Karyotype and C-banding pattern of mitotic chromosomes in alfalfa, Medicago sativa L.

Numerous cytogenetic studies have been performed on alfalfa (Medicago sativa L. 2n= 4x= 32), but only a few have examined the somatic chromosomes. Because the major factor limiting the study of somatic chromosomes of M. sativa is their rather uniform morphology, characterization was attempted using the C-banding technique instead of the traditional Feulgen method. Chromosome morphology and position of the heterochromatic bands resulted in satisfactory characterization of the chromosomes and provided further evidence of the autotetraploid origin of the species. It was possible to identify the homologous chromosomes and arrange them into eight groups of four. The ideogram of the basic genome of eight chromosomes was constructed. The impact of these results on cytogenetic studies and breeding research in alfalfa is discussed.     

Cytological and genetical studies of a male sterile celery

Summary The inheritance and nature fo male sterility of a cerley (Apium graveolens L.) strain (MS1) is reported. Male sterility in MS1 is determined by a a recessive genotype for a single locus. Tests for linkage with the isozyme chromosome markers SDH-1 and PGM-1 were negative. MS1 male sterility was associated with a defective tapetum characterized by prominent vacuoles and premature degeneration. The stamens in the male sterile strain persisted in the flowers up to stigma receptivity, while in the male fertile plants they dropped before style expansion. The male sterile flowers produced normal amounts of nectar, resulting in cross pollination by various species of pollinators. It was estimated that the sterile strain produced 30% less seed than normal male fertile. Its possible use for hybrid celery seed production is discussed.Research supported by grants from the California Celery Research Board and BARD I-483-82.     

八倍体小黑麦与七倍体杂种回交配子间竞争规律的研究

当八倍体小黑麦与七倍体杂种回交时,七倍体×八倍体(以下简称“七×八”)组合的子房受精正常,80％的受精子房不能形成有胚乳的种子,有胚乳种子中能成株的仅有20％,回交效率为1％～2％,远低于八倍体×七倍体(以下简称“八×七”)组合的29.07％。通过分析“八×七”回交种子和七倍体F_1杂种根尖染色体数分布发现,八倍体小黑麦雌配子R染色体平均丢失率为0.133,具28染色体数的整倍体配子对27染色体数的非整倍体配子不具有竞争优势;父本七倍体杂种雄配子R染色体的平均丢失率为0.713,整倍体雄配子的竞争能力是非整倍体(染色体数27)雄配子的48.2倍。“七×八”组合回交效率低的原因可能是雌配子间竞争能力低,各种R染色体数的雌配子都能参与双受精,由于不完整的R组染色体对胚乳发育的干扰,大部分合子不能形成能成株的种子。     

Characterization of Triticum aestivum/Psathyrostachys juncea derivatives by genomic in situ hybridization

Using the genomic in situ hybridization (GISH) technique, one translocation line, seven translocation-addition lines, five translocation plus translocation addition lines and two ditelosomic addition lines were identified in backcross progenies of Triticum aestivum L. -Psathyrostachys juncea (Fisch.) Nevski intergeneric hybrids. No complete P. juncea chromosomes were detected in the 25 lines studied. The results suggest that intact P. juncea chromosomes may be difficult to isolate in a wheat background. This revised version was published online in July 2006 with corrections to the Cover Date.     

Tan-Spot Resistance Screening of Aegilops Species

Two hundred and twelve accessions of 8 diploid and 10 polyploid species of Aegilops were evaluated for resistance to tan-spot disease of wheat, caused by Pyrenophora tritici-repentis (Died.) Drechs., under greenhouse conditions. One or more accessions of Ae. bicornis, Ae. biuncialis, Ae. Crassa, Ae. columnaris, Ae. cylindrica, Ae. speltoides, Ae. squarrosa. Ae. triaristata. Ae. triuncialis, and Ae. Ovata showed resistance following a 24-hour post-inoculation wet period. With a 36-hour wet period, diploids became only slightly or moderately susceptible and resistant polyploids became susceptible. A 48-hour wet period resulted in still greater susceptibility of both diploid and polyploid species.     

Chromosome Studies in the Genus Alstroemeria

Chromosomes of 11 cultivars of Alstroemeria were studied to determine their somatic constitutions. Two cultivars, ‘Eureka’ and ‘Zebra’, were diploid (2n = 2×= 16), six cultivars, ‘Yellow King’, ‘King Cardinal’, ‘Mona Lisa’, ‘Appelbloesem’, ‘Pink Triumph’ and ‘Rosita’ were triploid with 2n = 3×= 24, one cultivar, ‘Orange Beauty’ was a hypertriploid (2n = 3×+ 1 = 25), one cultivar, ‘Luciana’ was a hypotetraploid (2n = 4×– 1 =31) and one cultivar, ‘Jubilee’, was true tetraploid (2n = 4×= 32). This result suggests that polyploid cultivars may have more market value in this cut flower, Alstroemeria.     

Production of an interspecific hybrid in Gypsophila by ovule-embryo culture

Summary We have succeeded in producing useful interspecific hybrid using ovule-embryo culture between Gypsophila paniculata L. Red Sea and G. manginii, an incompatible combination by ordinary cross breeding methods. The hybrid plant had double flowers with a color of pale purplish pink. Hybrid characteristics of the plant were firmed by observation of plant form, flower type, chromosome number and peroxidase isozyme patterns.     

水稻早世代稳定现象的研究进展

早世代稳定现象首先在水稻杂交育种过程中发现,该现象可以早世代固定杂种基因型,这为培育可以多代利用的杂交种,开辟了美好的前景。本文就早世代稳定现象的历史、发展及应用前景作一论述。     

Mapping QTL of Fiber Yield and Quality Traits in F2 Populations of Chromosome Segment Substitution Lines from Gossypium hirsutum × Gossypium barbadense

In this study, F₂ populations from two chromosome segment substitution lines MBI7455 and MBI7358, were quantified using SSR to evaluate the parents' genotype and detect QTL related to fiber quality plus yield traits of cotton. Results show that the recurrent parent (CCRI45) hosted 96.70% and 95.60% of chromosome segment substitution in MBI7455 with 12 chromosome segments and in MBI7358 with 16 chromosome substitution segments of Gossypium barbadense, respectively. In the F₂ population, the average rate of chromosome substitution of the recurrent parent (CCRI45) was 96.44%, and the average segments of chromosome substitution of Gossypium barbadense was 13.42, with an average segments of homozygous donor chromosome value of 3.90. Analysis showed 19 fiber quality-related QTL with a phenotypic variance of between 2.52%-13.11% and seven yield traits-related QTL with a range of 2.93%-11.40% phenotypic variance, resulting in a total of 26 QTL. The CSSLs could be used to detect QTL for fiber yield and quality traits, which offer an important foundation for the cotton molecular-assisted breeding.     

Production and characterization of Raphanus sativus-Brassica rapa monosomic chromosome addition lines

Breeding of Raphanus sativus‐Brassica rapa monosomic chromosome addition lines (MALs, 2n = 19) was carried out by backcrossing the synthesized amphidiploid line, Raphanobrassica (R. sativus×B. rapa, 2n = 38, RRAA, line RA89) with R. sativus cv. ‘Shogoin’ (2n = 18, RR). In the first cross of Raphanobrassica× radish, four sesquidiploidal BC₁ plants (2n = 28, RRA, RA89‐36‐1, RA89‐31‐1, RA89‐31‐2, RA89‐31‐3) were successfully developed. In these plants, the chromosome configurations of 9II + 10I and 10II + 8I were observed frequently at first metaphase (MI) of meiosis in pollen mother cells (PMCs). The RA 89‐36‐1 plant produced many seeds in the reciprocal backcrosses with radish. About 50% of the BC₂ plants obtained from the cross of RA89‐36‐1 plant × radish were 2n = 19 plants, followed by 2n = 18 plants (24%) and 2n = 20 plants (19%). In the reciprocal cross, 2n = 19 plants were also developed at the rate of 40%. From analysis of specific morphological traits, 2n = 19 plants were classified into eight types (a‐h). When 25 selected primers were used in polyacrylamide gel electrophoresis, random amplified polymorphic DNA (RAPD) markers derived from B. rapa for each type of MAL were detected in numbers between three for e‐type and 16 for b‐type. RAPD markers specific for each type alone were from one (OPE 05‐344) for h‐type to nine for b‐type. In the g‐type, no marker specific to this type alone was observed. However, 19 bands were common between at least two types. These MAL plants exhibited predominantly the chromosome configuration of 9II + 1I at MI of PMCs, pollen and seed fertility being the same level as the radish cv. ‘Shogoin’. From the morphological traits and DNA markers, eight different MAL types among 10 expected were identified.