EMS Induction of Early Flowering Mutants in Spring Rape (Brassica napus)

Studies were undertaken to induce early flowering mutants by ethyl methanesulphonate (EMS) treatments of Brassica napus seeds. EMS treatments for 12 h of a highly inbred B. napus line TBS had adverse effects on M¹ plant development and fertility only when concentrations were greater than 1%. However, an EMS concentration of 1.5% did not reduce M₁ plant fertility to an extent which significantly reduced production of M₂ seeds. Genetic changes induced by EMS treatment and affecting flowering time were of three main types: (1) Changes within a polygenic system reflected by increased variation in flowering time among M₂ families. As the increase in variation was due primarily to a higher frequency of later flowering plants, these polygenic changes would be of little value in developing better-adapted cultivars. (2) Induction of a recessive mutation at a major gene locus which caused M₃ plants homozygous for the mutant gene to flower at least 20 days earlier than the parental line TB8. (3) Induction of a dominant mutation at a major gene locus which affects flowering time by causing a substantial reduction in vernalization requirement. M₂ plants carrying the mutant gene flowered as early as 59 days before the parental line. These major gene mutations could be rapidly exploited in the development of agronomically superior cultivars for short-season, lower rainfall environments in Western Australia.     

Improvement of seed yield in Vicia faba L. By using experimental mutagenesis. II. Comparison of gamma-radiation and ethyl-methane-sulphonate (EMS) in production of morphological mutants

Summary Gamma-rays and EMS have been used in two dosages to test their effectiveness in inducing mutations in one major (cv. Aguadulce) and one minor (cv. Manfredini) Vicia faba cultivar. The plants of the M₁ and M₂ generations showed reduced emergence, survival, and fertility. EMS was more effective than gammarays in inducing mutations giving a mutation frequency in M₁ and a frequency of M₂ mutants from two to four times higher. The two mutagenic agents do not seem to differ in mutation spectrum. The minor cv. Manfredini was more sensitive to the lower dosage of gamma-rays than the major cv. Aguadulce. Both mutagens proved to be effective in enlarging the morphological variation of both cultivars.Research work supported by C.N.R. special grant I.P.R.A.-Sub-project 1. Paper N. 515.     

Chasmogamous mutant,a novel character enabling commercial hybrid seed production in mungbean

Mungbean (Vigna radiata (L.) Wilczek) is a self-pollinating crop that displays significant hybrid vigor in seed yield of F₁ hybrids. Thus there is the possibility to use hybrid varieties as a breakthrough to raise the yield plateau of mungbean. However, hybrid mungbean seeds can only be accomplished by hand-pollination and thus commercial production is not possible. To encourage hybrid seed set, the plant breeder needs to develop characters that promote higher outcrossing rate such as open flower (chasmogamy). In this experiment, new chasmogamous mutants were induced by gamma irradiation at the rate of 100 and 200 Gy. The mutants were identified at a low rate of 0.4–0.7% in the M₂ generation of accession V1197, and observed for their purity by growing in plant-to-row in the M₃ and M₄ generations. A uniform chasmogamous line was hybridized to normal flower lines to study the inheritance of this character. All F₁ plants had normal flowers, while the F₂ plants segregated well with 3 normal : 1 chasmogamous ratio. When the F₁ was backcrossed to the chasmogamous parent, the progeny gave a ratio of 1 normal to 1 chasmogamous. Thus, chasmogamy was controlled by a single recessive gene, cha.     

Semi-dominant genes confer additive tolerance to metribuzin in narrow-leafed lupin (<Emphasis Type="Italic">Lupinus angustifolius</Emphasis> L.) mutants

Narrow-leafed lupin (Lupinus angustifolius L.) is a grain legume well-adapted to sandy acid soils in a Mediterranean climate. Improved metribuzin tolerance in lupin cultivars is considered essential to protect crops from herbicide damage in Australia. This paper reports on the inheritance of metribuzin tolerance in two induced mutants Tanjil-AZ-33 and Tanjil-AZ-55 over the susceptible wild type cv. Tanjil. Both mutants were highly tolerant to 800 g/ha metribuzin with no foliage damage, but cv. Tanjil died and reciprocal F₁ hybrids had intermediate tolerance with foliage damage. The F₂ populations of both crosses, Tanjil-AZ-33 × Tanjil and Tanjil-AZ-55 × Tanjil, had a segregation ratio of 1:2:1 for highly tolerant: damaged:dead plants. Progeny tests (F₃) of selected F₂ single plants confirmed that highly tolerant F₂ plants were homozygous and damaged F₂ plants were heterozygous. Clearly a single semi-dominant gene conferred metribuzin tolerance in both mutants. An allelism test revealed that the two mutants had two non-allelic tolerance genes with F₂ plants segregating in a 15:1 ratio for survival and death at 800 g/ha metribuzin. The tolerance gene in Tanjil-AZ-33 was designated as Mt3 and the gene in Tanjil-AZ-55 as Mt5. At 4,000 g/ha metribuzin, 1/16 of F₂ plants from the cross between the two mutants had no herbicide damage, suggesting the additive effects of the two tolerance genes, whilst the rest were damaged or dead. Combining these two tolerance genes, Mt3 and Mt5, increased tolerance further by approximately five-fold.     

Induction of mutations for heat tolerance in potato by using in vitro culture and radiation

Heat tolerant mutants were obtained in two commercial potato cultivars, `Kufri Jyoti' and `Kufri Chandramukhi' through in vitro mutagenesis of in vitro propagated plantlets. Gamma-irradiated (20 and 40 Gy) shoots were micropropagated for three cycles (M₁V₃). A large number of the micropropagated shoots produced microtubers at 28 ^°C. Microtubers induced at high temperature had distorted shape but showed normal germination in field. Under stress conditions of high temperature, the frequency of chlorophyll variants increased in the gamma irradiation-derived material, however, nearly 40% of the plants had normal leaf tissue, whereas control plants showed completely damaged leaves. This revised version was published online in July 2006 with corrections to the Cover Date.     

The allelic relationship between A IP(internal pigmentation) and A RC (red cabbage) in Brassica oleracea var. capitata L.

Summary Internal anthocyanin pigmentation (IP), previously reported to be controlled by a single gene dominant to aa of normal green cabbage, was studied further to determine its relationship to A ^RC A ^RC of red cabbage. When IP line R52 was crossed with an early red cabbage line. F₁ heads were pigmented throughout, but pigment intensity was intermediate. Subjective classification of F₂ plants by pigmentation intensity and distribution scores gave a ratio of 1 intense red throughout (red cabbage):2 medium red throughout:1 medium to light red, restricted to the central portion of the head (IP). The genotypes A ^RC A ^RC: A ^RC A ^IP: A ^IP A ^IP. respectively, are proposed to explain these 3 phenotypic classes. F₂ progenies contained no normal green plants, supporting the conclusion that A ^IP and A ^RC are alleles.Technical Paper 7052, Oregon Agricultural Experiment Station.     

Genetics of novel corolla colours in periwinkle

Inheritance of a novel corolla colour in periwinkle [Catharanthus roseus (L) G. Don], viz. magenta, was studied by crossing an accession MJ, possessing this corolla colour, with cultivar Nirmal, possessing white corolla. The accession MJ was also crossed with another accession OR, possessing another novel corolla colour, viz. orange-red, to determine the relationship between genes governing magenta corolla and orange-red corolla. The F₁ plants of the cross MJ× Nirmal had pink corolla and red eye. In the F₂ generation, five kinds of corolla colours were observed: (i) pink corolla and red eye, (ii) rose corolla and red eye, (iii) magenta corolla and red eye, (iv) white corolla and red eye and (v) white corolla. The observed frequencies of the five kinds of plants fitted a ratio of 144:27:9:12:64. The progeny of the backcross, F₁ × MJ, segregated into three kinds of plants, (i) pink corolla and red eye, (ii) rose corolla and red eye and (iii) magenta corolla and red eye, in the ratio of 2:1:1, while the backcross, F₁ × Nirmal, segregated into two kinds of plants, (i) pink corolla and red eye and (ii) white corolla, in the ratio of 1:1. Two new genes (proposed symbols O^m and J) appeared to be involved in the determination of magenta and rose corolla colours. Interaction between four independent genes R, W, O^m and J, appeared to explain the observed segregation in the cross MJ × Nirmal. The F₁ plants of the cross MJ × OR had scarlet-red corolla and red eye. The segregation data of F₂ and backcross generations suggested that genes governing orange-red corolla and magenta corolla were allelic to each other. Two new and non-parental corolla colours viz., rose corolla and scarlet-red corolla, were observed in the progeny of the crosses of the present study.     

Crossability and cytology of hybrid progenies in the cross between Brassica campestris and three wild relatives of B. oleracea,B. bourgeaui,B. cretica and B. montana

Summary Crossability and cytology were examined in F₁, F₂, B₁ and hybridsplants of F₁ hybrids of Brassica campestris and three wild relatives of B. oleracea, B. bourgeaui, B. cretica and B. montana, respectively. The F₂ plants were obtained after self-and open pollination of the F₁ hybrids. The B₁ and hybrid plants were produced after the F₁ hybrids backcrosses with B. campestris and crossed with B. napus, respectively. After crossing the F₁ hybrids, many seeds of the F₂, B₁ and hybrid plants were harvested. Multivalent formation was high in the chromsome configuration for the PMCs of F₂, B₁ and hybrid plants, suggesting that crossing over might occur between them. Many different types of aneuploids were obtained in the progenies of the F₂, B₁ and hybrid plants. It is suggested that different types of normal egg cells may be produced by one-by-one or little-by-little chromosome addition. The possibility is discussed of gene transfer from B. bourgeaui, B. cretica and B. montana, to cultivated plants, B. campestris and B. napus.     

Increasing mutagenic efficiency of gamma-radiation in rice by irradiation of seeds at extremely low temperature

Summary Dry seeds of rice, Oryza sativa L., containing about 13 percent moisture, were exposed to ⁶⁰Co gamma raysat extremely low temperature (–196°C). M₁ damage on survival rate, seedling height and seed set were found to become much smaller in the cooling treatment than in the not-cooled control. Chlorophyll and heading date mutation frequencies in the M₂ generation were not affected by the decreased M₁ damage caused by the cooling treatment, and the mutation frequencies could be significantly increased by applying higher doses combined with the cooling treatment. Frequency of sterile or semi-sterile mutants in the M₂ generation was found to be significantly lower in the cooling treatment than in the not-cooled control.It is assumed from the experimental results that extremely low temperatures during irradiation could reduce the amount of physiological damage and gross chromosome aberrations. This results in an increased efficiency of producing minute deletions and/or point mutations.     

Identification of alleles at two loci controlling resistance to Phomopsis stem blight in narrow-leafed lupin (Lupinus angustifolius L.)

The genetics of resistance to Phomopsis stem blight caused by Diaporthe toxica Will., Highet, Gams & Sivasith. in narrow-leafed lupin (Lupinus angustifolius L.) was studied in crosses between resistant cv. Merrit, very resistant breeding line 75A:258 and susceptible cv. Unicrop. A non-destructive glasshouse infection test was developed to assess resistance in the F₁, F₂, selected F₂-derived F₃ (F_2:3) families, and in selfed parent plants. The F₁ of Unicrop × 75A:258 (and reciprocal cross) was very resistant, and the F₂ segregated in a ratio of 3:1 (resistant: susceptible), which suggested the presence of a single dominant allele for resistance in 75A:258. In Merrit × Unicrop (and reciprocal), the F₁ was moderately resistant, and the F₂ segregated in a ratio of 3:1 (resistant: susceptible). Thus Merrit appeared to carry an incompletely dominant resistance allele for resistance. The F₁ of Merrit × 75A:258 (and reciprocal) was very resistant and the F₂ segregated in a ratio of 15:1 (resistant: susceptible), which supported the existence of independently segregating resistance alleles for resistance in 75A:258 and Merrit. Alleles at loci for early flowering (Ku) and speckled seeds (for which we propose the symbol Spk) segregated normally and independently of the resistance alleles. Resistant F₂ plants gave rise to uniformly resistant or segregating F_2:3 families, whereas susceptible F₂ plants gave rise only to susceptible F_2:3 families. However, the variation in resistance in the F₂ and some F_2:3 families of crosses involving 75A:258, from moderately to extremely resistant, was greater than that expected by chance or environmental variation. We propose the symbols Phr1 to describe the dominant resistance allele in 75A:258, and Phr2 for the incompletely dominant resistance allele in Merrit. Phr1 appears to be epistatic to Phr2, and expression of Phr1 may be altered by independently segregating modifier allele(s). This revised version was published online in July 2006 with corrections to the Cover Date.     

Allelic relationship between spontaneous and induced mutant genes for stem fasciation in chickpea

Stem fasciation is a morphological abnormality observed in plants where the stem is widened and leaves and flowers or pods are clustered at the apex. Several spontaneous mutants and one induced mutant for stem fasciation are found in chickpea (Cicer arietinum L.). This study was aimed at determining allelic relationship between spontaneous and induced mutant genes controlling stem fasciation and effects of stem fasciation on grain yield. Two spontaneous (ICC 2042 and ICC 5645) and one induced (JGM 2) stem fasciation mutants were crossed in all combinations, excluding reciprocals. The F₁ and F₂ plants from a cross between the two spontaneous mutants had fasciated stem. This indicated the presence of a common gene (designated fas1) for stem fasciation in the two spontaneous mutants. The F₁s of the crosses of the induced mutant JGM 2 with both spontaneous mutants had normal plants and segregated in a ratio of 9 normal : 7 fasciated plants in F₂. Thus, the gene for stem fasciation in the induced mutant JGM 2 (designated fas2) is not allelic to the common gene for stem fasciation in spontaneous mutants. The two genes in dominant condition produced normal non‐fasciated stem. The fasciated and the non‐fasciated F₂ plants did not differ significantly for number of pods per plant, number of seeds per plant, grain yield per plant and seed size, suggesting that it is possible to exploit the fasciated trait in chickpea breeding without compromising on yield.     

Allelic relationships of genes controlling number of flowers per axis in chickpea

Genetic variation for number of flowers per axis in chickpea (Cicer arietinum L.) includes single-flower, double-flower, triple-flower and multi-flower traits. A double-flowered (DF) line ICC 4929, a triple-flowered (TF) line IPC 99-18 and a multi-flowered (MF) line JGM 7 were intercrossed in all possible combinations and flowering behavior of parents, F₁s and F₂s was studied to establish allelic relationships, penetrance and expressivity of genes controlling number of flowers per axis in chickpea. The F₁ from ICC 4929 (DF) × IPC 99-18 (TF) cross were double-flowered, whereas F₁ from ICC 4929 (DF) × JGM 7 (MF) and IPC 99-18 (TF) × JGM 7 (MF) crosses were single-flowered. The F₂ from ICC 4929 (DF) × IPC 99-18 (TF) cross gave a good fit to a 3:1 ratio for double-flowered and triple-flowered plants. The F₂ from ICC 4929 (DF) × JGM 7 (MF) cross segregated in a ratio of 9:3:3:1 for single-flowered, double-flowered, multi-flowered and double-multi-flowered plants. The F₂ from IPC 99-18 (TF) × JGM 7 (MF) cross segregated in a ratio of 9:3:4 for single-flowered, triple-flowered and multi-flowered plants. The results clearly established that two loci control number of flowers per axis in chickpea. The double-flower and triple-flower traits are controlled by a single-locus (Sfl) and the allele for double-flowered trait (sfl ^d ) is dominant over the allele for triple-flower trait (sfl ^t ). The three alleles at the Sfl locus has the dominance relationship Sfl > sfl ^d > sfl ^t . The multi-flower trait is controlled by a different gene (cym). Single-flowered plants have dominant alleles at both the loci (Sfl_ Cym_). The double-flower, the triple-flower and the multi-flower traits showed complete penetrance, but variable expressivity. The expressivity was 96.3% for double-flower and 76.4% for double-pod in ICC 4929, 81.2% for triple-flower and 0.0% for triple-pod in IPC 99-18, and 51.3% for multi-flower and 24.7% for multi-pod in JGM 7. Average number of flowers per axis and average number of pods per axis were higher in JGM 7 than double-flowered line ICC 4929 and triple-flowered line IPC 99-18. The results of this study will help in development of breeding strategies for exploitation of these flowering and podding traits in chickpea improvement.     

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.     

Analysis of genic male sterility in Brassica oleracea

Summary The male sterility system MS-1 of Brassica oleracea was studied in order to elucidate if nucleo-cytoplasmic interactions determine this system. Crosses of male sterile MS-1 genotypes with heterozygous MS-5 genotypes gave fully fertile F₁ progenies. Selfing of seven F₁ plants resulted in five F₂ populations showing a 9:7 segregation ratio and two a 3:1 ratio for fertile and male sterile plants. Two F₂ progenies deviated from the expected 9:7 or 3:1 segregation ratios for fertile and male sterile plants. Thermosensitivity and distortion of the meiosis are suggested as the causal factors underlying the deviation of the segregation ratios. It was concluded that nuclear factors determine the male sterility in the MS-1 system, because the presence of a nucleocytoplasmic interaction in this system should have given only a 3:1 segregation ratio for fertile and male sterile plants in the F₂ generation.     

Inheritance of adult-plant resistance to Phytophthora capsici in pepper

Summary Inheritance studies were conducted to determine the genetic basis of adult-plant resistance in pepper (Capsicum annuum L.) to Phytophthora capsici. F₁, backcrosses and F₂ populations were developed using the resistant parent Criollo de Morellos 334 and susceptible parents Agronômico 10-G and Yolo Wonder. Pepper plants, at 36 days post-emergence, were inoculated near the base of the stem with an inoculum suspension of 5×10⁴ zoospores/ml. Segregation ratios in the F₂ generation of 13 resistant to 3 susceptible plants fit a 2-gene model for resistance with dominant and recessive epistasis.     

Induced mutations in winged bean (Psophocarpus tetragonolobus L. DC) with low tannin content

Four mutants of winged bean (Psophocarpus tetragonolobus (L.) DC) with altered tannin content were selected among the M₃ seeds present on M₂ plants following mutagenic treatment of seeds of cvs UPS 122 and Kade 6/16 using gamma radiation from a Co⁶⁰ gamma source. These mutants were selected from the most chimeric parts of the M₁ plant, which had earlier been identified to be the first mature pods on the M₁ plant and the earliest formed M₂ seeds in the M₁ pods. The indirect selection of tannin mutants was based on searching for seed coat colour changes in M₃ seeds. Cv UPS 122 yielded the mutants 3/1-10-12 and X22 from 1958 and 1883 M₂ plants respectively. Cv Kade 6/16 yielded the mutants 3/9-0-12 and 3/4-10-7 from 1442 and 1011 M₂ plants respectively. One of the mutants, 3/4-10-7, which was the only desirable one, had a level of tannin of about 25% of the wild type cv. Kade 6/16. The other three mutants had similar or increased tannin levels. This revised version was published online in July 2006 with corrections to the Cover Date.     

Allozyme evaluation of upright common bean genotypes

Summary In common bean (Phaseolus vulgaris L.) the diaphorase (DIA) allozyme variant Diap-2 ¹⁰⁵ is frequently present in plants with upright, type II plant architecture. The genetic relationship between upright plant architecture and Diap-2 ¹⁰⁵ was investigated in eight F₂ populations derived from crosses between navy bean and pinto bean parental lines differing for type I, II, and III growth habit and DIA genotype. Segregation at the Diap-2 locus followed the expected 1:2:1 ratio in all eight F₂ populations and when pooled across F₂ populations. F₂ data from 1345 individuals indicated that plant architecture and the Diap-2 locus are not linked (r=0.03, P=0.333). However, the Diap-2 ¹⁰⁵ allozyme was present in 71% of advanced navy, pinto, and great northern genotypes with type II plant architecture. Due to random drift, Diap-2 ¹⁰⁵, initially associated with type II architecture through founder effect, may be maintained in such genotypes without providing greater fitness or without being associated with a locus or linked loci governing upright plant architecture.     

Parent-offspring correlation estimate of heritability for early blight resistance in tomato, Lycopersicon esculentum Mill.

This study estimated the heritability (h ²) of early blight (EB) resistance in filial progeny of a cross between a susceptible (`NC84173';mid-season maturity) and a resistant (`NC39E'; late-season maturity)tomato breeding lines. It addition, it examined the potential of identifying progeny with mid-season maturity and EB resistance. A total of 162F₂ plants were grown under field conditions in 1998 and evaluated for disease symptoms three times during the season, and the area under the disease progress curve (AUDPC) and final percent defoliation (disease severity) were determined. The F₂ plants were self-pollinated and F₃ seeds produced. The 162 F₃ progeny families, consisting of 20 plants per family, were grown in a replicated field trial in 1999 and evaluated for EB resistance (final percent defoliation) and plant maturity(days to 50% ripe fruit). The distributions of the final percent defoliation values in the F₂ and F₃ generations indicated that resistance from `NC39E' was quantitative in nature. Estimates of h <sup>2</sup> for EB resistance, computed as the correlation coefficients between F<sub>3</sub>progeny family means and F<sub>2</sub> individual plant values, ranged from0.65 to 0.71, indicating that EB resistance of `NC39E' was heritable. Across F₃ families, a negative correlation (r = –0.46, p< 0.01) was observed between disease severity and earliness in maturity, indicating that plant maturity affected disease severity. However, several F₃ families were identified with considerable EB resistance and mid-season maturity, indicating that resistance from `NC39E' might be useful for the development of commercially acceptable EB resistant tomato cultivars. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic analysis of a novel dominant rice dwarf mutant 986083D

This study was to determine the agronomic and genetic characteristics of a novel rice dominant dwarf mutant 986083D (japonica) and its potential in breeding. 986083D derived from the anther culture of an autotetraploid indica/japonica hybrid and its progeny segregated into normal and dwarf plants. Homozygous and heterozygous 986083D plants looked similar phenotypically, showing shortened stature, erect leaves, more tillers and poor fertility. The segregation ratio of dwarf to normal plants fit the expected 3:1 by χ²-test in 77 out of 88 tested lines. Crosses between homozygous 986083D and eight other rice varieties had uniform semi-dwarf F₁ plants. The F₁ plants from crosses between heterozygous 986083D and five other varieties had normal and semi-dwarf plants close to the expected ratio of 1:1. The reduction of plant height in F₁ plants ranged from 40.0 to 53.5% in a subtropical environment and from 37.5 to 48.2% in a temperate environment. 986083D showed moderate sensitivity to exogenously applied GA₃ in terms of elongation of shoots and induction of α-amylase activity in the endosperm. Linkage analysis showed that the dominant dwarf gene (designated as Dx) in 986083D was not allelic to D53. Dx was roughly mapped to the short arm of chromosome 8. All results showed that 986083D was a novel mutant controlled by single dominant gene, providing a valuable material in rice breeding. Ruizhen Qin, Yang Qiu contributed equally to this work.     

Transfer of resistance to race 2 of Plasmodiophora brassicae from Brassica napus to cabbage (B. oleracea ssp. capitata). III. First backcross and F2 progenies from interspecific hybrids between B. napus and B. oleracea ssp. capitata

Summary The first backcross and F₂ progenies from triploid F₁ and tetraploid F₁ hybrids between B. napus and 2x and 4x B. oleracea ssp. capitata (cabbage) were studied for their general morphology, resistance to race 2 of the clubroot pathogen, chromosome number and meiotic chromosome behavior. No linkage was apparent between resistance and the major morphological characters. Unreduced gametes played a large part in the successful formation of seed of the B₁ and F₂ progeny. B₁ plants with low chromosome numbers were selected for use in recurrent backcrosses. The potential use of anther culture to extract gametic progenies from resistant B₁ and F₂ plants with higher chromosome numbers was suggested. The presence of homoeologous pairing observed in all the plants is considered advantageous for selecting suitable progeny in later generations.