Mating system and DNA polymorphism of monokaryons with different mating type of Stropharia rugoso-annulata

The mating system of Stropharia rugoso-annulata Farlow apud Murrill was studied by pairing single spore isolates from the same fruitbody, and the genetic diversity of monokaryotic strains with different mating types was evaluated by the RAPD technique. Basidiospores could germinate normally on PGP (potato/glucose/peptone) medium at 30 °C. Analysis of self- and cross-pairings revealed that Stropharia rugoso-annulata was heterothallic and tetrapolar. RAPD analysis detected polymorphism among monokaryotic strains, with more genetic variation within monokaryotic strains with non-parental mating type compared to monokaryotic strains with parental mating type. These results were in general agreement with the existing knowledge, confirming the validity and usefulness of the RAPD technique. Therefore, the RAPD technique will provide an exciting and valuable tool for a large-scale study on identification and genetic resources of monokaryotic strains, and should lead to a more efficient understanding and utilization of genetic diversity of monokaryotic strains in cross breeding by breeders.     

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。     

Molecular Differentiation of Sexually Incompatible Strains of Agaricus bitorquis Using RAPD and AFLP Markers

Twenty RAPD primers amplified 216 DNA fragments in nine germplasm strains and two newly developed hybrids of Agaricus bitorquis, out of which 98.61% were polymorphic. Six AFLP primer-combinations generated a total of 271 AFLP fragments in nine germplasm strains and six newly developed hybrids, out of which 91.14% were polymorphic. Dendrograms based on UPGMA algorithm and SAHN clustering clearly showed two major phylogenetic groups with both the DNA markers in the germplasm and the hybrids clustered with their parental groups. Genetic similarity between the two groups was 6.52% with RAPD and 18.13% with AFLP markers. Ten most informative primers were identified for initial screening of uncharacterized germplasm using RAPD analysis. Further, AFLP revealed a great power of detection of genetic diversity and validated its usefulness for guiding breeding programmes. The findings are of immediate value to breeders to explore hybridization between genetically diverse parents within the sexually compatible groups. Present study is the first report on the exploitation of AFLP markers in button mushroom for molecular characterization and mushroom breeding.     

Genetic relationships among melon breeding lines revealed by RAPD markers and agronomic traits

 RAPD markers and agronomic traits were used to determine the genetic relationships among 32 breeding lines of melon belonging to seven varietal types. Most of the breeding lines were Galia and Piel de Sapo genotypes, which are currently being used in breeding programmes to develop new hybrid combinations. A total of 115 polymorphic reliable bands from 43 primers and 24 agronomic traits were scored for genetic distance calculations and cluster analysis. A high concordance between RAPDs and agronomic traits was observed when genetic relationships among lines were assessed. In addition, RAPD data were highly correlated with the pedigree information already known for the lines and revealed the existence of two clusters for each varietal type that comprised the lines sharing similar agronomic features. These groupings were consistent with the development of breeding programmes trying to generate two separate sets of parental lines for hybrid production. Nevertheless, the performance of certain hybrids indicated that RAPDs were more suitable markers than agronomic traits in predicting genetic distance among the breeding lines analysed. The employment of RAPDs as molecular markers both in germplasm management and improvement, as well as in the selection of parental lines for the development of new hybrid combinations, is discussed. Received: 25 July 1997 / Accepted: 6 October 1997     

Determination of genetic relationships among shape Phaseolus vulgaris populations in a conical cross from RAPD marker analyses

Random-amplified polymorphic DNA (RAPD) markers were used to determine genetic relationships among Phaseolus vulgaris breeding populations. Genetic distances were calculated from the distribution of 317 RAPD markers among 8 parents, 10 individuals from 8 cycle-one populations, 10 individuals from 6 cycle-two populations and 10 individuals from 2 cycle-three populations of a conical cross. Genetic distances between populations and parents were consistent with their degree of relationship in the crossing scheme indicating that a RAPD analysis is a sensitive and useful method for categorizing breeding materials according to their genetic similarities. Genetic variation among individuals within populations increased from cycle one to cycle three and variation among populations within the cycles decreased from cycle one to cycle three in the conical cross. The results showed that this crossing scheme can be used to collect the genetic diversity in eight parents into a single plant breeding population. Abbreviations: CBB, common bacterial blight; GD, genetic distance; RAPD, random-amplified polymorphic DNA     

Heterozygosity and hybrid performance in larch

Random Amplified Polymorphic DNAs (RAPD) were used for estimating genetic distances between 12 European larches (Larix decidua) and 12 Japanese larches (L. kaempferi) that were the parents in a factorial mating design. One hundred and eleven fragments were used for establishing genetic distances based on Jaccard's coefficient between parents. Thirteen fragments differentiated the larch species. The genetic distance between individuals of the same species (D _J =0.39 in the Japanese larch and 0.45 in the European larch) was lower than the genetic distance between species (D _J =0.72). A UPGMA dendrogram based on genetic distances clearly clustered each larch species, confirming the speciation at a molecular level. Correlations between genetic distances of the parents and performances of the hybrid families were established for various quantitative traits. Significant values were found for growth characters and branch insertion angle, which suggested an effect of general heterozygosity level on hybrid traits. These correlations also evolved with tree age: the maximal correlation was noticed on 6-year-old trees for height. The lack of correlation between parental genetic distances and hybrid performances for the other quantitative traits suggested that these characters were controlled by fewer genes. The results of this study show that crosses between genetically distant parents produce hybrids with excellent growth performances; this represents a potential selection criterion of the genitors.     

利用RAPD技术检测香菇双—单杂交后代

利用ＲＡＰＤ技术对香菇６个双单杂交菌株及其两个双核体基因组ＤＮＡ进行了检测,结果显示：１－３号杂交菌株之间的相似系数为０．８９３－０．９６２,它们与其亲本Ｓ之间的相似系数为０．８４２－０．８５９;４－６号杂交菌株之间的相似系数０．８５７－０．９２５,与其亲本ＳＳＯ１之间相似系数为０．７０８－０．９０２;表明杂交菌株与其双核体亲本基因组具有较大差异,杂交菌株之间存在着不同程度差异,６个杂交菌株是真正     

Characterization of zygotic and nucellar seedlings from sour orange-like citrus rootstock candidates using RAPD and EST-SSR markers

A series of crosses designed for introgression of mandarin (Citrus reticulata Blanco) and pummelo (C. maxima Merr.) germplasm, to develop an alternative rootstock to sour orange (C. aurantium L.), were carried out. It is necessary to identify those hybrids that yield nucellar seedlings for rootstock propagation. Rootstocks can be developed through traditional plant breeding methods; however, the ability to screen and select for economically important traits (such as production of true nucellar seedlings) in an efficient fashion is limited by the difficulties of screening techniques based on whole plant performance. To address these problems, we have used randomly amplified polymorphic DNA (RAPD) and fluorescently labeled expressed sequence tag simple sequence repeat (EST-SSR) molecular markers. A total of 204 individual seedlings obtained from 34 hybrid parental plants were successfully characterized using five RAPD primers. Ten hybrid parents and their progenies, found to be genetically similar among themselves, were selected for more scrutiny using eight EST-SSR primer pairs. The degrees of genetic similarity (nucellars) among progeny seedlings were determined and compared with that of their parents. The mean genetic similarity varied from 67–99% among the selected rootstock candidates screened. The genetic similarity relationship identified using RAPD and EST-SSR molecular markers was highly concordant (p = 0.001). Two elite rootstock candidates (B6R5T56; B6R11T129) that seem to be ideal for future mandarin and pummelo derived rootstock breeding programs have been identified. Our results indicate that either RAPD or EST-SSR analyses could be equally successful in identifying true nucellars among the progenies obtained from introgression crosses of mandarin and pummelo, thus improving the accuracy of early selection in a citrus rootstock breeding program.     

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.     

香菇亲本菌株及其杂交后代的RAPD分析*

运用随机扩增多态性DNA（RandomamplifiedpolymorphicDNA,RAPD）技术对源于两个香菇（Lentinulaedodes）双核菌株的孢子单核体、原生质体单核体及其杂交后代进行了基因组DNA多态性分析。用9个随机引物共扩增出116条DNA片段,其中82．5％具有多态性。综合分析9个随机引物的扩增谱带,可将所有供试亲本单核体清楚地分开,且早核体聚类分析的结果与其来源及遗传背景相吻合。此外,用两个双核亲本菌株的各4个不同交配型的孢子单核体两两支配所得的所有杂交组合,也均可与双核亲本菌株明确地区分开来。因此,在杂交育种中,RAPD分析可为亲本的选配及杂种的鉴定提供可靠依据。     

香菇亲本菌株及其杂交后代的RAPD分析

运用随机扩增多态性DNA（RandomamplifiedpolymorphicDNA,RAPD）技术对源于两个香菇（Lentinulaedodes）双核菌株的孢子单核体、原生质体单核体及其杂交后代进行了基因组DNA多态性分析。用9个随机引物共扩增出116条DNA片段,其中82．5％具有多态性。综合分析9个随机引物的扩增谱带,可将所有供试亲本单核体清楚地分开,且早核体聚类分析的结果与其来源及遗传背景相吻合。此外,用两个双核亲本菌株的各4个不同交配型的孢子单核体两两支配所得的所有杂交组合,也均可与双核亲本菌株明确地区分开来。因此,在杂交育种中,RAPD分析可为亲本的选配及杂种的鉴定提供可靠依据。     

Genetic parameters of intra- and inter-specific hybrids of Eucalyptus globulus and E. nitens

Intra-specific hybrids within Eucalyptus nitens and E. globulus were compared directly with inter-specific E. nitens × globulus using common parents. Diameter (age 2, 4, 6, 10 years) and Pilodyn (age 6 years) were used as indirect measures of growth and wood density, respectively. Genetic parameters were estimated for all cross types and traits. A direct comparison of the general combining ability with the general hybridising ability was made. Heterosis was estimated for intra- and inter-specific hybrids. The intra-specific hybrids in both species exhibit intermediate heritabilities and levels of additive genetic variance. The inter-specific F1 E. nitens × globulus exhibited high incidence of abnormalities at young ages and high levels of later age mortality. The mean performance of surviving inter-specific F1 hybrids was generally intermediate for all traits, to varying degrees, between the parental intra-specific crosses, and there is little evidence for significant heterosis. Different provenances of E. globulus may exhibit different responses to hybridisation. In this case, the inter-specific F1 hybrids, using Taranna E. globulus, appear to perform worse on average than those using King Island provenance for growth traits. There is evidence that specific hybrid families are produced that outperform most of the pure species families for one or other of the traits examined; however, there is no reliable quantitative genetic method of predicting which parents should be used.     

Growth performance of hybrid families by crossing selfed lines of Betula pendula Roth

Hybrid breeding is an effective approach in many agricultural crops. In allogamous tree species severe inbreeding depression and long reproductive cycles generally prohibit its use. However, three generations of selfing in silver birch (Betula pendula Roth) were obtained by forcing trees to flowering under greenhouse conditions. Hybrids were produced by crossing first-, second and third-generation selfed lines. The effects of different levels of parental inbreeding on the growth performance of hybrid families were observed in a 9-year-old field progeny test. Also, provenance crosses were carried out between selfed lines from different parts of Finland and several other European countries. Observations of growth performance of the provenance hybrids were made in the same trial. The results indicated that the mean stem volumes were significantly different between classes of parental in breeding coefficients (F_P) (P<0.0001), and were positively correlated with F_P (r=0.9106, P<0.05). Within-family variation of the hybrid families decreased with an increase of F_P. The performance of the provenance crosses between parents at a relatively close distance did not depart significantly from the standard controls. However, when the cross distance was extended far to the south, hybrids grew faster, indicating either higher heterozygosity or an extended growth period.     

Genome‐wide association analyses reveal the genetic basis of combining ability in rice

Combining ability is a measure for selecting elite parents and predicting hybrid performance in plant breeding. However, the genetic basis of combining ability remains unclear and a global view of combining ability from diverse mating designs is lacking. We developed a North Carolina II (NCII) population of 96 Oryza sativa and four male sterile lines to identify parents of greatest value for hybrid rice production. Statistical analyses indicated that general combining ability (GCA) and specific combining ability (SCA) contributed variously to different agronomic traits. In a genome‐wide association study (GWAS) of agronomic traits, GCA and SCA, we identified 34 significant associations (P < 2.39 × 10^?7). The superior alleles of GCA loci (Ghd8, GS3 and qSSR4) accumulated in parental lines with high GCA and explained 30.03% of GCA variance in grain yield, indicating that molecular breeding of high GCA parental lines is feasible. The distinct distributions of these QTLs contributed to the differentiation of parental GCA in subpopulations. GWAS of SCA identified 12 more loci that showed dominance on corresponding agronomic traits. We conclude that the accumulation of superior GCA and SCA alleles is an important contributor to heterosis and QTLs that greatly contributed to combining ability in our study would accelerate the identification of elite inbred lines and breeding of super hybrids.     

Extending the rapeseed gene pool with resynthesized <Emphasis Type="Italic">Brassica napus</Emphasis> II: Heterosis

Hybrid breeding relies on the combination of parents from two differing heterotic groups. However, the genetic diversity in adapted oilseed rape breeding material is rather limited. Therefore, the use of resynthesized Brassica napus as a distant gene pool was investigated. Hybrids were derived from crosses between 44 resynthesized lines with a diverse genetic background and two male sterile winter oilseed rape tester lines. The hybrids were evaluated together with their parents and check cultivars in 2 years and five locations in Germany. Yield, plant height, seed oil, and protein content were monitored, and genetic distances were estimated with molecular markers (127 polymorphic RFLP fragments). Resynthesized lines varied in yield between 40.9 dt/ha and 21.5 dt/ha, or between 85.1 and 44.6% of check cultivar yields. Relative to check cultivars, hybrids varied from 91.6 to 116.6% in yield and from 94.5 to 103.3% in seed oil content. Mid-parent heterosis varied from −3.5 to 47.2% for yield. The genetic distance of parental lines was not significantly correlated with heterosis or hybrid yield. Although resynthesized lines do not meet the elite rapeseed standards, they are a valuable source for hybrid breeding due to their large distance from present breeding material and their high heterosis when combined with European winter oilseed rape.     

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.     

DNA marking of some quantitative trait loci in the cultivated edible mushroom <Emphasis Type="Italic">Pleurotus ostreatus</Emphasis> (Fr.) Kumm.

Fungi of the genus Pleurotus, in particular, species Pleurotus ostreatus (common oyster mushroom) are among most cultivated fungi in the world. Due to intense rates of development of studies in this field, efficient breeding programs are highly required in the search for new P. ostreatus strains. The principal traits used worldwide for selecting strains are intensity of fruitbearing, fruit body cap color (for some consumptive markets), and mycelium growth rate. In this connection, the objective of this work was to study these quantitative traits and to find molecular markers, which could be employed to accomplish breeding programs. In general, we found 12 genomic loci (quantitative trait loci, QTLs) controlling mycelium growth rate of oyster and six QTLs responsible for the fruit body cap color. The genetic map of P. ostreatus was constructed, and all markers of quantitative traits found by us were located on this genetic map. The obtained linkage map can be a useful tool for the accomplishment of breeding programs to improve economically important traits of oyster mushroom.     

Heterotic patterns in rapeseed (<Emphasis Type="Italic">Brassica napus</Emphasis> L.): I. Crosses between spring and Chinese semi-winter lines

Chinese semi-winter rapeseed is genetically diverse from Canadian and European spring rapeseed. This study was conducted to evaluate the potential of semi-winter rapeseed for spring rapeseed hybrid breeding, to assess the genetic effects involved, and to estimate the correlation of parental genetic distance (GD) with hybrid performance, heterosis, general combining ability (GCA) and specific combining ability (SCA) in crosses between spring and semi-winter rapeseed lines. Four spring male sterile lines from Germany and Canada as testers were crossed with 13 Chinese semi-winter rapeseed lines to develop 52 hybrids, which were evaluated together with their parents and commercial hybrids for seed yield and oil content in three sets of field trials with 8 environments in Canada and Europe. The Chinese parental lines were not adapted to local environmental conditions as demonstrated by poor seed yields per se. However, the hybrids between the Chinese parents and the adapted spring rapeseed lines exhibited high heterosis for seed yield. The average mid-parent heterosis was 15% and ca. 50% of the hybrids were superior to the respective hybrid control across three sets of field trials. Additive gene effects mainly contributed to hybrid performance since the mean squares of GCA were higher as compared to SCA. The correlation between parental GD and hybrid performance and heterosis was found to be low whereas the correlation between GCA_{(f + m)} and hybrid performance was high and significant in each set of field trials, with an average of r = 0.87 for seed yield and r = 0.89 for oil content, indicating that hybrid performance can be predicted by GCA_{(f + m)}. These results demonstrate that Chinese semi-winter rapeseed germplasm has a great potential to increase seed yield in spring rapeseed hybrid breeding programs in Canada and Europe.     

利用RAPD标记分析鸵鸟种群的遗传变异

为探讨分子遗传标记在鸵鸟（Struthio camelus)育种中的应用,利用RAPD技术分析了我国养殖的三个主要要鸵鸟品种内和品种间的遗传变异。蓝颈鸵鸟、澳洲灰和非洲黑三个品种在品种内和品种间显示出低水平的变异。品种间的遗传距离好地说胆了三个品种的育种改良过程。同时预示出用澳洲灰与其他品种鸵鸟进行杂交育种的可行性。选择的20条在鸡中能稳定扩增的RAPD引物其75％能在鸵鸟基因组中扩增出产物。显示出两种禽类DNA具有同源性、为今后利用鸡的微卫星引物对鸵鸟进行基因扫描（genome scan）分析奠定基础。     

RAPD and pedigree-based genetic diversity estimates in cultivated diploid potato hybrids

In this study, RAPD and pedigree data were used to investigate the genetic relationships in a group of 45 diploid hybrid potato clones used in the breeding and genetics program of the Agriculture and Agri-Food Canada Potato Research Centre in Fredericton, New Brunswick, and used for the potato after-cooking darkness program at the Nova Scotia Agricultural College. These hybrids were derived from crossing primitive cultivated South American diploid species such as Solanum phureja or Solanum stenotomum and wild diploid species such as Solanum chacoense and other wild Argentine species with haploids of Solanum tuberosum. These hybrids have subsequently undergone up to 30 years of breeding and selection, for adaptation to local growing and storage conditions, processing traits and pest resistances. The objectives of this study were to estimate the level of genetic similarity (GS) among these sets of clones and to investigate the correlation between RAPD-based GS and f, based on pedigree information. Genetic similarity coefficients varied from 0.29 to 0.90 with a mean of 0.65 when based on the RAPD data, whereas the coefficient of parentage varied from zero to 0.75 with a mean of 0.11. The degree of relationship between the similarity matrices based on RAPD and pedigree was measured by comparing the similarity matrices with the normalized Mantel test. A low positive correlation (R = 0.104, p = 0.999) between the two matrices was observed. Cluster analysis using GS divided the clones into many subgroups that did not correspond well with the grouping based on pedigree. The level of genetic variation present in this set of potato clones is very high. Rigorous selection pressure aimed at different breeding purposes may result in the genetic differentiation of the clones from the same origin.