A comprehensive evaluation and first molecular report of Theileria ovis infection in small ruminants in Saudi Arabia

A total of 1000 clinically healthy small ruminants comprising 500 sheep and 500 goats from five districts within Riyadh Province in Saudi Arabia were investigated by routine Giemsa staining for hematozoan parasites. Out of these, 100 sheep and 95 goat samples were investigated by PCR using three pairs of hemoprotozoan-specific primers. Based on microscopic examination, 33.2% of sheep and 25.2% of goats were found infected with hemoprotozoan parasites, while PCR detected hematozoan infection in 46% of sheep and 33.7% of goats. Extensive molecular characterization of hematozoan infection using six pairs of species-specific primers revealed the dominance of Theileria ovis, rather than any other species, which is recorded for the first time in small ruminants in Saudi Arabia. Prevalence of T. ovis in sheep and goats was found to be the highest in Riyadh (32, 48%) followed by AL-Kharj (31, 35%), Ad-Dawadimi (31, 33%), AL-Majmaah (15, 27%), and Rumah (17, 23%). The highest parasite prevalence was recorded in the 3 years of age and >?4 years of age ruminants, while the lowest prevalence was recorded in <?1 year of age ruminants. No noticeable differences in parasite prevalence between male or female ruminants were recorded. Partial sequencing of 18S rRNA gene revealed the infection of the studied ruminants with four new isolates of T. ovis. Further characterization of the pathogenicity and the clinical effects of these T. ovis isolates in sheep and goats is highly needed. The current results can be helpful in protecting and improving livestock industry in the countries that depend on a high number of small ruminants.

     

Induction of Drought Tolerance in Maize (Zea mays L.) due to Exogenous Application of Trehalose: Growth,Photosynthesis, Water Relations and Oxidative Defence Mechanism

The present investigation was conducted to assess the ameliorative effects of foliar‐applied trehalose on growth, photosynthetic attributes, water relation parameters and oxidative defence mechanism in two maize cultivars under field water deficit conditions. Various components of the experiment comprised two maize cultivars (EV‐1098 and Agaiti‐2002), two water‐stress levels (irrigation after 2 weeks and irrigation after 3 weeks during the entire period of growth), and two levels of trehalose (0 and 30 mm ) and four replicates of each treatment. Water stress significantly reduced the plant biomass production, photosynthetic attributes and water relation parameters in both maize cultivars. In contrast, water stress considerably increased the leaf malondialdehyde (MDA) contents, the activities of antioxidant enzymes such as peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT), and the levels of non‐enzymatic compounds such as ascorbic acid and tocopherols. In contrast, water stress caused a marked reduction in leaf phenolic contents. Foliar‐applied trehalose significantly increased plant biomass production, and improved some key photosynthetic attributes and plant–water relation parameters. The ameliorative effect of exogenously applied trehalose was also observed on the activities of some key antioxidant enzymes (POD and CAT) and non‐enzymatic compounds (tocopherols and phenolics). Overall, exogenously applied trehalose considerably improved drought tolerance of maize plants by up‐regulating photosynthetic and water relation attributes as well as antioxidant defence mechanism.     

Evaluation of genetic diversity of Aegilops tauschii accessions using morphological characters

A collection of sixty-three accessions of Ae. tauschii belonging to different eco-geographical regions were used to evaluate its genetic diversity by 15 morphological characters. The data recorded were analyzed on all accessions using multivariate analyses. Principal component analysis (PCA) indicated that first six principal components with eigenvalues more than 1 explained 77.2% of the variability amongst accessions. Through cluster analysis according to Euclidian distance and UPGMA method, accessions divided into three groups. Knowledge of genetic diversity in Aegilops species provides different levels of information which is important in the management of germplasm resources.     

Salt‐Induced Regulation of Some Key Antioxidant Enzymes and Physio‐Biochemical Phenomena in Five Diverse Cultivars of Turnip (Brassica rapa L.)

A greenhouse experiment was carried out to examine the differential morpho‐physiological responses of five cultivars of turnip (Brassica rapa L.) to salt stress. Five diverse cultivars of turnip (shaljum desi surakh, shaljum purple top, shaljum golden bal, neela shaljum, and peela shaljum) were subjected for 6 weeks to varying levels of NaCl, i.e. 0, 80 and 160 mm in Hoagland’s nutrient solution in sand culture. Imposition of varying levels of salt substantially decreased shoot and root fresh and dry weights, chlorophyll contents, leaf osmotic potential, relative water contents, different gas exchange attributes, total phenolics, malondialdehyde, activities of superoxide dismutase, peroxidase catalase, and leaf and root K⁺ levels while enhanced the proline contents, membrane permeability, level of H₂O₂, leaf and root Na⁺ and Cl^? and leaf Ca²⁺ in all turnip cultivars under study. Of all cultivars, peela shaljum and neela shaljum were consistently higher in their growth than the other turnip cultivars at all salt concentrations of the growth medium. Photosynthetic capacity (A) and stomatal conductance (g_s) were higher in high biomass‐producing cultivars, i.e. peela shaljum and neela shaljum, which provide to be potential selection criteria of salt tolerance in turnip. However, the regulation of antioxidant system was cultivar‐specific under saline conditions.     

Changes in Hormonal Balance: A Possible Mechanism of Pre‐Sowing Chilling‐Induced Salt Tolerance in Spring Wheat

There is a lack of knowledge about factors contributing to the chilling‐induced alleviatory effects on growth of plants under salt stress. Thus, the primary objective of the study was to determine whether chilling‐induced changes in endogenous hormones, ionic partitioning within shoots and roots and/or gaseous exchange characteristics is involved in salt tolerance of two genetically diverses of wheat crops. For this purpose, the seeds of two spring wheat (Triticum aestivum) cultivars, MH‐97 (salt intolerant) and Inqlab‐91 (salt tolerant) were chilled at 3°C for 2 weeks. The chilled, hydroprimed and non‐primed (control) seeds of the two wheat cultivars were sown in both Petri dishes in a growth room and in the field after treatment with 15 dS m^?1 NaCl salinity. Chilling was very effective in increasing germination rate and subsequent growth when compared with hydropriming and control under salt stress. Results from field experiments clearly indicated the efficacy of chilling over hydropriming in improving shoot dry biomass and grain yield in either cultivar, particularly under salt stress. This increase in growth and yield was related to increased net photosynthetic rate, greater potential to uptake and accumulate the beneficial mineral elements (K⁺ and Ca²⁺) in the roots and reduced uptake and accumulation of toxic mineral element (Na⁺) in the shoots of both wheat cultivars when grown under salt stress. Salt‐stressed plants of both wheat cultivars raised from chilled seed had greater concentrations of indoleacetic acid, abscisic acid, salicylic acid and spermine when compared with hydropriming and control. Therefore, induction of salt tolerance by pre‐sowing chilling treatment in wheat could be attributed to its beneficial effects on ionic homeostasis and hormonal balance. The results presented are also helpful to understand the chilling‐induced cross adaptation of plants in natural environments. Moreover, efficacy of pre‐sowing chilling treatment over hydropriming suggested its commercial utilization as a low risk priming treatment for better wheat crop production under stressful environments.     

小麦茎秆木质素代谢及其与抗倒性的关系

以抗倒性不同的6个小麦品种为材料,观测了茎秆基部第二节间的木质素含量及苯丙氨酸转氨酶(PAL)、酪氨酸解氨酶(TAL)、肉桂醇脱氢酶(CAD)和4-香豆酸: CoA连接酶(4CL)活性以及不同时期茎秆抗折力和倒伏指数的变化,探讨木质素含量与抗倒伏能力的关系。不同小麦品种的茎秆木质素含量存在明显差异。茎秆抗折力大、倒伏指数小的品种(济麦20和济麦22),其茎秆木质素含量高,PAL、TAL、CAD和4CL活性强。相关分析表明,茎秆木质素含量与实际倒伏率呈显著负相关(r = -0.83, P<0.05);与抗折力呈显著正相关(r = 0.86, P<0.05);PAL、TAL和CAD活性与木质素含量呈显著正相关(r =0.78, 0.77, 0.85, P<0.05),4CL活性与木质素含量呈不显著正相关(r =0.39, P>0.05)。研究表明,较高的PAL和CAD活性是木质素含量高的酶学基础,茎秆木质素含量可作为小麦品种抗倒伏性评价的一个重要指标。     

叶籽银杏GbMADS5基因的克隆与序列分析

MADS-box基因是一类编码转录因子的基因大家族,在植物的发育过程中具有重要作用。本研究采用RT-PCR技术从叶籽银杏（Ginkgo biloba var.epiphylla Mak.）中克隆了MADS-box基因GbMADS5。序列分析表明,该基因编码区全长为666bp,含有一个完整的开放阅读框,编码221个氨基酸残基组成的蛋白质,具有典型的植物MADS-box基因结构,编码肽链包含了MADS区、I区、K区和C末端,但该基因不具有拟南芥（Arabidopsis thaliana）AG基因的N端区域。GbMADS5基因编码的蛋白序列与其它植物的MADS-box蛋白序列有着较高的一致性,与裸子植物（Gymnospermae）的AG基因相似性最高,其中与苏铁（Cycas revolute）的同源性高达91.07%。系统发育树分析显示,GbMADS5基因属于AG亚家族基因。     

Genetic mapping of bph20(t) and bph21(t) loci conferring brown planthopper resistance to Nilaparvata lugens St?l in rice (Oryza sativa L.)

Brown planthopper(BPH) is one of the most serious and destructive insect pests of rice in most rice growing regions of the world. In this study, two major resistance genes against BPH have been identified in an Oryza rufipogon (Griff.) introgression rice line, RBPH54. Inheritance of the BPH resistance in RBPH54 was studied by screening the resistance in parents, F1, F2 and BC1 generations against BPH biotype 2. A population of BC3F2 lines was developed and SSR markers were employed for the gene mapping, and new markers were designed for fine mapping of the resistance genes, while sequence information of BAC/PAC clones was used to construct physical maps of the genes. The results showed that the BPH resistance in RBPH54 was governed by recessive alleles at two loci, tentatively designated as bph20(t) and bph21(t). The locus bph20(t) was fine mapped to the short arm of chromosome 6 about 2.7 cM to the upper marker RM435 and 2.5 cM to lower marker RM540 and in a 2.5 cM region flanked by two new SSR markers BYL7 and BYL8 which were developed in the present study. The other BPH resistance locus bph21(t) was initially mapped to a region 7.9 cM to upper marker RM222 and 4.0 cM to lower marker RM244 on the short arm of chromosome 10. For physical mapping, the bph20(t)-linked markers were landed on BAC/PAC clones of the reference cv., Nipponbare, released by the International Rice Genome Sequencing Project. The bph20(t) locus was physically defined to an interval of about 75 kb with clone P0514G1. Identification and location of these two genes in the present study have diversified the BPH resistance gene pool, which give benefit to the development of resistant rice cultivars, and the linkage PCR-based SSR markers for the bph20(t) and bph21(t) genes would help realize the application of the genes in rice breeding through marker-assisted selection.     

Tortuosity Analysis under the Unsaturated Flow Framework

Eurasian Soil Science - In this study, we developed a general mathematical relationship to determine hydraulic tortuosity. An optimization code was run in MATLAB R2014a software, using Monte Carlo...     

Genetic Analysis of Egyptian Date (<Emphasis Type="Italic">Phoenix dactylifera</Emphasis> L.) Accessions Using AFLP Markers

Forty-seven samples of date palm (Phoenix dactylifera L.) collected from eight locations in Egypt were studied using four sets of amplified fragment length polymorphism (AFLP) markers with near infrared fluorescence labeled primers. These samples belonged to 21 named accessions and 9 of unknown pedigrees. A total of 350 bands were scored and 233 (66.6%) were polymorphic. Twenty-seven Egyptian accessions and ‘Medjool’and ‘Deglet Noor’accessions from California could beclassified into the major cluster. This major cluster may represent a major group of date palm germplasm in North Africa. There were four other clusters, each containing one or two accessions. The variety ‘Halawy’and one accession of unknown provenance were most likely from hybridization between two clusters. Six groups of accessions of which had the same names, revealed similar but not identical AFLP profiles suggesting these accessions might derive from seedlings rather thanthrough clonal offshoot propagation.