中国17个优良玉米自交系的分子标记杂合性及其与杂交种性状的关系研究

在玉米单交种育种中 ,鉴定高产杂交种和具有优良特性的自交系是一个重要的问题。研究以 1 7个优良玉米自交系为亲本 ,按照双列杂交配组合 ,利用 RAPD技术分析了 1 7个自交系的多态性以及 RAPD标记与 9个重要农艺性状 (包括产量 )的关系。基于 RAPD标记计算的相似系数聚类将 1 7个自交系分为 5个类群 ,经分析与系谱亲缘关系基本一致。杂交种性状及其特殊配合力与亲本间的遗传距离是高度相关的 ,与聚类前比较 ,聚类后平均遗传距离与平均产量、平均特殊配合力的相关系数显著提高 ,类间平均产量高于类内平均产量。RAPD技术可揭示优良玉米自交系的系谱亲缘关系 ,将自交系划分成不同的类群 ,从而为选择类间自交系杂交 ,进行亲本选配和分子标记辅助育种提供一种方法。     

A genetic linkage map of cowpea (Vigna unguiculata) developed from a cross between two inbred, domesticated lines

 We have constructed a genetic linkage map within the cultivated gene pool of cowpea (2n=2x=22) from an F₈ recombinant inbred population (94 individuals) derived from a cross between the inbreds IT84S-2049 and 524B. These breeding lines, developed in Nigeria and California, show contrasting reactions against several pests and diseases and differ in several morphological traits. Parental lines were screened with 332 random RAPD decamers, 74 RFLP probes (bean, cowpea and mung bean genomic DNA clones), and 17 AFLP primer combinations. RAPD primers were twice as efficient as AFLP primers and RFLP probes in detecting polymorphisms in this cross. The map consists of 181 loci, comprising 133 RAPDs, 19 RFLPs, 25 AFLPs, three morphological/classical markers, and a biochemical marker (dehydrin). These markers identified 12 linkage groups spanning 972 cM with an average distance of 6.4 cM between markers. Linkage groups ranged from 3 to 257 cM in length and included from 2 to 41 markers, respectively. A gene for earliness was mapped on linkage group 2. Seed weight showed a significant association with a RAPD marker on linkage group 5. This map should facilitate the identification of markers that “tag” genes for pest and disease resistance and other traits in the cultivated gene pool of cowpea. Received: 16 September 1996 / Accepted: 25 April 1997     

Evaluation of genetic distances between pepper inbred lines for cultivar protection purposes: comparison of AFLP, RAPD and phenotypic data

Summary  We evaluated concordance of AFLP and RAPD markers for estimating genetic distances of 47 pepper inbred lines belonging to five varietal types. It enabled us to see the efficiency of these markers for identification, estimation of distances between varieties and variety discrimination. Genetic distance and multidimensional scaling results showed a general agreement between AFLP and RAPD markers. Based on pattern scores, dendrograms were produced by the UPGMA method. Phenetic trees based on molecular data were consistent with the classification of variety group. The precision of the estimation of the genetic distance was given. The molecular genetic distances were correlated with distances based on a set of discriminating agronomic traits measured for identification and distinctiveness tests. The relationship between molecular and morphological distances appeared to be triangular. These results and their implications in the cultivar protection purposes of pepper hybrids are discussed. Received: 25 March 2000 / Accepted: 11 July 2000     

红莲型杂交稻(红莲2号)及其骨干亲本的RAPD分析与鉴定

利用RAPD技术,从248个随机寡核苷酸引物（10－mer）中筛出18个引物对红莲型杂交稻组合红莲2号及其亲本（T－07A、T－07B、YD6－05）,另6个红莲型胞质不育系的骨干恢复和汕优63及其亲本共14份水稻材料进行分析。共检测到173个多态性标记。聚类分析结果表明：不育系与保持系间因核背景相似,遗传差异很小;杂种（F1）的基因型更倾向于恢复系;恢复系与保持系间遗传距离的相对较大,但各恢复系之间的遗传距离较小。利用这些标记能有效地地区交组合中不育系,保持系、恢复系和杂种（F1）。     

Evaluation of genetic diversity of parental lines for development of heterotic groups in hybrid rice (Oryza sativa L.)

Knowledge of genetic diversity and potential heterotic relationships among parental lines is of significant importance in hybrid rice breeding programs. In the present study, in order to understand the genetic diversity among 96 parental lines, they were characterized for their diversity with respect to their morphological traits (n?=?12) and molecular markers using a set of 50 SSR markers. Morphological diversity was estimated using Mahalanobis D² statistics in terms of generalized group distance. Based on morphological diversity analysis, the 96 lines were grouped into 5 major and 13 monogenotypic clusters. In molecular marker analysis, the parental lines were consistently clustered into B (Maintainer group) and R (Restorer group) groups based on distance and model based approaches. Strong correspondence was observed between the pedigree of parental lines with molecular genotyping based grouping than morphological trait based grouping. From the results of the present investigation, it is evident that the available diversity among the two groups i.e., maintainer group (B) and restorer group (R) is sufficient for developing heterotic hybrids, but within the maintainer and restorer groups, the diversity is limited, the diversity among restorers was moderate, while it was low among the maintainers and hence efforts are needed for broadening their genetic base of parental lines for development and adoption of high-yielding hybrids.

     

Regression association analysis of fruit traits with molecular markers in cherries

The use of molecular markers supports the study of genetic marker–trait association of biological and agronomic interest in diverse genetic material. In this research, association between simple sequence repeat (SSR) and random amplified polymorphic DNA (RAPD) markers with fruit traits were investigated in two collections of cherries by applying multiple regression analysis (MRA). Thirty-eight SSR alleles and 135 RAPD fragments were found associated with 14 of affecting fruit traits. Some of SSR and RAPD markers were associated with more than one fruit trait in MRA. Such an association may arise due to pleiotropic effect of the linked quantitative trait locus on different traits. For example, some SSR and RAPD markers were associated with all four traits including fruit cracking, fruit firmness, total soluble solid (TSS) and fruit shape. Also, some markers had correlations with all four characters of TSS, anthocyanin, fruit skin color and fruit flesh color, indicating a significant correlation among these traits. Therefore, it is possible to use these markers along with morphological traits in cherry breeding programs for identification of suitable parents to produce mapping populations and hybrid cultivars. Also, these results could be useful in marker-assisted breeding programs when no other genetic information is available.     

利用RFLP、SSR、AFLP和RAPD标记分析玉米自交系遗传多样性的比较研究

利用 ＲＦＬＰ、ＳＳＲ．ＡＦＬＰ和ＲＡＰＤ ４种分子标记方法研究了 １５个玉米（Ｚｅａ ｍａｙｓ Ｌ．）自交系的遗传多样性,同时对４种标记系统进行比较。在供试材料中筛选到具多态性的ＲＦＬＰ探针酶组合５６个,６６对ＳＳＲ引物,２０个ＲＡＰＤ引物和９个ＡＦＬＰ引物组合,分别检测到多态性带１６７、２０１、８７和１０８条。ＳＳＲ标记位点的平均多态性信息量（ＰＩＣ）最大（０．５４）,ＡＦＬＰ标记位点最小（０．３６）,但ＡＦＬＰ标记具有最高的多态性检测效率（Ａｉ,３２．２）。４种分子标记所得遗传相似系数相关性显著,比较相关系数表明 ＲＡＰＤ可靠性较低。依据 ４种分子标记结果将 １５个供试自交系划分为塘四平头、旅大红骨、兰卡斯特、瑞德和ＰＮ共５个类群,与系谱分析基本一致。认为ＳＳＲ和ＲＦＬＰ两种分子标记方法适合进行玉米种质遗传多样性的研究。     

Relationship of restriction fragment length polymorphisms to single-cross hybrid performance of maize

Summary Isozymes and restriction fragment length polymorphisms (RFLPs) have been proposed for use in varietal identification and selection for agronomic traits. Although the use of isozymes for these purposes has been well documented, evaluation of the efficacy of RFLP technology as applied to crop improvement is far from complete. This investigation was conducted to study the relationship between RFLP-derived genotypes and heterotic patterns of a group of maize (Zea mays L.) inbred lines. A total of 22 inbreds was crossed to four testers (B73, B76, Mo17, and Va26) in combinations that minimized crossing within heterotic groups. Forty-seven single-cross progeny were subsequently evaluated for several agronomic traits (including grain yield and moisture, ear height, and root lodging) over 2–4 consecutive years at two to four Iowa locations in a randomized complete-block design. The inbred lines were subjected to RFLP analysis, which involved 47 genomic clones and the restriction enzymes EcoRI and HindIII. Hybrid RFLP patterns were predicted from their inbred parents. Modified Roger's distances were computed to estimate genetic distance among the inbred lines. Principal component analysis facilitated ascertainment of relative dispersion of the inbreds based on the frequency of variants at specific RFLP loci. Evident associations of variants with genes affecting agronomic traits were identified by principal component regression analysis, in which adjusted hybrid means were regressed on the matrix of hybrid variants frequencies. The hybrid means were adjusted by removing environmental effects, using residuals as dependent variables in the regression analysis. Results from this study suggest that RFLP analysis may be of value in allocating maize inbreds to heterotic groups, but no relationship between RFLP-based genetic distance and hybrid performance was apparent. Principal component regression identified variants potentially linked to genes that control specific agronomic traits.Joint contribution: USDA-ARS and Journal Paper No. J-13590 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA 50011, USA. Projects No. 2818 and 2778     

Variation among and within Capsicum species revealed by RAPD markers

 Germplasm characterization is an important link between the conservation and utilization of plant genetic resources. A total of 134 accessions from six Capsicumspecies maintained at the Asian Vegetable Research and Development Center were characterized using 110 randomly amplified polymorphic DNA (RAPD) markers. Ten pairs of potentially duplicated accessions were identified. Multidimensional scaling analysis of the genetic distances among accessions resulted in clustering corresponding to a previous species assignment except for six accessions. Diagnostic RAPDs were identified which discriminate among the Capsicumspecies. The diagnostic markers were employed for improved taxonomic identification of accessions since many morphological traits used in the identification of Capsicumare difficult to score. Three Capsicumaccessions, misclassified based on morphological traits, were reassigned species status based on diagnostic RAPDs. Three accessions, not previously classified, were assigned to a species based on diagnostic RAPDs. Definitive conclusions about the species assignment of three other accessions were not possible. The level of diversity between Capsicum annuumaccessions from the genebank and the breeding program were compared and no differences were observed either for RAPD variation or diversity. The utilization of genetic resources as a source of variance for useful traits in the breeding program may be the reason for the similarity of these two groups. Received: 1 September 1998 / Accepted: 28 December 1998     

Genetic distances revealed by morphological characters,isozymes, proteins and RAPD markers and their relationships with hybrid performance in oilseed rape (<Emphasis Type="Italic">Brassica napus</Emphasis> L.)

Genetic distances (GDs) based on morphological characters, isozymes and storage proteins, and random amplified polymorphic DNAs (RAPD) were used to predict the performance and heterosis of crosses in oilseed rape (Brassica napus L.). Six male-sterile lines carrying the widely used Shaan2A cytoplasm were crossed with five restorer lines to produce 30 F₁ hybrids. These 30 hybrids and their parents were evaluated for seven agronomically important traits and their mid-parent heterosis (MPH) at Yangling, Shaanxi province in Northwest China for 2 years. Genetic similarity among the parents based on 34 isozyme and seven protein markers was higher than that based on 136 RAPDs and/or 48 morphological markers. No significant correlation was detected among these three sets of data. Associations between the different estimates of GDs and F₁ performance for some agronomic traits were significant, but not for seed yield. In order to enhance the predicting efficiency, we selected 114 significant markers and 43 favoring markers following statistical comparison of the mean values of the yield components between the heterozygous group (where the marker is present only in one parent of each hybrid) and the homozygous group (where the marker is either present or absent in both parents of each hybrid) of the 30 hybrids. Parental GD based on total polymorphic markers (GD_total, indicating general heterozygosity), significant markers (GD_sign, indicating specific heterozygosity) and favoring markers (GD_favor, indicating favoring-marker heterozygosity) were calculated. The correlation between GD_favor or GD_sign and hybrid performance was higher than the correlation between GD_total and hybrid performance. GD_sign and GD_favor significantly correlated with plant height, seeds per silique and seed yield, but not with the MPH of the other six agronomic traits with the exception of plant height. The information obtained in this study on the genetic diversity of the parental lines does not appear to be reliable for predicting F₁ yield and heterosis.     

Fruit tree genetics at a turning point: the almond example

 The large size and the long generation time of fruit trees generally reduce the possibilities of obtaining genetic information on the transmission and heritability of useful agronomic traits in these species. However, from breeding work carried out with fruit trees, an important amount of data is now available, although large differences are apparent among the different species. There is not much information known about almond compared to what is available on other Prunus fruit species, but more data have been accumulated on it than on most of the other nut trees, thus making almond special among all the temperate fruit and nut species. Only five qualitative traits have been described in almond, with an additional two also possibly qualitative. Heritabilities have been estimated for an important number of quantitative traits, mainly phenological times and fruit characters. Important information is available on molecular markers, including enzymes, RFLPs, RAPDs and other recently developed markers. Linkages, however, have only been established among molecular markers, allowing accurate genetic maps to be built but not yet enabling agronomical characters to be located in these maps, probably because the latter have not been sufficiently studied. The effectiveness of the application of genetic maps in plant breeding will depend on the accuracy of the study of different agronomic traits and their expression, implying more field work and recognition of this work. Ultimately, any new fruit cultivar has to be grown in the field and has to allow the grower to make a profit. Received: 1 June 1997 / Accepted: 1 September 1997     

A comparison of RAPD and isozyme analyses for determining the genetic relationships among Avena sterilis L. accessions

Isozyme analysis is a valuable tool for determining genetic relationships among breeding lines and populations. The recently developed DNA technologies which can assay a greater proportion of the plant genome are providing a plentiful array of additional genomic markers. The objective of this research was to compare random amplified polymorphic DNA (RAPD) versus isozyme-based estimation of relationships among 24 accessions of a hexaploid wild oat, Avena sterilis L. The accessions were evaluated for variation in 23 enzyme systems and by 21 10-mer primers. A total of 77 polymorphic isozyme bands and 115 polymorphic RAPD bands were observed. Two matrices of genetic distances were estimated based on band presence/ absence. These matrices were subsequently utilized in cluster analysis and principal coordinate analysis. Both isozymes and RAPDs were proficient at distinguishing between the 24 accessions. The correspondence between the elements of both distance matrices was moderate (r=0.36**). Nevertheless, the overall representation of relationships among accessions by cluster analysis and ordination was in considerable agreement. The two techniques contrasted most notably in pair-by-pair comparisons of relationships. RAPD analysis resulted in a more definitive separation of clusters of accessions. The most significant impact of the DNA-based markers probably will be the more accurate determination of relationships between accessions that are too close to be accurately differentiated by isozymes.The research reported in this publication was funded by the North Carolina Agricultural Research Service, the North Carolina Biotechnology Center, and by a Heisenberg Fellowship (HE 1497/3-2) provided by the German Research Council to Manfred Heun     

Comparison of RAPD and RFLP genetic markers in determining genetic similarity among Brassica oleracea L. genotypes

Genetic similarity among 45 Brassica Oleracea genotypes was compared using two molecular markers, random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphisms (RFLPs). The genotypes included 37 broccolis (var. italica), five cauliflowers (var. botrytis) and three cabbages (var. capitata) which represented a wide range of commercially-available germplasm, and included open-pollinated cultivars, commercial hybrids, and inbred parents of hybrid cultivars. Fifty-six polymorphic RFLP bands and 181 polymorphic RAPD bands were generated using 15 random cDNA probes and 62 10-mer primers, respectively. The objectives were to compare RFLP and RAPD markers with regard to their (1) sampling variance, (2) rank correlations of genetic distance among sub-samples, and (3) inheritance. A bootstrap procedure was used to generate 200 random samples of size n (n=2,3,5,... 55) independently from the RAPD and RFLP data sets. The coefficient of variance (CV) was estimated for each sample. Pooled regressions of the coefficient of variance on bootstrap sample size indicated that the rate of decrease in CV with increasing sample size was the same for RFLPs and RAPDs. The rank correlation between the Nei-Li genetic similarity values for all pairs of genotypes (990) based on RFLP and RAPD data was 0.745. Differences were observed between the RFLP and RAPD dendrograms of the 45 genotypes. Overlap in the distributions of rank correlations between independent sub-samples from the RAPD data set, compared to correlations between RFLP and RAPD sub-samples, suggest that observed differences in estimation of genetic similarity between RAPDs and RFLPs is largely due to sampling error rather than due to DNA-based differences in how RAPDs and RFLPs reveal polymorphisms. A crossing algorithm was used to generate hypothetical banding patterns of hybrids based on the genotypes of the parents. The results of this study indicate that RAPDs provide a level of resolution equivalent to RFLPs for detemination of the genetic relationships among genotypes.     

Inheritance of random amplified polymorphic DNA markers in cassava (Manihot esculenta Crantz)

The informativeness and inheritance of randomly amplified polymorphic DNA (RAPD) markers were investigated in an intraspecific F1 progeny derived from two heterozygous parents. The analysis confirmed the utility of RAPD markers for comparing candidate parents for the development of a molecular genetic map, and provided numerous markers for linkage analysis in a crop with a very limited history of classical or molecular genetic studies. Six potential parental lines (themselves F1 hybrid clones) showed between 1.82 and 0.62 segregating bands per primer in three hybrid families. Forty-three percent (309) of 722 primers produced polymorphic products in the most informative of these three crosses, revealing 328 single-dose (SD) markers segregating 1:1 for presence/absence in a progeny of 90 individuals. A second class of informative markers were those present in both parents but segregating in the progeny. Fifty-seven or 67% of the monomorphic but segregating markers exhibited the 3:1 ratio expected for SD dominant markers in a cross between heterozygotes. Linkage groups were constructed from the segregation of SD RAPD markers originating in the female (TMS 30572) and the male (CM2177-2) parent. Key words : RAPDs, molecular markers, genetic segregation, Manihot, single-dose markers.     

A genetic map of melon (Cucumis melo L.) based on amplified fragment length polymorphism (AFLP) markers

 Genetic maps facilitate the study of genome structure and evolution, and the identification of monogenic traits or Mendelian components of quantitative traits. We evaluated 228 RAPD, microsatellite and AFLP markers for linkage analysis in melon (Cucumis melo L.) varieties MR-1 (resistant to Fusarium wilt, powdery and downy mildews) and Ananas Yokneum (AY; susceptible to these diseases) and constructed a detailed genetic map. The mapping population consisted of 66 backcross progenies derived from AY×(MR-1×AY). Despite a relatively low level of polymorphism in the species, AFLP markers were found to be more efficient in mapping the melon genome than RAPD or microsatellite markers. The map contains 197 AFLPs, six RAPDs and one microsatellite marker assigned to 14 major and six minor linkage groups, and covers 1942 cM with the average distance between adjacent markers of approximately 10 cM. The maximum distance allowed between markers is 27.5 cM. About 11% of the intervals (20 out of 173) are over 20 cM (but less than 27.5 cM). The map has immediate utility for identifying markers linked to disease resistance genes that are suitable for marker-assisted breeding. The use of microsatellite markers for integration with other maps is also discussed. Received: 12 March 1997 / Accepted: 20 May 1997     

Genetic diversity and its relationship to hybrid performance and heterosis in rice as revealed by PCR-based markers

Ten elite inbred lines (four japonica, six indica), chosen from those widely used in the hybrid rice breeding program at Human Hybrid Rice Research Center in China, were crossed to produce all possible hybrids excluding reciprocals. The 45 F₁ hybrids along with the ten parents were evaluated for eight traits of agronomic importance, including yield potential, in a replicated field trial. The ten parents were analyzed with 100 arbitrary decamer oligonucleotide primers and 22 microsatellite (simple sequence repeats, SSRs) primer sets via polymerase chain reaction (PCR). Out of the 100 random primers used, 74 were informative and amplified 202 non-redundant bands (variants) with a mean of 2.73 bands per polymorphic primer. All 22 microsatellite primer sets representing 23 loci in the rice genome showed polymorphisms among the ten parents and revealed 90 alleles with an average of 3.91 per SSR locus. Cluster analysis based on Nei's genetic distance calculated from the 291 (202 RAPDs, 89 SSRs) non-redundant variants separated the ten parental lines into two major groups that corresponds to indica and japonica subspecies, which is consistent with the pedigree information. Strong heterosis was observed in hybrids for most of the traits examined. For the 43 diallel crosses (excluding 2 crosses not heading), yield potential, its components (including panicles per plant, spikelets per panicle and 1000-grain weight) and their heterosis in F₁ hybrids showed a significant positive correlation with genetic distance. When separate analyses were performed for the three subsets, yield potential and its heterosis showed significant positive correlations with genetic distance for the 15 indica x indica crosses and the 6 japonica x japonica crosses; however, yield potential and its heterosis were not correlated with genetic distance for the 22 indica x japonica crosses. Results indicated that genetic distance measures based on RAPDs and SSRs may be useful for predicting yield potential and heterosis of intra-subspecific hybrids, but not inter-subspecies hybrids.     

Qualitative and quantitative characterization of RAPD variation among snap bean (Phaseolus vulgaris) genotypes

Ten snap bean (Phaseolus vulgaris) genotypes were screened for polymorphism with 400 RAPD (random amplified polymorphic DNA) primers. Polymorphic RAPDs were scored and classified into three categories based on ethidium bromide staining intensity. An average of 5.19 RAPD bands were scored per primer for the 364 primers that gave scorable amplification products. An average of 2.15 polymorphic RAPDs were detected per primer. The results show that primer screening may reduce the number of RAPD reactions required for the analysis of genetic relationships among snap-bean genotypes by over 60%. Based on the analysis of the distribution of RAPD amplification, the same number of polymorphic RAPDs were amplified from different genotypes for all RAPD band intensity levels. A comparison of RAPD band amplification frequency among genotypes for the three categories of bands classified by amplification strength revealed a measurable difference in the frequencies of RAPDs classified as faint (weakly amplifying) compared to RAPD bands classified as bold (strongly amplifying) indicating a possible scoring error due to the underscoring of faint bands. Correlation analysis showed that RAPD bands amplified by the same primer are not more closely correlated then RAPD bands amplified by different primers but are more highly correlated then expected by chance. Pairwise comparisons of RAPD bands indicate that the distribution of RAPD amplification among genotypes will be a useful criterion for establishing RAPD band identity. For the average pairwise comparison of genotypes, 50% of primers tested and 15.8% of all scored RAPDs detected polymorphism. Based on RAPD data Nei's average gene diversity at a locus was 0.158 based on all scorable RAPD bands and 0.388 if only polymorphic RAPD loci were considered. RAPD-derived 1 relationships among genotypes are reported for the ten genotypes included in this study. The data presented here demonstrate that many informative, polymorphic RAPDs can be found among snap bean cultivars. These RAPDs may be useful for the unique identification of bean varieties, the organization of bean germplasm, and applications of molecular markers to bean breeding.     

Natural hybridization and hybrid zones between Quercus crassifolia and Quercus crassipes (Fagaceae) in Mexico: morphological and molecular evidence

Hybrid zones provide interesting systems to study genetic and ecological interaction between different species. The correct identification of hybrids is necessary to understand the evolutionary process involved in hybridization. An oak species complex occurring in Mexico formed by two parental species, Quercus crassifolia H. & B. and Q. crassipes H. & B., and their putative hybrid species, Q. dysophylla, was analyzed with molecular markers (random amplified polymorphic DNA [RAPDs]) and morphological tools in seven hybrid zones (10 trees per taxa in each hybrid zone) and two pure sites for each parental species (20 trees per site). We tested whether geographic proximity of hybrid plants to the allopatric site of a parental species increases its morphological and genetic similarity with its parent. Seventeen morphological traits were measured in 8700 leaves from 290 trees. Total DNA of 250 individuals was analyzed with six diagnostic RAPD primers. Quercus crassifolia differed significantly from Q. crassipes in all the examined characters. Molecular markers and morphological characters were highly coincident and support the hypothesis of hybridization in this complex, although both species remain distinct in mixed stands. Clusters and a hybrid index (for molecular and morphological data) showed that individuals from the same parental species were more similar among themselves than to putative hybrids, indicating occasional hybridization with segregation in hybrid types or backcrossing to parents. Evidence does not indicate a unidirectional pattern of gene flow.     

Genetic relationships among ten endod types as revealed by a combination of morphological,RAPD and AFLP markers

The genetic relationships among ten types of endod (Phytolacca dodecandra) cultivated by the Institute of Pathobiology of the Addis Ababa University to combat the disease bilharzia in Ethiopia were studied using morphology and molecular markers. A total of 18 morphological characters, 194 amplified fragment length polymorphism (AFLP) and 42 random amplified polymorphic DNA (RAPD) markers were used to determine genetic proximity between types. Genetic distance and cluster analysis of the AFLP data revealed the lack of genetic difference between E47 and E48 but relatively wider genetic difference among the other endod types. Cluster and principal component analyses performed on the AFLP and RAPD markers demonstrated the presence of distinct separation of E56 but not that of E44 from the others. The AFLP and RAPD data, thcrefore, did not support the hypothesis that the superiority of E44 in agronomic traits and molluscicidal potency is linked to its distinct genetic difference from the other endod types. Matrices correspondence tests demonstrated the presence of greater correspondence between AFLP and RAPD data (r = 0.842) but not between the morphology and that of AFLP and RAPD. This indicates the correspondence more between the two DNA markers systems than either of them with morphological traits. The cophenetic correlation coefficients also revealed poor fit for morphology (r = 0.716), good fit for RAPD (r = 0.872) and very good fit for AFLP (r = 0.975), reflecting the hyper-variability and higher resolving power of AFLP.     

Genetic variation in monoploids of diploid potatoes and detection of clone-specific random amplified polymorphic DNA markers

Randomly amplified polymorphic DNA (RAPD) markers have been used to study the genetic variation among androgenetic monoploids of diploid Solanum species. Cluster analysis of pairwise genetic distances was used to construct a genetic relationship among anther donor and anther-derived potato plants. The clustering based on Rogers' distances resembled classifications based on parental origins and hybrid combinations. Six of the 32 RAPD primers used resulted in the selective amplification of DNA fragments which were polymorphic between the two S. phureja parental clones, 1.22 and A95. It should be possible to construct a genetic linkage map, without making crosses, using monoploids derived from a single heterozygous diploid clone and RAPD markers.