不同磷水平下澳洲坚果幼苗根系分泌物的差异

以生土为基质,研究澳洲坚果幼苗在3个施磷水平下排根的产生量、根系有机酸的分泌及磷素利用情况。结果表明:随着施磷水平升高,排根产生量、排根及非排根酸性磷酸酶活性均呈现先升高后降低的趋势;澳洲坚果幼苗排根及非排根分泌的有机酸种类至少有7种,但在分泌总量上差异明显,柠檬酸是其中的主要成分;随着土壤中磷素水平的增加,排根及非排根中柠檬酸的分泌量呈现减少趋势。综上所述,磷胁迫降低了根系酸性磷酸酶的活性,却提高了柠檬酸的分泌量,可能是由于澳洲坚果幼苗根系及叶片中的磷素含量随施磷水平升高而升高的原因。     

水分胁迫下丛枝菌根真菌对澳洲坚果幼苗磷利用效率的影响

基于云南热区澳洲坚果种植区季节性干旱及先天性低有效磷的土壤特征,探讨丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)接种对具有排根的引种作物-澳洲坚果幼苗磷利用的影响,为外来物种的本地驯化栽培提供理论依据。在正常水分与水分胁迫条件下,对盆栽的澳洲坚果幼苗分别接种土著丛枝菌根真菌(native arbuscular mycorrhizal fungi)和摩西球囊霉(Glomus mosseae),测定接种不同AMF对澳洲坚果幼苗生长、菌根定殖、酸性磷酸酶活性、柠檬酸分泌及磷素吸收等的影响。结果表明,接种土著AMF(N-AM)处理对澳洲坚果幼苗排根或非排根的侵染率显著高于接种摩西球囊霉(G-AM)处理,正常水分条件下N-AM处理的侵染率最高;两种水分条件下,接种AMF的植株地上部和地下部干重更高,正常水分处理下达到最大。菌根侵染率与排根产生量之间显著正相关,水分胁迫显著抑制了植株的排根产生量;与不接种相比,接种处理能显著提高排根产生量。接种AMF后根系对磷素的活化、吸收及转化能力显著升高,表现为接种的澳洲坚果幼苗根系、茎秆和叶片中全磷含量较高,两种水分条件下均表现为N-AM>G-AM>CK;菌根与排根相互协调共同发挥作用,显著改善了澳洲坚果幼苗根系对磷素的活化和吸收能力,且菌根比排根发挥了更大作用,尤其在水分胁迫条件下。两种AMF均能与澳洲坚果幼苗建立共生关系,N-AM处理的幼苗各指标显著优于G-AM处理,可能是由于拥有多样性优势的土著AMF在澳洲坚果幼苗根系中定殖能力较强或是AMF真菌对外来物种澳洲坚果有正反馈作用。     

不同供磷水平对火龙果幼苗生长及养分吸收的影响

火龙果是热带地区重要的经济作物,近年来种植规模不断扩大,然而关于火龙果对磷吸收以及响应规律的研究仍然极其匮乏。本研究以‘软枝大红’火龙果为材料,采用盆栽方式,分析不同施磷水平（0、25、50、100、200 mg/kg）下火龙果幼苗根系形态和养分吸收量的差异,探究火龙果幼苗生长适宜的磷供应浓度。结果表明：火龙果幼苗在供磷水平25 mg/kg和50 mg/kg,地上部生物量分别为37.1 g/株和36.2 g/株,显著高于其他处理;供磷水平未影响地上部磷和钾吸收,但当供磷水平在50 mg/kg时,氮吸收量显著高于供磷水平0、100和200 mg/kg处理;火龙果幼苗在供磷水平25 mg/kg和50 mg/kg,总根长分别为1068.8 cm和1069.6 cm,显著高于其他处理;供磷水平50 mg/kg的根表面积显著高于0 mg/kg和200 mg/kg处理;土壤碱解氮含量和总根长及根表面积呈显著负相关,表明供磷水平通过影响根系生长间接影响火龙果幼苗对氮素的吸收。综上所述,供磷水平在50 mg/kg可改善火龙果幼苗根系形态,促进幼苗对氮素吸收。     

局部施磷对橡胶树根系及植株生长的影响

采用盆栽分根试验，设计了5个局部施磷区比例，研究了局部等量施磷对橡胶树幼苗根系及植株生长的影响。结果表明：局部施磷区占盆栽土壤1/4以上时，可促进根系的发生，根系总长度及根系总表面积增加，但植株叶片磷含量及株高无显著影响；局部施磷区占盆栽土壤1/4以下时，根系数量、总长度、总表面积、生物量、叶片磷含量及株高均显著下降。     

基于玉米大豆轮作的黑土玉米农田酶活性对不同耕层厚度的响应

在重建不同厚度黑土层的定位模拟试验区开展免耕玉米大豆轮作试验,设置3个黑土耕层厚度,分别为10、20和30 cm,重点研究耕层厚度对玉米生育期内关键土壤酶活性的影响,分析乳熟期根际和非根际土壤的酶活性及其速效养分的差异。研究表明,不同生育期不同耕层厚度的玉米农田土壤脲酶活性变化差异不明显;土壤蔗糖酶活性变化差异显著;土壤磷酸酶活性在同一生长期不同耕层厚度差异明显,磷酸酶对耕层厚度的反应更为敏感。相同耕层厚度中不同土层深度间酶活性也有明显差异,0～10 cm土层的酶活性高于21～30 cm土层酶活性。乳熟期玉米根际土壤的脲酶、蔗糖酶、磷酸酶均在10 cm耕层厚度中活性最强。不同耕层厚度处理时,玉米农田土壤的根际土壤酶活性高于非根际土壤。30 cm耕层厚度速效氮含量根际土显著高于非根际土壤,有效磷含量无显著差异,根际土的速效钾含量均低于非根际土。     

丛枝菌根真菌对澳洲坚果幼苗的生长效应

将澳洲坚果种子进行表面消毒,并播种于盛装已灭菌珍珠岩的塑料育苗盒中,观察其幼苗期接种丛枝菌根真菌【Arbuscular Mycorhiza Fungi,AMF（CL.mosse）】对澳洲坚果幼苗生长效应的影响。试验结果表明,AMF对澳洲坚果幼苗的生长发育均有重要的促进作用。AMF 能促进澳洲坚果幼苗的生长及其幼苗叶片蛋白质及糖分的积累;能促进其根系磷酸酶的活性,磷酸酶活性与AMF侵染率存在显著相关性。接种AMF可增强澳洲坚果幼苗根系活力,促进其根系对N,P等矿质养分的吸收和积累,并促进澳洲坚果植株的光合作用,提高其幼苗     

利用根箱法解析大豆苗期氮磷吸收及其在根际分布的特征

应用根箱法对2种不同大豆基因型苗期的氮、磷吸收及其在根际分布进行比较研究.结果表明,高产品种北丰11单位根长及根表面积吸收的氮、磷量及植株体内的氮、磷含量均高于低产品系海9731,北丰11表现出较强的吸收养分能力.土壤有效氮、磷在根际的分布趋势不同,根际有效氮含量高于非根际,而有效磷含量则低于非根际,但全氮和全磷的含量无明显变化.不同基因型间,活化根际养分能力差异较大,北丰11在0-8 mm内的根际土壤有效氮、磷含量均高于海9731,这种差异的原因与2基因型根际pH值的差异有一定关系,北丰11根际pH较低.     

不同施磷水平对橡胶幼苗光合与生理代谢的影响

通过盆栽试验研究不同施磷水平对橡胶树幼苗叶片光合与代谢的影响,为橡胶幼龄胶园施肥量提供科学依据。以热研7-33-97嫁接苗为材料,设置5个施磷水平(不施磷为对照)对橡胶树幼苗叶片磷含量、光合作用和代谢特征的影响。结果发现：在土壤施磷水平为1 000 mg/kg时,可以保障橡胶幼苗的正常生长,同时增加光合速率和促进生理代谢;低浓度施磷水平(≤500 mg/kg)时,表现为施磷不足;高浓度施磷水平(≥2 000 mg/kg)对橡胶幼苗叶片光合和生理代谢造成抑制作用。     

燕麦不同磷效率品种苗期对不同磷源的利用研究

为了探究燕麦不同磷效率品种对有机磷的利用能力,选取磷高效品种燕科1号和磷低效品种MARION为供试材料,在土培盆栽条件下,设置植酸态磷(OP)、无机磷(KP)和不施磷(CK)三个磷处理,研究苗期不同磷处理对燕麦不同磷效率品种生物量、磷累积量、根际土壤酸性磷酸酶活性和土壤有效磷含量的影响。结果表明:(1)OP处理下,燕科1号和MARION的生物量较KP处理显著提高,分别提高70.4%、 9.4%;燕科1号的根冠比显著低于MARION。(2)与CK比较,OP处理可显著提高燕麦地上部、全株磷含量,但比KP处理磷含量低;在OP处理下,燕科1号地上部磷含量比MARION提高15.1%,全株磷含量比MARION降低8.6%。(3)与CK比较,OP处理可以提高燕麦根际土壤有效磷含量,但显著低于KP处理;相同处理下,燕科1号根际土壤有效磷含量均低于MARION。(4)两个燕麦品种在不同磷处理下,燕麦根际土壤酸性磷酸酶活性变化不同,燕科1号根际土壤酸性磷酸酶活性在KP和OP处理比CK分别提高35.2%、26.5%,差异均达到显著水平;MARION在KP和OP处理比CK分别降低4.4%、14.1%,OP与CK之间差异显著。磷高效品种燕科1号利用植酸态有机磷能力高于磷低效品种MARION。     

乙烯对低磷胁迫下大豆根形态和生理特性的影响

利用沙培方法研究了乙烯对磷胁迫下大豆幼苗的生理影响。结果表明:磷胁迫下大豆主根长度降低50%,侧根长度增加46%,侧根数目增加64%。缺磷时大豆根系磷含量降低,根系活力和根系组织酸性磷酸酶活性分别是全磷培养植株的1.2和1.3倍;与供磷植株相比,缺磷时大豆干物质累积量显著降低,缺磷主要抑制了地上部分干物质累积,而根系干物质累积几乎不变,根冠比增大。磷胁迫使大豆乙烯含量增加,但乙烯释放量被乙烯拮抗剂Co2+抑制。外源乙烯利抑制全磷大豆主根伸长,促进缺磷大豆侧根生长;乙烯拮抗剂Co2+逆转了低磷和乙烯对主根的抑制,减少侧根数目。乙烯利能够增加大豆幼苗根系活力和根系组织酸性磷酸酶活性,降低大豆生物量,增加根冠比,且磷胁迫时效果更为明显。     

Extreme resistance to infection by potato virus X in genotypes of wild tuber-bearingSolanum species

Summary Clones derived from thirty-one different accessions (nineteen of Argentine origin) belonging to eightSolanum species were screened for resistance to infection by potato virus X strain cp (PVX cp) by mechanical inoculation of plantlets that had been micropropagated in vitro. Estimates of PVX multiplication obtained by enzyme linked immunosorbent assay and slot blot nucleic acid hybridization allowed the identification of resistant clones derived from five accessions belonging toS. commersonii S. oplocense, S. sparsipilum andS. tuberosum andigena. Resistant genotypes supported PVX concentrations 5 to 15 times smaller than did the susceptible control cultivar Spunta. Graft inoculation test confirmed the presence of extreme resistance similar to that conferred by the ‘immunity’ gene X¹ (also called RX_act).     

Studies on natural repellents against potato tuber moth (Phthorimaea operculella Zeller) in country stores

Summary The effects of the leaves of five plant species, one from each of the generaAmbrosia, Anemone, Eupatorium, Eucalyptus andLantana, on potato tuber moth were investigated under indigenous storage conditions at the Central Potato Research Station, Shillong (1800 m above sea level). Their action was compared with that of a biological insecticide (spores ofBacillus thuringiensis), a chemical insecticide (carbaryl), and an untreated control. The data collected after six months storage on tuber damage, sprout damage and the rotting indicated that the leaves ofLantana aculeata provided most protection to the tubers, reducing damage from over 70% in the check to below 5%, and sprout damage from over 45% to below 3%. Next best wasEucalyptus globulus followed byB. thuringiensis. They may be used on tubers stored for table use or for seed as they had no adverse effect on germination or on the yield of a subsequent crop.     

先玉335、郑单958和京科968抗虫能力的比较研究

以先玉335、郑单958、京科968为材料,以玉米螟(Ostrinia furnacalis)、黏虫(Mythimna separata)和禾谷缢管蚜(Rhopalosiphum padi)为供试昆虫,探究玉米品系大喇叭口期对玉米螟和黏虫及抽雄期对禾谷缢管蚜抗性差异,测定其主要抗虫化合物丁布类物质的含量。结果发现,京科968对玉米螟及禾谷缢管蚜抗性均高于另外两个品系;对黏虫的抗性,郑单958和京科968高于先玉335。大喇叭口期京科968中丁布类物质含量最高,抽雄期郑单958和京科968中主要丁布成分含量均高于先玉335,上述组织中丁布合成相关基因在郑单958及京科968中的表达量也均高于先玉335。本研究揭示杂交玉米抗虫性与抗性相关化合物含量及其相关基因表达间存在正向相关关系,为抗虫玉米分子育种提供理论参考。     

Mineral composition of some traditional Mexican teas

Teas of plant origin traditionally consumed by the Mountain Pima of Chihuahua, Mexico, were analyzed for mineral nutritional content. Fe, Cu, Zn, Ca, and Mg composition was determined for native teas made from shoots ofTagetes lucida, T. filifolia, Elytraria imbricata, andHolodiscus dumosus, and from root xylem ofCeanothus depressus andPhaseolus ritensis. Native uses of these teas are also described.     

In vitro antimicrobial activity of different accessions ofSolanum commersonii Dun. from Uruguay

Summary The in vitro antimicrobial activity of extracts from accessions ofSolanum commersonii Dun. collected in the south of Uruguay was investigated against five microorganisms including the pathogenRalstonia solanacearum. A total of 30 extracts corresponding to organic and aqueous extracts were studied. Interestingly, most of the positive results for growth inhibition were againstR. solanacearum. The extracts were also analyzed for the presence of glycoalkaloids and lectins. Six of the ten aqueous extracts showed lectin presence and a wide variation in the type and amounts of glycoalkaloids, was found. Results indicate that there is no clear relationship between the antimicrobial activity against the five microorganisms screened and the presence or amounts of lectins and glycoalkaloids, traditionally regarded as possible antimicrobial metabolites in theSolanum genus, which indicates the presence of as yet unidentified antimicrobial compounds.     

Effect of a continuous hot water treatment of potato tubers on seed-borne fungal pathogens

Summary The viability of five pathogens was decreased by treatment with hot water when tested in vitro.Polyscytalum pustulans was most sensitive andRhizoctonia solani least sensitive. Potato tubers were exposed to 55°C for 5 min in a commercial continuous hot water treatment plant using naturally contaminated seed tubers and tubers which had been inoculated by dipping in comminuted cultures. The frequency of eyes colonised byP. pustulans, Helminthosporium solani, andR. solani was reduced to virtually zero and the effect persisted on tubers subsequently stored at 4°C and at 15°C for up to 16 wk. Results withColletotrichum coccodes were inconclusive. Treatment suppressedPenicillium spp. which, however, rapidly recolonised the eyes during storage, leading to higher contamination levels in the treated than in the untreated tubers. With tubers inoculated withPhoma foveata, good control was achieved when the incubation period before treatment was 10 d but not when the period was 42 d.     

Evaluation of fungicides to control Petri disease pathogens in the grapevine propagation process

The efficacy of fourteen selected fungicides against Phaeomoniella chlamydospora and Phaeoacremonium aleophilum was evaluated in vitro by mycelial growth and conidial germination assays. Azoxystrobin, carbendazim and tebuconazole were the most effective fungicides against P. chlamydospora, while carbendazim and didecyldimethylammonium chloride were the most effective against P. aleophilum. An assay was also conducted with cubiet, hydroxyquinoline sulphate and didecyldimethylammonium chloride to determine their potential to prevent infections caused by these pathogens during the hydration stage in grapevine propagation. The results of this experiment demonstrated that P. chlamydospora and P. aleophilum were able to infect healthy cuttings during the hydration stage and showed that didecyldimethylammonium chloride was consistently the best treatment as a disinfectant soak for grapevine cuttings. Additionally, semi-commercial trials were conducted in two grapevine nurseries to evaluate the effectiveness of several strategies with carbendazim, flusilazole and hydroxyquinoline sulphate at different nursery stages. Soaking planting material in carbendazim during the hydration stage was the most effective treatment since neither P. chlamydospora nor P. aleophilum were isolated from planting material in either nursery.     

Screening for resistance to early blight (Alternaria solani) in potato (Solanum tuberosum L.) using toxic metabolites produced by the fungus

Summary The phytotoxic components of the culture filtrate of the fungusAlternaria solani Sor, which causes early blight in potato, were used in this study to differentiate between resistant and susceptible genotypes selected to represent a range of reactions when screened in the field. Detached leaflet assays, using spores and toxic metabolites from the culture filtrate, were compared with field ratings and a whole-plant glasshouse test. Rank correlations between several detached leaflet tests were highly significant (P<0.01) but the correlations between these tests and the glasshouse and field tests were poor. The disease ratings obtained in the various tests were clustered into four groups and assigned to resistance classes. For many of the genotypes there was a good correspondence between resistance classes for all test methods. Divergent results between tests were associated with foliage maturity characteristics of the genotypes. Contribution no. 3879050 of the Lethbridge Research Station.     

Evaluation of diploid potato clones for resistance to tuber soft rot induced by strains ofErwinia carotovora subsp.atroseptica,E. carotovora subsp.carotovora andE. chrysanthemi

Summary Tubers of clones from a diploid hybrid population ofSolanum phureja andS. stenotomum were screened for resistance to tuber soft rot caused by strains ofErwinia carotovora subsp.atroseptica (Eca),E. carotovora subsp.carotovora (Ecc) andE. chrysanthemi (Ech). Significant, positive correlations between resistance to the different strains and species were observed, indicating that screening for resistance to tuber soft rot could be accomplished by using just one of the three pathogens. Strains of Ecc and Ech were found to be much more virulent than strains of Eca. Inoculating with Ecc and Ech resulted in more distinct differences among susceptible, moderately resistant and resistant clones than inoculating with Eca.     

B9601-Y2溶磷解钾固氮能力及促玉米生长效果研究

为了明确淀粉芽孢杆菌B9601-Y2(Y2)的促生长机制,通过摇瓶培养,检测其溶磷解钾固氮活性;通过盆栽试验,探索Y2对玉米生长量和溶磷解钾量的影响。结果表明,在第7天时,Y2固氮量为2.9 mg/L,解钾量为13.5μg/mL;在第4天时,溶磷量达732μg/mL。与空白对照相比,Y2发酵液能增加玉米株高28.29%,根长27.21%,叶宽18.56%,鲜重80.93%,干重66.67%;提高土壤中速效氮、速效磷和速效钾含量分别为20.42%、111.01%和17.24%,提高植株氮、磷、钾含量45.46%、120.17%、68.45%。研究结果表明,Y2活化土壤中难溶性磷、钾和具有固氮能力,并能促进植株对氮、磷、钾营养的吸收利用。