Geographical differentiation of Asian taro, Colacasia esculenta (L.) Schott, detected by RAPD and isozyme analyses

Geographical differentiation and phylogenetic relationships of Asian taros, Colocasia esculenta (L.) Schott, and related species were analyzed by random amplified polymorphic DNA (RAPD) and isozymes of 13 enzyme systems with special interest in the accessions from the Yunnan area of China, which supposedly has served the secondary center of taro diversification and dispersal into the temperate Far East Asia. The RAPD analysis was found to be better suited for detecting genetic differences within taros and among its related species. However, both RAPD and isozyme analyses estimated quite similar genetic relationships within taros and between related species. Genetic differentiation was evident in the taro accessions of Nepal, Yunnan and other Asian areas; but, phylogenetic relationships between the differentiated taro groups were not clearly determined. When taro cultivation was introduced to a new area, only a small fraction of genetic variability in heterogeneous taro populations was transferred possibly causing random differentiation among locally adapted taro populations. Some of the Yunnan and Japanese accessions were found to be direct descendants of the common triploid population. Further analysis on taros from the eastern China and Korea is necessary to clarify the Yunnan's role in taro diversification and dispersal. The significant local differentiation in Asian taros was clearly demonstrated by RAPD and isozyme analyses in this study, and the results of this study will serve as a base to establish evolutionary and genetic relationships among Asian taros. This revised version was published online in August 2006 with corrections to the Cover Date.     

Evaluation of the genetic diversity among elite tea (Camellia sinensis var. sinensis) accessions using RAPD markers

The diversity of 27 superior tea (Camellia sinensis var. sinensis) accessions from Korea, Japan and Taiwan was examined with RAPD-PCR (Random Amplified Polymorphic DNA Polymerase Chain Reaction) markers. Out of the 50 primers screened, 17 primers generated 58 polymorphic and reproducible bands. A minimum of 3 primers was sufficient to distinguish all the 27 accessions studied. The Shannon's index used to partition diversity into inter- and intra-group, revealed that 71 percent of variability resided within groups and 29 percent between groups. Diversity was greatest within the Korean group followed by Taiwan and Japan. The relatively high diversity observed in Korea might reflect the larger genetic base of its plantations while the low diversity in Japan could be explained by the long and intensive tea selection programme in this country. A dendrogram based on the UPGMA-link method using Jaccard's distances and multivariate Factorial correspondence analysis clustered the tea accessions into two main groups, regrouping the Taiwan cultivars on the one side and the Korean and Japanese accessions on the other side. This suggests that the Taiwan tea studied here may have a different origin from that of Korea and Japan. This revised version was published online in July 2006 with corrections to the Cover Date.     

Recurrent phenotypic selection for forage yield in rye

Summary Cultivars of Cucurbita pepo and other Cucurbita species were characterized by RFLP analysis using different fragments of the ribosomal intergenic spacer (IGS) of Cucurbita pepo as hybridization probes. Several cultivars could be distinguished by a specific rDNA restriction pattern, whereas some cultivars showed an identical RFLP pattern suggesting a closer relationship. Other species of the genus Cucurbita exhibited strong cross-reaction with the C. pepo spacer probes, in contrast to DNA of Cucumis species which did not cross-hybridize.Abbreviations IGS intergenic spacer - ITS internal transcribed spacer - kbp kilo base pairs - rDNA ribosomal DNA - RFLP restriction fragment length polymorphism - rRNA ribosomal RNA     

Geographical distribution of allozyme patterns in shallot (Allium cepa var. ascalonicum Backer) and wakegi onion (A. × wakegi Araki)

Summary Shallot and wakegi were collected in the main islands of Indonesia, and in Japan, Korea, Taiwan, Malaysia, Thailand and Bangladesh. Five isozyme resolutions, phosphoglucomutase (PGM), glutamate oxaloacetate (GOT), glutamate dehydrogenase (GDH), esterase (EST) and peroxidase (POX) were employed for demonstrating inter-and intraspecific differences. A dendrogram separated 189 collected accessions into 25 types of wakegi onion and 18 types of shallot. All accessions of Japan, Korea and Taiwan were determined to be wakegi onion, whereas those of Bangladesh, Malaysia and Thailand were shallot. Twenty-six out of 165 Indonesian accessions indicated wakegi onion distribution in Sumatra, West Java province and in Sulawesi Island. This confirmed that there is mixed-cultivation of the two Allium species with no distinction made between them. Japan and Indonesia had respectively 12 and eight unique types of wakegi onion, while Korea had only one type. West Java showed the most various type of wakegi onion, whereas East Java had many types of shallot. Shallots collected from Bangladesh were distinetly different from those of South East Asian types.     

Cytology and pollen grain fertility in populations of Astragalus adsurgens Pall. indigenous to Yunwu Mountain in the Loess Plateau,north-west China

Summary The wild type populations of Astragalus adsurgens Pall. growing on the northern slopes of Yunwu Mountain were investigated as a part of the program on the reclamation of the Loess Plateau, north-west China.In 1990, plants were sampled from two populations indigenous to Yunwu Mountain and Liupan Mountain, and two populations cultivated in experimental plots. Pollen grain fertility of the plants showed a wide variation from 20 to 99%. In 1991, cytological analysis of chromosome behaviour during meiosis was carried out in order to clarify the causal factors of pollen grain sterility. In anaphase-1, a chromatid bridge and an acentric fragment as well as two chromatid bridges were observed in high frequencies. In addition, more than two chromatid bridges per nucleus existed in considerably high frequencies.These observations clearly indicate that inversions are dominant in populations of wild A. adsurgens indigenous to Yunwu Mountain. xxThis study was supported by a Grant-in-Aid for scientific research from the Ministry of Education, Science and Culture, Japan (No. 01102023).     

Allelic variation at high-molecular-weight glutenin subunit Loci, Glu-A1, Glu-B1 and Glu-D1, in Japanese and Chinese hexaploid wheats

Variation in the electrophoretic banding patterns of high-molecular-weight (HMW) glutenin subunits of 274hexaploid wheat (Triticum aestivum) varieties from China was examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis and 27 different major HMW glutenin subunits were identified. Each variety contained three to five subunits and 29different glutenin subunit patterns were observed in274 Chinese hexaploid wheats. Seventeen alleles were identified based on the comparison of subunits mobility with that previously identified in a set of standard hexaploid wheats. The Chinese hexaploid wheats exhibited allelic variation in HMW glutenin subunit composition and the variation differed from that of Japanese and hexaploid wheats of other countries. This revised version was published online in July 2006 with corrections to the Cover Date.     

Current status of tropical fruit breeding and genetics for three tropical fruit species cultivated in Japan: pineapple,mango, and papaya

Tropical fruit crops are predominantly produced in tropical and subtropical developing countries, but some are now grown in southern Japan. Pineapple (Ananas comosus), mango (Mangifera indica) and papaya (Carica papaya) are major tropical fruits cultivated in Japan. Modern, well-organized breeding systems have not yet been developed for most tropical fruit species. Most parts of Japan are in the temperate climate zone, but some southern areas such as the Ryukyu Islands, which stretch from Kyushu to Taiwan, are at the northern limits for tropical fruit production without artificial heating. In this review, we describe the current status of tropical fruit breeding, genetics, genomics, and biotechnology of three main tropical fruits (pineapple, mango, and papaya) that are cultivated and consumed in Japan. More than ten new elite cultivars of pineapple have been released with improved fruit quality and suitability for consumption as fresh fruit. New challenges and perspectives for obtaining high fruit quality are discussed in the context of breeding programs for pineapple.     

Isozyme variation in taro (Colocasia esculenta (L.) Schott) from Asia and Oceania

Summary Isozyme variation was studied in 1,417 cultivars and wild forms of taro collected in Asia and Oceania. Seven polymorphic enzyme systems (MDH, IDH, PGI, 6-PGD, ME, SkDH, and ADH) revealed 143 isozyme phenotypes, or zymotypes, each uniquely characterized by the presence or absence of 56 electromorphs. Results showed greater isozyme variation in Asia than in Oceania, with Indonesia being the area of greatest diversity. No correlations were found between zymotypes and morphotypes or ploidy levels (as described by other investigators). Multivariate analyses of the isozyme data indicated that the majority of the Indonesian cultivars were different from the Philippine and Oceanian taro cultivars. Oceanian cultivars constituted a continuum of clusters and are thought to have originated from a narrow genetic base introduced from Indonesia. If taro breeding is to have any future in Oceania, it is important to exchange genotypes to broaden the base of existing breeding programmes.     

Molecular stability of the ribosomal RNA genes in Solanum tuberosum plants recovered from slow growth and cryopreservation

Summary Ribosomal gene (rDNA) probes have been used to assess genomic changes in plants of (1) S. tuberosum cv Desiree subjected to slow growth and (2) S. tuberosum cv Golden Wonder recovered from cryopreservation. Restriction fragment length polymorphisms (RFLPs) were detected in two out of 16 DNA samples extracted from plants derived from slow growth, control plants did not show RFLP differences. Plants recovered from cryopreserved shoot-tips of Golden Wonder were unchanged in their ribosomal gene RFLP profile compared to the untreated controls. The use of rDNA probes as tools to assess stability, and the possible detrimental effects of slow growth, somaclonal variation, cryoprotectants, and freezing injury are discussed.     

Each species of Glycine collected in Taiwan has a unique seed protein pattern

Several annual and perennial species in the genus Glycine Willd., including G. soja, long-pod G. tomentella, short-pod G. tomentella and G. tabacina, collected in Taiwan and nearby islands were studied for variations of their seed proteins. SDS-PAGE and Western blotting were used to analyze the total proteins, the heat soluble proteins, six seed maturation proteins (GmPMs) and one seed storage protein. The various species had different patterns of seed heat soluble proteins. In addition,each species of Glycine collected in Taiwan exhibited unique seed maturation protein patterns. They had several cross-reactive polypeptides recognized by specific antibodies against GmPM1, GmPM2 and GmPM8, but only one polypeptide recognized by antibodies against GmPM4, GmPM5 and MP130. The long pod G. tomentella, which has been suggested as a new species and renamed as G. dolichocarpa, could be distinct from the short pod G. tomentella on the basis of the analysis of these biochemical markers. It is also indicated that these GmPM antibodies may be used to distinguish between and within other Glycine species. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mitochondrial DNA variation in finger millet (Eleusine coracana L. Gaertn)

Summary This study was conducted to classify 26 lines of finger millet from Africa and India into cytotype groups based on the Southern blot hybridization patterns obtained with maize and sorghum mitochondrial cloned gene probes. Five restriction endonuclease enzymes were used for single digestions on total cellular DNA, giving a total of 20 enzyme/probe combinations. There was a low level of polymorphism, with identical RFLP banding patterns in 23 of the 26 lines. However, mtDNA clone atp9 hybridized to a 3.6 Kb Xba1 fragment in ecotype SDFM-1143 from Malawi; but did not hybridize to a 3.0 Kb fragment present in all other ecotypes. Two Zimbabwean lines, SDFM 63 and SDFM 77, had an extra, low intensity 6.5 Kb Xba1 fragment hybridized by mtDNA clone cox1. This data enabled classification of the lines into 3 cytopype groups.     

The BamHI site in the Internal Transcribed Spacer Region of Mungbean ribosomal RNA gene is partially methylated

The 18s-5.8s-25s ribosomal gene (18s-25s rDNA) in higher plants is present in multiple copies, on different chromosomes, as tandemly repeated units. Among the multiple BamHI sites that occur in the repeat unit, only the site in the middle of the 25s rRNA coding region is methylated in most cereals and pulses. BamHI restriction enzyme analyses of the mungbean 18s-25s rDNA showed the presence of two populations. Nearly 50% of the 18s-25s rDNA population had BamHI site situated in the internal transcribed spacer region (ITS-BamHI) resistant to cleavage by BamHI. The amplified ITS fragment was completely digestible by BamHI showing that partial cleavage by BamHI is not due to variation in the recognition sequence but most probably due to methylation. The complete cleavage of the ITS-BamHI site by BstYI that recognizes BamHI site but is insensitive to methylation confirms that the ITS-BamHI site is methylated. Methylation is probably due to the presence of a guanosine residue adjacent to the 3′ cytosine in the recognition sequence. This revised version was published online in July 2006 with corrections to the Cover Date.     

Multiple resistance to diseases and pests in potatoes

Summary The potato has more characters of economic importance that need to be considered by the breeder than any other temperate crop. In Europe these include resistance to at least twelve major diseases and pests. Highest priority has been given to resistance to late blight (Phytophthora infestans), virus diseases (particularly those caused by potato leafroll virus and potato virus Y) and potato cyst nematode (Globodera rostochiensis andG. pallida). Useful sources of resistance are available and early generation screening techniques have been developed to allow positive selection for multiple resistance and the breeding value of clones used as parents to be determined. Progress in restriction fragment length polymorphism technology should result in more efficient selection in the future.     

Karyotypic and electrophoretic studies on taro and its origin

Summary Karyotypes and electrophoretic pattern of 15 strains of taro were studied. Strains collected from the northeast India hill state, Meghalaya were diploids and triploids whereas those from the plains of south India were diploids and of north India was a triploid. The diploids had 2n=28 and triploids showed 2n=42 chromosomes. The wild taro had the most asymmetrical karyotype. The protein content varied from 4.2 to 11.4 mg/g dry wt. The maximum protein content was found in a triploid strain 8 (11.4 mg/g dry wt) and minimum in the wild taro (4.2 mg/g dry wt). The number of protein bands was 7 in the wild taro (diploid) and 12 in one of the cultivated triploid strain. Meghalaya strains showed great variation with respect to leaf size and tuber shape and size. All the strains have diverged at morphological, karyotypic and genotypic levels. It is suggested that taro might have originated in the north-eastern India.     

Quantitative chromosome map of a representative indica rice

The somatic chromosomes of standard indica diploid rice, IR 36, were squashed on glass slides and stained with Giemsa. The condensation patterns (CP) of prometaphase chromosomes were quantitatively analysed using CHIAS III software. The relative length and centromeric index (CI) were converted from CHIAS III to numerical data and calculated by EXCEL program. The ideogram based on CP of indica rice was established. There were 2 pairs of satellite chromosomes and the result was confirmed by fluorescence in situ hybridization using 45S rDNA as a probe. This revised version was published online in July 2006 with corrections to the Cover Date.     

Isolation, sequence analysis, and linkage mapping of resistance-gene analogs in cowpea (Vigna unguiculata L. Walp.)

Degenerate oligonucleotides designed to recognize conserved coding regions within the nucleotide binding site (NBS) and hydrophobic region of known resistance (R)genes from various plant species were used to target PCR to amplify resistance gene analogs (RGAs) from a cowpea (Vigna unguiculata L. Walp.) cultivar resistant to Striga gesnerioides. PCR products consisted of a group of fragments approximately 500 bp in length that migrated as a single band during agarose gel electrophoresis. The nucleotide sequence of fifty different cloned fragments was determined and their predicted amino acid sequences compared to each other and to the amino acid sequence encoded by known resistance genes, and RGAs from other plant species. Cluster analysis identified five different classes of RGAs in cowpea. Gel blot analysis revealed that each class recognized a different subset of loci in the cowpea genome. Several of the RGAs were associated with restriction fragment length polymorphisms, which allowed them to be placed on the cowpea genomic map. The potential for using these sequences to isolate R genes, and subsequent direct manipulation of disease and pest resistance using genetic engineering is discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Application of image analysis for variety testing of mushroom

Summary A restriction enzyme map of the ribosomal RNA genes (rDNA) in Solanum tuberosum cultivars Golden Wonder and Desiree has been constructed. An heterologous probe pTa 71 containing the rDNA derived from wheat was used to detect and map the corresponding region in potato genomic DNA fragments. rDNA repeats of cultivars Desiree and Golden Wonder are similar with respect to their target sites for restriction enzymes, however, these cultivars have diverged with respect to the length of their intergenic spacer (IGS) sequences. IGS length variants may reflect the different breeding systems for Golden Wonder and Desiree. Furthermore, some of the 25S genes of both cultivars appear to have a 100–150bp insertion/deletion near their 3 end. The presence of RFLPs (restriction fragment length polymorphisms) in the IGS region could be used as a DNA fingerprint for potato cultivar identification; the ability to recognise IGS length variants may be of significance to potato phylogenetics and breeding.     

Molecular markers in some medicinal plants of the Apiaceae family

The internal transcribed spacers ITS1 and ITS2 in the18S-5.8S-26S rDNA repeat units were amplified and cloned from Angelica gigas Nakai, Angelica acutiloba (Siebold & Zucc.) Kitagawa, A. dahurica Maxim, Angelica decursiva (Miq.) Franch. & Savat, Bupleurum falcatum L. and Peucedanum japonicum Thunb. Sequence analyses showed that ITS1 is approx. 215 bp, the 5.8S gene is 162 bp and the ITS2 approx. 221 bp in all six species. The sequences are deposited at the EMBL Nucleotide Database. By including these new sequences in the Apiaceae phylogenetic tree, a third branch consisting of P. japonicum, A. gigas, P. decursivum and A. decursiva is added to theAngelica clade. Peucedanum does not forma distinct branch. The sequence obtained from Angelica dahurica collected in S. Korea is identical to that reported for the same species originating from China. A Bupleurum clade of three species was added to the tree showing closer relationship to theDaucus Laserpitium clade than the Angelica clade. RAPD analysis of all six species showed that the 10-base primer OPC-17 only, out of the20 Kit-C primers from Operon gave polymorphic banding patterns. This revised version was published online in July 2006 with corrections to the Cover Date.     

Variation of PGM and IDH isozymes for identification of alfalfa varieties

Growth habit, heading date and Vrn genotypewere examined for wheat landraces cultivated in China,Korea and Japan, to study their ecogeographicaldifferentiation in east Asia. Spring type landracesaccounted for 43.6% of the whole, and the frequencyvaried between the localities, being closely relatedto the degree of winter coldness. Spring typelandraces mainly adapted to north and south Chinawhere average January temperature is under –7 ^°Cand over 4 ^°C, respectively. On the contrary,winter type adapted to areas of average Januarytemperature from –7 ^°C to 4 ^°C. As toheading date, significant difference was not observedbetween spring and winter type landraces but betweenlocalities, and those cultivated in north China weresignificantly later in heading. It is thereforeindicated that spring type mainly adapts to areaswhere wheat is sown in spring to avoid frost injury,and where winter temperature is not low enough tovernalize winter type wheat. Genetic analysis forspring type landraces showed that the relativefrequency of four Vrn genes was different witheach other. Vrn3 was most widely and frequentlyfound among the four genes, followed by Vrn1 andVrn2. Only seven landraces proved to be thecarrier of Vrn4. The frequency was alsodifferent between localities. Genotype with Vrn1plus other dominant gene(s) adapted to spring sowingto avoid severely cold winter in north China, whilegenotype with only Vrn3 adapted to winter sowingin south China and southwest Japan. It is thereforeconcluded that at least three ecotypes, differing ingrowth habit and Vrn genotype, areallopatrically distributed in east Asia, as a resultof adaptation to winter coldness in each locality.     

Genetics of isozyme variants in Populus tremula,P. tremuloides and their hybrids

Summary Eight Populus tremula and six P. tremuloides clones as well as 49 full-sib families were studied in GOT, LAP, 6-PGDH, and SKDH by horizontal starch gel electrophoresis. For GOT one polymorphic zone was found and segregation of seven full-sib families suggests Mendelian inheritance. For LAP and 6-PGDH two zones each were clearly scored. For LAP two polymorphic loci were proposed based on the phenotypic segregation of isozyme variants in six and 34 full-sib families, respectively. In 24 full-sibs families the presence of null alleles was inferred for both loci. The genetic control of the upper zone of 6-PGDH was demonstrated by a segregation analysis of 17 full-sib families. SKDH also demonstrated a Mendelian inheritance pattern in 12 of the full-sib families analysed. The electrophoretic patterns of pollen were similar to those of buds, but migration rates of the supposed corresponding isozymes were slightly modified (Lap-B, Skdh, 6Pgdh-A). Lap-A was not present in pollen extracts and hybrid bands were not found when gels were stained for dimeric enzymes (6-PGDH, GOT).