Effect of Low Night Temperatures on Photosynthetic Activity of the Maize Seedlings (Zea mays L.)

Night chilling (5 °C) subsequently lowered photosynthetic intensity in the leaves of maize seedlings at 20 °C through an increase in leaf diffusive resistance brought on by lower tissue water content in morning hours. A more significant increase in leaf diffusion resistance was observed when soil temperature was lowered than in the case of lower air temperature.
The unfavorable effect of soil and air cooling temperature on photosynthesis was limited by air saturated with water vapour. However, as a result of lowering the night temperature from 5 °C to 1 °C, the efficiency of the protective influence of higher atmospheric humidity was decreased. This demonstrates that the participation of factors unrelated to plant water status in inhibiting photosynthesis increases with lower night temperatures.
An additional reason for inhibited photosynthesis following cool nights was a decrease in chlorophyll accumulation, below 50 μg per 1 cm² of leaf area.     

Studies on mutlispecific resistance of gastrointestinal nematodes to benzimidazoles on dairy-goat farms

Multispecific resistance to benzimidazoles was studied in three selected farms. These farms had bred dairy goats for more than 15 years. The helminths were introduced with the goats at the establishment of the farms which afterwards remained isolated. Nematode resistance could then be related to their own management practices. Faecal egg count tests and egg hatch assays were performed to assess intensity of resistance. The generic (infective larvae in faecal cultures) and specific richness (adult worms) were assessed. The resistant species were Trichostrongylus colubriformis, Teladorsagia circumcincta, Haemonchus contortus and Oesophagostomum venulosum. Faecal egg count reduction tests and egg-hatch assays did not match exactly. Faecal larval counts after treatments gave a distorted picture of multispecific resistance: Haemonchus and Oesophagostomum were very largely over represented. The number of species found in the three farms was relatively low compared with other reports in goat farms of the area. This reduction of diversity might also be due in part to characteristics of breeding management and history (use of permanent pasture and introduction of goats at the establishment of farm).     

酥梨采后灰霉病生防菌株的鉴定及抑菌作用

以微生物拮抗病原菌是防治病害安全高效的可行手段。通过对果实表面微生物进行筛选鉴定,以期得到一株可以有效抑制灰霉病的生物防治菌株。对拮抗菌株H-1进行形态学特征、生理生化特性分析,结合16S rDNA序列分析和gyrB 基因序列分析构建系统发育树;采用平板对峙法结合果实伤口试验考察拮抗菌H-1在体外及梨果表面的抑菌作用。结果表明：经鉴定H-I菌株为贝莱斯芽孢杆菌（Bacillus velezensis）;B. velezensis H-1在体外条件下可显著抑制灰葡萄孢霉（Botrytis cinerea）、细极链格孢（Alternaria tenuissima）和串珠镰孢菌（Fusarium verticillioides）的菌丝生长,其中对灰葡萄孢霉菌丝的抑制作用最强;果实伤口试验表明,1×1011 CFU/mL的B. velezensis H-1可完全抑制梨果表面灰霉菌生长。由此可见,B. velezensis H-1可以有效抑制梨果采后灰霉病的发生。     

Effects of straw and silicon soil amendments on some foliar and stem-base diseases in pot-grown winter wheat

Four foliar and two stem-base pathogens were inoculated onto wheat plants grown in different substrates in pot experiments. Soils from four different UK locations were each treated in three ways: (i) straw incorporated in the field at 10 t ha⁻¹ several months previously; (ii) silicon fertilization at 100 mg L⁻¹ during the experiment; and (iii) no amendments. A sand and vermiculite mix was used with and without silicon amendment. The silicon treatment increased plant silica concentrations in all experiments, but incorporating straw was not associated with raised plant silica concentrations. Blumeria graminis and Puccinia recondita were inoculated by shaking infected plants over the test plants, followed by suitable humid periods. The silicon treatment reduced powdery mildew ( B. graminis ) substantially in sand and vermiculite and in two of the soils, but there were no effects on the slight infection by brown rust ( P. recondita ). Phaeosphaeria nodorum and Mycosphaerella graminicola were inoculated as conidial suspensions. Leaf spot caused by P. nodorum was reduced in silicon-amended sand and vermiculite; soil was not tested. Symptoms of septoria leaf blotch caused by M. graminicola were reduced by silicon amendment in a severely infected sand and vermiculite experiment but not in soil or a slightly infected sand and vermiculite experiment. Oculimacula yallundae (eyespot) and Fusarium culmorum (brown foot rot) were inoculated as agar plugs on the stem base. Severity of O. yallundae was reduced by silicon amendment of two of the soils but not sand and vermiculite; brown foot rot symptoms caused by F. culmorum were unaffected by silicon amendment. The straw treatment reduced severity of powdery mildew but did not detectably affect the other pathogens. Both straw and silicon treatments appeared to increase plant resistance to all diseases only under high disease pressure.     

A mutation confers Monochoria vaginalis resistance to sulfonylureas that target acetolactate synthase

Acetolactate synthase (ALS) is the target enzyme for four distinct families of compounds: sulfonylureas (SUs), imidazolinones, triazolopyrimidine sulfonanilides, and pyrimidinyl oxybenzoates. We cloned and sequenced the fragments encoding ALS genes from biotypes of Monochoria vaginalis susceptible (S) and resistant (R) to SU-herbicides. The nucleotide sequences of the 39 bp Domain A region for R M. vaginalis biotype differed from that of the S biotype by a single nucleotide substitution at variable Pro codon of Domain A (CCT to TCT), predicting a Pro in the S but a Ser in the R biotype. No nucleotide differences between S and R M. vaginalis were observed in Domain D. We suggest that the amino acid substitution at Domain A region is responsible for resistance to SU-herbicides in M. vaginalis collected from Ushiku City, Ibaraki Prefecture, Japan.     

乌鲁木齐周边地区奶牛乳房炎沙门氏菌的分离鉴定及耐药性分析

为了解乌鲁木齐周边地区奶牛场奶牛乳房炎沙门氏菌的流行与耐药情况,本研究采集了5个牧场300份奶牛乳房炎奶样,进行沙门氏菌的分离、培养,利用荧光PCR方法鉴定,同时对分离出的阳性菌株采用纸片扩散法进行耐药性分析。结果表明：从奶牛乳房炎样品中分离出12株沙门氏菌,分离率4%;耐药性分析表明分离的沙门氏菌对氨苄西林、四环素、多西环素、链霉素耐药率超过50%,对氨曲南、诺氟沙星、多粘菌素B、头孢他啶敏感性大于70%。此外4株沙门氏菌分离株具有多重耐药性。本研究为本地区奶牛乳房炎的防治提供了依据。     

芽孢杆菌及其胞外多糖对空心菜和茼蒿Cd吸收及土壤团聚体的影响

本研究旨在探究产胞外多糖芽孢杆菌对蔬菜镉(Cd)积累及土壤结构的影响。采用以空心菜和茼蒿为供试材料的盆栽试验,研究了功能菌株Priestia megaterium YG35和Bacillus halodurans G20降低蔬菜吸收Cd的效果和可能作用机制。结果表明,与CK相比,菌株YG35、菌株G20及其胞外多糖处理显著增加空心菜和茼蒿可食用组织干质量(37.8%～115.1%),显著降低可食用组织Cd含量(21.9%～44.2%),并使茼蒿Cd含量(0.057～0.061 mg·kg^-1)达到安全可食用标准,显著降低根际土壤有效态Cd含量(3.7%～11.7%),显著(P<0.05)增加根际土壤多糖含量(35.9%～49.5%)和蔗糖酶活性(15.3%～28.4%),促进根际土壤团聚体向大粒径转化。研究表明,YG35和G20及其胞外多糖能降低蔬菜对Cd的吸收,促进蔬菜生长,改善土壤结构,具有在Cd污染土壤上实现蔬菜安全生产的应用潜力。     

纳米纤维素水凝胶的制备与表征及其对猪肉的保鲜作用

水凝胶因具有低毒性、高生物相容性和可降解性而常用于食品保鲜,但其机械性能和抗疲劳性有待提高。为了探究大豆种皮纳米纤维素对水凝胶机械性能和抗疲劳性的影响,并提高水凝胶的综合机械性能。因此,本研究通过-20 ℃低温循环冷冻-解冻法制备具有可拉伸、强韧、抗疲劳的聚乙烯醇/海藻酸钠/纳米纤维素水凝胶,探究水凝胶对猪肉货架期的影响。通过扫描电子显微镜、傅里叶红外变换光谱仪、X-射线衍射仪、热重仪和质构仪测定了水凝胶的理化性质和机械性能。研究结果表明,水凝胶内部单体之间以氢键和酯键交联,内部呈现多孔结构,断裂伸长率为230%、压缩强度为70 kPa、拉伸强度为17 kPa,经过多次循环拉伸仍具有良好的机械性能和较高的抗疲劳性。猪肉保鲜试验表明,水凝胶维持了猪肉色泽的稳定性,防止内部水分流失,并且将猪肉的保质期延长至10 d。因此,该水凝胶可用于食品包装以延长冷藏肉制品的保质期。同时,本研究为构建一种可拉伸、强韧、抗疲劳的多功能水凝胶提供了一种新的视角。     

耐热黄瓜新品种'津优4号'

‘津优４号’为耐热型黄瓜杂交种,夏季在３４～３６℃高温下可正常发育。对枯萎病、霜毒病、白粉病的抗性强,适合华北地区春露地及秋露地和越夏栽培。植株生长势强,春露地栽培产量可达７５ｔ／ｈｍ＾２。果实棒状,长３０ｃｍ左右,单瓜量１５０ｇ左右。商品性好,瓜色深绿,有光泽;瘤显著,密生白刺;果肉浅绿色,质脆,味甜,品质优。