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) Free Alert me when this article is cited Alert me if a correction is posted Services 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 (5) Citing Articles via Google Scholar Google Scholar Articles by Xu, S.J. Articles by Hymowitz, T. Search for Related Content PubMed Articles by Xu, S.J. Articles by Hymowitz, T. Agricola Articles by Xu, S.J. Articles by Hymowitz, T.

CROP BREEDING, GENETICS & CYTOLOGY

Monosomics in Soybean

Origin, Identification, Cytology, and Breeding Behavior

Dept. of Crop Sciences, Univ. of Illinois, 1102 South Goodwin Ave., Urbana, IL 61801 USA

soyui{at}uiuc.edu

	ABSTRACT

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion REFERENCES

 
An individual lacking one chromosome is called monosomic and is designated as 2n - 1. Monosomics are useful for locating genes to specific chromosomes and in the assignment of linkage groups. Monosomics are rare in diploid crops. The objective of this study was to determine the origin, morphology, cytology, fertility, and breeding behavior of two spontaneously produced monosomics in soybean [Glycine max (L.) Merr., ]. The two monosomic plants were identified among progenies of triplo 3 (BC₃) and triplo 6 (BC₄) trisomic plants, backcrossed to `Clark 63' as the recurrent parent. The two monosomics are designated as mono-3 and mono-6. The two monosomic and one disomic sibling plants were grown in the greenhouse to evaluate reproductive and morphological traits. Chromosome associations were examined at Metaphase I. F₁ hybrids from the crosses of monosomics with Clark 63 and selfed populations were used to evaluate breeding behavior. Morphologically, mono-6 was similar to the disomic, while mono-3 was smaller with reduced vigor. Both monosomics showed 19 II + 1 I chromosome association at Metaphase I. Pollen fertility in mono-3 was 8.8% and in mono-6 was 20.0%. Mono-3 and mono-6 produced 59 and 176 S₁ (first selfed generation) seeds. Female transmission (mono-3 Clark 63) in mono-3 was 6.5% and self-pollination yielded 3.5% 2n - 1 offspring. By contrast, mono-6 was not transmitted among 105 S₁ plants, although one plant with 39 normal chromosomes plus one acrocentric chromosome was found. This study demonstrates that monosomics in soybean are viable and fertile, but that the transmission rate is sporadic.

Abbreviations: PMC, pollen mother cell

	INTRODUCTION

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion REFERENCES

 
MONOSOMICS (2n - 1) are a useful tool in locating genes to specific chromosomes and associating classical and molecular linkage groups with chromosomes in diploid and allopolyploid plants (Singh, 1993). Monosomics in diploid plant species have not received much attention because they are generally sterile and not transmitted to the next generation.

The cultivated soybean is considered a diploidized allotetraploid (Hadley and Hymowitz, 1973; Shoemaker et al., 1996). Because of its allotetraploid nature, soybean male and female gametophytes tolerate a higher number of extra chromosomes than most diploid species (Xu et al., 2000). Thus far, only one monosomic in soybean, identified from the progeny of a desynaptic mutant, has been reported (Skorupska and Palmer, 1987). Recently, we identified two monosomics among progenies of soybean primary trisomics . The objective of this study was to determine the origin, morphology, cytology, fertility, and breeding behavior of the two monosomic plants.

	Materials and methods

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion REFERENCES

 
Mono-3 and mono-6 monosomic soybean plants were found among progenies of triplo 3 (BC₃) and triplo 6 (BC₄) backcrossed to Clark 63. Triplo 3 and triplo 6 were identified respectively from aneuploid lines KS:TH775 and SRF 70:11 (Ahmad et al., 1992; Ahmad and Hymowitz, 1994; Xu et al., 1998b). Clark 63 was used as the recurrent parent because it belongs to Maturity Group IV and produced abundant pollen grains in our greenhouse conditions.

The two monosomic and one disomic sibling plants were individually planted into 20-cm clay pots. They were grown in the greenhouse at temperatures ranging from 25 to 30°C under supplemental lights to provide a uniform day length of 16 h. Morphological features of the three plants were evaluated during vegetative growth stages. The length and width of 10 intermediate trifoliolate terminal leaflets were measured when the plants reached senescence according to the procedures of Gwyn et al. (1985). The 100-seed weight for mono-6 and the disomic and 50-seed weight for mono-3 were recorded after harvesting.

Meiosis was studied in the mono-3 and mono-6 plants. The procedures for meiotic analysis were the same as those reported by Singh and Hymowitz (1988). Young flower buds were fixed in a mixture of 3:1 (v/v) 95% ethanol/propionic acid (70 mL 95% ethanol and 30 mL double-distilled water), with the addition of 1 g of ferric chloride per 100 mL of fixative. After 24 to 48 h of fixation, buds were transferred to 70% ethanol and stored at 0 to 4°C in a refrigerator. Anthers with meiotic stages were stained in 1% (w/v) propiono-carmine for 1 wk in a refrigerator and were squashed in 45% acetic acid (45 mL glacial acetic acid and 55 mL double-distilled water). Meiotic chromosome configurations at Metaphase I (50 pollen mother cells [PMCs]) and chromosome migration at Anaphase I (5 PMCs in mono-3 and 13 PMCs in mono-6) were analyzed using a Nikon Optiphot-2 Microscope (Nikon Inc., Instrument Group, Garden City, NY). Photomicrographs were taken under 100 oil plane objective using Kodak Technical Pan film 2415 (Eastman Kodak Company, Rochester, NY) and printed on Kodak Polycontrast III RC Glossy Paper (Eastman Kodak). At anthesis, pollen samples were stained with Lugol solution (Iodine/Potassium Iodide Solution, Sigma Cat. no. L-6146, Sigma Chemical Co., St. Louis, MO), and 500 pollen grains were counted from two flowers per sample.

The two monosomic plants were crossed with Clark 63 in order to determine the female transmission rate of the monosomics. The hybridization procedure was the same as that reported by Singh et al. (1998). The young flower buds were emasculated and pollinated immediately with pollen from Clark 63. At maturity, both crossed and selfed pods from the two monosomics and selfed pods from the disomic sib were harvested. Total number of pods and seeds from self-pollination were counted, and an average number of seeds per pod was calculated.

Chromosome numbers of F₁ and S₁ plants from the two monosomic plants were determined at mitotic metaphase or prometaphase by using the cytological methods described by Singh et al. (1998) and Xu et al. (1998a). Seeds were germinated in a sand bench in the greenhouse. Root tips from actively growing 7- to 10-d-old seedlings were collected and pretreated with 0.05% (w/v) 8-hydroxyquinoline for 4 to 5 h at 16°C. The root tips were fixed in a 3:1 (v/v) mixture of 95% ethanol and propionic acid for 24 h. Root tips were hydrolyzed in 1 M HCl for 11 to 15 min at 60°C and stained in Schiff's reagent for 2 h at room temperature. Feulgen stain was drained and the root tips were rinsed with cold double distilled water and stained with Carbol fuchsin stain overnight in a refrigerator. After staining, root tips were washed three to four times with cold double-distilled water and stored in cold double-distilled water in a refrigerator (Xu et al., 2000). Root tips were squashed in 45% acetic acid. Mitotic observation and photographic procedures were the same as for the meiotic analysis described above. Monosomic plants and any other aneuploids from the progenies of mono-3 and mono-6 were grown to maturity in the greenhouse.

	Results and discussion

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion REFERENCES

 
Origin of Monosomics
Mono-3 and mono-6 were discovered in the backcross progenies of triplo 3 (BC₃) and triplo 6 (BC₄), respectively. The extra chromosomes in triplo 3 and triplo 6 were identified based on pachytene chromosome analysis (Singh and Hymowitz, 1990). Because triplo 3 (BC₂) was used as male and triplo 6 (BC₃) as female in the backcrosses to Clark 63, mono-3 probably originated from an n - 1 sperm and mono-6 from an n - 1 egg. We did not attempt to identify the chromosomes in the two monosomic plants. The missing chromosomes in the two monosomics are most likely the same as the extra chromosomes in their respective parental primary trisomics. Primary trisomics are a principal source of monosomics in plants (Singh, 1993). In primary trisomics, three homologous chromosomes predominately form 1 III and 1 II + 1 I configurations. The derivation of monosomics from primary trisomics is generally associated with nondisjunction and lagging of chromosomes during meiosis, leading to male and female spores lacking one complete chromosome. In most cases, the missing chromosome in a monosomic progeny of a primary trisomic plant is the same as the extra chromosome in the primary trisomic parent plant.

The frequency of monosomics from the progenies of primary trisomics is very low (Singh, 1993). In this study, mono-3 was found among five plants from the cross of Clark 63 triplo 3 (BC₂), but an additional 177 plants from 2n (2n + 1) crosses contained either or , except for one hypertriploid plant with 2n = 61 chromosomes (Xu et al., 2000). Mono-6 was discovered among 1244 plants from the crosses of (2n + 1) 2n.

Morphology
Both mono-3 and mono-6 had smaller leaflets than the disomic sibling plant. Mono-3 was slow in vegetative growth and possessed small stature with fewer branches. However, mono-3 produced plumper pods and larger seeds than the disomic plant (Table 1) . Mono-6 was morphologically indistinguishable from the disomic prior to the flower stage. The mono-6 plant matured 3 mo later than its disomic sib plants; however, flowering was not delayed. Mono-6 set wrinkled pods, and the seeds were much smaller than those of the disomic plant (Table 1).

Monosomics in allotetraploid tobacco (Nicotiana tabacum L.; Clausen and Cameron, 1944) and cotton (Gossypium hirsutum L.; Endrizzi and Ramsay, 1979) showed a better growth rate than those in diploids. Monosomics in allotetraploids usually differ from one another and from normal counterparts for certain morphological features (Singh, 1993). Mochizuki (1970) reported that some monosomics in durum wheat [Triticum turgidum L. var. durum (Desf.) Mk., ] were a little weak, but they grew well and set seed. However, monosomics in allohexaploids such as common wheat (T. aestivum L.) and cultivated oat (Avena sativa L.) did not express distinct morphological alterations (Singh, 1993). That the deleterious effect of monosomy in mono-3 and more so in mono-6 was less than that associated with most monosomics of diploid species supports the hypothesis that soybean is an allotetraploid.

Cytology
Chromosomes associated at Metaphase I almost exclusively as 19 II + 1 I in mono-3 and mono-6 (Fig. 1A) . One of 50 PMCs studied in mono-6 had 18 II + 3 I. At Anaphase I, two of five PMCs in mono-3 and six of 13 PMCs in mono-6 showed a 19 to 20 chromosome migration (Fig. 1B). The other three and seven PMCs in mono-3 and mono-6, respectively, had one laggard chromosome.

View larger version (21K): [in this window] [in a new window]   Fig. 1 Meiotic pairings at Metaphase I and chromosome distributions at Anaphase I in the pollen mother cell (PMCs) of monosomics in soybean. (A) A PMC with 19 II + 1 I (arrow) in mono-6. (B) An anaphase I PMC showing 19:20 chromosome distribution in mono-6. Bar represents 10 µm

Fan and Tai (1985) reported high frequencies (14.7 and 61.9%) of PMCs with a trivalent configuration at diakinesis in two monosomics in rapeseed (Brassica napus L., ). The trivalent associations might be an indication of homology of univalent and bivalent chromosomes. Although soybean is considered a diploidized allotetraploid, a trivalent configuration was not observed in mono-3 and mono-6 PMCs. This may be due to lack of segmental homology among soybean chromosomes or to genetic control of chromosome pairing. Singh and Hymowitz (1985) demonstrated strong preferential pairing between homologous chromosomes in the species of the subgenus Glycine Willd. This suggests that soybean may possess a gene similar to the Ph (pairing homoeologous) gene in wheat, which suppresses homoeologous chromosome pairing and regulates homologous chromosome pairing (Okamoto, 1957; Riley and Chapman, 1958).

Pollen Fertility and Seed Set
The two soybean monosomics contained fully stained, darkly stained, partially stained, and unstained pollen grains after Lugol (I₂KI) staining. The disomic plant showed 99% fully stained pollen grains (Fig. 2A) . A majority of the pollen grains in both mono-3 (77.8%) and mono-6 (65.2%) were partially stained, and only a small proportion (8.8 and 20.0%) were fully stained (Table 2 , Fig. 2B). This indicates that the deficiency of one chromosome in the diploid chromosome complement in soybean causes considerable reduction in pollen fertility.

View larger version (29K): [in this window] [in a new window]   Fig. 2 Pollen grains of disomics and monosomics in soybean. (A) Pollen grains of a disomic plant of mono-6 (control). (B) Pollen grains of mono-3 (notice three fully stained pollen grains). Bar represents 100 µm

Pollen fertility and seed set of monosomics depends mainly on their ploidy level and the magnitude of genetic defect specific to the missing chromosome. Relative pollen fertility and seed set of monosomics is low in diploids, moderate in tetraploids, and high in hexaploids (Singh, 1993). Khush and Rick (1966) recorded 25% pollen fertility in mono-11 of tomato. Pollen fertility in maize monsomics ranged from 3.4% (mono-9) to 46.9% (mono-6) (Weber, 1983). Wang and Iwata (1996) reported complete seed sterility and very low percentage cross-pollinations (0.11–3.89%) in all five monosomics of rice. The seed-sets of monosomics in durum wheat ranged from 0.5 (6B) to 23.3% (4A) (Mochizuki, 1970). By contrast, monosomics in hexaploid oat (A. byzantina C. Koch) were highly fertile, with seed-sets ranging from 69.1% (mono-21) to 99.4% (mono-19) (Morikawa, 1985). Two monosomics of soybean reported in this study and the monosomic line KS-6 reported by Skorupska and Palmer (1987) showed pollen fertility and seed set like that of the monosomics in tetraploid plants.

Breeding Behavior
Two (3.5%) monosomics and one trisomic were found among 58 S₁ progeny plants of mono-3 (Table 3, Fig. 3A) . Two additional monosomic plants (6.5%) were found among 31 F₁ plants from mono-3 x Clark 63 crosses. Three (UT98-65, UT98-66, and UT98-69) of these four monosomic plants from the original mono-3 plant grew to maturity in the greenhouse, while one plant died at the seedling stage. The general morphology and fertility of the three monosomics were similar to the original mono-3.

View larger version (21K): [in this window] [in a new window]   Fig. 3 Somatic chromosomes of the progenies of monosomics in soybean. (A) A metaphase cell with 2n = 39 chromosomes from selfed population of mono-3. (B) A metaphase cell with 2n = 39 + 1 acrocentric chromosome (arrow) from selfed population of mono-6. Bar represents 10 µm

Skorupska and Palmer (1987) reported two monosomic plants among 94 S₁ KS-6 progeny. The frequency (2.1%) is slightly lower than that of mono-3 (3.5%). Because KS-6 is an unknown monosomic, it is unknown if mono-3 has the same missing chromosome as KS-6. The results from our study and the report by Skorupska and Palmer (1987) suggest that the transmission rate of soybean monosomics is sporadic. Mono-3 and KS-6 could be transmitted to the next generation in a very low frequency, but mono-6 was not transmitted after self-pollination. These soybean monosomics differ from other diploid plant species where the monosomic condition has not been found to be transmitted to the next generation (Singh, 1993).

Monosomics of diploid plants produce spores with n and n - 1 chromosomes in equal frequency. However, a spore lacking any chromosome cannot usually survive or compete with normal spores because genes for normal gametophytic development might be present on each of the chromosomes (Weber, 1991). Since monosomics from our study and KS-6 examined by Skorupska and Palmer (1987) of soybean were transmitted, the genes on the missing chromosomes in these monosomics must be compensated for by genes on other chromosomes. Indeed, the female transmission (6.5%) of mono-3 is very similar to some monosomics in tetraploid species (Clausen and Cameron, 1944; Mochizuki, 1970).

In this study, one plant with from mono-3 and one plant with chromosome from mono-6 were identified. The unrelated aneuploid types have been reported in the progenies of monosomics in plants (Singh, 1993). Monosomics in the soybean may be useful for locating recessive genes to chromosomes by examining pseudodominance, investigating dosage effects of some biochemical traits, and mapping molecular markers.Rick 1943

	ACKNOWLEDGMENTS

 
Research was supported by the Illinois Agricultural Experiment Station and the Illinois Soybean Program Operating Board grants 93-19-131-3 HY and 97-23-182-3 HY.

Received for publication July 19, 1999.

	REFERENCES

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion REFERENCES

 

• Ahmad F., Hymowitz T. Identification of five new primary simple primary trisomics in soybean based on pachytene chromosome analysis. Genome 1994;37:133-136.
• Ahmad F., Singh R.J., Hymowitz T. Cytological evidence for four new primary trisomics in soybean. J. Hered. 1992;83:221-224.[Free Full Text]
• Andrews G.Y., McGinnis R.C. The artificial induction of aneuploids in Avena. Can. J. Genet. Cytol. 1964;6:349-356.
• Clausen R.E., Cameron D.R. Inheritance in Nicotiana tabacum. XVIII. Monosomic analysis. Genetics 1944;29:447-477.[Free Full Text]
• Endrizzi J.E., Ramsay G. Monosomes and telosomes for 18 of the 26 chromosomes of Gossypium hirsutum. Can. J. Genet. Cytol. 1979;21:531-536.
• Fan Z., Tai W. A cytogenetic study of monosomics in Brassica napus L. Can. J. Genet. Cytol. 1985;27:683-688.
• Gwyn J.J., Palmer R.G., Sadanaga K. Morphological discrimination among some aneuploids in soybean (Glycine max (L.) Merr.): I. Trisomics. Can. J. Genet. Cytol. 1985;27:608-613.
• Hadley H.H., Hymowitz T. Speciation and cytogenetics. In: Caldwell B.E., ed. Soybeans: Improvement, production, and uses. Madison, WI: ASA, 1973:97-116 Agron. Monogr. 16..
• Khush G.S., Rick C.M. The origin, identification, and cytogenetic behavior of tomato monosomics. Chromosoma (Berlin) 1966;18:407-420.
• Mochizuki A. Production of three monosomic series in emmer and common wheat. Seiken Zihô 1970;22:39-49.
• Morikawa T. Identification of the 21 monosomic lines in Avena byzantina C. Koch cv. Kanota. Theor. Appl. Genet. 1985;70:271-278.
• Morrison J.W. Chromosome behaviour in wheat monosomics. Heredity 1953;7:203-217.
• Okamoto M. Asynaptic effect of chromosome. V. Wheat Inf. Serv. 1957;5:6.
• Rick C.M. Cyto-genetic consequences of x-ray treatment of pollen in Petunia. Bot. Gaz. 1943;104:528-540.
• Riley R., Chapman V. Genetic control of the cytologically diploid behaviour of hexaploid wheat. Nature (London) 1958;182:713-715.
• Shoemaker R.C., Polzin K., Labate J., Specht J., Brummer E.C., Olson T., Young N., Concibido V., Wilcox J., Tamulonis J.P., Kochert G., Boerma H.R. Genome duplication in soybean (Glycine subgenus soja). Genetics 1996;144:329-338.[Abstract]
• Singh R.J. Plant cytogenetics. Boca Raton, FL: CRC Press, 1993.
• Singh R.J., Hymowitz T. Diploid-like meiotic behavior in synthesized amphiploids of the genus Glycine Willd. subgenus Glycine. Can. J. Genet. Cytol. 1985;27:655-660.
• Singh R.J., Hymowitz T. The genomic relationship between Glycine max (L.) Merr. and G. soja Sieb. and Zucc. as revealed by pachytene chromosome analysis. Theor. Appl. Genet. 1988;76:705-711.[ISI]
• Singh R.J., Hymowitz T. Identification of four primary trisomics of soybean by pachytene chromosome analysis. J. Hered. 1990;82:75-77.
• Singh R.J., Kollipara K.P., Hymowitz T. Monosomic alien addition lines derived from Glycine max (L.) Merr. and G. tomentella Hayata: Production, characterization, and breeding behavior. Crop Sci. 1998;38:1483-1489.[Abstract/Free Full Text]
• Skorupska H., Palmer R.G. Monosomics from synaptic KS mutant. Soybean Genet. Newsl. 1987;14:174-178.
• Wang Z.X., Iwata N. The origin, identification, and plant morphology of five rice monosomics. Genome 1996;39:528-534.
• Weber D.F. Monosomic analysis in diploid crop plants. In: Swaminathan M.S., et al. , ed. Cytogenetics of crop plants. New Delhi, India: Macmillan India Ltd, 1983:352-378.
• Weber D.F. Monosomic analysis in maize and other diploid crop plants. In: Gupta P.K., Tsuchiya T., eds. Chromosome engineering in plants: Genetics, breeding, evolution. Part A. Amsterdam, the Netherlands: Elsevier, 1991:181-209.
• Xu S.J., Singh R.J., Hymowitz T. A modified procedure for mitotic chromosome count in soybean. Soybean Genet. Newsl. 1998;25:107 a.
• Xu S.J., Singh R.J., Hymowitz T. Establishment of a cytogenetic map of soybean: Current status. Soybean Genet. Newsl. 1998;25:120-122 b.
• Xu S.J., Singh R.J., Kollipara K.P., Hymowitz T. Hypertriploid in soybean: Origin, identification, cytology, and breeding behavior. Crop Sci. 2000;40:72-77.[Abstract/Free Full Text]

This article has been cited by other articles:

				S.J. Xu, R.J. Singh, K.P. Kollipara, and T. Hymowitz Primary Trisomics in Soybean: Origin, Identification, Breeding Behavior, and Use in Linkage Mapping Crop Sci., November 1, 2000; 40(6): 1543 - 1551. [Abstract] [Full Text] [PDF]

This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services 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 (5) Citing Articles via Google Scholar Google Scholar Articles by Xu, S.J. Articles by Hymowitz, T. Search for Related Content PubMed Articles by Xu, S.J. Articles by Hymowitz, T. Agricola Articles by Xu, S.J. Articles by Hymowitz, T.