Exploitation Of Heterosis Research Articles

Parental combining ability as a good predictor of productive crosses in sweet sorghum [Sorghum bicolor (L.) Moench

The exploitation of heterosis through the development and deployment of hybrids for commercial cultivation is one of the effective approaches for genetic enhancement of crop plants for traits of economic importance. Developing an objective criterion of choosing the parents for developing and testing hybrids is essential for maximizing the success of heterosis breeding. A set of 18 crosses produced from parents differing in their gca effects for bio-energy traits such as millable cane yield, juice volume and juice sugar content (as indicated by Brix %) were evaluated in replicated trial in the experimental plots of the Department of Genetics and Plant Breeding, University of Agricultural Sciences, Bangalore during 2006-07. The utility of parental general combining ability for producing high frequency of superior crosses for a set of bio-energy traits in sweet sorghum was investigated. The study suggested that parents with contrasting gca effects produce crosses with higher sca and heterotic potential for the bio-energy traits. The use of female parents with higher gca effects is important for realizing greater probability of crosses with sca effects and heterosis in desirable direction for bio-energy traits.

Hybrid Breeding in Durum Wheat: Heterosis and Combining Ability

Hybrid breeding facilitates a maximum exploitation of heterosis. The objectives of our research were to (i) examine the magnitude of heterosis over the mid‐ and better parent for yield, yield components, and quality traits in Central European spring durum wheat and (ii) investigate the efficiency of parental selection based on mid‐parent value or general combining ability effects. Sixteen inbred lines and 40 incomplete factorial crosses were field‐evaluated for eight agronomic traits at 10 environments in Germany. For grain yield, the hybrids yielded on average 10% higher than the mid‐parent performance, and the maximum superiority was 22%. The significantly positive contrast between inbreeding depression and mid‐parent heterosis for grain yield indicated the presence of positive additive x additive epistatic interactions. Furthermore, the best hybrid outperformed the best line variety by 1.01 Mg ha−1 We conclude that there is a potential for hybrid breeding in durum wheat.

Heterosis for Fruit Yield and Related Horticultural Traits in Bell Pepper

Heterosis is the increase of size, yield, and vigor through cross-breeding rather than interbreeding; without increases there is no heterosis. Heterosis has a slightly more extensive coverage than hybrid vigor; that is, though all hybrid vigor is heterosis, not all heterosis can be with equal propriety termed hybrid vigor. Heterosis breeding is a potential method to achieve improvement in production and productivity of bell pepper that otherwise cannot be achieved through existing traditional methods. A study of heterosis in 24 bell pepper hybrids developed through Line × Tester mating design involving the fully inbred lines, ‘Kandaghat Selection’, ‘EC-464115’, ‘EC-464107’, ‘HC-201’, ‘AC-48’, ‘SKAU-SP-613-1’, ‘PBC-631’, and ‘SKAU-SP-633-1’ and the testers ‘California Wonder’, ‘Yolo Wonder’, and ‘Solan Bharpoor’ was carried out at the Vegetable Experimental Farm of CSK Himachal Pradesh Agriculture Univ., Palampur, Himachal Pradesh, India, during the summer rainy seasons of 2007 and 2008 (February to August). Heterosis was studied for the quantitative traits days to 50% flowering, days to first harvest, plant height, harvest duration, fruit yield per plant, fruit per plant, marketable fruit per plant, fruit length, fruit width, pericarp thickness, average fruit weight, and lobes per fruit. Among the traits, fruit per plant exhibited maximum heterosis over standard check ‘Aishwarya’ followed by marketable fruit per plant, harvest duration, and fruit yield per plant. Heterosis for yield was generally accompanied by heterosis of yield components. On the basis of heterosis and mean performance, ‘EC-464107’ × ‘Yolo Wonder’ was the best cross-combination followed by ‘Kandaghat Selection’ × ‘Solan Bharpoor’, ‘SKAU-SP-633-1’ × ‘Yolo Wonder’, ‘AC-48’ × ‘Solan Bharpoor’, and ‘EC-464115’ × ‘California Wonder’ for fruit yield per plant. These crosses also had high heterosis for most of the component traits. These hybrids offer high scope for the exploitation of heterosis. These cross-combinations can also be released as hybrids after further field testing.

Finding heterosis for fiber traits in intervarietal crosses of cotton, Gossypium hirsutum L.

Raising yield and fiber quality of cotton through heterosis (hybrid vigor) has been an objective of plant breeders and scientists. Heterosis over mid parent for fiber-related traits was calculated in three crosses of cotton (Gossypium hirsutum L.) involving five cotton varieties, viz., CIM 506, CIM 702, CIM 443, FH 1000 and CIM 1100 being commercially grown in Pakistan. Heterosis was observed for all four characters. The cross CIM 443 × CIM 1100 showed maximum positive heterosis (8.57%) for ginning outturn (GOT) (%) followed by fineness (7.81%) and staple length (1.01%). Therefore, the cross CIM 506 × CIM 1100 appeared to be promising for providing potential breeding materials for further commercial exploitation of heterosis in Pakistan, and heterosis breeding has a great potential for increasing stagnant cotton yields around the world.

Appraisal of a Chemical-Hybridizing Agent for Emasculation in Rice

Rice productivity can be enhanced through exploitation of heterosis in hybrids with a possible positive impact on food security. Making planned crosses is difficult in rice because of the morphology and size of the inflorescence. This study was undertaken to investigate the efficacy of a gametocide (ethrel) as an emasculating agent. Experiments were conducted at ICRISAT Research Station at Samanko in Mali during 2004–2005. A factorial arrangement in a randomized complete-block design involving three levels of concentrations of the gametocide and five application stages was undertaken for two seasons. Morpho-physiological trait responses and spikelet sterility data were recorded on the female treated plants. Ethrel could induce 40 to 49% male sterility in rice. Percentage of empty spikelets and male sterility increased with increasing concentration of ethrel, reaching a peak between 2,000 ppm (2.0 g L−1) and 4,000 ppm (4.0 g L−1). Male sterility induction of 41.5% and 42.8% at 2000 ppm was achieved in 2004...

Haploids in flowering plants: origins and exploitation

The first haploid angiosperm, a dwarf form of cotton with half the normal chromosome complement, was discovered in 1920, and in the ninety years since then such plants have been identified in many other species. They can occur either spontaneously or can be induced by modified pollination methods in vivo, or by in vitro culture of immature male or female gametophytes. Haploids represent an immediate, one-stage route to homozygous diploids and thence to F(1) hybrid production. The commercial exploitation of heterosis in such F(1) hybrids leads to the development of hybrid seed companies and subsequently to the GM revolution in agriculture. This review describes the range of techniques available for the isolation or induction of haploids and discusses their value in a range of areas, from fundamental research on mutant isolation and transformation, through to applied aspects of quantitative genetics and plant breeding. It will also focus on how molecular methods have been used recently to explore some of the underlying aspects of this fascinating developmental phenomenon.

Genic markers for wild abortive (WA) cytoplasm based male sterility and its fertility restoration in rice

Commercial exploitation of heterosis is essential for enhancing productivity of rice. The use of cytoplasmic male sterility (CMS) and fertility restoration system greatly facilitates large scale production of hybrid seed. The wild abortive (WA) cytoplasm is most widely used for hybrid seed production in rice. The present study was undertaken to develop molecular markers for both WA cytoplasm based male sterility and its fertility restoration for use in efficient hybrid breeding. High degree of genetic differentiation of WA-cytoplasm from its normal fertile counterpart was observed due to DNA rearrangements involving five (coxI, coxIII, cob, atp6 and rps3) mitochondrial genes. Cleaved amplified polymorphic sequence (CAPS) markers based on five mitochondrial genes namely, coxIII, cob, atp9, rps3 and 18SrRNA polymorphic between CMS and maintainer line were developed. The utility of these informative markers was demonstrated in purity testing of the CMS line Pusa6A being used in commercial hybrid seed production. Fertility restoration was found to be controlled by a major locus in the Basmati restorer line PRR78, which was mapped to a short marker interval of 0.8 cM and a physical interval of 163.6 kb on rice chromosome 10. A total of 13 pentatricopeptide repeat (PPR) motif containing genes were predicted in a 1.66 Mb region on the long-arm of this chromosome of which, four were present in the marker interval containing the fertility restorer gene. High degree of conservation of gene order was observed between japonica and indica for the predicted PPR genes. A sequence tagged site (STS) and a genic non-coding microsatellite (GNMS) marker were designed based on one of the candidate PPR motif containing genes present in the marker interval, which were validated using F2 population and other known restorer lines. The candidate gene based marker identified in the present study would be useful in marker assisted selection (MAS) for fertility restorer gene in hybrid breeding programme based on WA-CMS of rice.

Visual assessment of sweet maize lines phenotype, according to UPOV descriptor, as indicator of heterosis

The organisation of germplasm into genetically divergent groups is of extreme importance for the development of hybrid varieties in which the identification and exploitation of heterosis is very important for the final result of breeding. It can also be beneficial for breeding of self-pollination varieties, clones and synthetics. The discovery of heterotic groups in standard grain quality maize significantly improved the process of testing. The improvement in sweet maize was relatively modest in comparison to standard grain quality maize due to a relatively narrow genetic base of sweet maize, then poorly defined heterotic relations, scarce sources of germplasm that satisfy commercial standards, poor seed vigour, low quality of root and stalk, as well as, a short period of time for the estimation of yield and quality. The efficiency of hybrid breeding programmes would be significantly higher if heterosis could be predicted prior to the evaluation in the field. The application of the multivariate analysis method to data of phenotypic characterization according to the UPOV Descriptor was an attempt to establish whether such a procedure can be beneficial for the determination of related groups and whether the phenotypic distance, obtained on the basis of a visual estimation of a plant group, can be an indicator of heterosis. Obtained results indicate that clustering is highly analogous to the pedigree. Since sweet maize breeders have at their disposal less significant genetic variability and search for the development and defining of heterotic groups, as such a procedure can be useful in both, the process of the hybrids development and the process of new inbreed development and genetic variability increasing. Certainly, further systematic studies aimed at this direction are necessary to reliably ascertain that the phenotypic distance is a justifiable indicator of heterosis.

Combining Ability of Inbred Lines Derived from a Yellow Dent Maize Synthetic CMS 61

A breeding program based on heterosis exploitation needs the knowledgment of the germplasm to produce good combinations in superior hybrids. A study was conducted to evaluate inbred lines, derived from synthetic maize CMS 61, in a diallel mating design.

The International Conference on “Heterosis in Plants”

The commercial exploitation of heterosis or hybrid vigor through the development and cultivation of hybrid cultivars is one of the landmark achievements in plant breeding. Ever since the two pioneering publications by George H. Shull 100 years ago, in which he scientifically described heterosis and laid the foundation of modern hybrid breeding in maize, the exploitation of heterosis in crop and tree species has greatly expanded and the acreage under hybrid cultivars has steadily increased. Thus, hybrid breeding has made commendable contributions in meeting the food, feed, and fiber needs of the burgeoning population of the world, and benefitted farmers and consumers. It also promoted the development of a viable seed industry, which was a tremendous stimulus for the research in plant breeding. The overwhelming importance of heterosis attracted many scientists to study the underlying genetic causes of this unique phenomenon. Vast data sets were generated and analyzed in different disciplines. To compile and discuss the accumulated information, two international conferences were organized in the past: The first conference was held in 1950 at Iowa State College in Ames and lasted for 4 weeks. The second conference was organized in 1997 by CIMMYT in Mexico City. Both conferences proved to be landmarks in research on heterosis and its exploitation in plant breeding. In recent years, there have been new developments in agriculture. On one hand, intensive agriculture is adversely affecting the natural resources and the arable land available for food production is decreasing with the increasing demand of plants for industrial purposes and renewable resources of energy. On the other hand, our needs for food and feed production are increasing, because of an ever growing population and improving living standards. Further, future agriculture is expected to face serious challenges due to the impending climate changes. Consequently, serious concerns are being expressed about the food security of our planet. A viable option to meet the increasing demands is the enhancement of productivity per unit of resources on a sustainable basis. In this scenario, optimal exploitation of heterosis can play a key role. It enables plant breeders to provide cultivars possessing high genetic potential. A better understanding of the causes underlying heterosis will facilitate the development of new breeding approaches for rapid and efficient exploitation of heterosis. The recent advances in genomics, bioinformatics and related fields have provided researchers with novel tools and approaches to investigate heterosis. Multidisciplinary teams of scientists are working on their application to link the new results for a better understanding of heterosis at various biological levels (DNA, mRNA, proteins and metabolites). These advances have expanded the disciplinary domain and knowledge at a rapid pace. Therefore, the University of Hohenheim considered it appropriate to organize and host a third international conference on ‘‘Heterosis in Plants’’ in Stuttgart, Germany, from 7 to 9 September 2009. The main aims of the conference were (1) to summarize the progress in theory and experimental studies on heterosis at different biological levels during the past 12 years, (2) to promote a better understanding of the biological processes underlying heterosis and (3) to stimulate further advances in the exploitation of heterosis in plant breeding by the application of new genomic tools. A. E. Melchinger (&) Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, 70593 Stuttgart, Germany e-mail: melchinger@uni-hohenheim.de

Combining Ability Analysis for Bread Wheat (Triticum Aestivum L.)

Choice of promising genotypes from a diverse genetic base and subsequent utilization for hybridization is one of the strategies for improving productivity of bread wheat. The data from eight parents andtheir F1 progenies of half-diallel crosses were analyzed for combining ability for yield and yield related traits in triplicate randomized complete block design in 2005 at Sinana, south-east Ethiopia. Significant differences among all the genotypes were apparent for all traits, except for biomass per plant. Both GCA and SCA mean squares revealed significant differences in plant height, harvest index, grain yield per plant, 1000-kernel weight and maturity traits, indicating the important of both additive and non-additive gene actions in the inheritance of thesetraits with the predominant effect of non-additive gene action. For the remaining traits, only mean square due to GCA showed significant variation, indicating the greater importance of additive gene action in controlling the inheritance of these characters. Abola gave highly significant GCA effects in the desirable direction and was the best general combiner for most of the traits, followed by Galema and Sofumer, while Dashen was the only parent which showed significant positive GCA effect for grain yield per plant. Cross combinations of Dashen x Galema, Abola x Dure, Dashen x Meda-Welabu, Abola x Galema, and Galema x Dure, exhibited significant SCA effects in the desired direction for at least two and, at most, for four traits, for which SCA variance showed significantdifferences. Hence, these crosses revealed possibility for commercial exploitation of heterosis as well as selection of potential homozygous lines from transgressive segregants for improvement of yield levels of bread wheat.Keywords: Combining Ability; Diallel Cross; GCA; SCA; Triticum aestivum

Heterosis in fingerlings from a diallel cross between two wild strains of silver perch (Bidyanus bidyanus)

Cross-breeding was investigated as a strategy to improve performance of the Australian native freshwater fish, silver perch (Bidyanus bidyanus Mitchell) through the exploitation of heterosis during the fingerling phase of production. Growth, and mid and best parent heterosis of two wild strains, Cataract Dam (C< C,) and Murray River (M< M,) and their reciprocal crosses (C< M, and M< C,) were evaluated in cages and ponds through summer, and in tanks in a re-circulating aquaculture system during winter. The M C cross grew significantly faster than the reciprocal cross and pure strains in cages and tanks, had the lowest coefficients of variation of weight and length and was 20.9% and 16.0% heavier than midparent and best-parent average, respectively, when grown in ponds. Differences in growth between the reciprocal crosses were also evident, with C M expressing significantly less heterosis in cages and tanks. Faster growth of M C was attributed to greater appetite; however, at sizes approaching 250 g this feeding vigour diminished. The results of this study suggest that use of the M C cross has the potential to reduce the length of the culture period and lower costs of silver perch production.

Molecular diversity and relationships among elite maize inbreds from US and CIMMYT populations and current heterotic groups in China

Exploring extensive maize germplasms from diverse origins is helpful to broaden the genetic base of maize. This study was performed to assess genetic diversity and genetic distance among representative inbreds from known heterotic groups in China and broadly based American populations. A total of 36 maize inbreds, 18 each from America and China, were evaluated at 109 simple sequence repeat (SSR) loci. SSR data revealed greater genetic diversity with an overall mean polymorphic information content (PIC) of 0.66 and mean number of 6 alleles per locus. Among the alleles, 25.5 and 19.8% were inbred-specific to Chinese and American inbreds, respectively. The inbreds were clustered into five groups, Reid Yellow Dent (RYD), Iowa Corn Borer Synthetic No. 1 (BSCB1), Luda Red Cob (LDRC), Lancaster Surecrop (LSC) and Tangshan Sipingtou (TSSPT). Most of the inbreds released from US hybrids and their derivatives clustered with BSSS inbreds, enhancing the RYD heterotic group. However, the inbreds from two-ear composite (BS11) and CIMMYT population (Pool41) were not clustered as independent groups. Two inbreds, B109 and B73, and those from BSCB1 could be promising for the exploitation of heterosis and broadening germplasm sources for Chinese maize improvement programs.

Genetic divergence analysis in Eucalyptus camaldulensis Dehnh.

Eucalyptus camaldulensis Dehnh. is one of the important tree species used in modern plantation forestry programme. The genetic divergence analysis helps in assessing the genetic diversity within the species and also provide information for developing breeding plan, establishment of seed orchards and exploitation of heterosis through hybridization. In the present study attempts were made to assess the genetic diversity among the different open pollinated families of E. camaldulensis based on growth parameters at 24 months of age in three different locations.

Genotypes of Heading Date of Middle Indica Rice in the Mid‐lower Region of the Yangtze River

Abstract Middle indica cultivars are planted in the middle to lower regions of the Yangtze River. Hybrid combinations with these cultivars have a high yield potential but the presence of late‐transgressive‐segregants limits the further exploitation of heterosis. To understand the genetic basis of the heading date in these middle maturing cultivars, we carried out a genetic analysis of 10 typical middle‐season cultivars using a number of heading date isogenic lines under both long and short day conditions. The results showed that Teqing, 752, CDR22, Bo B, 9311 and II‐32B carry two photoperiod sensitive genes E1 or Se‐1 and E3, and Teqing, 752 and CDR22 carry a dominant early‐heading gene Ef‐1 while Bo B, 9311 and II‐32B carry a recessive late‐heading gene ef‐1. Based on the findings of the present and previous works on Guichao 2, Minghui 63, Nanjing 11 and Pei'ai64S, it was concluded that all of these middle indica cultivars carried the recessive allele hd2, which could inhibit the expression of E1 or Se‐1, and they formed rational combinations of genotype for heading date during a long period of evolution. The effects of the different combinations of genotype for heading date on rice cultivation and extension were discussed, and genetic basis of broad adaptability of hybrid middle indica cultivars was analyzed.

Fine mapping of S31, a gene responsible for hybrid embryo-sac abortion in rice (Oryza sativa L.)

Partial abortion of female gametes and the resulting semi-sterility of indica x japonica inter-subspecific rice hybrids have been ascribed to an allelic interaction, which can be avoided by the use of wide compatibility varieties. To further understand the genetic mechanism of hybrid sterility, we have constructed two sets of hybrids, using as male parent either the typical japonica variety Asominori, or the wide compatibility variety 02428; and as female, a set of 66 chromosome segment substitution lines in which various chromosomal segments from the indica variety IR24 have been introduced into a common genetic background of Asominori. Spikelet semi-sterility was observed in hybrid between CSSL34 and Asominori, which is known to carry the sterility gene S31 (Zhao et al. in Euphytica 151:331-337, 2006). Cytological analysis revealed that the semi-sterility of the CSSL34 x Asominori hybrid was caused primarily by partial abortion of the embryo sac at the stage of the mitosis of the functional megaspore. A population of 1,630 progeny of the three-way cross (CSSL34 x 02428) x Asominori was developed to map S31. Based on the physical location of linked molecular markers, S31 was thereby delimited to a 54-kb region on rice chromsome 5. This fragment contains eight predicted open reading frames, four of which encode known proteins and four putative proteins. These results are relevant to the map-based cloning of S31, and the development of marker-assisted transfer of non-sterility allele inducing alleles to breeding germplasm, to allow for a more efficient exploitation of heterosis in hybrid rice.

Classical genetic and quantitative trait loci analyses of heterosis in a maize hybrid between two elite inbred lines.

The exploitation of heterosis is one of the most outstanding advancements in plant breeding, although its genetic basis is not well understood yet. This research was conducted on the materials arising from the maize single cross B73 x H99 to study heterosis by procedures of classical genetic and quantitative trait loci (QTL) analyses. Materials were the basic generations, the derived 142 recombinant inbred lines (RILs), and the three testcross populations obtained by crossing the 142 RILs to each parent and their F(1). For seedling weight (SW), number of kernels per plant (NK), and grain yield (GY), heterosis was >100% and the average degree of dominance was >1. Epistasis was significant for SW and NK but not for GY. Several QTL were identified and in most cases they were in the additive-dominance range for traits with low heterosis and mostly in the dominance-overdominance range for plant height (PH), SW, NK, and GY. Only a few QTL with digenic epistasis were identified. The importance of dominance effects was confirmed by highly significant correlations between heterozygosity level and phenotypic performance, especially for GY. Some chromosome regions presented overlaps of overdominant QTL for SW, PH, NK, and GY, suggesting pleiotropic effects on overall plant vigor.

Genetic diversity of African maize inbred lines revealed by SSR markers

Knowledge of genetic diversity (GD) and relationships among maize inbred lines is indispensable in a breeding program. Our objectives were to (1) investigate the level of genetic diversity among maize inbred lines and (2) assess their genetic structures by applying simple sequence repeat (SSR) markers. Fifty-six highland and mid-altitude maize inbred lines obtained from CIMMYT programs in Ethiopia and Zimbabwe were genotyped using 27 SSR loci. All of the genotypes studied could unequivocally be distinguished with the combination of the SSRs used. In total, 104 SSR alleles were identified, with a mean of 3.85 alleles per locus. The average polymorphism information content (PIC) was 0.58. GD expressed as Euclidean distance, varied from 0.28 to 0.73 with an average of 0.59. Cluster analysis using unweighted pair group method with arithmetic average (UPGMA) suggested five groups among the inbred lines. Most of the inbred lines adapted to the highlands and the mid-altitudes were positioned in different clusters with a few discrepancies. The pattern of groupings of the inbred lines was mostly consistent with available pedigree information. The variability detected using SSR markers could potentially contribute towards effective utilization of the inbred lines for the exploitation of heterosis and formation of genetically diverse source populations in Ethiopian maize improvement programs.

Comparative growth and viability of hybrids between two populations of Chinese shrimp (Fennropenaeus chinensis)

Fenneropenaeus chinensis is confined to the Yellow Sea and Bohai Sea in China and the West Coast of the Korean Peninsula. Intra- and intercross populations were produced between Rushany (YP) and Korean (KN) populations. Seven traits were recorded. The heterosis of hybrids was computed and comparison between treatments was performed by ANOVA. At the fourth month after post-larvae, six indexes of growth trait and viability showed a range of heterosis, ranging from 0.514% to 14.950%. At the fifth month after post-larvae, six indexes of growth trait and viability ranged from -9.000% to 19.090%. The negative heterosis was observed in CL, HST and viability. The heterosis of KN female xYP male tended generally to increase as the age of the Chinese shrimp increased while the heterosis of YP female xKN male tended to decrease. The results indicated that the viability of reciprocal hybrids were not significantly different (P > 0.05) from their parents during the experiment. The result of ANOVA indicated that the F1 hybrids were significantly different (P 0.05) from their parents. The multiple comparisons of LSD test indicated that the hybrids of KN female xYP male were significantly different (P < 0.05) from the KN parents in TW. The results indicate that in experimental conditions, the F-1 hybrids created from two populations of Chinese shrimp showed a certain level of heterosis for growth performance and viability. The crossing scheme may improve growth performance and viability in Chinese shrimp, but the improvement may be limited because effective crossbreeding requires the maintenance of pure, preferably inbred, lines and possibly involves specialized sire and dam lines. Therefore, the exploitation of heterosis through single crossbreeding in Chinese shrimp is of limited utility in practical commercial shrimp aquaculture in spite of the potential of significant heterosis. The crossbreeding of different populations can be applied in the establishment of base populations.

Introgression of genomic components from Chinese Brassica rapa contributes to widening the genetic diversity in rapeseed (B. napus L.), with emphasis on the evolution of Chinese rapeseed

In spite of its short history of being an oil crop in China, the Chinese semi-winter rapeseed (Brassica napus L., 2n = 38, AACC) has been improved rapidly by intentional introgression of genomic components from Chinese B. rapa (2n = 20, AA). As a result, the Chinese semi-winter rapeseed has diversified genetically from the spring and winter rapeseed grown in the other regions such as Europe and North America. The objectives of this study were to investigate the roles of the introgression of the genomic components from the Chinese B. rapa in widening the genetic diversity of rapeseed and to verify the role of this introgression in the evolution of the Chinese rapeseed. Ten lines of the new type of rapeseed, which were produced by introgression of Chinese B. rapa to Chinese normal rapeseed, were compared for genetic diversity using amplified fragment length polymorphism (AFLP) with three groups of 35 lines of the normal rapeseed, including 9 semi-winter rapeseed lines from China, 9 winter rapeseed lines from Europe and 17 spring rapeseed lines from Northern Europe, Canada and Australia. Analysis of 799 polymorphic fragments revealed that within the groups, the new type rapeseed had the highest genetic diversity, followed by the semi-winter normal rapeseed from China. Spring and winter rapeseed had the lowest genetic diversity. Among the groups, the new type rapeseed group had the largest average genetic distance to the other three groups. Principal component analysis and cluster analysis, however, could not separate the new type rapeseed group from Chinese normal rapeseed group. Our data suggested that the introgression of Chinese B. rapa could significantly diversify the genetic basis of the rapeseed and play an important role in the evolution of Chinese rapeseed. The use of new genetic variation for the exploitation of heterosis in Brassica hybrid breeding is discussed.