Interspecific hybrids of Cyclamen persicum Mill. and C. purpurascens Mill. produced by ovule culture

Summary Interspecific crosses were made to introduce the scent of flowers of C. purpurascens into C. persicum cultivars and ovule culture was used to rescue the abortive hybrid embryos. Cultivars of C. persicum diploid (CPD, 2n=2×=48) and C. persicum tetraploid (CPT, 2n=4×=96) were the pistillate parents and wild species of C. purpurascens (CP, 2n=34) were staminate parents. After pollination, crossed ovaries were collected periodically and examined using paraffin sections. Histological observations suggested that both hybrid ovules of CPD x CP and CPT x CP should be transferred to culture medium 35 days after pollination. Based up on this observation, crossed ovaries were collected 28 days after pollination and ovules with placenta were transferred to MS (1962) medium containing 3% sucrose. These ovules were cultured in the dark at 25° C. The hybrids (2n=41) derived from CPD x CP had the scent of C. purpurascens, whereas the hybrids (2n=65) derived from CPT x CP had the scent of C. persicum. Although both hybrids had complete genomes from the parents and produced a few viable pollen grains, they failed to yield viable seeds by self- and cross-pollination with fertile pollen grains of C. persicum cultivars.Abbreviations CPD C. persicum diploid - CPT C. persicum tetraploid - CP C. purpurascens     

Interspecific hybrids of Cyclamen persicum and C. graecum

Summary Interspecific crosses were made to introduce the disease resistance of Cyclamen graecum into C. persicum cultivars and the abortive hybrid embryos were rescued by ovule culture. Diploid and tetraploid cultivars of C. persicum (CPD, 2n=2x=48; CPT, 2n=4x=96) were the pistillate parents and wild form of C. graecum (CG, 2n=84) were the staminate parents. After pollination, crossed ovaries were periodically collected and examined using paraffin sections. Histological observations suggested that both hybrid ovules of CPD × CG and CPT × CG should be transferred to the culture medium 35 days after pollination. Based upon this observation, crossed ovaries were collected 35 days after pollination, then ovules with placenta were explanted on culture medium and cultured in the dark at 25°C. Plantlets were induced from ovules cultured in MS medium containing 3% sucrose and 10% coconut milk. The hybrids (2n=66) derived from CPD × CG failed to yield viable seeds by self-pollination, although they showed some pollen fertility. In contrast, the hybrids (2n=90) derived from CPT × CG showed high pollen fertility and yielded viable seeds by self-pollination. Furthermore, they were resistant to disease caused by Fusarium oxysporum f. sp. cyclaminis, Erwinia herbicola pv. cyclamenae and Pseudomonas marginalis pv. marginalis.Abbreviations CPD C. persicum diploid - CPT C. persicum tetraploid - CG C. graecum     

Interspecific hybridization between Cyclamen persicum Mill, and C. purpurascens Mill.

In order to introduce valuable traits from wild species of Cyclamen into C. persicum cultivars, crosses were made between C. persicum‘Reinweiß’and C. purpurascens. Crossing barriers between C. persicum‘Reinweiß’and C. purpurascens were due to late-acting incompatibility reactions. Interspecific hybrids were obtained by using ovary culture. The highest number of embryos was achieved from placentas excised 21 days and 35 days after pollination and transferred to Murashige-Skoog (M.S.)–medium containing 6% sucrose and 1% agar. The hybrids showed a habit and a chromosome number intermediate between the parents. The fragrant flowers were pale red-purple. The chromosome number in root tips was determined as 2n= 41 while in C. persicum it is 2n= 48 and in C. purpurascens 2n= 34. Due to the different parental chromosome sizes, chromosomes of distinct size were still observed in the hybrid. Pollen viability varied between 0.3 and 34.0%. Parents and interspecific hybrids also showed differences in the DNA content of leaf tissue. Flow cytometric analyses were useful in the early identification of hybrids.     

Chromosome associations and crossability with Iris ensata Thunb. in induced amphidiploids of I. laevigata Fisch. × I. ensata

Summary The chromosome associations of amphidiploids of I. laevigata × I. ensata were analysed and compared with those of the parental species and F₁ hybrids of I. laevigata × I. ensata. The F₁ hybrids showed partial chromosome associations. Their mean chromosome association per cell was 20.73I+3.63II, although the mean chromosome association per cell in the parental species was 0.09I+15.96II for I. laevigata and 0.03I+11.98II for I. ensata, respecively. In contrast, the normal association (28II) was partially restored in the amphidiploids. Their mean chromosome association per cell was 1.93I+26.48II+0.28III+0.03IV+0.03V. In this study, moreover, the crossability between I. ensata (2X and 4X) and the amphidiploids and between I. laevigata and the amphiliploids was examined. No hybrid plants were obtained from both reciprocal crosses between I. ensata (2X) and the amphidiploids and between I. laevigata and the amphidiploids. Only the cross of I. ensata (4X) × the amphidiploids in the reciprocal crosses produced hybrid plants. The observation of their somatic chromosome numbers indicates that these are true hybrid plants between autotetraploid I. ensata and the amphidiploids, and such plants can be called autoallotetraploids between I. ensata and I. laevigata. The interspecific cross-breeding of I. ensata using the autoallotetraploids is discussed.     

Intergeneric Hybrids between Aegilops squarrosa and Secale cereale and their Meiotic Chromosome Behaviour

Three hybrid plants with different combinations of D and R genomes were produced from crosses between Aegilops squarrosa (2×: and 4×) and Secale cereale (2× and 4×) using embryo culture. Production frequencies of mature hybrids, having the genomes DR, DDR and DDRR, were 2.0%, 5.2% and 2.2 %, respectively, of florets pollinated. Amphidiploids were obtained directly from the cross between tetraploid parents. The majority of their morphological features were intermediate between those of the parents but, as with rye, the rachis was tough. Diploid and triploid hybrids were completely seed-sterile, whereas the amphidiploid had an average self-fertility of 4.5 % with a range of 0 to 45 %. The somatic chromosome numbers of diploids, triploids and amphidiploids were 2n = 14, 21 and 28, respectively. At meiotic metaphase I, the mean chromosome associations were 0.01 III + 0.26 II + 13.4 I in diploids, 6.96 II + 7.1 I in triploids, and 10.5 II + 7.9 I in amphidiploids. In diploids, pairing between D and R chromosomes was observed in the form of end-to-end types without chiasmata. Homologous pairing between D chromosomes was predominant in plants having two sets of D genomes. Amphidiploids showed a diploid-like chromosome behaviour. Homoeologous pairing was not observed in either triploids or amphidiploids.     

萝卜-芥蓝异源四倍体的合成及GISH分析

通过萝卜(Raphanus sativus L.,2n=18,RR)与白花芥蓝(Brassica alboglabra Bailey,2n=18, CC)杂交,F1经秋水仙碱加倍合成萝卜-芥蓝异源四倍体（Raphanobrassica, 2n=36, RRCC）。经F₄~F₁₀代连续育性选择,F₁₀单株种子产量达32.3 g,每角粒数达14.9。基因组原位杂交显示F₁₀减数分裂行为类似于二倍体物种,表明该异源四倍体的细胞学行为已经稳定。育性观察表明,可育花粉足够各代生产种子,但低世代杂种出现高频瘪粒种子,胚珠败孕可能是其主要原因。该萝卜-芥蓝异源四倍体可以用作向油菜（B. napus L.,2n=38,AACC）转移萝卜基因的遗传桥梁。     

Fertility restoration of hybrids between Solanum melongena L. and S. aethiopicum L. Gilo Group by chromosome doubling and cytoplasmic effect on pollen fertility

Reproductive fertility traits were studied in the reciprocal hybrids of the eggplant(Solanum melongena L.) and S. aethiopicum L. Gilo Group, and in synthetic amphidiploids to discover whether fertility in these reciprocal hybrids was restored by chromosome doubling. Isozyme and RAPD analyses confirmed hybridity of the hybrids and amphidiploids. Analyses of chloroplast and mitochondrial DNAs confirmed that the cytoplasm of each of the hybrids and amphidiploids was from the maternal parent. Pollen sterility of S. melongena × S. aethiopicum Gilo Group [F₁ (Mel × Aet)] was restored by chromosome doubling, while the reciprocal hybrid S. aethiopicum Gilo Group ×S. melongena [F₁ (Aet × Mel)]and its amphidiploid did not produce any pollen grains; their microspores degenerated without being released from tetrads. Hence the cytoplasm of S. aethiopicum Gilo Group seems to beresponsible for their pollen-non-formation type sterility of the hybrid. Both the F₁ hybrids did not set any fruits by either selfing or backcrossing, while their amphidiploids set fruits after pollinating with pollen from the amphidiploid of F₁ (Mel × Aet). Seeds obtained from both the amphidiploids germinated normally. Chromosome doubling has been effective in restoring fertility of the hybrids. This revised version was published online in July 2006 with corrections to the Cover Date.     

The increase of seed fertility of Brassicoraphanus through cytological irregularity

Summary Amphidiploids (Brassicoraphanus) were produced by means of colchicine treatment of F₁ hybrids between Brassica japonica Sieb. and Raphanus sativus L. The cytology of the amphidiploids was studied from F₁ to F₃ generations. Some plants had the euploid chromosome number 2n=38, whereas others had the aneuploid number 2n=37. One or two of either quadrivalents or trivalents, as well as some univalents, were seen in most of the plants examined. All the plants showed a low seed fertility. In F₃ generation there arose some yellow-flowered plants, all of which showed a higher seed fertility than normal white-flowered plants. It is postulated that the change of flower colour might originate in the segmental exchange of only partially homologous chromosomes following multivalent formation. A gene causing white flower colour was perhaps closely linked to a gene causing sterility, and both genes were probably excluded together through the segmental exchange of the chromosomes. Therefore, it can be said that the increase of fertility was induced by cytological irregularity.     

Synthesis and preliminary characterization of a new species (amphidiploid) in Cucumis

A successful interspecific hybridization between cucumber (Cucumis sativus L., 2n = 14) and a wild it Cucumis species, C. hystrix Chakr. (2n = 24) was made via embryo rescue. Hybrid plants (2n = 19; 7 from cucumber and 12 from C. hystrix) were sterile, but morphologically uniform. Self-pollination and backcrossing of F₁ hybrid plants to either parent confirmed presence of both male- and female-sterility that were likely caused by lack of homology and improper pairing during meiosis. While the multiple-branching habit, densely brown hairs (on corolla and pistil), orange-yellow corolla, and ovate fruit of F₁ hybrid plants were similar to that of the C. hystrix parent, the appearance of the first pistillate flower was more similar to that of C. sativus parent. The diameter and internode length of the stem, and the shape and size of leaves and flowers were intermediate when compared to the parents. The chromosome number in the hybrid was doubled through somaclonal variation during embryo culture and regeneration process to restore the fertility. Pollen grains were released and fruits with viable seeds matured on fertile, synthetic amphidiploid plants. The results from flow cytometry indicated that, on average, 7.3% of the morphologically unique regenerants had the 4C DNA content of 2.35 pg relative to the 2C DNA content of the original F₁ hybrid at 1.17 pg and, therefore, were likely chromosome-doubled F₁ hybrids (2n = 38). Nutrition alanalysis indicated that the synthetic species had higher protein (0.78%)and mineral (0.35%) content compared to the normal pickling cucumber(0.62% and 0.27%, respectively), and could be considered a new Cucumis crop having a special place in the future agriculture. Preliminarily evaluation indicates that C. hystrix possesses a high level of root-knot nematode resistance, and that this resistance is partially expressed in the interspecific F₁ and chromosome-doubled F₁. This and the fact that the fruit morphology of the fertile amphidiploid differs during the growing season (e.g., short and long fruit) suggest that it could be useful in broadening the germplasm base of cucumber. This revised version was published online in July 2006 with corrections to the Cover Date.     

Risk assessment of outcrossing of transgenic rapessed to related species:

Summary The risk for a gene dispersal is reported for reciprocal crosses between a transgenic rapeseed variety resistant to the herbicide phosphinotricin and five related species. The first stages after pollination were cytologically observed and fertilized ovaries were established in in vitro culture for the production of interspecific hybrids. A similar classification was observed for the index of pollination compatibility and embryo yield. From the 243 embryos produced, 109 plantlets were obtained in a greenhouse. All the interspecific combinations tested were able to produce hybrid plants. A higher number of hybrids was obtained when rapeseed was used as the female parent. The hybrids had the expected triploid structure except for two amphidiploid, B. napus × B. oleracea, and one amphidiploid, B. napus × S. arvensis, plants with 56 chromosomes. The triploid hybrids were sterile or partially fertile but two of the amphidiploid plants, B. napus × B. oleracea, were fully fertile. The cytoplasm source did not seem to affect the fertility of the hybrids.     

Analysis of reproductive isolation between pearl millet (Pennisetum glaucum (L.) R.Br.) and P. ramosum, P. schweinfurthii, P. squamulatum, Cenchrus ciliaris

Crosses between pearl millet lines and Pennisetum ramosum, P. schweinfurthii, P. squamulatum or Cenchrus ciliaris were observed for the frequency and development of zygotes, the possibility of embryo rescue, and the fertility of F1 hybrids obtained. Eight per cent of the ovules from diploid millet × P. ramosum crosses showed small embryos which could not be rescued. However, 59% of the ovules from tetraploid millet × P. ramosum crosses showed well-developed embryos that were easy to rescue 14 days after pollination. F1 hybrids were male sterile but female fertile when pollinated by diploid millet. Both diploid and tetraploid millet ovules showed the presence of hybrid zygotes after pollination with P. schweinfurthii at rates ranging from 25% to 45%. The diploid millet× P. schweinfurthii hybrid zygotes often developed almost normal seeds giving, without embryo rescue, totally sterile plants. The tetraploid millet × P. schweinfurthii hybrid embryos were normal but the endosperm was severely defective. A hybrid obtained by embryo rescue was totally sterile. A diploid millet-P. schweinfurthii amphidiploid was obtained by somatic embryogenesis associated with colchicine treatment during callogenesis. This amphiploid plant was male sterile, but gave many seeds when pollinated by a tetraploid millet and few seeds when pollinated by a diploid millet. P. squamulatum pollinating diploid millets produced proembryos with large undifferentiated endosperms in 73% of the ovules. A normal seed set was observed on tetraploid millets pollinated by P. squamulatum and the resulting F1 hybrids were partially male and female fertile. Backcrosses of these hybrids were much more fertile when pollination was from a tetraploid millet rather than from a diploid millet. C. ciliaris pollinating a diploid millet showed, in 60% of the ovules, proembryos and endosperms similar to those observed with P. squamulatum and no hybrid could be rescued. Crosses with a tetraploid millet could not be attempted due to the pistil-pollen incompatibility of tetraploid millets available with C. ciliaris. Ploidy levels of mating partners do not seem to influence pistil-pollen compatibility, but play a major role in post-zygotic abortion. With adequate ploidy levels of parents, and embryo rescue, it seems that the pearl millet gene pool can be considerably enlarged by germplasm from many other species.     

Production of intergeneric hybrids between Brassica juncea and Diplotaxis virgata through ovary culture, and the cytology and crossability of their progenies

The cytogenetic study was investigated in the intergeneric F₁ hybrid, F₂and backcross progenies (BC₁). The plants used were Brassica juncea(2n=36) and Diplotaxis virgata(2n=18). Three intergeneric F₁ hybrids between two species were produced through ovary culture. They showed 36 chromosomes. It might consist one genome of B. juncea and two genomes of D. virgata. The morphology of the leaves resembled that of B. juncea. The color of the petals was yellow that was like in D. virgata. The size of the petal was similar to that of B. juncea. The mean pollen fertility was15.3% and the chromosome associations in the first meiotic division were(0–1)_IV+(0–2)_III+(8–12)_II+(12–20)_I. Many F₂ and BC₁seeds were harvested after open pollination and backcross of the F₁ hybrids withB. juncea, respectively. The F₂seedlings showed different chromosome constitutions and the range was from 28 to54 chromosomes. Most seedlings had 38chromosomes followed by 36, 40 and 54. The BC₁ seedlings also showed different chromosome constitutions and the range was from 29 to 62. Most seedlings had both 40and 54 chromosomes followed by 36, 46 and52. In the first meiotic division of F₂ and BC₁ plants, a high frequency of bivalent associations was observed in all the various kinds of somatic chromosomes. Many F₃ and BC₂ seeds were obtained by self-pollination and open pollination of both F₂ and BC₁ plants, and by backcrossing both F₂ and BC₁plants with B. juncea, respectively,especially, three type progeny with 36, 40or 54 chromosomes. The somatic chromosomes of the F₃ and BC₂ plants were further investigated. The bridge plants between B. juncea and D. virgata with 36 chromosomes may be utilized for breeding of other Brassica crops as well as B. juncea. This revised version was published online in July 2006 with corrections to the Cover Date.     

Morphology,cytology and forage potential of Pennisetum americanum (L.) K. Schum. x P. Purpureum Schum. amphidiploids

Summary F₁ hybrids between short-day photoperiod- sensitive maiwa bulrush millet, Pennisetum americanum (2n=14), and elephant grass, P. purpureum (2n=28), are triploid (2n=21), sterile, and can only be propagated vegetatively. Fertile amphidiploids, (2n=42, with 21 bivalents) were produced by colchicine treatment. Good seed set was obtained upon selfing the amphidiploids and the progeny exhibited variable pollen fertility and bivalent univalent and multivalent formation.Reciprocal crosses between elephant grass and the colchicine-induced amphidiploid failed to produce seeds. The maiwa millet x amphidiploid cross resulted in poor seed set and the reciprocal failed. Maiwa x amphidiploid hybrids were pollen sterile with 2n=21, rather than the expected 2n=28, indicating chromosome elimination.Morphologically, the amphidiploids and maiwa x amphidiploid hybrids closely resembled elephant grass and the F₁ hybrid. The amphidiploids showed no superiority over the F₁ hybrid and elephant grass in either forage yield or quality but one maiwa x amphidiploid genotype surpassed a promising local elephant grass selection in forage dry matter yield and flowered for a relatively short period.     

Meiosis and fertility in interspecific hybrids of Nicotiana tabacum L. ×N. glauca Grah. and their derivatives

Nicotiana glauca is of potential interest to breeders as it carries resistance to black root rot of tobacco. Cytological investigations of sexual interspecific hybrids of N. tabacum T′T′TT (2n = 4x = 48) cv. ‘Wiślica’ × N. glauca GG (2n = 2x = 24) were carried out. The analyses of chromosome association at diakinesis and metaphase I in the PMCs of amphihaploid F₁ T′TG (2n = 3x = 36) revealed low variable pairing with 0–5 bivalents. The sterile amphihaploids F₁ were converted into partial female fertile amphidiploids T′T′TTGG by chromosome doubling. Among 36 mature plants obtained, 15 were found to have chromosome numbers (2n = 6x = 72) and were verified as amphidiploids, 9 had (2n = 6x = 70 or 71) chromosomes while the remaining 12 were haploid. True amphidiploids, in spite of quite high chromosome pairing during meiosis, were very different in pollen fertility, ranging from 0% to 85%. Male fertility disturbances did not correlate with the degree of female fertility upon pollination with N. tabacum. Sesquidiploids T′TG (2n = 5x = 60) obtained from backcrossing the amphidiploids to parental tobacco showed more than 22 bivalents, 10–12 univalents and occasional multivalents that indicated the possibility of interchange events between N. tabacum and N. glauca genomes.     

Intergeneric crosses with Fragaria and Potentilla. I. Crosses between Fragaria moschata and Potentilla fruticosa

Summary Crosses between Fragaria moschata (2n=42) and Potentilla fruticosa (2n=14) produced many seeds; about half of these germinated, but only nine plants were obtained from 554 seedlings. Five plants died without flowering, and four were vigorous but sterile. Four plants had the expected chromosome number (2n=28), one plant had 21 chromosomes, and four were aneuploid with 23, 24, 25 and 27 chromosomes respectively. Response to growth substances giving elongated stem internodes and swollen but not succulent receptacles provided evidence that two of the plant were hybrids. It is suggested that all nine plants originated from a normal fertilisation which was followed in some cases by chromosome elimination at an early stage of embryo development.     

Production of interspecific hybrids between Alstroemeria pelegrina L. var. rosea and A. magenta Bayer by ovule culture

Interspecific hybrids were efficiently produced in the cross-incompatible combination between Alstroemeria pelegrina L. var. rosea and A. magenta Bayer by culturing immature ovules with placenta 7–14 days after pollination on 2 g/l Gelrite-solidified MS medium containing 3% (w/v)sucrose. The plants showed intermediate characteristics between the parents and their hybridity was confirmed by karyotype and DNA analyses. The mean number of chromosome association per PMC at metaphase I was 2.60I+6.70II, pollen stainability was20.8%, and they produced viable seeds after self-pollination. Furthermore, mature plants were obtained when the hybrids were backcrossed as male parents with both the parents. The backcross-progeny from A. pelegrina var. rosea × hybrids exhibited 3.8 to 79.7% pollen stainability and that from A. magenta × hybrids 78.8 to 98.3%. Almost all of these plants produced viable seeds after self-pollination, which implies that they can beutilized for breeding of novel cultivars of Alstroemeria. This revised version was published online in July 2006 with corrections to the Cover Date.     

Interspecific hybridization inBrassica juncea × Brassica hirta using embryo rescue

Summary Interspecific hybrids have been obtained in an otherwise incompatible cross betweenBrassica juncea × Brassica hirta through the in vitro culture of hybrid ovules and ovaries. The best response was observed from ovules and ovaries cultured 10–15 and 5–7 days after pollination respectively on a basal medium supplemented with indoleacetic acid, kinetin and casein hydrolysate. In some cases the basal cut end of the ovaries proliferated to form callus and shoots. The in vitro-derived hybrid seeds varied in their colour, size and shape, and the F₁ plants in the field showed a large diversity in their morphological traits. The hybrids were sterile, and had an intermediate number of chromosomes (2n=30).     

Incompatibility in diploid and tetraploid crosses of Cucumis sativus and Cucumis metuliferus

The African horned cucumber (Cucumis metuliferus Naud.; 2x = 2n = 24) contains genes that can confer resistance to many important cucumber (C. sativus L.; 2x = 2n = 14) pests [e.g., root-knotnematode, Meloidogyne incognita (Kofoid & White) Chitwood]. Cucumber is highly susceptible to this root-knot nematode species, and a recent screening of C. sativus accessions in the U.S. National Plant Germplasm collection did not identify sources of resistance. Thus,autotetraploids of Cucumis sativus and C. metuliferus were created to recover fertile resistant interspecific progeny. Autotetraploids were obtained at the highest rate when seeds were immersed in 0.5% colchicine for a period of 6 to 8 hrs. Treatment durations less than 6 hrs produced few tetraploids, and durations of 10 hrs or more were lethal to seeds or developing seedlings. Crosses between C. sativus and C. metuliferus were made using diploid and tetraploid lines in all possible combinations, including reciprocals. Fruit development occurred in crosses when diploid and tetraploid C. sativus were used as the female parent. However, seeds developed only in fruit of C. sativus (4n) ×C. metuliferus (2n) crossings. Seeds from these crosses, however,were flat and not viable. No fruit development occurred in crosses whereC. metuliferus was used as the female parent. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cytoplasmic homology between Aegilops mutica Boiss. and Ae. ovata L.

Summary Triticum aestivum L. em Thell. (2n=42; AABBDD), and T. durum Desf. (2n=28; AABB) genomes were substituted into the cytoplasms of Aegilops mutica Boiss. (2n=14; M_tM_t), Ae. heldreichii Holzm. (2n=14; MM), Ae. uniaristata Vis. (2n=14; M^uM^u), and Ae. ovata L. (2n=28; C^uC^uM^oM^o), to identify the M-genome diploid cytoplasm donor of Ae. ovata. Substitution of the T. durum genome into Ae. uniaristata cytoplasm resulted in a large proportion of shriveled inviable seeds. A few plump viable seeds were obtained all of which produced male-sterile plants having one univalent or telocentric chromosome from Ae. uniaristata. The T. aestivum plants having Ae. uniaristata or Ae. mutica cytoplasms were fertile. However, Ae. mutica was similar to Ae. ovata in the induction of delayed maturity and tall robust growth habit to the T. durum and T. aestivum plants. Cytoplasms of the other C- and M-genome diploids Ae. umbellulata Zhuk. (2n=14; C^uC^u) and, Ae. heldreichii (2n=14; MM) earlier had been shown to differ from that of Ae. ovata. Therefore, Ae. mutica is the most likely cytoplasm and M-genome donor to Ae. ovata.     

Intergeneric hybrids and an amphiploid between Elymus canadensis and Psathyrostachys juncea

Summary Fifty four hybrid plants between Elymus canadensis and Psathyrostachys juncea were obtained by handpollination and embryo culture. The average cross compatibility between both species was 31.2 percent. One amphiploid plant was induced by colchicine treatment. The hybrid and amphiploid plants resembled P. juncea in appearance but showed a higher plant height and dry matter yield than the parents. The hybrids showed extremely low pollen stainability and were completely sterile. With the exception of one plant (2n=3x+1=22), all hybrid plants were allotriploids (SHN, 2n=3x=21). The amphiploid plant (SSHHNN, 2n=6x=42) showed 58.9% pollen stainability and 11.6% seed fertility.Mean chromosome associations of the hybrids and amphiploid at metaphase I were 0.02IV+0.06III+2.03II+16.91I and 0.07III+18.00II+5.85I, respectively. Lagging chromosomes, chromosome bridges, abnormal cytokinesis, and micronuclei were occasionally observed at the anaphase, telophase, or tetrad stage.