Correlation of stylar ribonuclease isoenzymes with incompatibility alleles in apple

Fifty-six cultivars of apple were analysed for stylar ribonucleases; proteins were extracted from styles, separated by non-equilibrium pH gel electrofocusing and stained for activity. Excellent correlation was found between the ribonuclease bands revealed and the 11 known incompatibility, S, alleles, in 14 diploid cultivars genotyped in the classic work of Kobel by monitoring pollen tube growth after test crossing, and in 20 cultivars genotyped, at least partially, by more recent DNA methods. For 12 triploid cultivars studied by Kobel, the correlation was good but not perfect. Two apparent minor electrophoretic variants for S10 were noted and, to distinguish them from each other and also from the electrophoretically similar S3, isoelectric focusing was used. Ten cultivars were genotyped for the first time. In all, 14 ribonuclease bands that may correspond to the ‘new’ S alleles, S12 to S 25, were detected but these alleles should be regarded as provisional until confirmed by pollination tests, especially when the electrophoretic differences were only slight. Analysis of stylar ribonucleases is a convenient method of predicting S alleles in flowering material and thereby investigating incompatibility relationships. The polymorphism of the S locus makes it useful for checking the identity and parentage of cultivars. This revised version was published online in July 2006 with corrections to the Cover Date.     

Variation of prezygotic barriers in the interspecific hybridization between oilseed rape and wild radish

Escape of transgenes from genetically modified oilseed rape, Brassica napus, into wild radish, Raphanus raphanistrum, depends on sexual compatibility. The variation in prezygotic barriers of two different cultivars for interspecific hybridization with a population of wild radish was investigated by hand crossing and fluorescence microscopy of pistils. Significant differences were observed between oil seed rape cultivars in their ability to accept wild radish pollen germinating onto their stigma and the rate of fertilization of ovules. Some differences among the pollen donor plants were also detected. These results suggest that the rate of interspecific hybridization in the field would depend upon the oilseed rape cultivar and the genotype composition of the local wild populations. The implication of S-related genes, as revealed through identification by pistil tissue prints of class I and II S-types of SLG (S-Locus Glycoprotein) and SLR1 (S-Locus Related),and immuno-IEF, was not significant. This revised version was published online in August 2006 with corrections to the Cover Date.     

Self-incompatibility in Brassicaceae crops: lessons for interspecific incompatibility

Most wild plants and some crops of the Brassicaceae express self-incompatibility, which is a mechanism that allows stigmas to recognize and discriminate against “self” pollen, thus preventing self-fertilization and inbreeding. Self-incompatibility in this family is controlled by a single S locus containing two multiallelic genes that encode the stigma-expressed S-locus receptor kinase and its pollen coat-localized ligand, the S-locus cysteine-rich protein. Physical interaction between receptor and ligand encoded in the same S locus activates the receptor and triggers a signaling cascade that results in inhibition of “self” pollen. Sequence information for many S-locus haplotypes in Brassica species has spurred studies of dominance relationships between S haplotypes and of S-locus structure, as well as the development of methods for S genotyping. Furthermore, molecular genetic studies have begun to identify genes that encode putative components of the self-incompatibility signaling pathway. In parallel, standard genetic analysis and QTL analysis of the poorly understood interspecific incompatibility phenomenon have been initiated to identify genes responsible for the inhibition of pollen from other species by the stigma. Herewith, we review recent studies of self-incompatibility and interspecific incompatibility, and we propose a model in which a universal pollen-inhibition pathway is shared by these two incompatibility systems.     

Validation of two models for self‐incompatibility in autotetraploid perennial ryegrass using high resolution melting‐based markers

Perennial ryegrass (Lolium perenne L.) displays a two‐locus gametophytic self‐incompatibility (SI) system that remains intact at the tetraploid level. Two models are plausible for SI in autotetraploids. In Model I: both alleles at the S locus and both at the Z locus in diploid pollen matching the female genotype results in incompatibility. In Model II: only one allele at S and one at Z locus in diploid pollen matching the female results in incompatibility. The goals were to determine which of the models best explains SI in our autotetraploid ryegrass population and to evaluate the efficiency of high‐resolution melting (HRM) genotyping for discriminating different iso‐allelic genotypes. The progeny of a cross between two autotetraploids was characterized with three HRM‐based markers co‐segregating with Z. Segregation ratios were used to make inferences about the mode of action of the SI system. The observed segregation differed significantly (P < 0.001) from the expected under Model I, but not from the expected under Model II (P = 0.463). Thus, Model II explains SI in this population, and HRM is an efficient tool to distinguish different iso‐allelic genotypic classes.     

高滑转率下车辆动力传动系的失稳与稳定性判据

建立了车辆动力传动系的力学模型,并用平均法对该力学模型进行了分析,得知：动力传动系在高滑转率下常失稳,从则在传动系中产生自激振动,对车辆产生了不利影响,给了传动系的稳定性判别式,讨论了影响传动系稳定性的因素,为研究抑制自激振动的措施提供了理论依据。     

微型自吸施涡管道泵的研制

针对市场要求，构思了一种新型结构的旋涡管道泵。文章了阐述其工作原理、自吸机理及水力设计方法，通过对样机20GL1.5-10-0.25试验结果进行分析，验证了该泵的设计方面的可取性和独到性。     

Effect of selection for pseudo-self compatibility in advanced inbred generations of Nemesia strumosa Benth.

Summary Highly pseudo-self compatible (PSC) Nemesia strumosa plants were selfed and intercrossed to produce progenies of the F₅ through F₇ generations. Though high PSC progenies were obtained, none were truebreeding. Progenies from crossing inbred high PSC plants to low PSC plants consisted of either mostly low PSC plants or both low and intermediate plants. A backcross to the high PSC parent of a progeny from a low times high cross produced a family with a PSC frequency distribution skewed toward low PSC but with a few high PSC plants. These data may be explained if PSC genes at some or most loci are incompletely dominant to non-PSC genes and threshold numbers of PSC genes are required for PSC expression and for 100% PSC plants. Dominance may also occur at some loci. Although only a small number of genes may be required to produce a high PSC plant, the total number of PSC genes may be large.Scientific Journal Series Paper No. 11,676 of the Minnesota Agricultural Experiment Station.     

Crossability relationships between the common potato, Solanum tuberosum spp. tuberosum, and its wild diploid relatives S. kurtzianum and S. ruiz-lealii

The common potato, Solanum tuberosum spp. tuberosum (tbr), is a tetraploid species with a narrow genetic base, but with a large number of related species that harbor great genetic diversity for numerous characters of agronomic interest. S. kurtzianum (ktz) and S. ruiz-lealii (rzl) are wild diploid relatives with potential resistance to adverse biotic and abiotic factors. To evaluate if this wild germplasm can be incorporated by conventional crosses into the tbr gene pool, pollen-pistil compatibility relations and seed set in interspecific crosses with tbr were investigated. In 4x tbr × 2x ktz crosses and the reciprocals, 89% and 52.2% of genotypic combinations (respectively) were compatible at the pollen-pistil level. Seeds were obtained from some genotypic combinations in both directions of the cross, suggesting that functional 2n gametes might be produced by particular ktz genotypes. In 2x rzl × 4x tbr crosses and their reciprocals, 35% and 11.7% (respectively) of the genotypic combinations were compatible at the pollen-pistil level, but no seeds were obtained. These results indicate that the reproductive isolation between 4x tbr and 2x ktz is incomplete, and that gene exchange between them is feasible. Moreover, further studies will have to be carried out with rzl to ascertain its crossability with 4x tbr.     

辐照小麦雌雄配子克服远缘杂交不亲和性的研究

用六倍体小黑麦“黑杂266”作母本,3个春小麦品种“龙辐30138”、“龙麦11号”、“龙辐10271”为父本进行远缘杂交,杂交前用~(60)Coγ射线600—1600rad活体慢照射雄配子或雌配子。通过对受精过程的切片观察,授粉后6小时,辐照雄配子的有61.70％的胚囊解体,辐照雌配子的为70.00％,未经辐照的为59.38％。辐照处理明显提高了杂种的结实率,但是,结实率随剂量的增加而下降。试验表明,辐照雌配子和雄配子的适宜剂量分别为600rad和800rad,但不同品种间辐射敏感性有很大差别。辐照对杂种籽粒的完好率有明显提高。应用组织培养技术进行胚挽救,可使有胚无胚乳杂种种子获得幼苗。     

低剂量辐射对小麦与窄颖赖草属间杂交的促进与损伤双重效应

以小麦、窄颖赖草为材料 ,研究了低剂量γ射线辐照花粉对远缘杂交的作用。结果表明 ,适宜低剂量 (5～ 9Gy)辐照花粉能克服杂交不亲和性提高杂交结实率 ,但同时也有一定损伤 ,种子胚胎发育受到一定影响 ,表现出低剂量辐射的双重效应。