Relative susceptibility of different male-sterile cytoplasms in sorghum to shoot fly, <Emphasis Type="Italic">Atherigona soccata</Emphasis>

Summary The shoot fly, Atherigona soccata is an important pest of sorghum, and host plant resistance is one of the most effective components for managing this pest. Most of the hybrids grown in India based on milo cytoplasm (A₁ cytoplasm) are highly susceptible to shoot fly. Therefore, the present studies were undertaken to evaluate different male-sterile cytoplasms (CMS) for their relative susceptibility to sorghum shoot fly. Oviposition and deadheart formation were significantly lower on the maintainer lines as compared to the corresponding male-sterile lines. Among the cytoplasms tested, A₄M cytoplasm showed antixenosis for oviposition and suffered lower deadheart formation than the other cytoplasms tested. The A₄G₁ and A₄M cytoplasms suffered lower deadhearts in tillers than the other cytoplasms. Recovery following shoot fly damage in A₄M, A₃, and A₂ cytoplasms was better than in the other cytoplasms tested. The larval and pupal periods were longer and male and female pupal weights lower in A₄M and A₄VzM CMS backgrounds compared to the other CMS systems. Fecundity and antibiosis indices on CMS lines were lower than on the B-lines. The A₄M cytoplasm was found to be relatively resistant to sorghum shoot fly, and can be exploited for developing shoot fly-resistant hybrids for sustainable crop production in future.     

Characterization of host tolerance to Striga hermonthica

Summary One of the most promising control options against the parasitic weed Striga hermonthica is the use of crop varieties that combine resistance with high levels of tolerance. The aim of this study was to clarify the relation between Striga infestation level, Striga infection level and relative yield loss of sorghum and to use this insight for exploring the options for a proper screening procedure for tolerance. In three pot experiments, conducted in Mali (2003) and The Netherlands (2003, 2004), four sorghum genotypes were exposed to a range of Striga infestation levels, ranging from 0.0625 to 16 seeds cm⁻³. Observations included regular Striga emergence counts and sorghum grain yield at maturity. There were significant genotype, infestation and genotype × infestation effects on sorghum yield. The relation between infestation level and infection level was density dependent. Furthermore, the relation between Striga infection level and relative yield loss was non-linear, though for the most resistant genotype Framida only the linear part of the relation was obtained, as even at high infestation levels only moderate infection levels were achieved. The results suggest that for resistant genotypes, tolerance can best be quantified as a reduced relative yield loss per aboveground Striga plant, whereas for less resistant genotypes the maximum relative yield loss can best be used. Whether both expressions of tolerance are interrelated could not be resolved. Complications of screening for tolerance under field conditions are discussed.     

Wild relatives of pigeonpea as a source of resistance to the pod fly (Melanagromyza obtusa Malloch) and pod wasp (Tanaostigmodes cajaninae La Salle)

Pigeonpea [Cajanus cajan (L.) Millsp.] is an important legume crop in South Asia, East and southern Africa, and the Caribbean. Pod fly (Melanagromyza obtusa Malloch) and pod wasp (Tanaostigmodes cajaninae La Salle) are important constraints to increase the production and productivity of pigeonpea under subsistence farming conditions. Host plant-resistance can be used as an important component for the management of these pests, and therefore, we evaluated 28 accessions of wild relatives of pigeonpea for resistance to these pests. There were significant inter- and intra-species differences in the relative susceptibility to pod fly and pod wasp damage. Accessions belonging to Cajanus scarabaeoides (L.) Thouars, C. sericeus (Benth. ex Bak.) van der Maesen, Rhynchosia bracteata Benth. ex Bak., C. acutifolius (F.v. Muell.) van der Maesen, C. lineatus (W. & A.) van der Maesen, and C. albicans (W. & A.) van der Maesen showed resistance to pod fly damage, while those from C. platycarpus (Benth.) van der Maesen, C. cajanifolius (Haines) van der Maesen and R. aurea DC. were susceptible. For the pod wasp, some of the accessions from C. scarabaeoides, C. albicans, Flemingia stricta Roxb., and R. bracteata (Roxb.) Wight showed a resistant reaction, while ICPW 83 belonging to C. scarabaeoides showed a susceptible reaction. ICPW 141, ICPW 278, and ICPW 280 (C. scarabaeoides), ICPW 214 (R. bracteata), ICPW 14 (C. albicans), and ICPW 202 (F. stricta) showed resistance to both pod fly and pod wasp damage. There was considerable variation in accessions belonging to different species for their susceptibility to pod fly and pod wasp, which can be exploited to breed for resistance to these pests. There was a negative association between pod wasp and pod borer damage, and therefore, it is important to keep track of the relative susceptibility of pigeonpea genotypes to pod wasp, while breeding for resistance to pod borers.     

湿地保护立法中管理机制的创新实践——以《四川省湿地保护条例》为例

湿地不仅是生物资源生存和发展的重要栖息地之一,而且对维护生物多样性,保持生态平衡,实现人与自然和谐、社会经济的可持续发展具有重要意义。鉴于湿地资源对四川省经济社会发展的重要意义,为切实加强湿地保护,在国家尚无湿地保护单行法律法规的情况下,四川省经过反复立法调研,并借鉴其他省份的经验,出台了这一地方性法规,将湿地保护管理正式纳入法制化轨道。     

植物诱导抗病性研究的现状与展望

本文综述了国内外植物诱导抗病性研究的成果，重点评述了植物诱导抗病性的特性、诱导因子和诱抗机制等方面的进展状况，并对植物诱导抗病性研究的前景及应用问题阐明了自己的观点。     

稻瘟病抗性的生理生化机制

对稻瘟病抗性的生理生化机制进行了综述,可知抗性来自于一系列的机理:结构防御,多种酶的活性的升高,抑制物质的产生.     

滤膜过滤器新的理论模型初步探讨

通过对滤膜过滤器的过滤机理进行分析，认为过滤器在使用期间，滤膜中每个毛细管的过滤性能随时间和空间位置的变化而变化，因而对过滤器性能的评价还应从系统的、全面的、宏观统计的观点来综合反映，由此可根据多孔介质流体动力学理论模型来准确地反映滤膜过滤器的性能变化。     

甘蔗褪绿线条病致病机理研究初报

甘蔗植株受褪绿线条病感染后，不同品种叶片中叶绿素的含量发生不同程度降低，而过氧化物酶和酸性转化酶活性却产生不同程度提高。这些生理病变似与叶绿体解体、线粒体肿大、淀粉植的累积和降解密切相关。     

小型轴流滚筒结构及工作参数优化试验

解决动力偏低是小动力拖拉机配套联收机的关键问题,为寻求降低脱粒、分离部件功耗的途径,本研究设计了专用试验台架,用正交试验法,就脱粒滚筒的结构、工作参数优化等问题,进行了两年的室内试验。结果表明,当喂入量在0.75kg/s时,脱粒、清选全部功耗可控制在4.4kW以下。文中对根据试验结果研制的飞龙-0.75联收机的功耗、性能、田间实测情况也作了简要介绍。     

水稻中抗品种抗褐稻虱机制的研究

褐稻虱在中抗水稻品种上的刺探频率低于抗级品种。虽然褐稻虱在中抗品种上能正常取食,但同化利用率较低。中抗品种受害后,无论是植株损害系数、光合作用强度降低程度或产量损失率均显著较感虫品种的少,说明了受害后较之感虫品种具有较强的补偿能力。另外,水稻品种受害后呼吸强度均较健株的明显降低。