber trees(Hevea brasiliensis):Molecular and physiological mechanisms.A systematic approximation review

The rubber tree Hevea brasiliensis(Willd.Ex Adr.De Juss.)Müell Arg.]is an important source of latex for the production natural rubber.Natural rubber is an important biopolymer used in various industries,but aspects related to hormonal regulation in biosynthesis are still unknown,which would allow optimizing its production.We review the molecular and physiological mechanisms of increases latex regeneration and flow by the stimulation of rubber trees with exogenous applications of ethylene and jasmonate.We found that the increase in latex regeneration by ethylene is due to the increase in gene level expression and enzymatic activity of key photosynthesis and glycolysis enzymes for the generation of precursors in the first phase of rubber biosynthesis.Latex flow is supported by up-regulated genes in sucrose metabolism such as invertases,induction of sucrose transporters(SUT),and aquaporins(PIP)to maintain flow and turgor pressure in laticifers.Meanwhile,the increase in latex yield mediated by jasmonate may be due to the induction of laticifer differentiation in the long term and in the short term be mediated by the induction of small rubber particles(SRPP)as non-enzymatic cofactors in the production of latex.This information contributes to the knowledge of latex biosynthesis,which allows for a greater support for the exogenous application of jasmonates and ethylene to regulate its production.

Insights into the role of major bioactive dietary nutrients in lamb meat quality:a review

Feed supplementation withα-linolenic acid(ALA)and linoleic acid(LA)increases their content in muscle,ALA increases n-3 polyunsaturated fatty acids and decrease n-6/n-3 ratio in muscle,and LA increases rumenic acid.However,high LA supplementation may have negative effects on lambs’lipid oxidative stability of meat.When the sources of ALA and LA are fed as fresh forage,the negative effects are counterbalanced by the presence of other bioactive compounds,as vitamin E(mainlyα-tocopherol)and polyphenols,which delay the lipid oxidation in meat.There is a wide consensus on the capability of vitamin E delaying lipid oxidation on lamb meat,and its feed content should be adjusted to the length of supplementation.A high dietary inclusion of proanthocyanidins,phenolic compounds and terpenes reduce the lipid oxidation in muscle and may improve the shelf life of meat,probably as a result of a combined effect with dietary vitamin E.However,the recommended dietary inclusion levels depend on the polyphenol type and concentration and antioxidant capacity of the feedstuffs,which cannot be compared easily because no routine analytical grading methods are yet available.Unless phenolic compounds content in dietary ingredients/supplements for lambs are reported,no specific association with animal physiology responses may be established.

Evaluation of drought indices to identify tolerant genotypes in common bean bush(Phaseolus vulgaris L.)

Drought is one of the major abiotic stresses often causing negative impacts on bean crops in the Andean region in Colombia. An experiment under the greenhouse conditions was carried out to assess the effect of a prolonged drought period(15 days) at two different phenological stages(vegetative or reproductive) on grain yield and yield components of five bush bean cultivars(ICA-Cerinza, Bachue, NUA35, Bianca, and Bacatá). Nine tolerance indices including stress susceptibility index(SSI), tolerance(TOL), mean productivity(MP), geometric mean productivity(GMP), stress tolerance index(STI), yield stability index(YSI), yield index(YI), Harmonic mean(HM), and drought sensitivity index(DSI) were calculated based on grain yield under non-stressed(YP) and drought(YS) conditions. Based on the different drought indices, genotypes ICA-Cerinza and NUA35 had the best performance under drought conditions in both studied phases, which reflected in a reduction of grain yield ~≤40%. The biplot analysis also showed a clear superiority of these two genotypes at both phenological stages. Results also showed that SSI was more effective to identify genotypes less affected by drought. The above results allowed us to conclude that ICA-Cerinza and NUA35 may be considered for agricultural areas where long periods of water deficit are expected and can be used in breeding programs for drought tolerance.

Modelling the impacts of cover crop management strategies on the water use,carbon exchange and yield of olive orchards

Cover crops have long been proposed as an alternative soil management for minimizing erosion rates in olive stands while providing additional ecosystem services.However,the trade-off between these benefits and the competition for water with the trees makes the definition of optimal management practices a challenging task in semiarid climates.This work presents an improved version of OliveCan,a process-based simulation model of olive orchards that now can simulate the main impacts of cover crops on the water and carbon balances of olive orchards.Albeit simple in its formulation,the new model components were developed to deal with different cover crop management strategies.Examples are presented for simulation runs of a traditional olive orchard in the conditions of southern Spain,evaluating the effects of different widths for the strip occupied by the cover crop(Fcc)and two contrasting mowing dates.Results revealed that high Fccresulted in lower olive yields,but only when mowing was applied at the end of spring.In this regard,late mowing and high Fccwas associated with lower soil water content from spring to summer,coinciding with olive flowering and the earlier stages of fruit growth.Fccwas also negatively correlated with surface runoff irrespective of the mowing date.On the other hand,net ecosystem productivity(NEP)was substantially affected by both Fccand mowing date.Further simulations under future climate scenarios comparing the same management alternatives are also presented,showing substantial yield reductions by the end of the century and minor or negligible changes in NEP and seasonal runoff.

Effects of precipitation changes on the dynamics of sparse elm woodland in Northeastern China

Elm(Ulmus pumila L.)is the dominant tree species in the sparse elm woodland,the original vegetation in the Horqin Sandy Land.The effects of changes in precipitation on U.pumila trees have not been fully studied.We determined a dynamic model by considering the five stages in the U.pumila life cycle,i.e.seed,seedling,and juvenile,mature and over-mature tree stages.The effects of changes in precipitation on population density and age structure were then evaluated.Population density,after averaging all study developmental morphology stages,ranged from 16.67 individuals/m2 to 25.01 individuals/m2 under a mean annual precipitation(MAP)of 80%to 120%,respectively.This suggests that population density could increase as MAP also increased.The proportion of seedlings,and juvenile,mature and over-mature trees were 95.23%,4.58%,0.19%and 0.01%,respectively,under all precipitation levels.This indicates that precipitation had little effects on the developmental stages of the studied U.pumila populations in the Horqin Sandy Land.Additional water supply might be provided in addition to the natural rainfall that occurs in the region,for contributing to maintain U.pumila population density in the Horqin Sandy Land.

Identification of Candidate Genes Related to Polyploidy and/or Apomixis in <i>Eragrostis curvula</i>

This work was aimed at identifying genes that show altered expression profiles in response to changes in ploidy and/or reproductive mode (from sexual to apomictic) in the African grass Eragrostis curvula. A differential display analysis was performed on leaf and flower transcriptomes from a series of genetically related euploid plants, including tetraploid apomictic, diploid sexual, and tetraploid sexual plants. More than 100 primer combinations were used to generate 11,864 total markers, yielding 1293 differential bands. Of these bands, 11.84% to 6.74% were related to ploidy and 0.71% to 2.17% to the reproductive mode, depending on the tissue. A small percentage of bands showed similar expressions between the tetraploid apomictic and the diploid sexual plants. Expression-based similarity dendrograms were constructed. Our data suggested that ploidy is more decisive than tissue type in defining the transcriptome structure. Out of 102 fragments sequenced, 50 showed strong homology to known genes. The differentially expressed genes were mapped in silico onto maize chromosomes. Several candidates mapped within the linkage group syntenic to the Tripsacum dactyloides diplospory-governing region. The evidence indicates that expression of genes located around the diplospory-associated region may be strongly influenced by ploidy and may be silenced in the apomictic genotype. These findings are discussed in the context of diplospory molecular control and its connection with ploidy.

The Spatial-Temporal Heterogeneity of Understory Light Availability in a Temperate Forest of North China

The spatial-temporal variation of understory light availability has important influences on species diversity and community assembly.However,the distribution characteristics and influencing factors of understory light availability have not been fully elucidated,especially in temperate deciduous,broad-leaved forests.In this study,the understory light availability was monitored monthly(May–October)in a temperate deciduous,broad-leaved forest in Henan Province,China.Differences in the light availability among different months and habitat types were statistically analyzed using Kruskal–Wallis method,respectively.Partial least squares path modeling(PLS-PM)was used to explore the direct and/or indirect effects of stand structure,dominant species and topographic factors on the light environment.Results showed that there were differences in light environments among the four habitat types and during the studied six months.The PLS-PM results showed that the stand structure and the dominant species were negatively correlated with the light environment,and the path coefficient values were−0.089(P=0.042)and−0.130(P=0.004),respectively.Our result indicated that the understory light availability exhibit a distinct spatial and temporal heterogeneity in temperate deciduous,broad-leaved forest of north China.The characteristics of woody plant community,especially the abundance of one of the dominant plant species,were the important factors affecting the understory light availability.

Water Consumption and Vegetative Growth Progress in Resistant and Susceptible Olive Cultivars Infected by Verticillium dahliae

Purpose: Water consumption and vegetative growth in resistant (“Frantoio”) and susceptible (“Picual”) olive cultivars infected with Verticillium dahliae were assessed. Methods: Plants were inoculated with the pathogen and disease evaluated in growth chamber. Mean daily water consumption and vegetative growth were recorded during 13 weeks. Results: Water consumption significantly decreased in inoculated plants compared to non-inoculated plants during the 3rd - 6th weeks after inoculation period. From the 9th week, a significantly lower consumption occurred in infected “Picual” plants compared with “Frantoio” plants. Vegetative growth was reduced in inoculated plants of both cultivars, although the reduction of the fresh weight was remarkably higher in “Picual” compared with controls due to defoliation and tissue desiccation, impeding the production of new shoots and leaves. Conversely, in “Frantoio”, defoliation was significantly reduced to low levels. Conclusions: Water consumption and vegetative growth in plants of resistant (“Frantoio”) and susceptible (“Picual”) olive cultivars inoculated by Verticillium dahliae were consistently associated with the progress of the wilt symptoms and the level of resistance of the cultivar. Growth and water consumption reductions in “Picual” were irreversible in almost all plants, while “Frantoio” plants were able to maintain water translocation, overcome the infection and avoid vascular occlusion, and restart vegetative growth.

Ocurrence of Entomopathogenic Fungus from Flea Ctenocephalides canis(Siphonaptera:Pulicidae)

The objective of this study was to isolate entomopathogenic fungus from fleas (Ctenocephalides canis Curtis) collected from Cannis familiaris specimens. From 60 collected fleas, two dead insects presented white mycelia growth on the body surface, changing to a creamy color as time passed;the insects presented a mummified aspect, typical characteristic caused by entomopathogenic fungus. This fungus was identified as Beauveria bassiana (Balsamo-Crivelli) Vuillemin by their mycelia characteristics, macro- and micro-morphology. Up to our knowledge, this is the first report of entomopathogenic fungus isolated from adult C. canis fleas.

Genetic diversity and population structure of invasive and native populations of Erigeron canadensis L.

Invasive alien plants threaten biodiversity across the world.Erigeron canadensis(horseweed)is one of the most problematic agricultural weeds and represents a classic example of intercontinental invasion.Here,we studied the genetic diversity and population structure of invasive alien populations from the Jiangsu and Zhejiang Provinces in China and native populations from Alabama,in the USA.We used 10 polymorphic SSR loci to genotype 312 individuals from 5 native and 5 invasive populations to estimate the genetic diversity and structure.Invasive populations from Jiangsu and Zhejiang Provinces showed,on average,similar genetic diversity to native populations from Alabama,indicating no severe genetic bottlenecks during the invasion.STRUCTURE revealed that low population differentiation occurred,and that only two genetic groupings were detected in both native and invaded ranges.The high diversity observed in the invasive populations suggested multiple introductions and/or the introduction of genetically diverse propagules during initial colonization.Our study provides new insights toward understanding the invasion dynamics of this globally noxious weed in Eastern China.Preventing gene flow via seed dispersal between invasive and native populations should be examined to prevent the introduction and dispersal of herbicide-resistant individuals and inform management practices.

Senecio bonariensis Hook.&Arn.promising arsenic phytoextractor from water in laboratory and field trials

The use of plant species to cleanse groundwater with excessive concentrations of arsenic(As)derived from contact with weathered materials has become a valuable option to treat it.The aim of this work was to analyze the bioaccumulation capacity of As of Senecio bonariensis(Asteraceae)through controlled laboratory tests and uncontrolled trials in the field in order to generate a low cost method applicable in rural areas that do not have systems of water treatments.Plants collected from the natural environment were arranged in hydroponic crops under controlled and uncontrolled conditions,in the first case with increasing concentrations of As for 45 days,and in the second,with a constant concentration of As for a period in a range between 45 and 90 days.The plants were processed and dried for the measurement of As.In both tests,in all the samples there was a noticeable accumulation of As,generally greater in roots than in leaves.Under controlled conditions the plants accumulated more As in relation to greater concentration of this element in the water.In all the trials a high bioaccumulation of As was found,which turns the plant into a hyperaccumulator.Due to the ability of S.bonariensis to accumulate As,and even more because of the great biomass produced by this species,it becomes an excellent one to be used for the remediation of arsenical waters.