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71.
72.
Variation of Parthenium hysterophorus in response to soil quality: implications for invasiveness 总被引:1,自引:0,他引:1
Summary The performance of Parthenium hysterophorus , native to the tropical Americas and invasive to several countries, was evaluated for response to soil quality. Phenological (six stages) and quantitative growth variables [relative growth rates in height (Rh ) and diameter (Rd )] were measured every fortnight. Based on harvest data, the variables, root:shoot (R:S) ratio, specific leaf area (SLA), relative growth rate in biomass (Rw ), net assimilation rate (NAR) and dry matter allocation to plant components, were determined. High clay content in soils prolonged the rosette stage, enhanced Rh and Rd and hampered root growth, but promoted biomass allocation to shoots. The extreme degree of plant mortality was observed, with only 33.3% individuals surviving to reproduce in the soils with highest clay contents. This appears to be one of the most important findings that certainly has a major bearing on the range of adaptation of the weed. Seed mass declined whereas seed production increased in relatively coarser soils with the exception of nearly pure sand. In soils rich in clay, plants produced a smaller number of larger seeds. These data suggest that variation in fundamental functional traits would enable P. hysterophorus to adjust to a variety of habitat conditions. 相似文献
73.
74.
Infection processes of Pyrenophora semeniperda on seedling and adult wheat leaves and wheat ears were investigated. Almost 100% germination of conidia occurred on seedling leaves, compared with 20–30% on adult leaves. Appressoria formed over the anticlinal epidermal cell walls and haloes always accompanied infection. Sometimes papillae formed within the leaves as a resistance mechanism. Infection hyphae ramified through the intercellular spaces of the mesophyll resulting in cellular disruption. The infection processes on floral tissues were similar to those observed on leaves; however, no infection occurred on anther, stigmatic or stylar tissues. Infection of ovarian tissue occurred both with and without appressoria formation. Hyphae grew mainly in the epidermal layers and appeared unable to breach the integumental layer as no growth was observed in endosperm or embryo tissues. The optimum dew period temperature for conidial germination was 23·6°C, compared with 19·9°C for lesion development, 20·4°C for the production of infection structures on seedling leaves and 23·7°C for floret infection. Leaf disease development occurred in a logistic manner in response to dew period, with maximum infection observed after 21 h compared with > 48 h in seeds. An initial dark phase during the dew period was necessary for infection and temperature after the dew period had an effect, with significantly more numerous and larger lesions being formed at 15°C compared with 30°C. Seedling leaves were found to be more susceptible than older leaves, under both field and controlled environment conditions. Infection of wheat seeds following inoculation of ears, or after harvest burial of inoculated disease-free seeds, was demonstrated. In the latter, 3-week-old seedlings were slightly stunted, whereas older plants were unaffected. The apparent unimportance of this plant pathogen as a cause of leaf disease in relation to its poor adaptation to dew periods and dew period temperature is discussed, along with the importance of its seed borne characteristics. 相似文献
75.
枯草芽孢杆菌(Bacillus subtilis)S9对植物病原真菌的溶菌作用 总被引:19,自引:1,他引:19
本研究共分离了976株细菌分离物,发现来自甘蔗根围的1株枯草芽孢杆菌(Bacillus subtilis)S9对立枯丝核菌(Rhizoctonia solani)、终极腐霉(Pythium ultimum)和西瓜枯萎病菌(Fusarium oxysporum f.sp.niveum)在PDA平板的对峙培养过程中不形成抑菌圈,但4d后可使上述植物病原真菌的菌丝溶解。扫描电镜观察发现S9菌株在待测的立枯丝核菌表面形成了溶菌斑。S9菌株对立枯丝核菌的作用过程是通过吸附在病原真菌的菌丝上,并随菌丝生长而生长,而后产生溶菌物质消解菌丝体。液体共培养测定也证明了S9菌株具有上述作用。本研究还发现,S9菌株对植物病原真菌的拮抗真菌绿色木霉(Trichoderma viride)、鲜红毛壳菌(Chaetomium cupreum)和球毛壳菌(Chaetomium globosum)的生长没有影响。盆栽试验证明了S9菌株可有效地控制立枯丝核菌(R.solani)引起的番茄苗期病害。S9菌株与其它拮抗真菌混合具有促进防治植物病原真菌引起的植物病害的潜力。 相似文献
76.
调查分析稻粒黑粉病、穗颈稻瘟等两系杂交稻制种穗期主要病害的发生原因,提出了清除菌源、轮换制种、健身栽培、对口药剂防治等防治措施。 相似文献
77.
本文综述了对螟虫长距茧蜂的研究概况,包括该寄生蜂的主要生物学习性、对玉米螟自然寄生率及田间防治玉米螟效果等。 相似文献
78.
通过室内与大田试验,明确O3对日光温室黄瓜病虫害的防治效果。研究结果表明,在病害发生初期,用O3发生器隔天施放O3,每天施放3次,每次40min,间隔20min,O3浓度维持约1mg/kg,施放后7天,对黄瓜霜霉病、白粉病、细菌性角斑病及灰霉病防治效果分别为63.4%、53.6%、68.7%和65.0%。室内施放O3 60s,间隔20min,持续12h,对温室白粉虱、南美斑潜蝇成虫杀伤力为100%。O3对黄瓜植株安全,但随着黄瓜生育期的推进,对O3的忍受能力依次减弱。苗期忍耐O3最大浓度为1~2mg/kg,结果期0.4~1mg/kg,后期0.2~0.4mg/kg。O3防治黄瓜病虫害新技术具有安全、有效、方便、无二次污染等特点,尤其在黄瓜定植前对棚室进行大剂量消毒,可不留死角,且有效地解决了硫磺等药物消毒所造成棚内一些设施的破坏及对生态环境污染的难题,具有广阔的推广应用前景。 相似文献
79.
R.B. Mabagala 《European journal of plant pathology / European Foundation for Plant Pathology》1997,103(2):175-181
Surface and internal populations of Xanthomonas campestris pv. phaseoli, causal agent of common bacterial blight of bean, on and in flower buds, blossoms and pods of seven bean (Phaseolus vulgaris) genotypes were studied. Bean plants were grown in the field and artificially inoculated at the seedling stage (18 days old). The pathogen was recovered in high numbers from flower buds, blossoms, pods and seed of both resistant and susceptible bean genotypes. Significant differences (P = 0.05) in population levels of X. c. pv. phaseoli between stages of reproductive tissue development were observed. Infected seed from resistant bean genotypes had no visible symptoms. Such seed may play an important role in the epidemiology of common bacterial blight because they are difficult to detect and may occur at low frequency in seed lots, as was the case in the current study. 相似文献
80.
Y. Antignus M. Lapidot N. Ganaim J. Cohen O. Lachman M. Pearlsman B. Raccah A. Gera 《Phytoparasitica》1997,25(4):319-330
Received April 24, 1997; received in final form June 29, 1997. Symptoms resembling tomato spotted wilt virus (TSWV) infections
were documented among ornamental and vegetable crops in commercial greenhouses and open fields in Israel. Plants exhibiting
these symptoms were collected from January 1992 to December 1996. Among cultivated plants analyzed for TSWV by enzyme-linked
immunosorbent assay (ELISA), 19 species representing five families were found to be infected; natural infection was also recorded
in six plant species of weeds. Virus identity was characterized by host range, serology and electron microscopy. Serological
reaction with the isolates, found in Israel, using antisera from different sources as well as the sequence analysis of the
nucleocapsid gene, demonstrated that the Israeli isolates of TSWV are a member of tospovirus serogroup I, type I (BR-01 strain).
No virus transmission was found in seeds collected from virus-infected vegetable and ornamental crops. A non-radioactive molecular
probe derived from the cloned nucleocapsid isolate enables specific detection of the virus in crude sap from infected plants.
The detection of TSWV in Israel constitutes a severe potential threat to the ornamental and vegetable industry. 相似文献