Resynthesizing <Emphasis Type="Italic">Brassica napus</Emphasis> from interspecific hybridization between <Emphasis Type="Italic">Brassica rapa</Emphasis> and <Emphasis Type="Italic">B. oleracea</Emphasis> through ovary culture

Using three varieties of Brassica rapa, cv. Hauarad (accession 708), cv. Maoshan-3 (714) and cv. Youbai (715), as the maternal plants and one variety of B. oleracea cv. Jingfeng-1 (6012) as the paternal plant, crosses were made to produce interspecific hybrids through ovary culture techniques. A better response of seed formation was observed when ovaries were cultured in vitro at 9–12 days after pollination on the basal MS and B5 media supplemented with 6-benzylaminopurine (BA) and naphthylacetic acid (NAA). The best response was observed for cross 714×6012 with the rate of seeds per ovary reaching 43.0%. Seeds for cross 715×6012 showed the best germination response (66.7%) on the regeneration medium (MS+1.0 mg l^–1 BA+0.05 mg l^–1 NAA). In all three cross combinations, good response in terms of root number and length of plants was observed on the root induction medium (MS+1.0 mg l^–1 BA+0.1 mg l^–1 NAA). A better response was observed for the regenerated plants cultured for 14 days than for 7 days. The ovary-derived plants with well-developed root system were hardened for 8 days and their survival rate reached over 80%. Cytological studies showed that the chromosome number of all plants tested was 19 (the sum of both parents), indicating that these regenerated plants were all true hybrids of B. rapa (n = 10) × B. oleracea (n = 9). The regenerated plants were doubled with colchicine treatment, and the best response in the crosses 708×6012, 714×6012 and 715×6012 was observed when treated with 170 mg l^–1 colchicine for up to 30 h and their doubling frequency reached 52, 56 and 62%, respectively.     

Intergeneric hybridization of Diplotaxis erucoides with Brassica napus. I. cytogenetic analysis of F1 and BC1 progeny

Summary Intergeneric hybrids (F₁) Diplotaxis erucoides (DeDe) x Brassica napus (AACC) and the first backcross to B. napus (BC₁) have been obtained through in vitro culture of excised ovaries. The chromosome numbers of F₁ and BC₁ plants proved the occurrence of unreduced gametes. The study of metaphase I chromosome pairing showed that autosyndesis in De genome and allosyndesis between De and A/C genomes might exist. The male fertility of the F₁ plants was low. Some male-sterile plants were found in F₁ and BC₁ progeny. The possibilities of creating addition lines B. napus-D. erucoides and of obtaining a new cytoplasmic male sterility in B. napus are discussed.     

Predicting transgressive segregants in early generation using single seed descent method-derived <Emphasis Type="Italic">micro-macrosperma</Emphasis> genepool of lentil (<Emphasis Type="Italic">Lens culinaris</Emphasis> Medikus)

In a self-fertilised crop like lentil, the identification of transgressive segregants for economically important trait such as seed yield is an important aspect of any practical breeding programme. The prediction of expected transgressive segregants in F₁ generation obtained as a ratio of additive genic effect [d] and additive variance (D) i.e. [d]/√D was studied in 28 crosses of lentil generated in a diallel fashion involving four parents each of macrosperma (exotic) and microsperma (Indian) types, respectively, resulting in three hybridization groups. The seed material advanced to F₂, F₃ and F₄ generations through single seed descent method was evaluated to determine the observed transgressive segregants for seed yield/plant. The observed frequency of crosses showing more than 20% transgressive segregants in F₂ to F₄ generations were exhibited in 9(32%) crosses, of which 7(77%) crosses were of macrosperma × microsperma type. Genotypes Precoz and HPL-5 of the exotic group (macrosperma) produced maximum number of transgressive segregants with the genotypes L-259, L-4145 and PL-406 of the Indian origin (microsperma). Goodness of fit (non-significant χ² value) in F₂ generation was observed for 19(68%) crosses of the total genepool, out of which 9(56%) crosses each in F₃ and F₄ generation belonged to the macrosperma × microsperma group, depicting it as the gene pool of paramount importance to obtain maximum transgressive segregants, therefore establishing the efficacy of the method used.     

Intra- and intergenomic relationships in interspecific hybrids between Brassica (B. rapa, B. napus) and a wild species B. maurorum as revealed by genomic in situ hybridization (GISH)

Interspecific hybridization plays a crucial role in plant genetics and breeding. The efficiency of interspecific crosses to a considerable extent depends on the genetic relatedness of genomes from parental species. Interspecific hybrids involving Brassica maurorum (2n = 16, MM) and two Brassica crop species, viz B. rapa (2n = 20, AA) and B. napus (2n = 38, AACC), were produced and analyzed for their meiotic chromosome pairings in pollen mother cells (PMCs) by using genomic in situ hybridization (GISH) with the labeled DNA of B. maurorum (MM) as probe. In hybrids B. maurorum × B. rapa (2n = 18, MA), all chromosomes remained unpaired in 28% PMCs, and the maximum of autosyndetic bivalents was two and one among the chromosomes of A and M genomes, with the average per cell being 0.27 and 0.12, respectively. Up to two allosyndetic bivalents between A and M genomes appeared, averagely 0.48 per cell. In hybrids B. maurorum × B. napus (2n = 27, MAC), the maximum of autosyndetic bivalents in M genome was two and the average was 0.11, while the maximum of allosyndetic bivalents between M and A/C genomes was two and the average was 0.78. The 2–7 bivalents formed by A/C-genome chromosomes showed their high homology. The results were compared and discussed with the chromosome pairings in the hybrids of B. maurorum with B. juncea and B. carinata with respect to the genome relationships and the potential for chromosome recombination.     

Development and characterisation of a <Emphasis Type="Italic">Brassica carinata</Emphasis> inbred line incorporating genes for low glucosinolate content from <Emphasis Type="Italic">B. juncea</Emphasis>

The presence of high levels of sinigrin in the seeds represents a serious constraint for the commercial utilisation of Ethiopian mustard (Brassica carinata A. Braun) meal. The objective of this research was the introgression of genes for low glucosinolate content from B. juncea into B. carinata. BC₁F₁ seed from crosses between double zero B. juncea line Heera and B. carinata line N2-142 was produced. Simultaneous selection for B. carinata phenotype and low glucosinolate content was conducted from BC₁F₂ to BC₁F₄ plant generations. Forty-three BC₁F₄ derived lines were selected and subject to a detailed phenotypic and molecular evaluation to identify lines with low glucosinolate content and genetic proximity to B. carinata. Sixteen phenotypic traits and 80 SSR markers were used. Eight BC₁F₄ derived lines were very close to N2-142 both at the phenotypic and molecular level. Three of them, with average glucosinolate contents from 52 to 61 micromoles g⁻¹, compared to 35 micromoles g⁻¹ for Heera and 86 micromoles g⁻¹ for N2-142, were selected and evaluated in two additional environments, resulting in average glucosinolate contents from 43 to 56 micromoles g⁻¹, compared to 29 micromoles g⁻¹ for Heera and 84 micromoles g⁻¹ for N2-142. The best line (BCH-1773), with a glucosinolate profile made up of sinigrin (>95%) and a chromosome number of 2n = 34, was further evaluated in two environments (field and pots in open-air conditions). Average glucosinolate contents over the four environments included in this research were 42, 31 and 74 micromoles g⁻¹ for BCH-1773, Heera and N2-142, respectively. These are the lowest stable levels of glucosinolates reported so far in B. carinata.     

Interspecific hybridization between Brassica carinata and Brassica rapa

The crossability between Brassica carinata (BBCC, 2n=34) and Brassica rapa (AA, 2n=20), and the cytomorphology of their F₁ hybrids were studied. Hybrids between these two species were only obtained when B. carinata was used as the female parent. The hybrid plants exhibited intermediate leaf and flower morphology, and were found to be free from white rust and Alternaria blight diseases. One of the four F₁ plants was completely male sterile, while the remaining plants had 4.8, 8.6, and 10.9% stainable pollen, respectively. No seed was produced on hybrid plants under self pollination or in backcrosses; but seed was obtained from open pollination. The occurrence of the maximum of 11 bivalents as well as up to 44.8%) of cells with multivalent associations in the form of trivalents (0‐2) and a quadrivalent (0‐1) in the trigenomic triploid hybrid (ABC, 2n = 27) revealed intergenomic homoeology among the A, B and C genomes. Meiotic analysis of F₁ hybrids indicated that traits of economic importance, such as disease resistance, could be transferred from B. carinata to B. rapa through interspecific crosses.     

Morphological,cytological and reproductive characterization of tri-species hybrids (GOS) between <Emphasis Type="Italic">Pennisetum glaucum</Emphasis>, <Emphasis Type="Italic">P. orientale</Emphasis> and <Emphasis Type="Italic">P. squamulatum</Emphasis>

New tri-species hybrids (GOS) in the genus Pennisetum involving the cultivated species pearl millet (P. glaucum L.) and two wild species, viz. P. squamulatum Fresen and P. orientale L. C. Rich, are reported. Six hybrid plants were recovered after crossing a backcross hybrid (2n = 3x = 23, GGO) between P. glaucum (2n = 2x = 14, GG) and P. orientale (2n = 2x = 18, OO) with F₁s (2n = 6x = 42, GGSSSS) between P. glaucum (2n = 4x = 28, GGGG) and P. squamulatum (2n = 8x = 56, SSSSSSSS). The hybrids were perennial, morphologically intermediate to their parents, and represented characters from the three contributing species. The hybrids contained 2n = 44 chromosomes (GGGSSO) representing 21, 14 and nine chromosomes from P. glaucum, P. squamulatum and P. orientale, respectively. Meiotic and flow-cytometric analysis suggested origin of these hybrids from unreduced female and reduced male gametes. Average chromosome configuration (8.42_I + 14.32_II + 1.62_III + 0.52_IV) at Meiosis showed limited inter-genomic pairing indicating absence of significant homology between the three genomes. The hybrids were male sterile (except one) and highly aposporous. P. orientale was identified to induce apospory in hybrid background with P. glaucum at diploid and above levels, though it was quantitatively affected by genomic doses from sexual parent. A case of inducible and recurrent apospory is presented whereby a transition from Polygonum-type sexual embryo-sacs to Panicum-type aposporous embryo-sacs was observed in diploid interspecific hybrids. Results supported independent origin and partitioning of the three apomixis-components (apomeiosis, parthenogenesis, and functional endosperm development), reported for the first time in Pennisetum. Potential utilization of GOS hybrids in understanding genome interactions involved in complex traits, such as perenniality and apomixis, is discussed.     

Development of late-bolting F<Subscript>1</Subscript> hybrids of Chinese cabbage (<Emphasis Type="Italic">Brassica rapa</Emphasis> L.) allowing early spring cultivation without heating

We developed new F₁ hybrids of Chinese cabbage (Brassica rapa L. ssp. pekinensis) that allow cultivation earlier in spring without heating by introducing extremely late-bolting alleles at two homologs of the flowering repressor Flowering Locus C (BrFLC2 and BrFLC3) from non-heading ‘Leafy Green Parental Line No. 2’. These new F₁ hybrids were produced by the following four steps. First, the extremely late bolting selected lines were developed. These selected lines headed in spring after overwintering cultivation, whereas the conventional F₁ cultivars flowered. Secondly, an investigation of the three plantings showed that our F₁ hybrids formed heads when seeds were sown from mid-February to early March, whereas the conventional F₁ cultivar did not form heads because of premature bolting. Thirdly, we identified some F₁ hybrids with extremely late bolting during early spring cultivation in an investigation of many F₁ hybrids. Finally, based on an investigation across four cold regions for 2 years, we compared the commercialization rate, defined as the proportion of plants greater than 2000 g in weight and with a flowering stalk less than 10 cm long. Then we identified a F₁ of MS02 × 12-04 which had a high commercialization rate on average (92%), whereas the rates of three conventional F₁ cultivars were only 0–2%. In the near future, these F₁ hybrids will be valuable late-bolting cultivars despite climate change, permitting stable cultivation and harvest over wide regions.     

Genetic and histological characterization of a novel recessive genic male sterile line of <Emphasis Type="Italic">Brassica napus</Emphasis> derived from a cross with <Emphasis Type="Italic">Capsella bursa</Emphasis>-<Emphasis Type="Italic">pastoris</Emphasis>

In a previously made cross Brassica napus cv. Oro (2n = 38) × Capsella bursa-pastoris (2n = 4x = 32), one F₁ hybrid with 2n = 38 was totally male sterile. The hybrid contained no complete chromosomes from C. bursa-pastoris, but some specific AFLP (amplified fragment length polymorphism) bands of C. bursa-pastoris were detected. The hybrid was morphologically quite similar to ‘Oro’ except for smaller flowers with rudimentary stamens but normal pistils, and showed good seed-set after pollination by ‘Oro’ and other B. napus cultivars. The fertility segregation ratios (3:1, 1:1) in its progenies indicated that the male sterility was controlled by a single recessive gene. In the pollen mother cells of the male sterile hybrid, chromosome pairing and segregation were normal. Histological sectioning of its anthers showed that the tapetum was multiple layers and was hypertrophic from the stage of sporogenic cells, and that the tetrads were compressed by the vacuolated and disaggregated tapetum and no mature pollen grains were formed in anther sacs, thus resulting in male sterility. The possible mechanisms for the production of the male sterile hybrid and its potential in breeding are discussed.     

Haplotype analysis of <Emphasis Type="Italic">Viviparous</Emphasis>-<Emphasis Type="Italic">1</Emphasis> gene in CIMMYT elite bread wheat germplasm

Pre-harvest sprouting (PHS) greatly reduces the quality and economic value of wheat grain. In this study, a total of 168 International Maize and Wheat Improvement Center (CIMMYT) wheat germplasm lines were examined to characterize the haplotypes of Vp-1A, Vp-1B and Vp-1D, which are located on the long arms of chromosomes 3A, 3B and 3D, respectively. Among them, five new alleles of Vp-1Aa (the wild allele) were identified on chromosome 3A, and designated as Vp-1Ab, Vp-1Ac, Vp-1Ad, Vp-1Ae and Vp-1Af, respectively. The main difference between Vp-1Aa and the newly identified alleles was in the numbers of CTT repeats located in the third intron, but Vp-1Af also had 6 and 2 bp deletions at positions 2860–2865 bp and 2880–2881 bp, and possessed five SNPs within the same intron region. In the Vp-1B locus, several alleles (Vp-1Ba, Vp-1Bb, Vp-1Bc, Vp-1Bd, Vp-1Be and Vp-1Bf) have already been identified. In the present material only two, the already known allele Vp-1Bc, and a new one, designated as Vp-1Bg, were detected. Compared with Vp-Ba, Vp-1Bg had additional insertion of TCC at position 2372 bp and a 9 bp change from CTGCATC AC to GCATCAGTG at 2417–2425 bp. However, no polymorphism was detected in Vp-1D. The frequencies of Vp-1Aa Vp-1Ab, Vp-1Ac, Vp-1Ad, Vp-1Ae, and Vp-1Af were 65, 10, 11, 4, 5 and 5%, respectively. For Vp-1B, 155 out of the 168 lines were Vp-1Bc; the remaining 13 were Vp-1Bg. Analyses of the germination index (GI) and abscisic acid (ABA) sensitivity showed that genotypes with Vp-1Ab or Vp-1Af showed higher PHS resistance than the ones with other alleles, suggesting that they might be valuable for CIMMYT breeding program or germplasm introduction. The results presented here will underpin the introduction of germplasm from CIMMYT and the improvement of PHS resistance, both in CIMMYT and elsewhere.     

Synthesis and cytogenetic characterization of intergeneric hybrids of Diplotaxis siifolia with Brassica rapa and B. juncea

Intergeneric hybrids involving a wild crucifer, Diplotaxis siifolia (2n = 20; D^sD^s), and two crop Brassica species, namely Brassica rapa (2n = 20; AA) and B. juncea (2n = 36; AABB), were developed through sequential ovary/ovule culture. Hybridization was successful only when D. siifolia was used as the female parent, indicating unilateral cross incompatibility. Hybrids were intermediate between the parents for morphological characteristics but had low male as well as female fertility. Meiotic studies of hybrids revealed partial homoeology between D^s and A/B genomes.     

Comparative genetic mapping of homoeologous genes for the chlorina phenotype in the genus <Emphasis Type="Italic">Triticum</Emphasis>

Triticum monococcum L. (2n = 2x = 14, A^mA^m genome) is one of the most ancient of the domesticated crops in the Middle East, but it is not the ancestor of the A genome of durum wheat (T. durum Desf. 2n = 4x = 28, genomes BBAA) and bread wheat (T. aestivum L., 2n = 6x = 42, genomes BBAADD). It has been suggested that some differentiation has occurred between the A^m and A genomes. The chlorina mutants at the cn-A1 locus located on chromosome 7AL have been described in T. aestivum L. and T. durum, and a chlorina mutant has been found in T. monococcum. The aims of our study were to establish linkage maps for chlorina mutant genes on chromosome 7A of T. aestivum and T. durum and chromosome 7A^m of T. monococcum and to discuss the differentiation that has occurred between the A and A^m genomes. The chlorina mutant gene was found to be linked with Xhbg234 (8.0 cM) and Xgwm282 (4.3 cM) in F₂ plants of T. aestivum ANK-32A/T. petropavlovskyi k54716, and with Xbarc192 (19.5 cM) and Xgwm282 (12.0 cM) in F₂ plants of T. durum ANW5A-7A/T. carthlicum #521. Both the hexaploid and tetraploid wheats contained a common marker, Xgwm282. In F₂ lines of T. monococcum KT 3-21/T. sinskajae, the cn-A1 locus was bracketed by Xgwm748 (25.7 cM) and Xhbg412 (30.8 cM) on chromosome 7A^mL. The distal markers, Xhbg412, Xgwm282, and Xgwm332, were tightly linked in T. aestivum and T. durum. The common marker Xhbg412 indicated that the chlorina mutant genes are located on chromosome 7AL and that they are homoeologous mutations.     

Interspecific hybridisation and genome size analysis in <Emphasis Type="Italic">Buddleja</Emphasis>

Interspecific hybrids Buddleja davidii × Buddleja weyeriana, Buddleja weyeriana × Buddleja davidii and Buddleja davidii × Buddleja lindleyana were generated using in vitro embryo rescue 10–11 weeks after manual pollination. The morphological variation within the F1 populations was limited. The F1 progeny of B. davidii × B. lindleyana was almost sterile and no F2 generation was obtained. From the other hybrids, F2 generations were made by self pollinations and back crosses. Hybrid nature of all F1 and F2 seedlings was confirmed by AFLP. Chromosome counting and genome size measurement for B. weyeriana (F2 selection of (diploid) B. globosa × (tetraploid) B. davidii) revealed a higher chromosome number (76 chromosomes) and genome size than expected, indicating 2n-gametes formation occurred during meiosis of B. globosa. The F1 hybrids B. weyeriana × B. davidii (76 chromosomes) had an intermediate genome size compared with the genome size of the parent plants, proving their hybrid nature. However, the F1 and F2 hybrids of B. davidii × B. weyeriana all had 76 chromosomes but had a lower genome size than expected, suggesting the occurrence of chromosome rearrangements in the genome of the hybrids. B. lindleyana had 38 chromosomes, while the F1 hybrids of B. davidii × B. lindleyana had 76 chromosomes. Also genome size measurements revealed that the F1 seedlings B. davidii × B. lindleyana had higher genome sizes than expected. Both the results of chromosome counting and genome size measurement indicate that 2n-gametes formation took place during meiosis of B. lindleyana.     

Broadening the genetic base of <Emphasis Type="Italic">Brassica napus</Emphasis> canola by interspecific crosses with different variants of <Emphasis Type="Italic">B. oleracea</Emphasis>

Broadening the genetic base of the C genome of Brassica napus canola by use of B. oleracea is important. In this study, the prospect of developing B. napus canola lines from B. napus?×?B. oleracea var. alboglabra, botrytis, italica and capitata crosses and the effect of backcrossing the F₁’s to B. napus were investigated. The efficiency of the production of the F₁’s varied depending on the B. oleracea variant used in the cross. Fertility of the F₁ plants was low—produced, on average, about 0.7 F₂ seeds per self-pollination and similar number of BC₁ seeds on backcrossing to B. napus. The F₃ population showed greater fertility than the BC₁F₂; however, this difference diminished with the advancement of generation. The advanced generation populations, whether derived from F₂ or BC₁, showed similar fertility and produced similar size silique with similar number of seeds per silique. Progeny of all F₁’s and BC₁’s stabilized into B. napus, although B. oleracea plant was expected, especially in the progeny of F₁ (ACC) owing to elimination of the A chromosomes during meiosis. Segregation distortion for erucic acid alleles occurred in both F₂ and BC₁ resulting significantly fewer zero-erucic plants than expected; however, plants with?≤?15% erucic acid frequently yielded zero-erucic progeny. No consistent correlation between parent and progeny generation was found for seed glucosinolate content; however, selection for this trait was effective and B. napus canola lines were obtained from all crosses. Silique length showed positive correlation with seed set; the advanced generation populations, whether derived from F₂ or BC₁, were similar for these traits. SSR marker analysis showed that genetically diverse canola lines can be developed by using different variants of B. oleracea in B. napus?×?B. oleracea interspecific crosses.     

Cyto-morphological evidence for segmental allopolyploid origin of Teasle gourd (<Emphasis Type="Italic">Momordica subangulata</Emphasis> subsp. <Emphasis Type="Italic">renigera</Emphasis>)

Teasle gourd [Momordica subangulata Blume subsp. renigera (G. Don) de Wilde, 2n = 56] exhibits morphological characters found in both M. dioica (2n = 28) and M. cochinchinensis (2n = 28). Morphological analysis of M. subangulata subsp. renigera suggests an allopolyploid origin. We present evidence elucidating the genomic relationships between M. dioica, M. cochinchinensis and M. subangulata subsp. renigera. A triploid M. dioica × M. subangulata subsp. renigera hybrid had an average of 12.76 bivalents, 13.84 univalents and 0.88 trivalents at metaphase I, while the M. cochinchinensis × M. subangulata subsp. renigera hybrid had an average of 13.08 bivalents, 12.96 univalents and 0.96 trivalents. F₁ hybrids of the two diploid species (M. dioica × M. cochinchinensis) showed an average of 9.12 bivalents and 9.76 univalents, suggesting that the genomes of these species are only partially homologous. A higher number of bivalents in the triploid hybrids suggests that M. subangulata subsp. renigera is a segmental allopolyploid of M. dioica and M. cochinchinensis and that its genomes have diverged from the parental genomes.     

Hybrids of <Emphasis Type="Italic">Avena sativa</Emphasis> with two diploid wild oats (CIav6956) and (CIav7233) resistant to crown rust

Two diploid accessions of wild oat, CIav6956 and CIav7233, were identified as carrying seedling resistance to oat crown rust (caused by Puccinia coronata f. sp. avenae; Pca). Two vigorous interploidy F₁ hybrids were generated from crosses involving the hexaploid oat cultivar Wintaroo and the diploid oat Avena strigosa Schreb. accession CIav6956. An additional interploidy F₁ hybrid, designated “F1-Aa1”, was produced from a cross of Wintaroo and the diploid oat accession CIav7233. All three hybrids were more vigorous and taller than the cultivated parent Wintaroo. The three F₁ hybrids contained full chromosome complements from both parents (2n = 4x = 28), but no seeds were obtained when the three F₁ hybrids were selfed. Meiotic analyses of the hybrids indicated that they exhibited a high degree of inter-genome and intra-genome pairing. Trivalent configurations were detected in 95–96% of meiotic cells and a minimum of three bivalents was present in all cells. An average chiasma frequency of 7.2–7.9 per cell was observed for the three F₁ hybrids. A fourth F₁ hybrid was subsequently generated from a cross between the diploid oat accession CIav7233 and Wintaroo. One octaploid (2n = 8x = 56) was generated from this hybrid and progeny were resistant to two Pca races. The chromosome number of the octaploid progeny varied between 51 and 54 chromosomes. Development of a chromosome addition line(s) with the crown rust resistance should be possible from these partial-octaploids.     

The Effect of A Genome Substitution on the Resistance of Brassica napus to Infection by Leptosphaeria maculans

Six accessions belonging to four subspecies of Brassica rapa, including three accessions of B. rapa subsp. sylvestris, were crossed with B. oleracea subsp. alboglabra in order to develop a series of synthetic B. napus lines with a common C genome but contrasting A genomes. Different A genomes had significant effects on the efficiency of B. napus resynthesis and the sexual compatibility of the synthetic lines with oilseed rape cultivars. The synthetic lines were used to investigate the effect of A genome substitution on the resistance of B. napus to infection by Leptosphaeria maculans, and to explore the potential for the use of wild forms of B. rapa in oilseed rape breeding programmes. Synthetic lines derived from two wild accessions of B. rapa, and their F₁ hybrids with oilseed rape cultivars, expressed high levels of resistance to L. maculans in glasshouse experiments. One of these lines also expressed high levels of resistance in field experiments in England and Australia when exposed to a genetically diverse pathogen population. All other synthetic lines and cultivars were highly susceptible in both glasshouse and field experiments. F₁ hybrids between oilseed rape cultivars and synthetic lines derived from B. rapa subsp. chinensis were significantly more susceptible than either parent.     

A new male sterile mutant LZ in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Genetic male sterility (GMS) genes in wheat (Triticum aestivum L.) can be used for commercial hybrid seed production. A new wheat GMS mutant, LZ, was successfully used in the 4E-ms system for producing hybrid wheat, a new approach of producing hybrid seed based on GMS. Our objective was to analyse the genetic mechanism of male sterility and locate the GMS gene in mutant LZ to a chromosome. We firstly crossed male sterile line 257A (2n = 42) derived from mutant LZ to Chinese Spring and several other cultivars for determining the self-fertility of the F₁ hybrids and the segregation ratios of male-sterile and fertile plants in the F₂ and BC₁ generations. Secondly, we conducted nullisomic analysis by crossing male sterile plants of line 257A to 21 self-fertile nullisomic lines as male to test the F₁ fertilities and to locate the GMS gene in mutant LZ to a chromosome. Thirdly, we conducted an allelism test with Cornerstone, which has ms1c located on chromosome 4BS. All F₁s were male fertile and the segregation ratio of male-sterile: fertile plants in all BC₁ and F₂ populations fitted 1:1 and 1:3 ratios, respectively. The male sterility was stably inherited, and was not affected by environmental factors in two different locations or by the cytoplasm of wheat cultivars in four reciprocal cross combinations. The results of nullisomic analysis indicated the gene was on chromosome 4B. The allelism test showed that the mutant LZ was allelic to ms1c. We concluded that the mutant LZ has common wheat cytoplasm and carries a stably inherited monogenic recessive gene named ms1g.