甜瓜松散型胚性愈伤组织诱导

为建立甜瓜松散胚性愈伤组织再生体系，给分子标记辅助育种、转基因育种、诱变育种等新型的育种技术提供优质材料，以甜瓜成熟叶片为外植体，调节培养基中激素、蔗糖浓度以及愈伤组织继代次数诱导甜瓜松散型胚性愈伤组织。结果表明，在2,4-D的作用下叶片能诱导出愈伤组织，在MS+0.1 mg/L 6-BA+2.0 mg/L 2,4-D+20 g/L蔗糖的培养基上，可以获得结构松散、质地较软呈黄绿色的愈伤组织；诱导松散型愈伤组织最佳培养基为MS+0.5 mg/L 6-BA+1.0 mg/L 2,4-D+30 g/L蔗糖，经过3次继代后可以获得生长速度较快，结构松散、质地较硬呈黄绿色的松散型愈伤组织；在MS+0.25 mg/L 6-BA+0.25 mg/L 2,4-D+40 g/L蔗糖的培养基上愈伤组织胚性化最好，继代5次，可获得结构松散、质地较硬，生长速度较快的松散型胚性愈伤组织。     

杜仲愈伤组织诱导及胚性愈伤组织的判别

为探索杜仲胚性愈伤组织诱导的条件,建立杜仲体细胞胚胎发生初步体系,以杜仲幼嫩叶片和未成熟合子胚为外植体、MS为基本培养基,探究外源激素配比、未成熟合子胚发育阶段与基因型对愈伤组织诱导的影响,并从形态学和细胞学对愈伤组织进行胚性的判断。试验结果表明：4种不同激素配比的培养基诱导出的叶片愈伤组织在形态上具有差异,MS+ 2,4-D 2 mg/L+ 6-BA 1 mg/L和MS+ 2,4-D 2 mg/L+6-BA 0.5 mg/L有利于叶片胚性愈伤组织诱导;在培养基MS+ 2,4-D 2 mg/L+ 6-BA 1 mg/L上,以未成熟合子胚为外植体诱导出4种类型愈伤组织,其中圆球形和颗粒型突起的愈伤组织具有胚性;未成熟合子胚采集时间对愈伤组织诱导率具有显著差异,6月14日采集的外植体愈伤诱导率最高,不同基因型差异不显著。     

火龙果花药培养诱导胚性愈伤组织及遗传稳定性

成年态火龙果茎段诱导的愈伤组织再分化较困难,进而影响到遗传转化效率。以红皮紫红肉的"紫红龙"火龙果花药为外植体,研究了小孢子不同发育时期、低温预处理时间、不同植物生长调节剂及浓度配比对花药诱导胚性愈伤组织的影响。结果表明,小孢子发育处于单核初期至单核靠边期的花药,其愈伤组织诱导率最高可达23.9%,但未能诱导出胚状体;而4℃低温预处理48 h,愈伤组织的诱导率可达32.8%;最适花药愈伤组织诱导的培养基为MS+2.0 mg/L 6-BA+1.0 mg/L 2,4-D+60 g/L蔗糖,诱导率为37.4%,胚性愈伤组织为黄绿色、致密状,外表有颗粒状突起。愈伤组织增殖培养基以MS+0.4 mg/L TDZ+0.8 mg/L KT效果较好,增殖系数达9.1倍以上。愈伤组织再分化培养基为MS+0.4 mg/L TDZ+0.5 mg/L 2,4-D+0.6 mg/L NAA时,愈伤组织再分化率达36.7%。通过火龙果花药诱导出愈伤组织,增殖获得大量胚性愈伤组织,再分化形成不定芽,经SRAP分子标记检测遗传性一致,能为火龙果基因工程育种和种苗快速繁育提供新的途径。     

宁夏枣树花药离体培养再生体系的建立

采用宁夏3个特色枣树品种的花药为外植体,探索MS培养基中不同激素、激素的不同浓度配比对愈伤组织诱导、不定芽分化的影响,建立其愈伤组织诱导及不定芽再生体系。结果表明,细胞分裂素6-BA对宁夏枣树胚性愈伤组织诱导起重要作用,AgNO3对愈伤组织分化不定芽影响显著。经过正交试验分析得出,最佳诱导培养基为MS+6-BA 1.0 mg/L+2,4-D1.0 mg/L+IBA 0.4 mg/L;最佳分化培养基是：MS+6-BA 1.5 mg/L +IBA 0.6 mg/L +AgNO3 0.5 mg/L。在最佳诱导培养基中灵武长枣诱导率最高,达89.0%,在最佳分化培养基中同心圆枣分化率最高,达88.0%。     

不同外源激素对油棕愈伤组织诱导的影响

以油棕幼胚为外植体,以N6培养基上添加不同浓度的生长素与细胞分裂素进行愈伤组织诱导研究。结果表明,无激素的培养基上不能诱导出愈伤组织,单独加入2,4-D、IAAIBA、6-BA中N6+2,4-D110mg/L的浓度愈伤组织形成率最高,为83.75%,诱导过程中褐化现象少。N6+2,4-D110mg/L+PVP5g/L+蔗糖6%+AC0.3%培养基促进愈伤组织的诱导和生长,适合进一步继代培养。     

汾阳核桃叶片愈伤组织的诱导、增殖及分化培养

试验中采取汾阳核桃一年生实生苗作为外植体材料,其中叶片愈伤组织的诱导、增殖及分化的基本培养基均为改良DKW。试验结果显示：诱导核桃叶片形成愈伤组织的最佳激素配比为：6-BA0.01mg/L+2,4-D0.01mg/L;促使核桃愈伤组织增殖的最佳激素配比为：BA0.01mg/L+2,4-D0.8mg/L;诱导核桃愈伤组织芽分化的最佳激素配比为：KT 0.8 mg/L +NAA0.4mg/L。     

糯玉米的成熟胚培养

以糯玉米成熟胚为外植体作离体培养,研究在培养基中添加植物激素,硝酸银及有机物等对玉米愈伤组织的诱导和胚性愈伤继代生长的影响。结果表明：在诱导培养阶段,N6+6-BA 0.2mg/L+2,4-D 2mg/L的培养基诱导率最高,愈伤质量好;在继代培养阶段,MS+6-BA 0.2mg/L+2,4-D 2mg/L +AgNO310mg/L或CW (Coconut Water) 10%的培养基可改善胚性愈伤的质量。     

紫花苜蓿愈伤组织诱导和分化研究

以紫花苜蓿SANDITI无菌苗下胚轴、茎、叶3种不同外植体,在附加不同激素浓度的MS培养基上诱导愈伤组织。结果表明,SANDIT最佳外植体为下胚轴,最佳下胚轴愈伤组织诱导培养基为MS+2,4-D 2.0 mg/L+6-BA 0.5mg/L。15 d继代1次,或适当降低2,4-D浓度,提高6-BA或KT浓度,可以降低愈伤组织褐化率。愈伤组织在6-BA0.5 mg/L,NAA 0.1 mg/L,GA31.0 mg/L,YE 250 mg/L,CH 250 mg/L的MS培养基上,可获得较高的分化率。     

新冬26小麦幼胚盾片再生体系的建立

以新冬26小麦的幼胚盾片为实验材料,研究不同激素及其不同浓度对愈伤组织诱导和分化的影响.结果表明:2,4-D和Dicamba组合诱导的愈伤组织分化率显著优于单独添加2,4-D或Dicamba.分化培养基中添加低浓度的ZT有利于根的分化.诱导培养基采用MS附加2,4-D 1.5 mg/L和Dicamba 0.5 mg/L,分化培养基采用R附加ZT1 mg/L和2,4-D0.01 mg/L对愈伤组织分化效果为最佳,绿苗分化率最高可达90％.本研究结果为建立高效、稳定的新疆主栽小麦品种的遗传转化系统奠定了基础.     

高羊茅高效组织培养再生体系的建立

植物分子育种与基因功能鉴定是建立在高效的组织培养再生体系基础上的。本研究以高羊茅(Festuca arundinacea Schreb)为材料,探讨了不同外植体状态、基本培养基类型、外源激素组合与固化剂种类与浓度对愈伤组织诱导的影响,并进行了愈伤组织分化长芽与生根研究。结果表明:愈伤组织诱导过程中,离体成熟胚比完整种子作外植体愈伤组织出现早、质量优、诱导率高;基本培养基的选择上以N6诱导率最高,MS最低;激素组合研究中高羊茅三个品种(SAFari, FirewarⅡ, Barleduc)在无6-BA培养基中,生长激素选择上都是2,4-D优于IAA,2~2.5 mg/L 2,4-D在三个品种中诱导率都在50%以上,而在添加0.5 mg/L 6-BA时诱导率都偏低;固化剂选择上则以Phytagel与Agarose二都最优,Phytagel固化剂最佳诱导浓度为2~4 g/L。分化长芽最佳培养基为MS+0.1 mg/L 2,4-D+0.1 mg/L 6-BA+0.5 mg/L NAA+20 mg/L AgNO3+2%蔗糖+0.6%琼脂,生根壮苗最佳培养基为1/2MS+0.5 mg/L NAA+3%蔗糖+0.3%Phytagel。本研究为高羊茅的高效转基因体系建立与CRISPR基因功能研究提供准备。     

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.     

Avoidance of leaf rust fungi in wild relatives of cultivated cereals

Summary Avoidance of rust fungi that was based on poor appressorium induction was previously found in Hordeum chilense. In the present study 95 accessions of Triticeae were screened for avoidance of Puccinia hordei. The percentage of appressorium formation per germinated spore ranged from 6 to 90%. On none of the 41 accessions of Aegilops, Agropyron, Elymus, Secale, Thinopyrum or Triticum studied was the rate of appressorium formation lower than 25%. Lower rates of appressorium formation were, however, found on accessions of wild barley species Hordeum brachyantherum, H. marinum, H. parodii and H. secalinum. Its implications in cereal breeding are discussed.     

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.     

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 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.     

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.