Gaps and perspectives of pathotype and race determination in <Emphasis Type="Italic">Golovinomyces cichoracearum</Emphasis> and <Emphasis Type="Italic">Podosphaera xanthii</Emphasis>

Golovinomyces cichoracearum and Podosphaera xanthii (family Erysiphaceae) are the most important species causing cucurbit powdery mildew (CPM), a serious disease of field and greenhouse cucurbits. Both species are highly variable in their pathogenicity and virulence, as indicated by the existence of large number of different pathotypes and races. Various independent systems of CPM pathotype and race determinations and denominations are used worldwide. CPM pathotype identification is based on intergeneric and interspecific differences in host-CPM interactions. The most commonly used set of CPM pathotype differentials includes one genotype from four species representing three agriculturally important cucurbit genera plus two genotypes from a fifth species, melon Cucumis melo L. CPM races are characterized by specialization on different cultivars or lines of one host species and have, to date, been differentiated only on melon (C. melo L.). The most frequently used set of melon differentials includes 11 genotypes that can differentiate CPM races originating from melon and other cucurbits, e.g., cucumber, Cucurbita spp., and watermelon. In this paper, we critically review the current state, gaps, and perspectives in our understanding of pathogenicity variation in these two CPM pathogens at the pathotype and race levels.     

Pollen morphology of Zehneria s.l. (Cucurbitaceae)

A growing body of experimental data obtained from sporoderm ontogenetic studies led to the appearance of the ‘micellar’ hypothesis. The hypothesis is that the sequence of sporoderm developmental events represents the sequence of self-assembling micellar mesophases, initiated by genomically given physico-chemical parameters, which are then picked up by physico-chemical self-assembly. However, besides morphological evidence, the best proof of this hypothesis would be an experimental modelling of sporoderm-like patterns. The main idea of this study is to remove the influence of the genome, selecting substances and their concentrations for simulations to replace it, and then to trace what ‘pure’ self-assembly is capable of constructing. Our aim in this study was to simulate mainly young structures in sporoderm development, i.e. the glycocalyx and the primexine. Several polysaccharide gels (as a callose substitute) and surfactants (as glycocalyx and sporopollenin monomer substitutes) were mixed at different concentrations and combinations, thermally set and left to condense. A number of patterns were obtained in colloidal solutions in the course of condensation, simulating structures at different stages of exine development. Their structures were observed and analysed with transmission electron microscopy (TEM). Our first experiments on the modelling of biological patterns in vitro have shown encouraging results.     

Anionic Antimicrobial and Anticancer Peptides from Plants

Anionic antimicrobial peptides (AAMPs) have been identified in a wide variety of plant species with net charges that range between ?1 and ?7 and structures that include: extended conformations, α-helical architecture and cysteine stabilized scaffolds. These peptides commonly exist as multiple isoforms within a given plant and have a range of biological activities including the ability to kill cancer cells as well as phytopathogenic bacteria, fungi, pests, molluscs, and other predatory species. In general, the killing mechanisms underpinning these activities are poorly understood although they appear to involve attack on intracellular targets such as DNA along with compromise of cell envelope integrity through lysis of the cell wall via chitin-binding and/or permeabilisation of the plasma membrane via lipid interaction. It is now becoming clear that AAMPs participate in the innate immune response of plants and make a major contribution to the arsenal of defence toxins produced by these organisms to compensate for their lack of some defence mechanisms possessed by mammals, such as mobility and a somatic adaptive immune system. Based on their biological properties, a number of potential uses for plant AAMPs have been suggested, including therapeutically useful anticancer agents and novel antimicrobial compounds, which could be utilized in a variety of scenarios, ranging from the protection of crops to the disinfection of hospital environments.     

Comparison of fatty acid patterns in plant parts and respective callus cultures of Cucumis melo

Root, hypocotyl, cotyledon, stem and leaf of Cucumis melo var. utilissimus seedlings were used for callus induction. Comparison was made between these parts, between callus tissues originating from all the parts and between each part and its callus, with respect to the fatty acid composition of total lipids. In all the parts there was a greater proportion of unsaturated fatty acids, the predominant fatty acid in root, stem and leaf being linolenic acid whilst in the cotyledon linoleic predominated. In the hypocotyl these two acids were present in equal amounts. In callus cultures the proportion of saturated acids was greater and the predominant fatty acid was palmitic. The major unsaturated fatty acid in callus cultures was linolenic. The analysis showed that callus tissue and its respective plant part had different fatty acid patterns and that all the callus cultures had very similar patterns irrespective of their origin.     

45S rDNA和5S rDNA在南瓜、丝瓜和冬瓜染色体上的比较定位

首次利用荧光原位杂交和双色荧光原位杂交技术对45S和5S rDNA在南瓜(Cucurbita moschata Duch)、丝瓜(Luffa cylindrical Roem)、冬瓜(Benincasa hispida Cogn)的有丝分裂中期染色体上进行了物理定位分析。南瓜有5对45S rDNA位点, 2对5S rDNA位点; 丝瓜具有5对45S rDNA位点, 1对5S rDNA位点; 冬瓜具有2对45S rDNA位点, 1对5S rDNA位点, 5S rDNA位点与其中一对45S rDNA位点都位于7号染色体短臂上, 并在物理位置上紧密相邻。45S rDNA在这3种作物染色体上数目变化较大, 但在染色体上都倾向分布在短臂末端, 其分布模式较为一致。5S rDNA在这3种作物染色体上数目相对保守, 但在染色体上分布的位置变化较大。文中讨论了45S rDNA和5S rDNA在植物基因组中不同的进化趋势。     

葫芦科瓜类作物分子标记辅助育种研究进展

综述了几种常用分子标记在葫芦科瓜类作物遗传图谱构建、重要性状基因定位、遗传多样性及亲缘关系分析、分子标记辅助选择及在葫芦科遗传育种中的应用,对目前葫芦科遗传育种中应用分子标记技术存在的问题和解决方案进行了探讨,并对葫芦科分子标记辅助育种的前景做了展望。     

Allozymic, morphological, phenological, linguistic, plant use, and nutritional data ofBenincasa Hispida (Cucurbitaceae)

Benincasa hispida, from tropical Asia, is cultivated primarily for its edible fruit. To explore its domestication and ethnobotany, we made collections from two regions where it may have been domesticated: (1) Southern China/Southeast Asia, represented by southern Yunnan Province (China) and northern Laos; and (2) the Indian subcontinent, represented by southeastern Nepal. Domestication has resulted in diverse fruit sizes, shapes, and colors; seed sizes and shapes; and, in some accessions, the loss of tendrils. Modern cultivars have larger fruit, earlier flowers, and lower nutritional content than traditional cultivars. Allozyme diversity was low, divergence between these two regions was low, and these results do not clarify the place of domestication. The greater morphological diversity of plants from Yunnan and Laos, as compared to Nepal, suggests domestication in the former region. In all accessions, male flowers precede females.Benincasa hispida is prominent in some traditional stories and rituals.     

瓜类枯萎病研究进展(综述)

瓜类枯萎病是由尖孢镰刀菌Fusarium oxysporum侵染引起,在全球大部分瓜类产区均有发生。该病已成为影响我国瓜类品质和产量的重要病害。本文从瓜类作物枯萎病的防治方法、致病机理和分子生物学研究等方面综述其研究现状,并对今后的研究方向进行展望。     

Improvement of pistillate flowers yield with GA3 in heavy metals treated plants

GA₃ can be beneficial to improve the flowering yield in Lagenaria siceraria (Mol.) Standl. and Luffa cylindrica L. (Roem) treated with HgCl₂ and . This paper reviews the literature on the possible involvement of gibberellins in flower development and suggests that plants under the stress of heavy metals can be treated with GA₃ to improve growth parameters, to avoid delay in flowering and likewise quality of fruit can be improved. Applied GA₃ (400 mg/l) caused precocious flowering, increasing the number of flowers in the treated plants. All data was compared with control plants grown under similar conditions. Both heavy metals caused significant delay in flowering, consequently leading to reduction in the number of flowers. However, when GA₃ was applied with HgCl₂ and , there was less decrease in staminate and pistillate flowers, revealing the dominant effect of GA₃. Current work reveals that inhibitory effects of heavy metals on flowering can be partially restored with GA₃ application.     

Effect of modified endogenous ethylene production on sex expression, bisexual flower development and fruit production in melon (Cucumis melo L.)

Members of the Cucurbitaceae family display a range of sexual phenotypes including various combinations of male, female, or bisexual flowers. Ethylene appears to be a key hormone regulating the sex determination process. Application of ethylene, or inhibition of ethylene action, increases or decreases the number of pistil-bearing buds, respectively. Elevated levels of ethylene production and expression of genes for ethylene biosynthesis, have been correlated with pistillate flower production. In this study, we sought to determine the effect of modified endogenous ethylene production on sex expression by constitutively expressing ACS (1-aminocyclopropane-1-carboxylate synthase), the first committed enzyme for ethylene biosynthesis, in transgenic melons (Cucumis melo L.). Most melon genotypes are andromonoecious, where an initial phase of male flowers is followed by a mixture of bisexual and male flowers. ACS melon plants showed increased ethylene production by leaves and flower buds, and increased femaleness as measured by earlier and increased number of bisexual buds. ACS melons also had earlier and increased number of bisexual buds that matured to anthesis, suggesting that ethylene is important not only for sex determination, but also for development of the bisexual bud to maturity. Field studies showed that ACS melons had earlier mature bisexual flowers, earlier fruit set, and increased number of fruit set on closely spaced nodes on the main stem. These results provide a direct demonstration of the importance of endogenous ethylene production for female reproductive processes in melon.