Effect of various plant factors on the expression of creeping-rootedness in lucerne (Medicago sativa L. complex)

Although agronomically interesting, selection of creeping-rootedness inlucerne, that is, the ability to form adventitious shoots on horizontal,spreading roots, remains difficult because of the complex and still unclear geneticcontrol of this character, coupled with the possible occurrence of external factorsthat affect unpredictably its expression. Two experiments were undertaken onprogenies of creeping-rooted plants, to verify previous findings and inferences,and test novel hypotheses, concerning the effect of various plant factors on theexpression of creeping-rootedness. The ultimate aim was to provide information onthe most appropriate germplasm, procedures, or indirect selection criteria, that wouldimprove the efficiency of breeding for this character. The factors here examinedincluded genotype, age, kind of progeny, vigour, spreading ability, and undergroundmorphology. Some genotypes appeared to be good donors of the character, whereasothers did not. The proportion of creeping-rooted plants increased in allcases with the plant age. Selfing consistently depressed the expression ofthe character compared with clonal propagation or crossing. It is suggestedthat the effect of age and selfing on the penetrance of creeping-rootedness ismediated through their effect on plant vigour. Both aerial and root vigour showedindeed an effect per se on the presence of the character. Beside thevigour, possible indirect selection criteria were identified in the frequenciesof swollen zones and latent stem primordia on horizontal roots. Proportion ofcreeping-rooted plants in progenies after one year of growth appeared as a simple anduseful criterion to predict future trends. Consistent with previous conclusions, theresults provided evidence that a combination of family and individualselection may enhance the character expression.     

羊草草原枯枝落叶中能量特征 分析

在草原生态系统中，以枯枝落叶为主体的能量的输入，积累和释放，是能量流动的主要环节。每年因植物的枯死，转移到枯枝落叶的能量为３９４９．６７９ＫＪ．ｍ６２．ａ，其季节变化呈指数形式。现存枯枝落叶中贮存的能量为３４２４．１０ＫＪ．ｍ＾２，经１年分解后，残留在枯枝落叶的能量为２２８２．４３ＫＪ．ｍ＾２，释放出的能量为１１４１．６０ＫＪ．ｍ＾２，能量释放的季节动态呈Ｓ型曲线。     

包心菜无菌苗子叶及叶片原生质体高频分裂和高频植株再生

以包心菜子叶和叶片原生质体为材料。经不同液体培养基(Bp1,Bp2,B1)浅层培养,再生细胞高频分裂并形成愈伤组织。愈伤组织经扩增后转移到分化培养基上诱导植株分化,从这两种原生质体中获得了再生植株。在原生质体培养过程中,原生质体及细胞团的褐化程度与培养基中的有机成分的多少有关。原生质体的分化频率与培养基中植物激素种类关系甚大。在植株分化时,谷氨酰胺和腺嘌呤对植株分化有很大促进作用。另外,原生质体的来源及原生质体培养基对原生质体植株分化能力均有不同的影响。     

Effect of planting density of maize on the progress and spread of northern leaf blight fromExserohilum turcicum infested residue source

Effect of plant density (37,037, 44,444 and 55,555 plants/ha) on the increase of northern leaf blight in time and space on two maize cultivars planted at spacings of 90, 75 and 60 between rows and 30 cm within rows was investigated.Exserohilum turcicum infested maize residue was used as an inoculum source. Maize density did not significantly affect the disease indices, but significantly influenced the grain yield of the two cultivars. In contrast, the two cultivars differed significantly (P0.01) in disease severity, but not grain yield. Higher disease severities and grain yields were associated with higher plant densities, whereas the apparent infection rate was lower in higher plant density. Distance from the maize residue (inoculum source) significantly influenced disease severity. The percentage leaf area blighted, area under disease progress curve and disease progress curve intercept decreased with distance from the maize residue area, but the apparent infection rate on EV8429-SR appeared to increase with distance. Disease gradients (b) were higher in closely planted maize and flattened with time in one location only.     

Infection pressure of potato virus YN

Potato virus Y^N (PVY^N) infection was determined by the tobacco test in Swifterbant (Eastern Flevoland). In plots with beet, wheat and seed potatoes the infection exhibited an identical course. No differences were found either between PVY^N infection in the border and that in the middle of a field planted with ware potatoes, although infection pressure was clearly higher here than in the plot with seed potatoes. A barrier crop of 10 rows of wheat did not decrease the infection pressure of the virus.From August onwards, the spread of PVY^N in Lienden (Betuwe) was followed. Here virus transmission was found continuously, even until mid-November.Potato volunteers outside as well as in potato fields are serious infection sources. In 1976 and in 1977 virus spread was detected before the flight ofMyzus persicae, as determined with yellow Moericke traps. Infection pressure can be measured more efficiently by the tobacco test than by aphid trapping. The effect of rogueing at the time of virus spread should be reconsidered.If infection pressures in different areas or successive years are to be compared, the tobacco test should be standardized. A proposal to this effect is made.Samenvatting In Swifterbant (Oostelijk Flevoland) werd de infectie met het aardappel-Y^N-virus (PVY^N) bepaald met behulp van de tabakstoests. In percelen met bieten, tarwe en pootaardappelen bleek de infectie hetzelfde verloop te hebben. Tussen het infectieverloop van PVY^N in de rand en in het midden van een veld consumptieaardappelen werd eveneens geen verschil gevonden. Wel was de infectiedruk hier duidelijk hoger dan in het pootgoedperceel. Een barrier crop van 10 rijen tarwe verminderde de infectiedruk niet.De volgende conclusies kunnen worden getrokken. Aardappelopslag buiten en in aardappelvelden vormt een zeer belangrijke infectiebron. Zowel in 1976 als in 1977 vond de virusverspreiding plaats vóór de vlucht vanMyzus persicae begon, zoals deze werd bepaald met behulp van de gele Moericke vangbakken. Het effect van opzuiveren ten tijde van de virusverspreiding dient aan een nader onderzoek te worden onderworpen. De infectiedruk kan met de tabakstoets op meer directe wijze worden vastgesteld dan met bladluisvangsten mogelijk is.Wil men overgaan tot het vergelijken van de infectiedruk in verschillende gebieden of in verschillende jaren, dan dient de tabakstoets te worden gestandaardiseerd. Een voorstel hiertoe wordt gedaan.     

Toxicity of fenpropimorph to fenarimol-resistant isolates of Penicillium italicum

Fenarimol-resistant isolates ofPenicillium italicum with cross-resistance to imidazole and triazole fungicides which inhibit ergosterol biosynthesis were tested for their sensitivity to fenpropimorph. Radial growth tests on PDA showed that the isolates (n=6) lacked cross-resistance to fenpropimorph or displayed enhanced sensitivity to the fungicide (negatively correlated cross-resistance). Control of blue mold decay of oranges incited by the wild-type isolate could be achieved by dipping fruits in suspensions of fenpropimorph at a concentration of 100 mg ml^–1. Decay of oranges incited by the fenarimol-resistant isolates was controlled at the same or at a lower concentration (30 mg ml^–1), thus showing that the normal or increased sensitivity to fenpropimorph is also expressed under in vivo conditions.Samenvatting Fenarimol-resistente isolaten vanPenicillium italicum met kruisresistentie tegen imidazool-en triazoolfungiciden die de ergosterolbiosynthese remmen, werden getoetst op hun gevoeligheid voor fenpropimorf. Radiale groeiproeven op PDA toonden aan dat de isolaten (n=6) geen kruisresistentie bezaten met fenpropimorf of een verhoogde gevoeligheid voor het middel vertoonden (negatief gecorreleerde kruisresistentie). Op sinaasappels konPenicillium-rot, veroorzaakt door het wild-type bestreden worden door middel van een dompelbehandeling met fenpropimorf bij een dosering van 100 g ml^–1). Bestrijding van rot veroorzaakt door fenarimil-resistente isolaten werd verkregen bij dezelfde of een lagere dosering (30 g ml^–1); aldus werd aangetoond dat de normale of verhoogde gevoeligheid voor fenpropimorf ook in vivo tot uiting komt.     

Characterisation of energy-dependent efflux of imazalil and fenarimol in isolates of Penicillium italicum with a low,medium and high degree of resistance to DMI-fungicides

Differential accumulation of [¹⁴C]imazalil and [¹⁴C]fenarimol by germlings of wild-type and DMI-resistant isolates ofPenicillium italicum was studied at various pH values. At pH 7 and 8 the low-resistant isolate E_300–3 accumulated 22% and 35%, respectively, less imazalil than the wild-type isolate W₅. Imazalil accumulation at pH 5 and 6 was similar. Isolate E_300–3 also accumulated less fenarimol as compared with the wild-type isolate. This difference was much more obvious than for imazalil and was observed at all pH values tested. Differences in accumulation of both imazalil and fenarimol between low (E_300–3), medium (H₁₇) and high resistant (I₃₃) isolates were not observed. These results suggest that decreased accumulation of DMIs is responsible for a low level of resistance only and that additional mechanisms of resistance might operate in isolates with a medium and high degree of resistance. With all isolates fenarimol accumulation was energy-dependent. This was not obvious for imazalil.The wild-type and DMI-resistant isolates had a similar plasma membrane potential as determined with the probe [¹⁴C]tetraphenylphosphonium bromide ([¹⁴C]TPP⁺). Various test compounds, among which ATPase inhibitors, ionophoric antibiotics and calmodulin antagonists, affected the accumulation of [¹⁴C]TPP⁺, [¹⁴C]imazalil and [¹⁴C]fenarimol. No obvious correlation between the effects of the test compounds on accumulation levels of the fungicides and [¹⁴C]TPP⁺ could be observed. These results indicate that the plasma membrane potential does not mediate the efflux of DMI fungicides byP. italicum.     

以白菜为例的转基因植物环境安全性评价研究

以转除草剂抗性基因的白菜为例,通过对具体事实的展现和分析,介绍了关于转基因植物环境安全性评价的方法,以及目前国际上关于转基因作物的一些比较一致的结论。针对我国的农业生态环境,结合试验结果,讨论了获得的转基因白菜的环境安全性。     

浑善达克沙地植物蒸腾特征的研究

采用 L i-1 60 0型气孔仪测定了浑善达克沙地主要建群乡土植物种不同季节的蒸腾速率及其环境因子的日进程 ,结果表明 :浑善达克沙地中榆树、黄柳、圆叶桦、砂杞柳、羊草蒸腾速率的日变化均呈单峰曲线 ,而叉分蓼和楔叶茶子呈双峰曲线。同一种植物在不同样地土壤水分条件下 ,蒸腾速率不同。各植物种蒸腾速率的季节变化明显 ,7、8月份蒸腾速率高 ,6月份最低。各植物种中 ,黄柳为低蒸腾植物。回归分析表明 ,影响蒸腾速率最主要的因子为光照强度 ,其次为气温和空气相对湿度 ;蒸腾速率与各因子呈线性相关 ,其关系可用方程 Tr=a+b RH+c T+d Q表示。通过蒸腾速率的比较 ,提出了浑善达克沙地植被恢复应以建立“人工疏林草原”为主。     

Effects of phosphodiesterase inhibitor-induced insulin resistance on glucose and lipid metabolism in rats

AIM:To investigate the effects of milrinone (a selective phosphdiesterase III inhibitor PDE₃) on insulin secretion, blood glucose, plasma free fatty acids (FFA) and dose-response relationship, and assess possible effects of milrinone on glucose metabolism and insulin sensitivity in conscious rats.METHODS:The catheterized nonstressed rats were administered by the varying doses of milrinone (1, 5, 25 μmol/kg) and were compared with controls. A hyperinsulinaemic- euglycaemic clamp was established in awake rats, and milrinone(25 μmol/kg) and 25% dimethyl sulfoxide (DMSO, as a control) were given at 120 min during hyperinsulinaemic- euglycaemic clamp. Glucose turnover was decided by gas chromatograph mass spectrometer (GC-MS).RESULTS:After dosing, plasma FFA levels in 3 milrinone groups significantly increased compared with the controls and before dosing. The percentages of elevation of FFA by the different milrinone doses were very similar, 50%, 52%, 55% for 1, 5, 25 μmol/kg respectively at 2 min after dosing. Plasma insulin levels were significantly elevated in the 5 and 25 μmol/kg groups, and the effect of milrinone on glucose concentration was detectable only 25 μmol/kg group. During hyperinsulinaemic clamp, there were significant increase in plasma FFA (from 173.1±15.2 to 633.8±87.3 μEq/L) and hepatic glucose production (HGP), and a significant decrease in glucose infusion rates (GIR) (to about 21%).CONCLUSION:These data suggest that milrinone impaires the abilities of insulin to suppress lipolysis and HGP, and insulin-mediated glucose utilization in peripheral tissue. Therefore, milrinone administration may induce an acute insulin resistancein vivo.