Antifungal activities of hyoscyamine and scopolamine against two major rice pathogens: <Emphasis Type="Italic">Magnaporthe oryzae</Emphasis> and <Emphasis Type="Italic">Rhizoctonia solani</Emphasis>

The antifungal activities of hyoscyamine and scopolamine, major alkaloids extracted from the desert plant Hyoscyamus muticus, against two rice pathogens, Magnaporthe oryzae and Rhizoctonia solani, were studied. The minimum inhibitory concentration of hyoscyamine that resulted in distinctive inhibition (MIC₅₀) was 1 μg/ml for both fungi. Exposure to hyoscyamine caused the leakage of electrolytes from the mycelia of both fungi. Hyoscyamine (>1 μg/ml) irreversibly delayed or inhibited conidial germination and appressorium formation in M. oryzae grown on polystyrene plates. Hyoscyamine effectively inhibited the attachment of conidia to the surface of rice (Oryza sativa) leaves and inhibited appressorium formation on the leaves. A high concentration of scopolamine (1000 μg/ml) also delayed or inhibited conidial germination in M. oryzae, but conidial germination was restored after washing the conidia with water. Antifungal activity of hyoscyamine was reduced by scopolamine. Magnaporthe oryzae infection was significantly suppressed (by >95%) in leaves of intact rice plants treated with hyoscyamine (10 μg/ml). Moreover, 10 μg hyoscyamine/ml significantly reduced the disease severity index for sheath blight to ≤0.2, when compared with the disease index of control plants (>7.0). Hyoscyamine (>20 μg/ml) completely inhibited sclerotial germination and development of R. solani by delaying the initiation, maturation, and melanization of the sclerotia. These results suggest that tropane alkaloids may be useful for controlling blast and sheath blight diseases of rice and for studying the mechanisms that regulate conidial germination in M. oryzae and sclerotial germination and development in R. solani.     

Analyses of leaves from open field-grown transgenic poplars overexpressing xyloglucanase

The transgenic expression of Aspergillus xyloglucanase cDNA (AaXEG2) with 35S promoter in the leaves of open field-grown poplars was studied. The level of xyloglucan in the transgenic poplars was decreased to 15–16% in the non-fertile soil (forest-field soil) and to 21–22% in the fertile soil (farming-field soil) compared with that of the wild-type poplars. The leaves exhibited a smaller surface area with more rounded teeth than those of the wild-type plants, similar to the sun leaf variety that was grown in the incubation room and subsequently greenhoused. The majority of total veins with water-conducting vascular bundles were shorter in the leaves of the transgenic poplars than those of the wild type. This decrease in vein length may result from a decrease in xyloglucan during leaf development, from which large numbers of proteins were markedly downregulated in the leaves of the transgenic plants via proteomic analysis. It seems likely that the leaves of the transgenic poplars came to relax the edges of their tooth rather than extend their veins as a result of the loosening of the xyloglucan cellulose networks in the leaves.     

农垦58S及其籼型衍生系光温敏不育基因的等位性研究

本文研究了农垦585及其衍生的7个籼型光、温敏核不育系双列杂交F1和部分组合F2在长日高温条件下的育性表现。结果表明,光敏不育系农垦585、8902528775,以及温敏不育系培矮645、88015和25585等6个不育系的不育主基因等位;温敏不育系W61545和92025的不育主基因等位,但与前6个不育系非等位。     

一个未知的卷叶基因的识别和定位

利用籼稻窄叶青８号和粳稻京系１７的杂交Ｆ１以及衍生的ＤＨ系,对水稻籼粳交的卷叶性状进行遗传分析;结果表明,叶片平展对卷曲为显性,卷叶植株受两对隐性基因控制。应用ＤＨ系已构建的分子图谱将这两对卷叶基因定位于第１染色体的Ｃ９４９—Ｇ３７０和第５染色体的ＲＧ１３—ＲＧ５７之间,其中第１染色体的卷叶位点,与经典遗传图谱已定的ｒｌ－１位于同一区段,本研究沿用该名。第５染色体上的卷叶基因是一个未定位的新基因,暂定名为ｒｌ－７,且这两对基因存在基因互补作用。     

栽培稻远缘杂种育性遗传问题评述

评述了种间杂种和亚种间杂种不育性的遗传。它们可能存在共同的基因系统。讨论了克服栽培稻远缘杂交育种障碍的途径。在籼粳亚种间杂种中,有证据表明在S—5附近存在一个控制杂种染色体联会的ds基因,S—5与ds的非等位互作使染色体交叉频率和亲和性同表达。     

水稻双胚苗(Rice Twins)遗传研究

水稻双胚苗为隐性性状受一对主效基因控制,并存在若干修饰基因,使双胚苗率表现数量遗传特征;不同双胚苗品系遗传基础不同;水稻双胚苗同水稻的无融合生殖育着密切的联系。     

水稻亚种间杂种的再生力及其与头季稻农艺性状的相关性

 对水稻亚种间杂种再生力与头季稻主要农艺性状的通径分析表明， 出穗期和有效穗数对杂种再生力有极显著的直接作用，出穗期的直接作用最大。每穗粒数通过有效穗数间接影响杂种再生力，亚种间杂种的超亲晚熟和超亲优势普遍存在并呈极显著正相关。讨论了作为复合性状的再生力的遗侍基础的复杂性及其改良措施。     

Genetic diversity and pathogenicity of <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> isolated from wilted Welsh onion in Japan

Thirty isolates of Fusarium oxysporum from wilted Welsh onion plants were examined for their diversity in nucleotide sequences of the ribosomal DNA (rDNA) intergenic spacer (IGS) region and for pathogenicity with regard to five Welsh onion cultivars. Phylogenetic analysis based on the IGS sequences revealed polyphyletic origins of the isolates and a relationship between phylogeny and pathogenicity; low virulence isolates differed genetically from those with high and moderate virulence. Mating type analysis revealed that all F. oxysporum isolates were MAT1-1 idiomorphs, suggesting that the pathogens may be clonal in the fields examined.     

Pathogenic variation and molecular characterization of <Emphasis Type="Italic">Fusarium</Emphasis> species isolated from wilted Welsh onion in Japan

Thirty-two isolates of Fusarium species were obtained from wilted Welsh onion (Allium fistulosum) grown on nine farms from six regions in Japan and identified as F. oxysporum (18 isolates), F. verticillioides (7 isolates), and F. solani (7 isolates). The pathogenicity of 32 isolates was tested on five commercial cultivars of Welsh onion and two cultivars of bulb onion in a seedling assay in a greenhouse. The Fusarium isolates varied in the degree of disease severity on the cultivars. Five F. oxysporum isolates (08, 15, 17, 22, and 30) had a higher virulence on the cultivars than the other isolates. The host range of these five isolates was limited to Allium species. Molecular characterization of Fusarium isolates was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the internal transcribed spacer (ITS) regions of ribosomal DNA. The 32 isolates were grouped into eight types (four types for F. oxysporum, one for F. verticillioides, and three for F. solani). Restriction patterns of the ITS region were not related to pathogenicity. However, the haplotypes obtained with five enzymes (RsaI, HinfI, HaeIII, ScrFI, and MspI) and the phylogenetic analysis permitted the discernment of the three Fusarium species. The PCR-RFLP analysis should provide a rapid, simple method for differentiating Fusaruim species isolated from wilted Welsh onion in Japan.