HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Related articles in Crop Science Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Chen, Q.-F. Articles by Zeller, F. J. Search for Related Content PubMed Articles by Chen, Q.-F. Articles by Zeller, F. J. Agricola Articles by Chen, Q.-F. Articles by Zeller, F. J. Related Collections Crop Cytology Crop Genetics Other Grain Crops

CROP BREEDING, GENETICS & CYTOLOGY

A Study of Cytology, Isozyme, and Interspecific Hybridization on the Big-Achene Group of Buckwheat Species (Fagopyrum, Polygonaceae)

^a Institute of Plant Genetics and Breeding, School of Biological Technology and Engineering, Guizhou Normal University, Baoshan Beilu 116, Guiyang 550001, P.R. China
^b Technical Univ. of Munich, Lehrstuhl fuer Pflanzenbau und Pflanzenzuechtung, Lange Point 51, D-85350 Freising-Weihenstephan, Germany

^* Corresponding author (cqf1966{at}163.com, chenqf1228013{at}hotmail.com).

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Eleven accessions of eight species belonging to the big-achene group of genus Fagopyrum Moench were studied on the basis of interspecific hybridization, GOT (i.e., glutamate oxaloacetate transaminase) isozyme band characteristics, and cytology. Following normal pollination, there were high crossabilities (8–37%) among these different species, but all hybrid seeds were empty except the crosses among F. esculentum Moench, F. esculentum var. homotropicum (Ohnishi) Q-F. Chen (= F. homotropicum Ohnishi), and F. esculentum subsp. ancestrale Ohnishi, indicating that there are no reproductional isolations among F. esculentum, F. esculentum var. homotropicum, and F. esculentum subsp. ancestrale. The cytological observation showed that the hybrid F. esculentum x F. esculentum var. homotropicum shows eight normal bivalents in meiosis of pollen mother cells. In addition, the results of GOT isozyme showed that F. esculentum, F. esculentum var. homotropicum, and F. zuogongense possess common GOT isoenzyme bands. Fagopyrum megaspartanium and F. pilus show unique GOT bands as well as karyotypes supporting the classification of individual species. The cytological analyses showed that tetraploid F. cymosum and F. giganteum are allotetraploids with two different size genomes. The identities of the different genomes in the big-achene group of genus Fagopyrum and the putative progenitors of common buckwheat are discussed.

Abbreviations: GOT, glutamate oxaloacetate transaminase (EC 2.6.1.1) • m, median chromosome • MI, the first metaphase of meiosis • RAPD, random amplified polymorphic DNA • SAT, satellite chromosome • sm, submedian chromosome

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
BUCKWHEAT, an important nonpoaceous crop, is highly nutritious and possesses great potential for food, forage, and medicine (Li and Zhang, 2001; Zeller, 2001). Buckwheat has seed proteins with amino acid composition close to the standard protein quality suggested by FAO and better than those in cereal crops (Radovic et al., 1999; Rout et al., 1997; Rout and Chrungoo, 1999). The rutin present in high content in buckwheat can cure many human diseases (Lin, 1994, p. 97–105).

Buckwheat species native to China have been systematically classified since 1913 (Chen, 1999a; Ohnishi and Matsuoka, 1996; Ye and Guo, 1992). According to their classifications, Fagopyrum includes about sixteen species divided into two groups: (i) the big-achene group, including common buckwheat (F. esculentum Moench), F. esculentum subsp. ancestrale Ohnishi, tartary buckwheat [F. tataricum (L.) Gaertn.], annual diploid F. homotropicum Ohnishi, annual tetraploid F. zuogongense Q-F. Chen, perennial tetraploid F. cymosum Meisn., perennial diploid F. megaspartanium Q-F. Chen, and perennial diploid F. pilus Q-F. Chen, and (ii) the small-achene group, including F. gracilipes (Hemsl.) Dammer ex Diels., and F. pleioramosum Ohnishi. The two groups exhibit large differences in morphology and genetics (Chen, 1999a, 1999b; Ohnishi and Matsuoka, 1996).

The three natural perennial species in the big-achene group were considered as one species, F. cymosum (Ye and Guo, 1992; Ohnishi and Matsuoka, 1996), designated as the perennial F. cymosum complex, which Chen (1999a)(1999b) has reclassified as different species. In addition, a man-made tetraploid species, F. giganteum Krot. synthesized from the cross of 4x F. tataricum and 4x F. cymosum (Krotov and Dranenko, 1973), also exists. Because of the similarities in morphology among these taxa, more information to clarify the taxonomy of these perennial species of the big-achene group is needed.

Common buckwheat is diploid (2n = 2x = 16) (Stevens, 1912, see Lin, 1994). Chen (1999a)(1999b) reported that F. megaspartanium and F. pilus are also diploid. Zu et al. (1984) reported that the chromosomes of common buckwheat are similar to each other in size and all have a median kinetochore (m). The karyotype analysis of chromosomes (Chen, 2001a) showed that F. esculentum, F. tataricum, F. megaspartanium, and F. pilus are all diploid species with two pairs of satellite chromosomes and their karyotype formulas are 12m + 4m (SAT), 12m + 4sm (SAT), 8m + 4sm + 4m (SAT), and 12m + 2m (SAT) + 2 sm (SAT), respectively. Fagopyrum zuogongense is tetraploid with karyotype formula 24m + 4sm + 4m (SAT). The different chromosomes of the same species are very similar in size. The karyotypes of F. cymosum and F. giganteum have not been reported.

To improve the low grain set and productivity of common buckwheat, many hybridizations among buckwheat species have been attempted. Though there are great difficulties to get interspecific hybrids, some interspecific crosses have been successful among F. esculentum, F. tataricum, the F. cymosum complex, and F. zuogongense (Chen, 1999b; Krotov and Dranenko, 1973; Lee et al., 1994; Shaikh et al., 2002; Ujihara et al., 1990; Woo et al., 1999). The high interspecific crossabilities in the large-achene group of buckwheat showed that there are close relationships among the species of this group (Chen, 1999b).

No studies have evaluated all the big-achene species simultaneously, especially those described by Chen (1999a) and Ohnishi and Matsuoka (1996), such as F. homotropicum, F. zuogongense, F. megaspartanium, and F. pilus. In this study, these four newly identified species are described on the basis of their morphology, crossability, isozyme, and cytology, to provide some clues on the genetics, breeding, taxonomy, and phylogeny of buckwheat.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Eleven accessions belonging to eight buckwheat species were evaluated. The description and origin of these accessions are listed in Table 1. More than 20 plants of each accession were grown in the growth chamber at 15 to 28°C at the Technical University of Munich, Freising, Germany, between July 2001 and November 2002. No bees or other insects were present.

Hybrid seeds were germinated by floating on 0.2% (w/v) KNO₃ solution at room temperature and were transplanted to pots in the growth chamber.

Cytological Observation of Meiosis and Mitosis
Chromosomal observation of the parents and their hybrids were conducted as follows. More than 10 plants per species and more than 50 metaphase cells per plant were observed. For meiotic investigation of pollen mother cells, young inflorescences of parents and hybrid plants were fixed in Carnoy I solution and stained in 2% (w/v) aceto-carmine. The improved procedure for observation of mitotic chromosomes in root tips followed Chen (1999a). Briefly, the root tips were first treated with 0.3% 8-hydroxyquinoline for 15 to 20°C for 3 h; fixed in Carnoy I solution overnight; hydrolyzed in 3 mol/L HCl at 60°C for 20 min; washed in distilled water for 5 min and treated in 4% (v/v) cellulase-pectinase at 37°C for 5 h. They were then washed and soaked in distilled water for 90 min, followed by smear preparations. Air-dried slides were stained in freshly prepared 3% Giemsa solution (pH = 7.0).

Karyotype Analyses of F. cymosum and F. giganteum
Karyotype analyses was conducted as described by Li and Zhang (1996)(p. 5–40). The absolute length of the chromosome (AL, µm) = the length of the magnified chromosome (mm) x 1000/magnification. The relative length of the chromosome (RL, %) = (the length of the chromosome/total length of all chromosomes) x 100. The arm ratio (AR) = the length of long arm of the chromosome/the length of short arm of the chromosome. The length ratio (L/S) = the length of the longest chromosome/the length of the shortest chromosome. The position of centromere and the karyotype class followed Levan et al. (1964, see Li and Zhang, 1996) and Stebbins (1971, see Li and Zhang, 1996), respectively.

PAGE Analyses of Glutamate Oxaloacetate Transaminase (EC 2.6.1.1, GOT)
Isozyme experiments in buckwheat have shown little variation among different accessions in the same species (Ohnishi, 1993; Chen, 1999a) but abundant variation among different buckwheat species. In our preliminary experiment, the GOT isozyme has been shown to be an excellent marker that clearly reflects the differences among different buckwheat species, and thus is analyzed in this study. The polyacrylamide gel electrophoresis (PAGE) method of GOT isozyme analyses was described by Hu and Wan (1996)(p. 96–104). The GOT extract was from the powder of a dry seed whose peel had been removed. The parameters of bio-gel for separation were T (total concentration of Acr and Bis) = 7.5%, C (the rate of Bis in T) = 2.8%. More than 50 seeds for each species were assayed for GOT.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Interspecific Crossability
The grain set rates of 17 crosses among eight species were evaluated (Table 2). The crossabilities among F. esculentum (E2), F. esculentum subsp. ancestrale (EA), and F. homotropicum (H) were high (23–34%) and the crosses resulted in normal seeds, indicating that their relationships are very close. The crossabilities among F. esculentum (E2 and E4), F. tataricum (T2 and T4), F. zuogongense (Z), F. megaspartanium (M), F. pilus (P), F. cymosum (C), and F. giganteum (G) were 8 to 37%, indicating that their relationships among these species may also be close. However, the hybrid seeds obtained were all empty, probably due to different ploidy levels or pronounced reproductive isolation.

The seeds of the cross F. esculentum (E2) x F. homotropicum (H), however, were easy to germinate and the hybrid plants could be grown normally, indicating that the achene dormancy of F. homotropicum is controlled by the sporophyte genotypes. The hybrids produce homostyle flowers with the seed-shattering habit, set seeds normally by self-pollination, and have a strong main stem and large leaves. Obviously, the hybrids are similar to their male parent, but their height, the size of flowers and seeds, and other morphological traits are between those of the parents.

Cytological observations showed that F. esculentum subsp. ancestrale (EA) and F. homotropicum (H) are diploid and that the hybrid of the cross F. esculentum (E2) x F. homotropicum (H) reveals eight normal bivalents in meiosis of pollen mother cells and with normal pollen grains, indicating that they are very close in relationship.

Cytological Observation and Karyotype Analyses of Chromosomes of F. cymosum and F. giganteum
The results of chromosomal observations of 4x F. cymosum and synthetic 4x F. giganteum clearly showed two different groups of chromosomes based on size (Fig. 1 and 2 ; Tables 3, 4, and 5). Since all chromosomes have the very similar size within each of the recognized diploid species in the big-achene group of buckwheat (Chen, 1999a, 2001a), the results indicated that F. cymosum and F. giganteum were allotetraploid, containing two differently sized genomes.

View larger version (57K): [in this window] [in a new window]   Fig. 1. The chromosomes of F. cymosum and F. giganteum. a and d are the metaphase of chromosomes of F. cymosum and F. giganteum in the mitotic cell of root tips, respectively. b and e are the karyotypes of chromosomes of F. cymosum and F. giganteum, respectively. There is obviously one larger (No. 1–8) and one smaller (No. 9–16) genome. c and f are the chromosomes of F. cymosum and F. giganteum in the meiosis MI of pollen mother cells, respectively. There are eight larger (marked with arrows) and eight smaller bivalents.

View larger version (18K): [in this window] [in a new window]   Fig. 2. The karyotype models of genomes X, Y, M, and T in F. cymosum and F. giganteum.

The X genome has the RL range of 6.17 to 8.03% in X and Y genomes with four pairs of submedian (sm) chromosomes, and Y genome has 4.45 to 5.95% in the X and Y genomes with one pair of sm chromosomes.

As to the two different genomes in F. giganteum, the larger one is designated M and the smaller one T. The average of the absolute length of chromosomes in Genomes M and T is 1.95 µm, with standard deviation 0.71, and variation coefficient 36.31%. It is clear that the deviation of absolute length of chromosomes in F. giganteum is greater than that in F. cymosum. The average of absolute length of Genome M is 2.58 µm, longer than that of genome X (2.18 µm), genome Y (1.53 µm), and genome T (1.32 µm). And the standard deviation (SD), variation coefficient (%) and L/S in genome M are 0.32 µm, 12.49%, and 1.51, respectively, similar to those in genome T, X, or Y. The order of the absolute length is largely M > X > Y > T.

The M genome has the RL range 6.69 to 10.11% in the M and T genomes with two pairs of sm chromosomes and the T genome has the RL range 3.48 to 5.60% in the M and T genomes with one pair of sm chromosomes. Besides, the T genome has two pairs of SAT chromosomes.

The karyotype formulas of genomes X and Y in F. cymosum and genomes M and T in F. giganteum are 3m + 4sm + 1m (SAT), 7m + 1sm, 6m + 2sm, and 5m + 1sm + 2m (SAT), respectively (Tables 3 and 4).

Glutamate Oxaloacetate Transaminase
The results showed that the GOT isozyme zymographs of various achenes of the same accession are similar. For accurate comparison among accessions, the zymographs of all accessions were prepared on a single Bio-gel plate (Fig. 3 and 4) . From these figures, the following observations could be made. Common buckwheat, F. homotropicum and F. zuogongense, have only the GOT-5 band. F. tataricum and F. pilus have very similar zymographs. Fagopyrum megaspartanium and F. giganteum share the GOT-5 of common buckwheat indicating a close relationship. Fagopyrum pilus shares similar GOT-2 and GOT-3 bands with F. cymosum and F. giganteum shows similar GOT-4 and GOT-5 with F. megaspartanium and GOT-3 with F. tataricum.

View larger version (40K): [in this window] [in a new window]   Fig. 3. Zymographs of GOT isozyme on a PAGE gel. The symbols are explained in Table 1.

View larger version (10K): [in this window] [in a new window]   Fig. 4. Idiograms of GOT isozyme of eight types of buckwheat. E = F. esculentum, H = F. homotropicum, Z = F. zuogongense, T = F. tataricum, C = F. cymosum, P = F. pilus, M = F. megaspartanium, G = F. giganteum.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

There have been many reports about phylogeny based on polymorphism of RAPD, cpDNA, rDNA, rbcL, and accD genes among buckwheat species (Ohnishi and Matsuoka, 1996; Ohsako and Ohnishi, 2000; Sharma and Jana, 2002; Suvorova et al., 1999; Yasui and Ohnishi, 1998a, 1998b). Although these reports showed that different natural populations of F. cymosum complex varied considerably, they could not provide evidence whether F. cymosum is autotetraploid or allotetraploid and whether the different types of the F. cymosum complex were actually different species. In the present study it is clearly evident that F. cymosum is an allotetraploid (Fig. 1, 2; Table 3) very likely possessing two different genomes. More cytological studies between authentic F. pilus and F. megaspartanium (Chen 1999a, 1999b) species and diploid F. cymosum accession from Sichuan (Ohnishi, 2000) are needed to verify the systematics of the F. cymosum complex.

The two types (diploid and tetraploid) of natural populations of F. homotropicum are here designated F. homotropicum complex. According to the results in this study, the diploid type of the F. homotropicum complex is very similar to common buckwheat in morphology, and it can be crossed with diploid F. esculentum easily. Their hybrid has eight bivalents in meiosis of pollen mother cells, indicating that they have the same genome. We suggest that the diploid type of the F. homotropicum complex should be classified as F. esculentum var. homotropicum.

Because F. zuogongense, F. esculentum, and F. homotropicum share similar chromosome, morphology, and isozyme alleles (Chen, 1999a, 1999b; Chen, 2001a, 2001b; Ohnishi and Asano, 1999; Ohnishi and Matsuoka, 1996), F. zuogongense may be one of the tetraploid types of the F. homotropicum complex. Ohnishi and Asano (1999) reported that the fixed heterozygosity at polymorphic loci and the disomic inheritance at these loci observed in isozyme analyses strongly suggest the allopolyploid origin of tetraploid type of the F. homotropicum complex. Fagopyrum zuogongense has 16 bivalents at MI stage of meiosis of pollen mother cells (Chen, 1999a, 1999b) and its genomes have their own karyotypic properties (Chen, 2001a). Reproductional isolation between F. zuogongense and autotetraploid F. esculentum is evident (this study and Chen, 1999b), suggesting that F. zuogongense may be allotetraploid and should retain its species position.

The Genomes of the Big-Achene Group of Fagopyrum Species
This study discovered that there are two clearly differentiated groups of chromosomes based on size in the tetraploid F. cymosum and F. giganteum used in this study, indicating that they are all allotetraploid.

Lin (1994) and Chen (2001a) reported that F. esculentum has larger chromosomes than F. tataricum. The karyotype analyses (Chen, 2001a) showed that F. esculentum, F. tataricum, F. megaspartanium, and F. pilus all have their own karyotypic properties and that the karyotypes of F. esculentum and F. tataricum are close to those of F. megaspartanium and F. pilus, respectively. Their genomes are tentatively designated E, T, M, and P, respectively. Because we do not know the origin of the two genomes in the allotetraploid F. cymosum in this paper, they are designated X and Y. According to the results of GOT isozyme analysis in this study, one of them may be from F. pilus with genome P. Since genome P is smaller than genome E and M, genome P may be identical to genome Y.

Yamane et al (2003) showed that, on the basis of variation of cpDNA sequences, there are two types of tetraploid F. cymosum, arisen allopatrically, suggesting that the tetraploids had multiple origin. Ujihara et al. (1990) reported that there are 16 bivalents in the hybrids between autotetraploid common buckwheat and tetraploid type of F. cymosum complex, indicating that four genomes of the tetraploid F. cymosum are homologous, suggesting that there may be autotetraploid types besides the allotetraploid types in the F. cymosum complex and that the tetraploid type of F. cymosum complex used by Ujihara et al. (1990) maybe autotetraploid.

Because F. giganteum is from a hybrid of a species of the perennial F. cymosum complex (including F. megaspartanium, F. pilus, allotetraploid and autotetraploid F. cymosum etc.) with F. tataricum (Krotov and Dranenko, 1973), and because its zymograph of GOT allozymes covers those of both F. megaspartanium and F. tataricum in this study, it is apparent that F. giganteum has genomes M (the larger chromosomes set) and T (the smaller chromosome set), derived from F. cymosum which is similar to that of F. megaspartanium and F. tataricum, respectively.

This study suggested that F. esculentum and F. esculentum var. homotropicum (= one type of F. homotropicum complex) have the same genome, E, on the basis of their GOT isozyme patterns, their ease of crossing, and the bivalent pairing in meiosis of their hybrid progeny. This study also showed that F. zuogongense has similar morphological characteristics and the same type of GOT isozyme as F. esculentum and F. esculentum var. homotropicum. Chen (1999b) reported that there are 16 bivalents in both F. zuogongense and the hybrid of autotetraploid F. esculentum with F. zuogongense, indicating that F. zuogongense has two similar genomes, here designated E and E', which they can pair with each other in meiosis. These analyses indicated that F. zuogongense maybe originated and speciated from hybrids of common buckwheat and F. esculentum var. homotropicum.

According to the above analyses, we assign the genome symbols listed Table 1 to the eight species in the big-achene group of Fagopyrum.

	ACKNOWLEDGMENTS

 
We are grateful to the Alexander von Humboldt Foundation for a research fellowship, to Prof. Dr. Ohmi Ohnishi (Plant Germ-Plasm Institute, Faculty of Agriculture, Kyoto University, Japan), Mr. Tian-Yun Wang (The Chinese Academy of Agricultural Sciences, Beijing, China), and Prof. Chi Yen (Triticeae Research Institute, Sichuan Agricultural University, Sichuan, China) for providing materials, and to the Nature Science Foundation of China (No. 30270852) and the Foundation of Guizhou Elitist for financing.

Received for publication February 14, 2003.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 

• Chen, Q.F. 1999a. A study of resources of Fagopyrum (Polygonaceae) native to China. Bot. J. Linnean Soc. 130:53–64.
• Chen, Q.F. 1999b. Hybridization between Fagopyrum (Polygonaceae) species native to China. Bot. J. Linnean Soc. 131:177–185.
• Chen, Q.F. 2001a. Karyotype analysis of five Fagopyrum species native to China. Guihaia 21(2):107–110.
• Chen, Q.F. 2001b. Discussion on the origin of cultivated buckwheat in genus Fagopyrum (Polygonaceae). p. 207–213. In Seung et al. (ed.) Advances in buckwheat research (I), Proceedings of the VIII International Symposium on Buckwheat, Korea. 30 Aug.–2 Sept. 2001 International Buckwheat Research Association, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.
• Hu, N.S., and X.G. Wan. (ed.) 1996. Isozyme technology and its application. Hunan Scientific and Technological Publisher, Hunan, China.
• Krotov, A.S., and E.T. Dranenko. 1973. An amphidiploid buckwheat, F. giganteum Krotov sp. nova. Byulleten Vsesoyuznogo Ordena Lenina Instituta Rastenievodstva Imeni N.I.Vavilova 30:41–45.
• Lee, B.S., A. Ujihara, M. Minami, and T. Hirose. 1994. Breeding of interspecific hybrids in genus Fagopyrum. (4). Production of interspecific hybrids ovule culture among F. esculentum, F. tataricum and F. cymosum. Breed. Sci. 44(suppl. 1):183.
• Li, M.X., and Z.P. Zhang. (ed.) 1996. Plant chromosomes and their research technology. China Agricultural Publisher, Beijing, China.
• Li, S.Q., and Q.H. Zhang. 2001. Advances in the development of functional foods from buckwheat. Crit. Rev. Food Sci. Nutr. 41(6):451–464.[Medline]
• Lin, R.F. (ed.) 1994. Buckwheat in China. Agricultural Publisher, Peking, China.
• Ohnishi, O. 1993. Population genetics of cultivated common buckwheat, F. esculentum Moench. IX. Concluding remarks on world survey of allozyme variability. Jpn. J. Genet. 68:317–326.
• Ohnishi, O., and Y. Matsuoka. 1996. Search for the wild ancestor of buckwheat. II. Taxonomy of Fagopyrum (Polygonaceae) species based on morphology, isozymes and cpDNA variability. Genes Genet. Sys. 71:383–390.
• Ohnishi, O., and N. Asano. 1999. Genetic diversity of Fagopyrum homotropicum, a wild species related to common buckwheat. Genet. Resour. Crop Evol. 46(4):389–398.
• Ohsako, T., and O. Ohnishi. 2000. Intra- and interspecific phylogeny of wild Fagopyrum (Polygonaceae) species based on nucleotide sequences of noncoding regions in chloroplast DNA. Am. J. Bot. 87(4):573–582.[Abstract/Free Full Text]
• Radovic, R.S., R.V. Maksimovic, M.J. Brkljacic, I.E.V. Gasic, and P.A. Savic. 1999. 2S albumin from buckwheat (Fagopyrum esculentum Moench) seeds. J. Agric. Food Chem. 47(4):1467–1470.[Medline]
• Rout, M.K., N.K. Chrungoo, and K.S. Rao. 1997. Amino acide sequence of the basic subunit of 13S globulin of buckwheat. Phytochemistry 45(5):865–867.[Medline]
• Rout, M.K., and N.K. Chrungoo. 1999. The lysine and methionine rich basic subunit of buckwheat grain legumin: Some results of a structural study. Biochem. Mol. Biol. Int. 47(6):921–926.[Medline]
• Shaikh, N.Y., L.M. Guan, and T.J. Adachi. 2002. Failure of fertilization associated with absence of zygote development in the interspecific cross of Fagopyrum tataricum x F. esculentim. Breed. Sci. 52(1):9–13.
• Sharma, T.R., and S. Jana. 2002. Species relationships in Fagopyrum revealed by PCR-based DNA fingerprinting. Theor. Appl. Genet. 105(2–3):306–312.[Medline]
• Suvorova, G.N., H. Funatsuki, and F. Terami. 1999. Phylogenetic relationships among cultivars, species, and hybrids in the genus Fagopyrum Mill. assessed by RAPD analysis. Russian J. Genet. 35(12):1428–1432.
• Ujihara, A.Y., Y. Nakamura, and M. Minami. 1990. Interspecific hybridization in genus Fagopyrum–Properties of hybrids (F. esculentum x F. cymosum) through ovule culture. Gamma Field Symposia 29:45–33.
• Woo, S.H., Y.J. Wang, and C.G. Campbell. 1999. Interspecific hybrids with Fagopyrum cymosum in the genus Fagopyrum. Fagopyrum 16:13–18.
• Yamane, K., and O. Ohnishi. 2001. Phylogenetic relationships among natural populations of pernnial buckwheat, Fagopyrum cymosum Meisn., revealed by allozyme variation. Genet. Resour. Crop Evol. 48(1):69–77.
• Yamane, K., Y. Yasui, and O. Ohinishi. 2003. Intraspecific cpDNA variations of diploid and tetraploid perennial buckwheat, Fagopyrum cymosum (Polygonaceae). Am. J. Bot. 90:339–346.[Abstract/Free Full Text]
• Yasui, Y., and O. Ohnishi. 1998a. Interspecific relationships in Fagopyrum (Polygonaceae) revealed by the nucleotide sequences of the rbcL and accD genes and their intergenic region. Am. J. Bot. 85:1134–1142.[Abstract]
• Yasui, Y., and O. Ohnishi. 1998b. Phylogenetic relationships among Fagopyrum species revealed by the nucleotide sequences of the ITS region of the nuclear rRNA gene. Genes Genet. Sys. 73:201–210.
• Ye, N.G., and G.Q. Guo. 1992. Classification, origin and evolution of genus Fagopyrum in China. p. 19–28. In R. Lin et al. (ed.) Proceeding of the 5th International Symposium on Buckwheat, Taiyuan, China. Chinese Agricultural Publishing House, Beijing, China.
• Zeller, F.J. 2001. Buckwheat (Fagopyrum esculentum Moench): Utilization, genetics, breeding. Bodenkultur 52(3):259–276.
• Zu, F.X., R.F. Lin, Y.Q. Li, and D.K. Liu. 1984. Preliminary study on chromosome of various types of buckwheat. Chinese J. Cytobiol. 3:130–131.

Related articles in Crop Science:

THIS ISSUE IN CROP SCIENCE

Crop Science 2004 44: 1507-1510. [Full Text]  

This article has been cited by other articles:

				Q.-F. Chen, S. L. K. Hsam, and F. J. Zeller Cytogenetic Studies on Diploid and Autotetraploid Common Buckwheat and Their Autotriploid and Trisomics Crop Sci., November 7, 2007; 47(6): 2340 - 2345. [Abstract] [Full Text] [PDF]

This Article Abstract Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Related articles in Crop Science Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Chen, Q.-F. Articles by Zeller, F. J. Search for Related Content PubMed Articles by Chen, Q.-F. Articles by Zeller, F. J. Agricola Articles by Chen, Q.-F. Articles by Zeller, F. J. Related Collections Crop Cytology Crop Genetics Other Grain Crops