Articles

Although laurel wilt disease was first reported in the United States in 2002 from redbay trees (Persea borbonia) around Savannah, Georgia it has rapidly spread throughout the southeastern coastal plain including Georgia and Florida. In the current study, transects were used to assess the spread and impact of the disease on two native bay trees redbay (P. borbonia) and swampbay (P. palustris) from north Florida in a semi-naturalized ecological preserve. Although tree size and mortality rates have been reported previously, this study provides the first size-based static life tables for both species. While a significantly higher percent (76%) of swampbay trees exhibited signs of laurel wilt disease compared to redbay trees (62%); redbay had more of its canopy damaged by the disease (41% vs. 32% for redbay vs. swampbay respectively); this resulted in a significantly smaller stem diameter for P. borbonia compared to swampbay, both species are experiencing significant declines due to the disease. Both species exhibited a Type III survivorship curve in which the vast majority of individuals were in the smallest size class (average stem diameter was only 2.5 and 3.6 cm for redbay and swampbay respectively). Although traditionally, population age (or size) structure that is heavily biased toward younger or smaller size classes suggests that the population is likely to expand in the future, for these bay trees high mortality rate due to beetle/fungal infestation of larger size classes is responsible for this trend; the smallest size classes are largely free from beetle infestation and laurel wilt disease because the stem diameter is likely insufficient to support beetle development. Results from this study suggest that swampbay is also highly susceptible to laurel wilt disease and its populations are likely to exhibit a similar (albeit slower) decline in Florida’s wetland and mesic ecosystems.

Tropical forests have long been of interest to biologists because of their high species diversity and their complicated patterns of community organization. The recent ecological studies which have demonstrated that tropical trees are diverse in their reproductive biology and dynamic population structure. Asynchronous flowering among the clones in a clonal seed orchard is an inherent problem resulting in poor seed and fruit set in them. These results in the complete defeat of the prime objective of establishment of clonal seed orchards (CSOs) i.e. abundant quality seed production poor flowering and asynchronous flowering between the clones are a major bottleneck in higher seed set in these clonal seed orchards across the country. Asynchrony found between clones may be attributed to the origin of clones, which are collected from different zonal populations as revealed by isoenzyme and DNA markers studies. This article reviews the work done in CSOs across the world and suggests an alternate strategy in designing the clonal seed orchards of the future.

Stable reference genes are indispensable for ensuring the fidelity of determined gene expression levels. However, the expression levels of reference genes are unable to remain constant under all possible experimental conditions. Therefore, the stability determination of reference genes is necessary in an experimental system set. In the preset study, the stability of nine cucumber candidate reference genes (CsACT, CsUBQ, CsEF1α, CsCYP, CsαTU, CsCACS, CsTIP41, CsYSL8 and CsHEL) subjected to stresses from Phytophthora melonis(P. melonis) were determined using four different analysis methods, including Delta Ct, BestKeeper, NormFinder and GeNorm. The study results revealed that CsUBQ and CsCYP were the most stable genes suitable as internal control in cucumber plants under attack by P. melonis condition.

The use of novel PGPR as bio inoculant is an alternative sustainable agricultural practice to improve soil health, grain quality, increase crop productivity, and conserve biodiversity. The aim of this study is to isolate, and characterized PGP bacteria colonizing tef rhizosphere during the seedling stage. For this concern, 426 samples of tef (Eragrostis tef) rhizosphere soils and roots were collected from East Shewa zone, Oromia regional state. 200 morphologically different bacterial pure colonies were isolated and screened for their PGP traits and biocontrol properties. Among these 40.5% isolates were positive for phosphate solubilization. 36% were positive for IAA production, 4.5% were positive for ammonia production, 19 % were positive for (EXPS), 15.5% were positive for protease production, 12.5% were positive for HCN productions, 9.5 % were positive for cellulase production, 4% were positive for amylase production, 3.5% were positive for chitinase production. For abiotic stress tolerance test, all of the isolates were grown well at 20oc and 30oc and neutral pH, 27% isolates were grown well at 4oc, 25.5% grew at 40oc, 25.5% were grown well on pH-9 and pH-11, 23.5% were tolerated pH-5, 3.5% grew at 50oc and 60oc, 13.5% were grown well on 5% NaCl (w/v), 3.5% were grown well on 10 and 15% NaCl (w/v), which indicated these isolates can survive in some extreme conditions. Totally 15 bacterial species having PGP traits, biocontrol properties, and abiotic stress tolerance ability were identified using the Biolog bacterial identification system. Among these, the majority of the identified PGPR have utilized carbohydrate, carboxylic acid, and amino acid, which are the main components of plant root exudates. The above results indicated that thus PGPR can be used as biofertilizers as well as biocontrol agents to replace agrochemicals to improve crop productivity. Hence, these species can be further formulated and used for greenhouse and field applications.

Ilex paraguariensis, also known as ‘Yerba mate’, occurs naturally in Argentina, Brazil and Paraguay and is also grown in these countries with different intensities. Leaves and branches of this plant are used in the preparation of a stimulant beverage that beside social importance has notorious health impact. However, the cultivated herbs present low productivity, due to deficiencies in cultivation and harvesting techniques, as well as due to the abiotic stresses that this species is subject to. The discovery and characterization of cold response mechanisms in plants such as Arabidopsis thaliana, began research in order to unravel the physiological and molecular mechanisms in response to cold in other plant species. In this work, we studied the physiological response observed in Ilex paraguariensis plants submitted to low temperatures (0°C), with or without a pre-moderate acclimatization treatment period of (8°C). Our results suggest the existence of an acclimation response in Ilex paraguariensis, similar to that described in other species of the same temperature.

The age-old battle between plants and viruses has many twists and turns. Plants acquired the RNAi factors to checkmate the viruses and the viruses encode VSRs to defeat RNAi for their own survival. Plants designed mechanisms to neutralize the toxic effects of VSRs and the viruses, in their turn, use host microRNAs to strengthen their infection processes. The infightings between these two entities will take different shapes with prolonged evolution and accordingly the researchers will dig these novel forms of duels not only to throw lights in the involved mechanisms but also to manipulate various antiviral strategies. Some of the research courses that might come up in the immediate future are discussed.

Many agriculturally important properties such as heterosis, inbreeding depression, phenotypic plasticity, and resistance for biotic and abiotic stresses are thought to be affected with epigenetic components. New discoveries related with epigenetics are likely to have a major impact on strategies for crop improvement in rice breeding. However, assessing the contribution of epigenetics to heritable variation in plant species still poses major challenges. Methylation of cytosine in DNA is one of the most important epigenetic mechanisms in plants. DNA methylation not only plays significant roles in the regulation of gene activity, but also it is related with genomic integrity. Although most of next generation sequencing (NGS) technologies do not require the use of target specific primer pairs to identify and study DNA cytosine methylation, validation studies of NGS uses selective primer pairs. Bisulfite sequencing technique is a gold method for DNA cytosine methylation studies. However, bisulfite sequencing requires the development of bisulfite primer pairs to selectively study DNA sequences of interest. In this study 9 bisulfite specific primer pairs were identified and validated. These primer pairs successfully amplified bisulfite converted and unconverted genomic DNA extracted from radicle and plumule of rice (Oryza sativa L.) seedlings. Results of the present study clearly revealed the occurrence of CG, CHG and CHH (H stands for C. T or A nucleotides) contents in studied DNA sequence targets were different indicating potential role of DNA cytosine methylation in these genes. Primer pairs reported in this study could be used to detect DNA methylation which is one of the most important epigenetic mechanisms affecting the development, differentiation or the response to biotic and abiotic stress in rice (Oryza sativa L.).

This study purposed to study the Preservative agents that are required to ensure that manufactured foods remain safe and unspoiled; work was conducted to evaluate the efficacy of essential oils from two eucalyptus species, Eucalyptus grandis and Eucalyptus crebra in food preservatives; to run this experiment flesh eucalyptus leaves collected from Ruhande Arboretum forest were submitted to hydrodistillation and yields(amount) of 0.38 and 0.34 % for Eucalyptus grandis and Eucalyptus crebra were obtained, respectively. Phaseolus vulgaris, Sorghum condatum, cooked Ipomoea batatas (sweet potatoes) and bread were the sample foods used to assess their preservative efficacy. Acanthoscelides obtectus and Stophilus oryzae were used as pests for Phaseolus vulgaris and Sorghum condatum respectively. For bread and cooked Ipomoea batatas, Rhizopus nigricans are used to assess the efficacy of these two essential oils to inhibit their growth; the obtained results revealed that those essential oils could act as insecticide in the storage of Phaseolus vulgaris and Sorghum condatum. Essential oil from Eucalyptus grandis protected these two foods against pests in the periods of 4 and 9 days, respectively while essential oil from Eucalyptus crebra protected them for the periods of 6 and 11days, respectively.

Aflatoxins, produced by Aspergillus spp., are strongly toxic and carcinogenic fungal secondary metabolites. Aflatoxin biosynthesis is a complex process and involves at least 30 genes clustered within an approximately 75 kB gene cluster. In this paper, we reviewed current status of the researches on the characterized structural genes involved in aflatoxin biosynthesis and their roles in aflatoxin-producing fungi, especially in A. flavus and A. parasiticus, which will improve our understanding of the mechanism of aflatoxin biosynthesis and regulation and provide reference for further study.

The halophyte Distichlis palmeri (Vasey) is a plant resource with high potential to be harvested in the coastal areas of northwestern Mexico; enlarge the knowledge and domestication for its incursion into the agricultural sector, plays an important role for arid areas with saline intrusion problems. However, its productivity depends on the supplementary supply of nitrogen, as well as other essential macro and micronutrients. The microorganisms considered beneficial are an alternative to chemical fertilization, highlighting those Plant Growth Promoting Bacteria (PGPB). In the present study, the inoculation of the Bacillus amyloliquefaciens (B.a.) as a halobacterium PGPB was evaluated to know the response in seeds of Distichlis spicatai obtained from natural population from colorado river in Delta north of the Gulf of California. Wild seed was collected and germinated previously inoculated with B. a., and sowed in germinated beds. Later, seedlings were planted under field and salinity conditions in the coast of Hermosillo, Sonora. Three treatments were examined (T1: B.a., T2: Chemical fertilization, T3: Negative control), with four repetitions each treatment. Each repetition consisted of experimental plots of 5 x 5 m, with a separation of 1 m between them. The harvest was carried out 600 days after sowing. The results indicate that treatments inoculated with halobacteria B.a., showed significant results in crude protein, non-protein nitrogen, neutral detergent fiber and acid detergent fiber, as well as spike length and number of seeds. The results obtained suggests the feasibility of biofertilizers where biomass and seed production are significant compared to non-inoculated controls.