濒危红树植物红榄李种子形态及萌发特性

濒危红树植物红榄李(Lumnitzera littorea(Jack.)Voigt)目前在中国数量稀少,处于濒临灭绝的边缘。为了解其濒危机制,本文研究了红榄李的种子形态及温度、盐度、光照和外源激素GA3对其种子萌发的影响。结果表明,种子萌发是在果实外果皮完全腐坏后进行,萌发率极低(11.7%)。适宜红榄李种子萌发的温度范围极为狭窄,最适宜的萌发温度是25℃,当低于15℃时,种子完全不能萌发,当高于30℃时偶有萌发现象但幼苗无法成活。最适宜的海水的盐度范围在5‰~10‰之间,高于30‰盐度下,种子完全不萌发,但在淡水环境下种子可以萌发(2.8%)。红榄李的种子在黑暗条件下无法萌发,周期性光照条件下,种子萌发率最高。100~200 mg/L浓度的外源激素GA3对红榄李种子萌发有显著促进作用,且能明显缩短种子萌发时间但无法有效减少种子萌发停滞时间。因此,红榄李种子存在明显休眠现象,种子萌发对果皮、温度、盐度和光照等微环境的适应性狭窄是红榄李处于濒危状态的主要原因之一。     

野生泸定百合种子休眠和萌发习性的研究

野生泸定百合属于百合科百合属多年生草本植物,其药用和园艺观赏价值极高,自然条件下泸定百合种子的萌发率极低,主要依靠幼芽鳞茎的形式来繁殖后代.为研究和确定云南野生泸定百合种子休眠和萌发的习性,本研究设置了不同光照、不同温度条件下种子的萌发试验,具体为在有光照(光照12 h/d)和无光照的黑暗条件下,分别设置了恒温20℃、30℃和20～30℃变温时种子的萌发试验;设置了5℃低温层积处理后种子的发芽试验,层积时间分别为7、14、21、28d和60 d;以及100mg/L赤霉素处理后,种子于光照和黑暗条件下的发芽试验.结果表明:恒温20℃和20～30℃变温的黑暗条件,适宜野生泸定百合种子的萌发,表现为萌发时间最短、发芽率达到了最高(45%);100 mg/L的GA3处理对种子的萌发有明显促进作用,可加快和缩短种子萌发时间,提高种子发芽率;而5℃的低温层积对野生泸定百合种子的萌发在萌发时间和发芽率方面没有明显促进作用.     

繁缕(Stellaria media(L.)Vill.)种子萌发特性的研究

对繁缕进行温度、光照、低温贮藏、赤霉素和破种皮处理实验,研究不同条件对种子萌发的影响。结果表明,繁缕种子萌发对温度敏感,对光照不敏感,最适宜的萌发温度为12℃,最适光照条件为8 h。低温贮藏处理可有效促进种子萌发,-70℃贮藏后种子萌发率达到93.25%。赤霉素对种子萌芽影响较显著,最适浓度为500 mg/L。破种皮处理后种子萌发效果最好,萌发率达到96.75%,并于5 d萌发完毕。     

壮瑶药野甘草种子萌发特性研究

研究壮瑶药植物野甘草种子萌发特性,为野甘草育种以及规范化种植提供科学依据。以野甘草种子为材料,测定不同温度和光照条件下种子发芽率,及聚乙二醇(PEG-6000)、赤霉素(GA)、硝酸钾浸种对种子萌发的影响。结果表明：（1）野甘草种子在20℃和35℃恒温条件下不萌发,25℃、30℃、15/25℃变温、20/30℃变温和25/35℃变温条件的发芽率分别为78%、43%、73%、94%和75%;（2）野甘草种子在全黑暗条件下不萌发,由黑暗转入光照后,种子正常萌发;（3）浓度为1%~5% PEG-6000、1~100 mg/L GA和1~5 mmol/L KNO₃浸种后,野甘草种子发芽率均显著高于蒸馏水对照处理,分别为86%~90%、93%~95%和87%~88%。野甘草种子为需光性种子,适宜发芽温度为20/30℃变温,PEG-6000(1%~5%)、GA(1~100 mg/L)和KNO₃(0.01~5 mg/L)浸种可促进野甘草种子萌发。     

巧玲花种子萌发最佳条件研究

为了探讨巧玲花种子萌发最适条件,在GA3浓度分别为0、100、500、1 000μ mol/L,温度依次为10、15、20、25、30℃,光照强度为0、24.9、35.5、67.325μmol/(m2·s)的条件下研究了GA3、温度、光照等因素对巧玲花种子萌发的影响.试验结果表明,1 000μmol/L GA3浓度、20℃温度、黑暗为巧玲花种子萌发的最适条件,巧玲花为喜低温型种子.     

基质、光照和温度对羊耳菊种子萌发的影响

为了研究羊耳菊种子的萌发特性,观察了不同基质、光照和温度等条件处理对羊耳菊种子萌发的影响.种子萌发试验的基质分别为纱布、滤纸及细河沙;光照条件分别为黑暗和自然光2种;萌发温度分别为10,15,20,25℃.结果表明:1)种子萌发最佳基质为细河沙;2)种子在光照条件下具有较高的萌发率;3)最适萌发温度为25℃,萌发率达53.75％.本研究可为羊耳菊资源利用提供科学依据.     

温度、光照和水分对珍稀濒危树种崖柏种子萌发的影响

以崖柏种子为试验材料,研究不同温度条件、光照和持续黑暗、不同浸种时间等对种子萌发的影响,探讨适宜崖柏种子萌发的环境条件。结果表明:适宜崖柏种子萌发的温度为25℃,种子发芽率为88%,20℃和30℃条件下的种子发芽率分别为77%和33%。种子萌发进程在20℃和30℃条件下比在25℃条件下开始的时间晚,萌发持续的时间长。高温会显著提高种子霉变率,30℃条件下的种子霉变率高达40%;光照不是崖柏种子萌发的必要条件。在连续黑暗条件下种子仍可萌发,且种子发芽率、发芽指数、发芽势、霉变率等无明显差别。但在光照下种子持续发芽的时间短,种子霉变率低;浸种72 h、96 h和120 h对崖柏的种子萌发没有显著影响,但浸种120 h的种子发芽率低,霉变率高。浸种72 h即可以满足崖柏种子萌发对水分的基本需求。     

海桐种子的休眠解除与萌发

观赏植物海桐(Pittosporum tobira(Thunb.)Ait.)种子的休眠和萌发特性已被进行了较充分的研究.TTC检测出新鲜海桐种子是高活力的(98%),但在5个恒温和1个变温(12 h/d的光周期)下,其萌发率仅为27%,这说明海桐种子处于休眠状态.经不同浓度(100mM和200 mM)的GA3溶液处理后,新鲜海桐种子的萌发率有所提高;在25/15℃与200 mM的处理下,其发芽率最高是41%,但仍不理想.当经过低温(5℃)处理一段时间(15、30、45、60、90d)后,海桐种子的萌发率显著提高,尤其是在25℃和25/15℃处理下,萌发率分别为87%和95%.此外,冷层积30 d和45 d的海桐种子经200 mM的GA3溶液处理后的萌发率分别达69%和94%,效果显著.可见,海桐种子的休眠是浅生理休眠,单一的GA3溶液处理不能有效地打破海桐种子的休眠,但冷层积90d或200mM GA3溶液处理冷层积45d的种子,可有效地解除其休眠;同时,温度对种子的萌发有较大影响,在适宜的萌发温度(25℃或25/15℃)与周期性(12h/d)光照下,种子的萌发率超过90%.由此推断,海桐种子在自然条件下难以萌发的原因与其生理休眠有关.     

不同处理方法对金银莲花种子发芽的影响

为了解金银莲花种子特征及萌发条件,笔者研究了其种子形态、不同的光照、温度、GA3和不同p H值的溶液对其种子萌发特性的影响。结果表明:金银莲花种子的直径为(0.704±0.048)mm,千粒重为(0.1102±0.05)g,种子离开母体时胚发育为成熟胚时期。其种子在光照条件下的萌发率高于黑暗条件;温度过高或过低均不利于种子萌发,其种子最适宜的发芽温度为25℃;一定浓度GA3溶液对金银莲花种子萌发有促进作用,浓度不宜过高;金银莲花种子对p H值有较广的适应性,p H 6~7时,种子的发芽率,发芽指数较高。因此,金银莲花种子为需光萌发,最适萌发温度为25℃,在中性偏弱酸的环境下种子易于萌发,50~400 mg/L的GA3处理其种子萌发率均可达到97%以上。     

黄精种子破眠技术研究

以黄精种子为材料,研究了不同光照、沙藏温度、温水及外源生长调节物质浸种对黄精种子萌发的影响,为进一步开展黄精有性繁殖提供技术支持.结果表明:在0℃低温沙藏120d的条件下,最有利种子的萌发;黑暗条件下种子萌发率比光照条件下萌发率高37.78％,其差异显著,说明黑暗更有利于黄精种子的萌发;40℃温水浸种24 ～30 h,可有效促进黄精种子的萌发,发芽率达到93.33％.适宜浓度的GA3、6-BA、水杨酸和壳聚糖均能促进黄精种子的萌发,显著缩短发芽时间,其发芽率、发芽势、发芽指数和活力指数等指标均明显高于对照.其中浓度为150 mg/L的GA3浸种24h,发芽率、发芽势、发芽指数及活力指数均最高,分别为91.11％、62.22％、0.87和5.16;100 mg/L的6-BA除了可以促进种子萌发,还可以打破黄精种子萌发过程中芽的休眠.     

A note on the origin of Kalanchoë x vadensis Boom & Zeilinga (Crassulaceae)

Summary K x vadensis is a hybrid of K. blossfeldiana and K. marmorata obtained after doubling the number of chromosomes.     

Mechanisms and diversity of resistance to sorghum shoot fly,Atherigona soccata

Sorghum shoot fly, Atherigona soccata, is one of the important pests of postrainy season sorghums. Of the 90 sorghum genotypes evaluated for resistance to this pest, RHRB 12, ICSV 713, 25026, 93046 and 25027, IS 33844‐5, Giddi Maldandi and RVRT 3 exhibited resistance in postrainy season, while ICSB 463, Phule Anuradha, RHRB 19, Parbhani Moti, ICSV 705, PS 35805, IS 5480, 5622, 17726, 18368 and 34722, RVRT 1, ICSR 93031 and Dagidi Solapur showed resistance in rainy season, suggesting season‐specific expression of resistance to A. soccata. ICSB 461, ICSB 463, Phule Yasodha, M 35‐1, ICSV 700, 711, 25010, 25019 and 93089, IS 18662, Phule Vasudha, IS 18551 and 33844‐5 and Barsizoot had fewer deadhearts than plants with eggs across seasons, suggesting antibiosis as one of the resistance mechanism. Five genotypes exhibited resistance with high grain yield across seasons. Correlation, path and stepwise regression analyses indicated that leaf glossiness, seedling vigour, trichome density, oviposition and leaf sheath pigmentation were associated with the expression of resistance/susceptibility to shoot fly, and these can be used as marker traits to select and develop shoot fly‐resistant sorghums.     

Reaction of tritordeum to Fusarium culmorum and Septoria nodorum

Summary Hordeum chilense is a wild barley extensively used in wide crosses in the Triticeae. It could be a valuable source of resistance to Fusarium culmorum and Septoria nodorum. Some H. chilense x Triticum spp. amphiploids, named tritordeums, were more resistant than the parental wheat line to these diseases, others were not. Average contents of ergosterol and deoxynivalenol (DON) suggested that resistance to colonization by Fusarium was the highest for Hordeum chilense, followed by tritordeum and wheat in decreasing order. In particular, the H. chilense genotypes H7 and H17 enhanced the wheat resistance to F. culmorum in its tritordeum offsprings. Resistance to S. nodorum in tritordeum was not associated with tall plant height. There is sufficient genetic variation for resistance to F. culmorum and S. nodorum among tritordeum to allow the breeding of lines combining short straw and resistance to both diseases.     

Disease resistance in protected crops and mushrooms

Summary Cultivars of tomatoes, cucumbers, lettuce and peppers have been bred for resistance to one or more pathogens. Some tomato and cucumber cultivars have resistance to a wide range of diseases. Resistance has been transient in many cases and a succession of cultivars with new genes or new combinations of resistance genes has been necessary to maintain control. There has been a number of notable exceptions and these have included durable resistance to such pathogens asFulvia fulva and tomato mosaic virus. With lettuce the resistance situation is complicated by the occurrence of fungicide resistant pathotypes. There are no strains ofAgaricus bisporus purposely bred for disease resistance.In protected flower crops only resistance to Fusarium wilt in carnations has been purposely bred but differences in disease resistance are apparent in cultivars of many ornamental crops. This is particularly so in chrysanthemums where there are cultivars with resistance to many of the major pathogens. Similar situations occur with other flower crops and pot plants. Cultivars of some species have not been systematically investigated for resistance.The need for genetic resistance will increase with the further reduction, in the limits on pesticide use and an increasing public awareness and importance of pesticide pollution.ADAS is an executive agency of the Ministry of Agiculture, Fisheries and Food and the Welsh Office.     

Genetic constitution and diversity in four narrow endemic redwoods from the family Cupressaceae

The genetic constitution and diversity of four relictual redwoods are discussed in this review. These include monotypic genera of the family Cupressaceae: coast redwood (Sequoia sempervirens), giant sequoia (Sequoiadendron giganteum), dawn redwood (Metasequoia glyptostroboides), and alerce (Fitzroya cupressoides). All four species are narrow endemics, share a number of common phenotypic traits, including red wood, and are threatened species. Fossil history suggests that the ancestors of redwoods probably originated during the Cretaceous and Tertiary periods and flourished thereafter for millions of years. Towards the end of the Tertiary period began their decline and struggle for existence that continued during the subsequent geologic upheavals and climate changes, until the survival of the present-day redwoods in the current restricted locations in the world (USA, China, and South America). Although two species, Sequoiadendron and Metasequoia, are diploids (2n = 22), and the other two are polyploids: Fitzroya a tetraploid (2n = 4x = 44), and Sequoia a hexaploid (2n = 6x = 66); they all share the same basic chromosome number x = 11. The genome size in the hexaploid Sequoia is one of the largest (31,500 MB) in the conifers, while the genome sizes of diploid Metasequoia and Sequoiadendron are about one-third (~10,000 MB) of Sequoia. Genetic diversity in the redwoods is lower than most other gymnosperms, except in Sequoia, which seems to rank near the upper quarter of the coniferous forest trees. Genomic research is sparse in the redwoods, and should be pursued for a better understanding of their genome structure, function, and adaptive genetic diversity.     

The induction in vitro of adventitious shoots in Rosa

Summary Adventitious shoots were formed on excised leaves, roots and callus of Rosa persica x xanthina and on excised leaves of R. laevigata and R. wichuraiana on culture media that included BAP and NAA as growth regulators. Shoots formed freely on freshly cultured callus of R. persica x xanthina but their production declined in successive cultures and ceased after twelve weeks. Transplantation to soil was improved by rooting plantlets in cellulose plugs in vitro and transferring plantlets to soil while still in the plugs.     

Distribution,ecology and reproductive biology of wild tomatoes and related nightshades from the Atacama Desert region of northern Chile

Over the past 20 years, several expeditions were made to northern Chile to collect populations of wild tomatoes (Solanum chilense, S. peruvianum) and allied nightshades (S. lycopersicoides, S. sitiens), and obtain information about their geographic distribution, ecology and reproductive biology. Restricted mainly to drainages of the Andean and the coastal cordillera, populations are geographically fragmented. The two nightshade species are rare and threatened by human activities. Adaptation to extreme aridity and soil salinity are evident in S. chilense and S. sitiens (the latter exhibits several xerophytic traits not seen in the tomatoes) and to low temperatures in S. lycopersicoides and S. chilense. All tested accessions are self-incompatible, with the exception of one S. peruvianum population collected at the southern limit of its distribution. Several distinguishing reproductive traits—anther color, attachment, and dehiscence, pollen size, and flower scent—suggest S. sitiens and S. lycopersicoides attract different pollinators than S. chilense and S. peruvianum. The four Solanum spp. native or endemic to Chile provide a variety of novel traits which, through hybridization and introgression with cultivated tomato, could facilitate development of improved varieties, as well as research on a variety of basic topics, including plant-pollinator interactions, abiotic stress responses, and evolution of reproductive barriers.     

The exploration of genetic resources of Portuguese cabbage and kale for resistance to several Brassica diseases

Summary Twenty three accessions of nine Portuguese cabbage and kale land races from different geographic origins were tested at the seedling stage for resistance to several important brassica diseases. Resistance to downy mildew (Peronospora parasitica), expressed as necrosis of the cotyledon mesophyll, was found in all the accessions. Type A resistance to cabbage yellows (Fusarium oxysporum f. sp. conglutinans race 1) was present in most of the landraces. Resistance to clubroot (Plasmodiophora brassicae race 6) was found in one accession of the Portuguese tree kale. High resistance to blackleg (Leptosphaeria maculans) and white rust (Albuco candida) was not detected, although several accessions showed 20 to 30% of plants with intermediate expression of resistance. All Portuguese cole accessions were susceptible to blackrot (Xanthomonas campestris pv. campestris).     

Production and characterization of intergeneric diploid cybrids derived from symmetric fusion between Microcitrus papuana Swingle and sour orange (Citrus aurantium)

Plants were regenerated from intergeneric somatic hybridization between embryogenic protoplasts of Microcitrus papuana Swingle and leaf-derived protoplasts of sour orange (Citrus aurantium L.) via electrofusion. The regenerated plants were morphologically similar to the leaf parent in growth vigor, leaf and branch structure. FCM analysis showed that they were diploids. Simple-sequence-repeat (SSR) and cleaved-amplified-polymorphic-sequence(CAPS) were employed for hybridity characterization. SSR banding patterns of the regenerated plants were identical to the leaf parent, sour orange, indicating that they possessed nuclear component derived from sour orange. DNA amplification with chloroplast and mitochondrial universal primers, followed by restriction endonuclease digestion, revealed polymorphism between the fusion parents. Therefore, this method was used to determine the cytoplasmic compositions of the regenerated plants. Banding patterns for all the polymorphic primer/enzyme combinations of the regenerated plants were similar to those of the embryogenic parent, M. papuana, suggesting that only the cytoplasmic components derived from the embryogenic parent were present in the regenerated plants. FCM, SSR and CAPS demonstrated that intergeneric diploid cybrids have been successfully obtained by symmetric fusion. Related results concerning nuclear and cytoplasmic composition of previous diploid somatic hybrids and potential mechanism for regeneration of such kind of plants are discussed herein. This revised version was published online in July 2006 with corrections to the Cover Date.     

Breeding barriers between the cultivated strawberry, Fragaria × ananassa, and related wild germplasm

Five-hundred interspecific and intergeneric crosses were performed among accessions of the wild strawberries Fragaria vesca(2x), Duchesnea indica (8x), Potentilla tucumanensis (2x) and 9 genotypes of the cultivated strawberry, Fragaria×ananassa (8x), following an incomplete diallele mating design. Crosses between D. indica and F.×ananassa produced many putative hybrids when D. indica was used as female but a few achenes and plants when used as male; therefore, pollen-pistil compatibility relations were analyzed by fluorescence microscopy in this direction of the cross. Of the genotypic combinations, 78.6% were incompatible at the stigma level and 17.2% at the first third of the style. Only 3.6% were pollen-pistil compatible and produced fruits with achenes (seven did not germinate or originated short-lived plants and nine produced normal plants). F.vesca×F.×ananassa crosses produced 35 hybrid achenes but only 14% germinated, yielding short-lived plants; histological analyses revealed that inviable seeds had less developed (or collapsed) endosperms and smaller embryos than control plump F. vesca seeds. P.tucumanensis was only used as male, with negative results. These species and genera are partially isolated by a complex system of pre- and post-zygotic barriers. Knowledge of their nature would allow the breeder to devise strategies to put the genetic variability available in the group into a useful form. This revised version was published online in July 2006 with corrections to the Cover Date.