Burrow characteristics of the co-existing sibling species Mus booduga and Mus terricolor and the genetic basis of adaptation to hypoxic/hypercapnic stress

Background  

We investigated the effects of energetic constraints on the breeding behaviour of male European treefrogs Hyla arborea and how calling males allocated additional energy supplied by feeding experiments.     

Natural silicates mixed with organic fertilizers enhance corn adaptation to salt stress and improve physical characteristics of sandy soil

Soil salinity is one of the major environmental constraints to crop productivity worldwide. Therefore, the development of cost-effective and environment-friendly techniques allowing increased crop productivity and soil fertility under saline conditions is rather urgent today. The objective of this investigation was to study the effects of mixtures containing natural silicates (analcite, bergmeal, and potassium silicate) and organic fertilizers (sapropel, peat) in corn (Zea mays L.). We specifically evaluated tolerance of corn to salinity stress and certain characteristics of saline soil (viz., redox potential, conductivity, and phytotoxicity) using a factorial pot experiment, modeling NaCl salinity levels of 0, 50, 100, 150, and 200 mM under greenhouse conditions. Growth, water balance, photosynthesis, catalase activity, and accumulation of nonenzymatic antioxidants (flavonoids and anthocyanins) were measured and evaluated. Salinity stress reduced shoot and root biomass by 8–49%, photosynthetic pigment content in leaves by 15–30%, deteriorated water balance, and activated nonspecific adaptive reactions (i.e., accumulation of enzymatic and nonenzymatic antioxidants) in the corn seedlings. All the tested silicon-containing mixtures stimulated corn seedling resistance to salt stress and reduced soil phytotoxicity. This was reflected in the stimulation of growth of the corn seedlings (accumulation of shoot biomass, and formation and growth of lateral roots). The content of photosynthetic pigments, flavonoids, anthocyanins, catalase activity increased 1.3–2 times compared with plants that received NaCl only. The difference between treatments and control was most pronounced at moderate levels of salinity (100–150 mM). The mixture containing silicon minerals and sapropel (9:1 proportion) showed the highest protective effect against salinity stress.     

共生菌毒素对亚洲玉米螟和玉米小斑菌杀虫抑菌活性的测定

利用从全国采集的土样中收集到的28个品系的昆虫病原线虫,分离并筛选出28株高毒力共生菌菌株,对高毒力菌株的杀虫毒素进行初步提取,并以亚洲玉米螟和玉米小斑菌作为供试昆虫和供试真菌,对其杀虫抑菌活性进行测定。结果表明：共生菌毒素对两种病虫害均有一定的胃毒活性和抑菌作用,其中菌株5-5B毒素的杀虫抑菌活性最为明显,处理后120 h对亚洲玉米螟的平均校正死亡率为43.70%,抑菌圈直径为34.00 mm。     

Understanding the genetic basis of rice heterosis:Advances and prospects

Heterosis, which describes the superior vigor and yield of F1 hybrids with respect to their parents, is observed in many rice hybrid crosses. The exploitation o...     

The occurrence of Fusarium species and mycotoxins in Kenyan wheat

Freshly harvested wheat grain samples were collected during the 2004 growing season to determine the presence of head blight-causing Fusarium species. Fungal contamination was determined by isolation on agar media, while mycotoxin analysis was by direct competitive enzyme-linked immunosorbent assay (ELISA). The wheat grain samples were highly contaminated with fungi, especially Epicoccum, Alternaria and Fusarium species. The mean Fusarium infection rate varied from 13% to 18%, with the major head blight-causing species being Fusarium poae, Fusarium graminearum, Fusarium equiseti and Fusarium avenaceum. F. graminearum isolates were found to be highly virulent (79% disease severity) and significantly reduced kernel weight. Most grain samples were contaminated with mycotoxins, with a mean incidence rate of up to 75% for deoxynivalenol (DON) and 86% for T-2 toxin. Other mycotoxins detected were zearalenone and aflatoxin B1. Co-occurrence of DON, T-2 toxin and zearalenone was found in up to 35% of the samples. The results suggested the presence of Fusarium head blight and associated mycotoxins in Kenya. The presence of several mycotoxins, even at such low levels, could pose chronic adverse health effects to human and livestock fed on the contaminated wheat products.     

玉米弯孢菌叶斑病菌拮抗链霉菌的分离及鉴定

从吉林省图们市地区土壤中分离得到1株对玉米弯孢菌叶斑病(CurvularialunataWaker)有拮抗作用的链霉菌菌株。研究其拮抗性表明,对革兰氏阴性菌、革兰氏阳性菌和多种病源真菌都有拮抗作用。根据形态特征、培养特征、生理生化特性及16SrDNA序列等方面的多项分类研究,确定其属于链霉菌属,并被命名为StreptomycestumenensisBPS2。该菌株在大多数培养基上生长良好,基内菌丝无横隔,不断裂,气生菌丝体形成孢子链,孢子丝呈波曲或直形。     

Screening of Natural Plant Volatiles to Control the Potato ( Solanum tuberosum ) Pathogens Helminthosporium solani , Fusarium solani , Phoma foveata and Rhizoctonia solani

The potential utility of natural volatiles in various essential oils (EOs) from plants as fumigants to control potato tuber (Solanum tuberosum L.) pathogens was assessed. The antifungal effects of the volatiles at various concentrations were studied at 10 °C both in vitro using conidial suspensions of Helminthosporium solani, Fusarium solani var. coeruleum and Phoma foveata plated on agar, and in vivo by inoculating potato tubers. The effects of the volatiles on the mycelial growth of Rhizoctonia solani were also studied, but only in vitro. Vapours of many of the EOs tested exhibited some fungicidal activity but volatiles of garlic, Allium sativum, were, with few exceptions, most effective on all four pathogens in all experiments. An exposure time of at least 2 weeks was usually required for good control of disease development in vivo. Vapours of A. sativum never stimulated conidial germination, as was observed with some other oils, or damaged tubers, but those of Armoracia rusticana caused tuber collapse. Volatiles from thyme (Thymus vulgaris) EO showed antifungal activity in vitro on all four pathogens, but did not control F. solani, P. foveata or H. solani in vivo. In contrast, sage (Salvia officinalis) EO was ineffective against P. foveata and H. solani in the in vitro system, but controlled disease development in vivo at similar doses. The sometimes conflicting results obtained in the two test systems show that screening in vitro only is insufficient for evaluation of potent antifungal substances to be used in practice.     

玉米自交系抗粗缩病特性的遗传基础及轮回选择效应研究

通过定向轮回选择对玉米自交系进行抗粗缩病特性改良,不仅能提高玉米自交系的抗病性,也随之提高了其组成杂交种的抗性水平。玉米抗粗缩病的性状为数量性状,由微效多基因所控制。一般自交系的抗病基因都不太纯合,这是抗病改良的基础。对自交系进行定向轮选的过程,是微效抗病基因向个体集中和量值增加的过程。     

防治眼菌蚊Bt.菌株的筛选与培养条件优化

通过11株Bt.菌株对平菇厉眼蕈蚊3龄幼虫的室内毒力测定试验,得出91019菌株对平菇厉眼蕈蚊3龄幼虫有较高的毒力效果,其发酵原液和250倍稀释液对平菇厉眼蕈蚊3龄幼虫的校正死亡率分别达到93.10%和82.76%。通过正交试验对91019菌株的各培养条件进行优化,得出理论最佳培养基组分及培养条件为:玉米粉1.0%、黄豆饼粉2.5%、酵母粉2.0%、鱼粉2.0%、蛋白胨0.4%,KH2PO4 0.5 g/L,CaCO3 4.0 g/L,MgSO4.7H2O0.5 g/L,ZnSO4.7H2O 0.02 g/L;接种量2.0%、pH7.0、装液量25 mL、培养温度25℃。     

檀香炭疽病病原鉴定及其生物学特性研究

针对海南省近几年来趋重发生的檀香炭疽病,通过对该病病原进行形态学观察,致病性测定及r DNAITS序列分析,并研究病原菌生物学特性。结果表明,檀香炭疽病病原为Colletotrichum fructicola,该菌菌丝及分生孢子均能在10~35℃条件下生长,且菌丝最适生长温度及分生孢子最适萌发温度为30℃。该菌菌丝生长能适应的p H值范围为4.0~11.0,最适p H值为6.0,分生孢子萌发p H范围为4.0~11.0,最适萌发p H为5.0,光照条件下最有利于菌丝的生长,而黑暗条件下有利于分生孢子的萌发。该病病原菌在以蔗糖、可溶性淀粉为碳源的培养基上生长较好,在以蛋白胨、尿素、酵母膏浸粉、硫酸铵为氮源的培养基上生长较好。     

昆虫病原线虫共生菌对小麦根腐病菌和小麦赤霉病菌的抑菌活性

为探索小麦根腐病和小麦赤霉病可持续控制的有效生防途径,以小麦根腐病菌和小麦赤霉病菌作为供试真菌,评价了昆虫病原线虫共生菌及其毒素的抑菌活性,并对高毒力菌株抗逆性进行了初探。结果表明,供试的28个昆虫病原线虫共生菌发酵液和毒素均有一定的抑菌活性,其中,高毒力共生菌菌株SY5发酵液和毒素对小麦根腐病菌的抑菌率分别为56.05%和67.41%,对小麦赤霉病菌的抑菌率分别为82.41%和83.32%;菌株SY5发酵液经50℃处理60 min及18 W紫外灯照射120 min后对小麦根腐病菌的抑菌率无明显变化,但对小麦赤霉病菌的抑菌率有所下降;常温保存150 d,抑菌活性略有下降。说明共生菌菌株SY5对小麦根腐病菌和小麦赤霉病菌抑菌活性显著,且具有一定的抗逆性,极具应用潜力。     

Growth, photosynthesis and root reserpine concentrations of two Rauvolfia species in response to a light gradient

Growth and secondary metabolites responses to light environment can be useful measurements to determine favourable habitat conditions for the cultivation and conservation of medicinal plants. We analyzed the growth, photosynthesis and root reserpine concentrations in seedlings of Rauvolfia vomitoria Afzel and Rauvolfia verticillatae (Lour.) Baill, two important medicinal plants yielding anti-hypertension alkaloids, at four different light levels (20%, 52%, 75% and 100% of full sunlight) in a shade house. Across all light intensities, seedlings of R. vomitoria grew faster with higher relative growth rate (RGR) than R. verticillatae, attributed to its higher photosynthetic capacities (light-saturated photosynthetic rate, A_max) and leaf area ratio (LAR). Typical shade-sun morphological responses to increasing light levels included decreased specific leaf area and LAR, whereas RGR and A_max was highest at median light levels for both species. R. vomitoria allocated higher leaf mass fraction and fine-root mass fraction, similar coarse root mass fraction, but lower stem biomass fraction than R. verticillatae. For fine roots, R. vomitoria had greater specific root length and small diameter than R. verticillatae, indicating its higher resource (water and nutrition) capture abilities. Both species had higher nitrogen concentration and lower reserpine concentration in fine roots than those of coarse roots. Neither reserpine concentration nor nitrogen was affected by light intensities. The reserpine concentration in coarse roots of R. vomitoria increased, whereas that of R. verticillatae decreased with increasing irradiance. Although not significantly, reserpine concentrations in coarse roots were positively correlated with A_max and RGR for both species across all light intensities. Shade or photosynthesis inhibition apparently did not increase alkaloid synthesis, which contrasted with the carbon/nutrient balance theory of plant defense. These results suggested that R. vomitoria and R. verticillatae could attain high biomass and yield of reserpine in high-light habitats (with max. in 75% sunlight), and intermediate-light habitats (with max. in 25–52% sunlight), respectively.     

共生菌对两种玉米病虫害杀虫抑菌活性的测定

利用40株昆虫病原线虫共生菌菌株,以亚洲玉米螟和玉米小斑病菌作为供试昆虫和供试真菌,对其杀虫抑菌活性进行测定。结果表明,共生菌发酵液对两种病虫害均有一定的活性。其中菌株A24-2的杀虫抑菌活性最为明显,处理后120h对亚洲玉米螟的平均校正死亡率为44.25%,抑菌圈大小为15.00mm。     

创制转Mad1基因球孢白僵菌工程菌株提高对玉米螟毒力

克隆来源于生防真菌绿僵菌的黏着蛋白基因Mad1,构建含玉米瘤黑粉菌热激蛋白启动子hsp70和以抗萎锈灵基因carboxin为筛选标记的遗传转化载体上,利用PEG介导的原生质体转化法导入到受体球孢白僵菌菌株D1-5中,获得转化子,经继代培养及分子检测,获得遗传稳定的基因工程菌株。利用蝗虫后翅及洋葱表皮进行吸附试验进行工程菌株的生物学功能鉴定,结果表明,野生型和工程菌的分生孢子对于洋葱表皮的吸附量无明显差异,工程菌的分生孢子对蝗虫翅膀的吸附显著高于野生型,表明Mad1基因的导入能够增加球孢白僵菌对昆虫组织的吸附,对植物表皮组织不存在吸附能力。对亚洲玉米螟幼虫室内毒力测定结果表明,转化后的工程菌株致死中时间比野生型缩短34.07%,杀虫效率显著提高。     

Development and growth of two Lesquerella species grown under different temperatures during the reproductive period

The genus Lesquerella is a promising source of hydroxy fatty acids (HFA). Several species such as Lesquerella fendleri and Lesquerella mendocina are candidate crops for arid and semi-arid cropping systems. Several reports are available on the environmental effects on growth and yield in Lesquerella, but information on the effect of temperature on plant growth and development specifically during the reproductive period in Lesquerella is limited. The objective of this work was to determine the effect of two contrasting thermal regimes after flowering on time to maturity, plant growth and biomass allocation to the different organs in L. fendleri and L. mendocina. A greenhouse experiment was conducted with plants grown at a range of 11–23 °C during the vegetative phase. After this stage, 50% of the plants of each species remained under the same temperature regime until maturity, whereas the other 50% was transferred to another module subjected to a range of 17–31 °C until maturity. The duration of the reproductive phase was reduced by 23 days in plants of both species in the 17–31 °C treatment compared to those at 11–23 °C, although no differences were observed when the length of the reproductive phase was measured in thermal-time units. Total plant biomass for both species was 20% greater in the 11–23 °C treatment. In L. fendleri, this increment occurred due to more vegetative shoot biomass, whereas in L. mendocina it was associated with greater reproductive and root biomass. No changes in biomass allocation were produced by temperature in L. fendleri, while in L. mendocina the lower temperature regime increased allocation to the reproductive organs, at the expense of a lower allocation to vegetative shoot. These results could be used to predict the specific temperature effects after flowering on yield under field conditions, and suggest that L. mendocina might be a promising perennial alternative for cooler sites.     

Screening of different citrus rootstocks and citrus-related species for resistance to Phyllocnistis citrella (Lepidoptera: Gracillariidae)

Nine citrus-related species and 349 citrus rootstocks were evaluated under either field or laboratory conditions for resistance to the citrus leafminer, Phyllocnistis citrella (Stainton). Field results confirmed the widespread susceptibility of citrus to the leafminer. Only 0.9% of the trees checked during one growing season escaped damage by flushing once early in the season. Laboratory assays showed that differences among citrus rootstocks existed, but levels of resistance detected were not high enough to establish a breeding program. Contrary to these results, two citroids, Murraya koenigii (L.) Sprengel and Glycosmis pentaphylla (Retzius) Corrêa, exhibited antibiotic effects against first instar larvae and may provide a source of pest-resistance genes for breeders.     

Effects of temperature and light on the hatching of overwintering eggs in three Japanese Sympetrum species

The aim of the present study was to obtain quantitative information on egg hatching with respect to temperature and light to clarify the effect of cultivation methods on three Japanese Sympetrum species. Eggs of three Sympetrum species were collected on October 2005 at Akita prefecture located at north of Japan, and the eggs had been laid on soil surface of paddy field till April 2006. The eggs (3 trays with 50 eggs each) were held under four constant temperatures (8, 13, 18 and 23°C) with a photoperiod (L:D 14:10; relative light intensity 3,000 Lux) and 23°C in darkness. No S. infuscatum eggs, but 67 and 60% S. frequens and S. darwinianum hatched in constant darkness. This result suggests that S.frequens and S.darwinianum do not require light for hatching, but S.infuscatum requires light for hatching. Eggs of S. darwinianum and S. infuscatum did not hatch at 8°C. In S. frequens, some eggs hatched but the hatching rate was significantly lower at 8°C than at higher temperatures (P < 0.05). At higher temperatures, the hatching rate did not differ significantly for three Sympetrum species. At 13°C, S. infuscatum hatched fastest, 0.18 for S. infuscatum, 0.11 for S. darwinianum and 0.08 for S. frequens. The mean head width of second stadium larva of S. frequens, S. darwinianum and S. infuscatum were 0.4 ± 0.01, 0.4 ± 0.01 and 0.6 ± 0.01 mm (SD), respectively. These results suggest that S. infuscatum may have a competitive advantage over S. frequens and S. darwinianum under conditions that favor S. infuscatum through hatching speed.     

布氏潜蝇茧蜂和长尾潜蝇茧蜂的触角电位反应

测定了布氏潜蝇茧蜂[Fopius vandenboschi(Fullaway)]和长尾潜蝇茧蜂[Diachasmimorpha longicaudata(Ashmead)]这2种寄生蜂对寄主植物挥发物中主要的9种化合物的触角电位反应。结果表明:布氏潜蝇茧蜂雌雄成虫均对朱栾倍半萜反应最大,并且均对石竹烯反应最小。长尾潜蝇茧蜂雌虫对α-法呢烯反应最大,对柠檬烯反应最小;雄虫对反-2-癸烯醛反应最大,对β-紫罗兰酮和石竹烯反应最小。     

A review of the biology and control of selected weed species in the genus Oxalis: O. stricta L., O. latifolia H.B.K. and O. pes-caprae L.

This review considers the distribution, weed problems, biology and control of Oxalis stricta, O. latifolia and O. pes-caprae. The rhizomatous O. stricta is a persistent seed-producing weed which invades horticultural crops in North America. Chemical control is generally most effective in situations where soil-applied residual herbicides can be used; in turfgrass however, foliage-applied herbicides provide suppression only. O. latifolia is widely distributed in a range of annual and perennial crops growing in temperate and tropical locations. This pernicious perennial weed reproduces exclusively by asexual structures, underground bulbs, stolons and tubers. The complexities of the perennating system have rendered ineffective a wide range of herbicide families as a means of restricting the spread of O. latifolia. Similarly, cultural methods of control have not been successful. O. pes-caprae also grows and perennates from bulbs. This weed is essentially a problem in cereal crops in Southern Australia and Mediterranean fruit orchards. Cultural and chemical control difficulties and inadequacies are similar to those in O. latifolia. Future research strategies involving weed physiology, herbicide action and cultural control including biological control are discussed in relation to obtaining improved control methods for the selected Oxalis species.