Inheritance of peroxidase isozymes in mulberry (Morus spp.)

Summary Electrophoretic variants of peroxidase in mulberry (Morus spp.) were demonstrated by thin-layer gel isoelectric focusing. Of these variants, three isozyme band groups were found to be controlled by codominant alleles at a single locus. The gene symbol Px ₁ was given to this locus, with alleles Px ₁ ¹ and Px ₁ ² assigned to the A6-A7-A8 and A7-A8-A9 band groups, respectively. The A6-A7-A8-A9 band group proved to be controlled by the Px ₁ ¹ and Px ₁ ² heterozygote.Additional experiments showed that among the three banding types, there were no statistically significant differences in leaf blade length, leaf blade width, length-width ratio of leaf blade, internode length, phyllotaxis, leaf shape, tree vigor and resistance to powdery mildew, but there were significant differences in leafstalk length.     

Leaf yield component combining abilities in mulberry (Morus spp.)

A line × tester analysis was carried out in mulberry (Morus spp.) to determine the genetic interaction in the expression of various quantitative characters including leaf yield. Eight clonal varieties were selected, 3 of them were designated as lines (♀) viz. Berhampore-1, China white and MS-5 and 5 of them were called as testers (♂) viz. Mandalaya, Kosen, Assamjati, MS-1 and Kajli. Combining ability studies were conducted on these parents along with their F₁ hybrids for the variables laminar index, growth rate, weight of 100 dry leaves, number of primary branches per plant, plant height, nodal distance, leaf-twig ratio, aerial biomass, moisture content, moisture retention capacity and leaf yield. Broad genetic variability was observed among the genotypes. The ratio of General Combining Ability (GCA) and Specific Combining Ability (SCA) indicated the predominance of non-additive genes in mulberry. While China white (female) and MS-1 (male) were the best general combiners among the parents, Berhampore-1 × Kajli was the best cross for leaf yield. Results suggest that selective crossing followed by proper screening may be the best approach for breeding of high yielding varieties in mulberry. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular evaluation of genetic variability in wild populations of mulberry (Morus serrata Roxb.)

Sixteen populations of the wild mulberry, Morus serrata Roxb., were analysed for their genetic diversity with the aim of using them in introgressive breeding programmes with cultivated relatives. Five genets from each population were collected from different natural populations of M. serrata present in Uttaranchal and Himachal Pradesh in India, and diversity of morpho‐anatomical traits and inter‐simple sequence repeat (ISSR) markers were studied. Significant amounts of genetic diversity were observed among these populations for morpho‐anatomical as well as DNA markers. The 17 ISSR primers generated a total of 95 DNA markers, 51 of which were polymorphic, revealing 67% polymorphism among the populations. The pair‐wise genetic distance, estimated from these DNA markers varied from 0.091 between Urgam‐3 and Kathpuria to 0.258 between Dakrakao‐1 and Dunda with an average genetic distance of 0.165. Clustering analysis grouped these 16 populations into three broad groups. The grouping showed a moderate correlation with the geographical distances. Based on the morphological traits and molecular genetic variability, plants of Urgam‐1, Bhowali farm, Nainitikar, Dunda or Korwa‐2 can be selected for breeding and conservation programmes.     

Relationships between amino acid contents and peroxidase isozymes in leaf blades of mulberry (Morus spp.)

Summary Varietal differences of amino acid contents and total nitrogen content were determined in the leaf blades of mulberry (Morus spp.) which is the food source of the silkworm. Between the peroxidase isozyme genotypes, Px ₁ ¹ Px ₁ ¹ or Px ₁ ¹ Px ₁ ¹ and Px ₁ ² Px ₁ ², there were significant differences at the 1% level in total amino acid content and contents of threonine, aspartic acid and serine, at the 5% levelin contents of isoleucine, glycine and phenylalanine. All of these amino acid contents were higher in Px ₁ ¹ Px ₁ ¹ and Px ₁ ¹ Px ₁ ¹ Px ₁ ¹ than in Px ₁ ² Px ₁ ². But there was no significant difference in contents of the other amino acids and total nitrogen between the genotypes.     

AFLP, ISSR and RAPD markers reveal high levels of genetic diversity among Lupinus spp.

The Lupinus genus includes a number of important crop species. The use of defined nucleotide sequences for the analysis of genetic diversity among these species has revealed modest levels of diversity. The aim of this study was to access AFLP, ISSR and RAPD markers to evaluate the genetic diversity among L. albus, L. angustifolius, L. cosentinii, L. hispanicus, L. luteus, L. mutabilis, L. pilosus and L. polyphyllus. Unexpectedly, low levels of genetic similarity were found (ranging from 0.205 to 0.432), regardless of the type of molecular marker used. Nevertheless, these techniques consistently showed a greater genetic similarity between L. pilosus and L. cosentinii, L. mutabilis and L. polyphyllus and among L. luteus, L. hispanicus and L. angustifolius, clearly separating the Old World from the New World species. Such low genetic similarity among Lupinus spp. is most unlikely to be due to differences in coding sequences but could be the result of a long diverging process concerning non‐coding regions, which would represent a very important proportion of these genomes.     

ISSR分子标记在丝瓜杂交种纯度鉴定的应用

品种纯度鉴定对种子质量的保证十分关键.为了鉴定丝瓜杂交种'农福丝瓜801'的遗传纯度,本研究利用ISSR分子标记技术对丝瓜杂交种'农福丝瓜801'及其亲本的DNA指纹进行分析,试验从100条引物中筛选出具有特异性ISSR引物3个(ISSR-820,ISSR-886,ISSR-891).结果 表明,ISSR-820为父母...     

Plant Regeneration and Genetic Variability from Tissue Cultures of Sunflower (Helianthus annuus L.)

Adventitious buds were induced from in vitro culture of sunflower (Helianthus annuus L.) cotyledons. Four inbred lines (G1, G2, G3 and HA89), an open pollinated variety (‘Argentario’) and two hybrids with specific genetic markers were used. Cotyledons were cultured in vitro on MS medium (Murashlge and Skoog 1962) containing various concentrations of kinetin and indole 3-acetic acid (IAA). The quantitative interactions between auxin and cytokinin, the age of the cotyledons and the 2,3,5-triiodobenzoic acid (TIBA) treatments have been found to influence shoot regeneration. The plantlets, after rooting, were successfully established on soil. Qualitative variation was noted in self-pollinated progeny of plants regenerated from culture of two inbreds. Chimerism in regenerated plants was indicated by sectoring of the genetic markers. Some culture-induced variant phenotypes were similar to known spontaneous mutation in sunflower but others have been not yet described. Preliminary data indicate that most of them may have single-gene recessive inheritance.     

Identification, characterisation, and chromosome locations of rye and wheat specific ISSR and SCAR markers useful for breeding purposes

Rye (Secale cereale L. and S. strictum) offers potential to increase the genetic variability and to introduce desirable characters for wheat improvements. Cytogenetic techniques have been used to screen wheat lines containing rye chromatin. These techniques are not adequate since they are highly technical and time consuming. They are not suitable for breeding programs that require rapid screening of large numbers of genotypes. The main objective of this study was to develop and characterize ISSR and SCAR markers that can distinguish wheat from rye genome. Total DNA from wheat, rye, and triticale accessions from different provenances were amplified with ISSR primers in PCR assays. Three wheat-diagnostic sequences were identified. In addition three rye-diagnostic ISSR markers of which, one marker specifically diagnostic for Secale strictum were characterized. Pairs of primers flanking these specific sequences were designed to produce SCAR markers. Two SCAR markers were rye genome-specific. One SCAR was present in all the seven rye chromosome, and another was specific to rye chromosomes two, three, four, and seven. These newly developed ISSR and SCAR markers should be useful to wheat breeders screening genotypes that may contain rye chromatins.     

DNA fingerprinting of Indian cashew (Anacardium occidentale L.) varieties using RAPD and ISSR techniques

Indian cashew breeding programme has produced 24 selections and 11 hybrids with increased yield and excellent nut characters. Molecular profiles of these varieties were developed using a combination of five RAPD and four ISSR primers pre-selected for maximum discrimination and repeatability. A total of 94 markers were generated which discriminated all the varieties with a probability of identical match by chance of2.8 × 10^-11. There was no correlation between the relationships based on molecular data and the pedigree of the varieties. Narrow range of average similarity values among major cashew breeding centres with only 3.6% of molecular variance partitioned between them was attributed to the exchange of genetic material in developing varieties. Difference in the average similarity coefficients between selections and hybrids was low indicating the need and scope for identification of more parental lines in enhancing the effectiveness of hybridisation programme. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic resources and breeding of Capsicum spp.

Five species of Capsicum have been domesticated in the American tropics, but breeding programs have concentrated on the non-pungent cultivars of C. annuum. Studies of the consequences of human selection during and after domestication support theoretical calculations that there will be significant amounts of genetic diversity within as well as between species. Breeders have only recently begun to exploit this diversity. Multiple resistances are available to several pests and diseases, but have to be transferred from one agronomic or market type of pepper to another. Problems in selecting simultaneously for multigenic resistances and polygenic quality characters may be eased by the development of molecular markers and a molecular linkage map for Capsicum. Ploidy changes (both tetraploidy and haploidy) are relatively easy to induce in Capsicum species. Doubled haploids have proved particularly valuable in the analysis of the genetically complex basis of some resistances to pests and diseases. Barriers to interspecific gene transfer are similar to those found in other genera of Solanaceae: unilateral incompatibility, post-fertilisation abortion, and nucleo-cytoplasmic interactions leading to male sterility or other abnormalities. Information on the occurrence and effects of these barriers should be available if or when breeders need to turn to interspecific hybridisation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetics,genomics and breeding of groundnut (Arachis hypogaea L.)

Groundnut is an important food and oil crop in the semiarid tropics, contributing to household food consumption and cash income. In Asia and Africa, yields are low attributed to various production constraints. This review paper highlights advances in genetics, genomics and breeding to improve the productivity of groundnut. Genetic studies concerning inheritance, genetic variability and heritability, combining ability and trait correlations have provided a better understanding of the crop's genetics to develop appropriate breeding strategies for target traits. Several improved lines and sources of variability have been identified or developed for various economically important traits through conventional breeding. Significant advances have also been made in groundnut genomics including genome sequencing, marker development and genetic and trait mapping. These advances have led to a better understanding of the groundnut genome, discovery of genes/variants for traits of interest and integration of marker‐assisted breeding for selected traits. The integration of genomic tools into the breeding process accompanied with increased precision of yield trialing and phenotyping will increase the efficiency and enhance the genetic gain for release of improved groundnut varieties.     

Genetic diversity among tea cultivars from China, Japan and Kenya revealed by ISSR markers and its implication for parental selection in tea breeding programmes

Tea plant [Camellia sinensis (L.) O. Kuntze] is an important beverage crop in the world. In recent years many clonal tea cultivars have been released, and they play major roles in improving the production and quality of tea. It is important to understand the genetic diversity and relatedness of these cultivars to avoid inbreeding and narrow genetic basis in future tea breeding. In the present study, genetic diversity and relationship of 48 tea cultivars from China, Japan and Kenya were evaluated by inter‐simple sequence repeat (ISSR) markers. A total of 382 ISSR bands were scored, of which 381 (99.7%) were polymorphic. The ISSR primers showed high ability to distinguish between tea cultivars according to their high Resolving Power (R_P) with an average of 7.4. The mean of Nei’s gene diversity (H) and Shannon’s information index (I) were 0.22 and 0.35, respectively. More abundant diversity was revealed among cultivars in China than those in Japan and Kenya. Within Chinese populations, the level of diversity in east China was higher than that in other regions. The coefficient of genetic differentiation (G_ST) was 0.202, which indicates a high degree of genetic variation within populations. This result was further confirmed by analysis of molecular variance, which revealed the variance component within the populations (92.07%) was obviously larger than that among populations (7.93%). The level of gene flow (N_m) was estimated to be 2.0. This could be explained by frequent natural cross‐pollination and seed dispersal among tea populations. The pairwise similarity coefficient between the cultivars varied from 0.162 to 0.538. A dendrogram of 48 tea cultivars was constructed where all the tested cultivars were divided into two groups. Our data show that the genetic relationship among tea cultivars can be determined by the ISSR markers. This will provide valuable information to assist parental selection in current and future tea breeding programmes.     

Screening for scab resistance by RAPD markers in cultivars of apple (Malus spp.)

Genetic markers are a much faster and more practical alternative to classical methods for the identification of genes for scab resistance present in different apple cultivars. In our study, 28 scab-resistant cultivars, four wild sources of the resistance genes and 10 susceptible cultivars were screened for the presence of the RAPD fragments OPM18/900, OPD20/600 and OPA15/900, which are reported to be linked to the Vf gene. All three marker fragments were successfully amplified with different protocols in Vf-resistant cultivars including ‘M. floribunda 821’. No marker fragments were amplified in susceptible cultivars, three out of four Va-resistant cultivars, three out of four Vm-resistant cultivars, two Vr-resistant cultivars, ‘Antonovka PI 172612’ and ‘M. pumila R 12740-7A’. All three markers were found in the cv. ‘Nova Easygro’, reported to possess the Vr gene, and the cv. ‘Reglindis’, reported to be Va-resistant. M. atrosanguinea of unknown origin showed the presence of OPD20/600 and OPA 15/900 marker bands. The cvs. ‘Nova Easygro’, ‘Reglindis’ and M. atrosanguinea are probably carriers of the VF gene.     

Cultivar identification and genetic relationship among selected breeding lines and cultivars in chickpea (Cicer arietinum L.)

Twenty two RAPD and 22 ISSR markers were evaluated for their potential use in determination of genetic relationships in chickpea (Cicer arietinum L.) cultivars and breeding lines. We were able to identify six chickpea cultivars/breeding lines by cultivar-specific markers. All of the cultivars tested displayed a different phenotype generated either by the RAPD or ISSR primers. Though ISSR primers generated less markers than RAPD primers, the ISSR primers produced higher levels of polymorphism (% of polymorphic markers per primer) than RAPD primers. A high level of within cultivar homogeneity was observed in chickpea. Cultivars/breeding lines originating from a common genetic background showed closer genetic relationship. Chickpea lines with similar seed type(kabuli or desi) had a tendency to cluster together. This revised version was published online in August 2006 with corrections to the Cover Date.     

Inter simple sequence repeat (ISSR) polymorphism and its application in plant breeding

Inter simple sequence repeat (ISSR)-PCR is a technique, which involvesthe use of microsatellite sequences as primers in a polymerase chainreaction to generate multilocus markers. It is a simple and quick methodthat combines most of the advantages of microsatellites (SSRs) andamplified fragment length polymorphism (AFLP) to the universality ofrandom amplified polymorphic DNA (RAPD). ISSR markers are highlypolymorphic and are useful in studies on genetic diversity, phylogeny, genetagging, genome mapping and evolutionary biology. This review providesan overview of the details of the technique and its application in geneticsand plant breeding in a wide range of crop plants.     

利用RAPD、ISSR标记分析国兰种质资源遗传多样性的研究

旨在分析不同地区国兰间的亲缘关系,为国兰资源的开发及新品种的选育提供分子水平的参考依据。利用RAPD和ISSR分子标记技术,对7种国兰的21个品种资源进行遗传多样性和亲缘关系分析。结果表明：39个RAPD和ISSR引物在供试材料中共扩增出96条带型清晰的谱带,其遗传中31条为多态性条带;通过UPGMA聚类分析表明,21个国兰品种资源间遗传距离在1.91~6.60之间,其中春兰资源的遗传距离在1.91~4.38之间,建兰资源的遗传距离在2.60~6.20之间,寒兰资源的遗传距离在2.20~5.80之间,墨兰资源的遗传距离在3.52~6.60之间,表现出了较高的遗传多样性。聚类分析结果与传统的形态学分类结果基本一致,也说明分子标记可以在分子水平反映遗传资源的遗传多样性,具有灵敏度高、结果真实可靠等优点。本研究结果显示国兰品种间的亲缘关系与地理位置分布相关,为兰属植物的分类及遗传多样性研究提供了一定的理论支撑。     

利用RAPD、ISSR标记分析白芨种质资源遗传多样性的研究

旨在分析不同地区野生驯化白芨居群间亲缘关系,为白芨资源保护和利用提供支撑。利用RAPD和ISSR标记技术从分子层面鉴别源于湖南、湖北、贵州、云南、江西等地的12个白芨资源遗传多样性差异,并通过UPGMA对该差异性进行了聚类分析。结果表明,在36条供试RAPD引物中有13条扩增带型清晰、多态性高,15条供试ISSR引物中有2条扩增带型清晰、多态性高,共获得40条多态性条带;通过UPGMA聚类分析表明,12份供试白芨种质资源间具有较高的遗传多样性,遗传距离最大可达0.975,供试材料总体上可分为两个支系,湖南、江西为一个支系,湖北、贵州和云南为一个支系。利用ISSR和RAPD标记可以从分子水平上揭示白芨的种质资源遗传多样性,同时,研究还发现ISSR标记能比RAPD标记扩增出更多的多态条带和获得更高的多态比率,且分析不受时间和地点限制,结果更稳定、可靠。本研究结果显示白芨居群间遗传差异性与地理距离呈现一定的相关性,对研究白芨物种的演化及遗传多样性提供了相关数据和理论支持。     

Comparing RAPD and AFLPTM analysis in discrimination and estimation of genetic similarities among apple (Malus domestica Borkh.) cultivars

Forty-one apple (Malus × domestica Borkh.) cultivars were screened for RAPD (Random Amplified Polymorphic DNA) and AFLP(Amplified Fragment Length Polymorphism) markers. RAPD analysis was performed with 35 arbitrary 10-mer primers, selected from 60 primers tested (kits A, C and E, Operon Technologies, Inc.). Of a total of 362bands observed, 208 (57.5%) were polymorphic. Three-hundred-and-eighty-one AFLP fragments were obtained with 8primer combinations, of which 218 (57.2%) were polymorphic. Cultivars differentiated through mutation were included in this study and showed identical patterns when analysed with both RAPD and AFLP analysis. The estimated genetic relationships were correlated (r = 73.7%) between the analysis with the two different markers. UPGMA analysis was performed and dendrograms were constructed using either the data apart from each(RAPD and AFLP) method or combined in a single joint matrix. The relationships among the forty-one studied cultivars were basically consistent with the known lineage and geographic origins of the cultivars. The four Portuguese cultivars included in this study clustered together and diverged from the other cultivars. Apparently they constitute an independent genetic pool, which could be of interest for apple plant breeders. This revised version was published online in July 2006 with corrections to the Cover Date.     

Isozyme electrophoretic characterization of 29 related cultivars of lily (Lilium spp.)

Isozyme banding patterns (IBPs) were studied for cultivars of lily (Lilium spp.) by means of horizontal starch‐gel electrophoresis (SGE). An array of continuous histidine‐citrate buffer systems at eight ranges of pH and four extraction buffers were tested. On the basis of this survey, the extraction buffer two (Eb‐2) and the buffer system E at pH 7.7 were found to be suitable for detection of lily isozymes. Using the SGE technique, IBP in catalase (CAT; EC 1.11.1.6), esterase (EST; EC 3.1.1.1), malate dehydrogenase (MDH; EC 1.1.1.37), malic enzyme (MAL; EC 1.1.1.40), peroxidase (POX; EC 1.11.1.7), phosphoglucomutase (PGM; EC 2.7.5.1), phosphoglucose isomerase (PGI; EC 5.3.1.9) and 6‐phosphogluconate dehydrogenase (PGD; EC 1.1.1.44) were assayed. In total 29 cultivars were tested in this study: nine were analysed for all eight enzyme systems, 16 cultivars for seven systems, three for six, and one for five enzyme systems. Some IBP were identified as section‐specific biochemical markers. Eight enzymes systems were analysed by constructing a dendogram using the unweighted pair group method, arithmetic average (UPGMA) cluster analysis. The analysis indicated that the lily cultivars could be separated from other Lilium species, except for two L. x formonlogi cultivars:‘Hakuba’ and ‘Hakuko’ which could not be distinguished from each other by the isozyme patterns assayed here. This study shows that isozymes can provide useful biochemical markers for lily cultivar identification and to estimate the phylogenetic relationships among those cultivars.