Diversity of root-knot nematodes in Moroccan olive nurseries and orchards: does <Emphasis Type="Italic">Meloidogyne javanica</Emphasis> disperse according to invasion processes?

Background

Root-knot nematodes (RKN) are major pest of olive tree (Olea europaea ssp. europaea), especially in nurseries and high-density orchards. Soil samples were collected from main olive growing areas of Morocco, to characterize Meloidogyne species and to discuss the contribution of biotic and abiotic factors in their spatial distribution.

Results

RKN were found in 159 soil samples out of 305 from nurseries (52.1% occurrence) and in 11 out of 49 soil samples from orchards (23.2% occurrence). Biochemical and molecular characterisation (PAGE esterase and SCAR) revealed the dominance of M. javanica both in nurseries and orchards with minor presence of M. incognita only in nurseries, and M. arenaria in only one nursery. RKN were distributed on aggregated basis. Frequent presence of M. javanica in orchards might have come from nurseries. In contrast, the detection of M. incognita in nurseries alone suggests that this species could not reproduce in orchards because of either the competition with other plant-parasitic nematodes or unfit local habitats. The impact of environmental variables (climate, habitat origin and physicochemical characteristics of the substrates) on the distribution of Meloidogyne species is also discussed.

Conclusion

Olive nurseries in Morocco are not able to guarantee the safety of rooted plants. As a result, olive production systems are exposed to strong RKN invasion risks. Consequently, the use of healthy substrates in nurseries may prevent plant-parasitic nematode induction in orchards.

     

High water content silk protein-based hydrogels with tunable elasticity fabricated via a Ru(II) mediated photochemical cross-linking method

Silk is very promising in the field of biomaterials as a natural biomacromolecule. Silk protein can be made into various forms of materials, including hydrogels. However, silk protein-based hydrogels have not attracted much attention due to its weak mechanical properties. Here, we report high water content silk protein-based hydrogels with tunable elasticity which were fabricated through Ru(II) mediated photochemically cross-linking tyrosine residues in regenerated silk protein. The regenerated silk protein was characterized by Fourier transform infrared spectroscopy (FTIR). The gelation kinetics of the silk protein was studied by rheology measurements. The compressive mechanical properties of the silk protein-based hydrogels was investigated using compressive tests and dynamic mechanical analysis (DMA). Compressive modulus of the hydrogels reached 349±64 MPa at 15 % strain. The fabricated silk protein-based hydrogels were also characterized by Scanning electron microscopy (SEM), revealing an interconnected porous network structure, typical of hydrogels, with an average pore size of approximately 130 μm. Finally, biocompatibility of the silk protein-based hydrogels was demonstrated through cell culture studies using a human fibroblast cell line, HFL1. The reported silk protein-based hydrogels represent a promising candidate for biomaterial applications.     

Nano-calcium carbonate reinforced polypropylene and propylene-ethylene copolymer nanocomposites: Tensile vs. impact behavior

Improvement of both the tensile and impact strength of the same polymeric material has always been a great challenge for the plastic industry. The study focuses on the effect of incorporation of calcium carbonate nanoparticles (0.3 wt% to 15 wt%) into three polypropylene (PP) based matrices viz. PP homopolymer, propylene-ethylene (PP-PE) copolymer and the blend of PP:PP-PE (30:70) to improve their impact behavior without hampering the tensile strength much. A loss in both the tensile and impact properties was observed in PP based nanocomposite. However, PP-PE based nanocomposites showed a significant improvement in impact strength (47 %) at 10 wt% loading with a loss of tensile strength by 22 %. To minimize this loss a blend of PP:PP-PE (30:70) was explored as a matrix. At 10 wt% loading, this matrix showed an improvement of 30 % in impact strength whereas the tensile loss was minimized to 10 %. Further, silane coupling agent which promoted good interfacial adhesion was used for best compositions. The variation of crystalline morphology of the nanocomposites with various formulations was analyzed using differential scanning calorimetry and X-ray diffraction.     

信鸽新城疫并发大肠杆菌病的诊治

鸽新城疫又称鸽瘟或鸽Ⅰ型副粘病毒病 ,是由鸽Ⅰ型副粘病毒引起的一种高度接触性、败血型传染病。主要表现为腹泻、神经紊乱、呼吸困难及浆膜、粘膜出血等 ;鸽大肠杆菌病是由大肠埃希氏杆菌感染所引起的局部或全身性感染的疾病。若新城疫和大肠杆菌并发 ,将给养鸽爱好者以很大的经济损失和精神打击。现将本人在临床上遇到的两起病例介绍给大家 ,以供参考。1发病情况2003年5月初 ,平顶山市郊西信鸽爱好者相继到我中心 ,叙述了其200多只信鸽参赛后大群出现拉稀、精神不振 ,个别眼流泪 ,有神经症状 ,用氟哌酸、阿莫西林、痢特灵、氯霉素治疗 ,…     

水稻条纹病毒在玉米和水稻上流行差异分析

为了明确水稻条纹病毒(RSV)在水稻和玉米上发生程度差异明显的原因,从一个侧面了解RSV流行本质,2004年在洪泽进行田间试验。采用黄盘诱集、盘扑、盘刮、肉眼计数等方法比较武育粳3号和掖单13上灰飞虱侵入和消长动态,结果表明两者均只有一个成虫侵入高峰,单位面积迁入虫量前者是后者的3.6倍,单株平均虫量相近。Dot-ELISA法测定灰飞虱带毒率为40%,成虫迁移扩散高峰期22d内两者接毒量约为每天百株137头带毒虫。武育粳3号有二代若虫发生,掖单13则无。逐日调查发病进程,结果显示水稻发病率为60%,玉米为0。室内抗性鉴定,掖单13对RSV的抗性比武育粳3号高4个级别。综合以上结果,寄主品种抗性决定了RSV在水稻和玉米上流行状况,二代若虫重复侵染是RSV在水稻上重发的另一主要原因。     

氮肥水平对油菜史力丰生育特性的影响

油菜品种史力丰苗期生长量较小,春后生长速度较快,春发势强。增施氮肥能显著提高史力丰光合面积、光合强度、干物质积累速度以及单位角果皮面积生产力。随着施氮量的增加,史力丰每亩角果数、千粒重增幅较大,但每角粒数变化不明显,高产栽培应主攻每角粒数。     

放牧对鸭茅能量积累及分配的影响

通过长期放牧试验，探讨了不同放牧强度下亚热带高山草地鸭茅种群能量积累规律及能量在不同构件之间的分配特征。在无放牧的对照草地及采食率分别为55％、65％、80％的放牧草地，鸭茅热值随放牧强度的增加而呈单峰曲线型变化，一定强度范围内的放牧干扰提高了鸭茅热值及能量的积累；根部能量的积累随放牧强度的提高而逐渐减少。在禁牧草地，鸭茅种群能量主要被低密度的大分蘖丛所分摊，随着放牧强度的提高，种群能量则逐渐均摊给高密度的小分蘖丛。     

西昌地区郁金香箱式促成栽培引种试验

对从荷兰引进的3个不同颜色系列切花郁金香品种,进行箱式促成栽培的品比试验,并测定郁金香切花的主要丰产指标.结果表明,黄色品系中黄色阿普多美（Gloden Apeldoorn）,白色品系中公园聚会（Garden Party）,红色品系中三弦琴（Balalaka）表现佳.