栝楼种子发芽特性的研究

本文研究栝楼种子的发芽特性。结果表明栝楼种子具有休眠特性,其休眠原因由种皮障碍引起,用２５￣３５℃变温发芽可打其休眠,但浸种４８小时的栝楼种子产生二次休眠,栝楼种子的最适发芽条件是砂床、２５￣３５℃变温,本文还提出了栝楼种生活力的快速测定方法。     

鹿茸草种子的休眠与萌发

将新收获的鹿茸草种子在25℃和30℃恒温条件下或20～30℃室内变温条件下做发芽试验均未能发芽,但TTC染色试验结果表明其具有生活力,由此证明该种子具有休眠特性.打破休眠试验结果表明:2～5℃低温湿藏处理80d可使其发芽率达67.5%,用200mg/L GA3浸泡48h可使其发芽率达86.9%.干种子在-18℃的密封条件下贮存2年后,仍保持有52%的发芽能力.     

变温培养对新疆野生蒲公英种子发芽及出苗影响的研究

不同的温度处理对蒲公英种子进行发芽特性研究表明,在25℃、15～25℃以及20～30℃的变温培养过程中,不同程度地影响了蒲公英种子发芽高峰日、发芽率、发芽指数、活力指数以及田间出苗率.其中15～25℃变温处理使种子发芽及出苗优于其它温度处理.     

楠木种子休眠与萌发特性的研究

为了解决育苗过程中楠木种子的休眠问题,对楠木种子的休眠和萌发特性进行了研究,结果表明:楠木种子的发芽抑制物质主要存在于除外种皮以外的其余部分,层积将使种子中的发芽抑制物质含量逐渐降低,抑制作用减弱,常温层积效果更明显,常温层积90d能完全解除楠木种子的休眠,发芽率可达80%以上;恒温25℃和变温30℃(日)/15℃(夜),萌发速度最快,发芽势和发芽率分别可达到45.5%和85.0%以上。     

板蓝根种子发芽试验标准化研究

本文针对目前我国大部分中药材种子无统一发芽测定方法及国家标准,种子质量控制无法可依的现状,借鉴国际种子质量检验规程,运用发芽势、发芽率和发芽指数等指标,对影响板蓝根种子发芽试验结果的影响因子:温度、发芽床及部分指标测定时间进行了研究.温度设20℃恒温和15～25℃变温两个处理,发芽床设纸上(TP)、纸间(BP)、褶裥纸(PP)和砂中(S)4个.试验确立了板蓝根种子发芽的标准条件:20℃恒温和15～25℃变温都适合板蓝根种子的萌发,以15～25℃变温为最适温度.发芽床以纸间最佳.根据种子萌发特性,确定了发芽势和发芽率的统计时间,4 d为初次计数时间,14 d为末次计数时间.     

禺毛茛种子贮藏与萌发特性的研究

通过设置不同的温度、光照、浸种和贮藏条件,研究禺毛茛种子的萌发特性和贮藏习性.结果表明,禺毛茛种子为光敏性种子,种子的发芽适温为15/25℃变温.新鲜的禺毛茛种子存在休眠现象,用清水和不同浓度的GA3溶液进行浸种未能打破其种子的休眠,而种子在贮藏1个月后休眠得到解除.低温和湿沙贮藏均有利于禺毛茛种子的萌发.     

东方野豌豆种子休眠及萌发特性研究

对东方野豌豆种子的休眠特性、破除种子休眠方法及种子萌发适宜条件进行了试验研究,结果表明:东方野豌豆种子具有硬实休眠特性,自然成熟种子硬实率为65.75％.采用砂纸打磨和98％浓硫酸浸种均可有效破除种子硬实休眠.98％浓硫酸浸种10～18 min破除东方野豌豆种子休眠效果最好,并对幼苗正常生长无影响.东方野豌豆种子适宜萌发温度范围为10～30℃,最适发芽温度为25℃恒温,最高发芽温度为30℃恒温,最低发芽温度为10℃恒温,最适发芽床为纸上发芽.置床第3天作为种子发芽的首次计数时间,第15天为末次计数时间.     

毛竹种子萌发特性研究

本文研究了环境因素和种子质量对毛竹种子萌发特性的影响。结果表明：影响毛竹种子萌发的环境因素中温度是主要决定因素。种子萌发的最适宜温度范围为20～30℃,低于15℃或超过35℃均不利于萌发,最适萌发温度25℃。变温处理有利于发芽整齐。在自然环境下光照不是毛竹种子萌发的必要条件,但高光强会抑制幼苗生长。种子饱满度是影响种子活力的重要因素之一,明显影响种子萌发进程、发芽整齐度及苗木健壮程度。GA3 处理能显著提高毛竹种子发芽势、发芽指数和活力指数,加快毛竹种子萌发进程,促进萌发后幼苗生长,GA3最适处理浓度范围为100～200mg/L。     

低温层积时间和发芽温度对花楸种子萌发的影响

以花楸新采收种子和2~5℃下密封贮藏2年的陈种子为材料,在10种低温层积时间和6种发芽温度下进行种子萌发试验。结果表明:新种子解除休眠需要的低温层积时间(120 d)比陈种子(105 d)长,解除休眠后的种子在5~25℃的范围内均能萌发,发芽温度越高种子发芽越早,超过25℃种子产生二次休眠;5℃和10℃发芽温度下解除休眠种子的发芽率和发芽指数较高,但发芽较晚。     

高温胁迫下白三叶种子萌发特性及耐热性研究

通过不同温度处理,对7个白三叶品种的种子萌发特性和耐热性进行了研究。结果表明,40℃胁迫下种子不发芽;在20～35℃范围内,白三叶种子发芽率随温度升高而降低,变温(20℃16 h,35℃8 h)处理可改善高温对种子萌发的抑制程度;相比变温和低温处理,高温(25～35℃)处理缩短了种子萌发所需的时间。高温处理可促进胚根的发育,变温处理对胚根也有这种作用,但抑制胚芽的生长。不同品种对高温的耐受能力不同,通过耐热性综合评价,可将白三叶品种划分为3个耐热等级,其中胡依阿属于耐热性强的品种,雷托、克劳和鄂牧1号耐热性中等,海法、路易斯安那和G 18耐热性较弱。     

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.