河南小麦新育成品种(系)白粉病抗性鉴定与分子标记检测

利用华北地区流行的白粉菌菌株E09和E20,分别对河南省小麦新品种(系)区域和预备试验参试材料908份(2009—2013年度)和412份(2009—2012年度)进行苗期白粉病抗性鉴定,同时利用与Pm2、Pm4a、Pm8和Pm21基因连锁的分子标记检测相关抗病基因的分布。结果显示,抗E09的材料占21.9%(199/908),抗E20的材料占9.5%(39/412),同时抗E09和E20的材料仅占3.6%(15/412)。在908份供试材料中,580份含有1BL/1RS,占63.9%,含Pm8或新的1RS来源抗白粉病基因;另有2份材料含6AL/6VS来源广谱抗白粉病基因Pm21,8份可能携带Pm2,2份可能含有Pm4a;有6份材料可能含有多个抗白粉病基因。表明河南省近年育成的小麦新品种(系)依然含有对我国白粉菌菌系有效的抗白粉病基因,但抗源遗传基础较窄,部分已经或正在丧失抗性,应加快引进和利用新的多样化抗病基因资源。     

Tissue culture-derived variation in crop improvement

Tissue culture generates a wide range of genetic variation in plant species which can be incorporated in plant breeding programmes. By in vitro selection, mutants with useful agronomic traits, e.g. salt or drought tolerance or disease resistance, can be isolated in a short duration. The successful use of somaclonal variation is very much dependent on its genetic stability in the subsequent generations for which molecular markers such as RAPDs, AFLPs, SSRs and others can be helpful. The potential of somaclonal variation has yet to be fully exploited by breeders, even though a few cultivars have been developed in crops such as Brassica juncea, rice and others. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development of SCAR markers linked to the Ns locus in potato

A random amplified polymorphic DNA marker OPG17₄₅₀ linked to the Ns gene that confers resistance of potato to potato virus S (PVS), was used to develop sequence‐characterized amplified region (SCAR) markers. After cloning and sequencing of OPG17₄₅₀ new polymerase chain reaction (PCR) primers were designed to generate dominant (SCG17₃₂₁) and codominant (SCG17₄₄₈) markers. For SCG17₄₄₈, polymorphism between susceptible and resistant genotypes was recovered after digestion of the marker with the restriction enzyme Muni. In addition to the band corresponding to ‘susceptible’ allele that does not contain the Muni cleavage site, two bands of approximately 251 bp and 197 bp were observed in the resistant genotypes. The usefulness of these SCAR markers was verified in diploid potatoes possessing the Ns locus from clone G‐LKS 678147/60, and in tetraploid potatoes derived from G‐LKS 678147/60 and from clone MPI 65118/3.     

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.     

A molecular marker linked to the Prv1 gene that confers resistance to Papaya ringspot virus-type W in melon

Papaya ringspot virus‐type W (PRSV‐W) is the most prevalent and important viral pathogen of cucurbits in Brazil. It can be effectively controlled by the incorporation of genetic resistance into susceptible melon cultivars. The present study identified amplified fragment length polymorphic (AFLP) markers linked to the PRSV‐W resistance Prv¹ allele. The susceptible yellow‐fleshed melon‐breeding line AF426^prv1 and its nearly isogenic‐resistant line AF426^Prv1, which carries the Prv¹ allele resident in the Indian cantaloupe U.S. Plant Introduction (PI) 180280, were screened for AFLP marker polymorphisms. Of 30 251 AFLP loci, only three were polymorphic between the nearly isogenic lines. Segregation analyses for these three polymorphic markers and the Prv¹ allele using a BC₁ population of 197 plants indicated close linkage (0.5% recombination frequency) between marker EK190 (HindIII‐CGA and MseI‐GTG; 190 bp) and Prv¹. Thus, EK190 might be a useful marker in breeding programmes aiming to develop melon cultivars resistant to PRSV‐W. The other two markers are closely linked to each other, but distantly linked to Prv¹.     

A contribution to the systematics of a piedmontese plum ecotype

Prunus domestica L., P. insititia L., P. salicina Lindl. and P. cerasifera Ehrh. are the most important species included in the plum group. Many ‘cultivars’ have an undefined origin and share very similar morpho‐phenological characteristics that make their identification difficult. This is the case of ‘Ramasin’, a group of Piedmontese genotypes whose fruits are small, ellipsoidal and very tasty. They are commonly considered as P. domestica varieties, even though on the basis of some morphological characteristics they are similar to other species such as P. insititia. In order to study the origin of this group, the DNA of 25 genotypes of ‘Ramasin’, and that of some ‘cultivars’ of P. domestica, P. insititia, P. cerasifera, P. salicina and two selections of P. spinosa L. was examined. The PCR‐RAPDs method (Random Amplified Polymorphic DNA amplified by Polymerase Chain Reaction) was used and all 69 primers that were tested generated more or less polymorphic bands. From the results of these analyses it can be supposed that the ‘Ramasin’ plums are a single genetically heterogeneous group. Moreover it can probably be assumed that ‘Ramasin’ arose from crosses between P. domestica and P. insititia.     

Assessment of genetic variability in grapefruits (Citrus paradisi Macf.) and pummelos (C. maxima (Burm.) Merr.) using RAPD and SSR markers

The genetic variability of 38 grapefruit (Citrus paradisi Macf.) and three pummelos (C. maxima (Burm.) Merr..) accessions was evaluated using RAPD, and single sequence repeat (SSR) analyses. Approximately49% of the 198 RAPD were polymorphic, and 4.6 alleles per SSR loci were identified. PIC values changed from 0.093 to 0.450. A UPGMA phenetic tree was constructed and two main grapefruit groups were identified. The grapefruit accessions `do Cabo' and `Siamesa-Filipinas'clustered very close to the pummelos in Group A. The Group B consisted of three sub-groups, which comprised all of the other grapefruit accessions. The majority of grapefruit accessions showed a narrow genetic base suggesting that the observed morphological polymorphism within the group must be associated with somatic mutations, which were not detected by these molecular markers. This revised version was published online in August 2006 with corrections to the Cover Date.     

Identification of sex in Carica papaya L. using RAPD markers

Brazil is currently the worlds largest producer of papaya (Carica papayaL.), producing fruits for both the domestic market and export. Only fruits from hermaphrodite plants are marketed because they have the necessary commercial characteristics, i.e. they are pear-shaped and have thicker flesh and a smaller internal cavity. Increased papaya yield has been limited mainly by the ratio of female to hermaphrodite (1: 2) plants normally occurring in orchards. This ratio causes great losses to papaya producers and the identification of the sex of seedlings during the nursery stage would be an important advance. In our study random amplified polymorphic DNA (RAPD) analysis was used to differentiate between the sexual forms of three commercial C. papaya cultivars belonging to the Solo group. RAPD assays using the BC210 primer were able to detect hermaphrodites in all of the cultivars tested. The BC210₄₃₈molecular marker was much better at papaya sex differentiation than other markers described in the literature. This revised version was published online in August 2006 with corrections to the Cover Date.     

Precision of genetic relationship estimates based on molecular markers

Genetic progress through selection is directly related to the amount of variability present in the population and the quality of genes contributed by the parents. Genetic relationships between lines were studied using DNA marker-based estimates of genetic similarity. A statistical methodology using the width of a confidence interval was developed to determine the number of probes to be surveyed and the precision in the estimation of genetic distance between pairs of cultivars. Precision was affected by type of genetic distance used, the number of cultivars, and amount of genetic diversity present in the studied group. The width of a (1-α)% confidence interval decreased as the number of RFLP fragments increased. Oat and wheat diversity studies were used to illustrate the methodology. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sclerotinia rot resistance in red clover: Identification of RAPD markers using bulked segregant analysis

Random amplified polymorphic DNA (RAPD) was used with the objective of identifying DNA markers linked to the sclerotinia crown and stem rot (SCSR) resistance of red clover. Bulked segregant analysis was used to detect polymorphism that should be linked to SCSR resistance. Two bulks were made by pooling previously extracted DNA. Each bulk (one resistant, and the other susceptible) consisted of eight genotypes from an F₂ population obtained from a cross between a susceptible and a resistant parent. A binomial model was used to select RAPD fragments with a low probability of no linkage with SCSR resistance. Four RAPD fragments were retained as candidate markers of SCSR resistance. Three are associated with resistance and one with susceptibility.