Genlou Sun

RAPD polymorphism of wild emmer wheat populations, Triticum dicoccoides, in Israel

Abstractu2002Genetic diversity in random amplified polymorphic DNAs (RAPDs) was studied in 110 genotypes of the tetraploid wild progenitor of wheat, Triticum dicoccoides, from 11 populations sampled in Israel and Turkey. Our results show high level of diversity of RAPD markers in wild wheat populations in Israel. The ten primers used in this study amplified 59 scorable RAPD loci of which 48 (81.4%) were polymorphic and 11 monomorphic. RAPD analysis was found to be highly effective in distinguishing genotypes of T. dicoccoides originating from diverse ecogeographical sites in Israel and Turkey, with 95.5% of the 100 genotypes correctly classified into sites of origin by discriminant analysis based on RAPD genotyping. However, interpopulation genetic distances showed no association with geographic distance between the population sites of origin, negating a simple isolation by distance model. Spatial autocorrelation of RAPD frequencies suggests that migration is not influential. Our present RAPD results are non-random and in agreement with the previously obtained allozyme patterns, although the genetic diversity values obtained with RAPDs are much higher than the allozyme values. Significant correlates of RAPD markers with various climatic and soil factors suggest that, as in the case of allozymes, natural selection causes adaptive RAPD ecogeographical differentiation. The results obtained suggest that RAPD markers are useful for the estimation of genetic diversity in wild material of T. dicoccoides and the identification of suitable parents for the development of mapping populations for the tagging of agronomically important traits derived from T. dicoccoides.

Identification of molecular markers linked to the Yr15 stripe rust resistance gene of wheat originated in wild emmer wheat, Triticum dicoccoides

Abstractu2002The Yr15 gene of wheat confers resistance to the stripe rust pathogen Puccinia striiformis West., which is one of the most devastating diseases of wheat throughout the world. In the present study, molecular markers flanking the Yr15 gene of wheat have been identified using the near-isogenic-lines approach. RFLP screening of 76 probe-enzyme combinations revealed one polymorphic marker (Nor/TaqI) between the susceptible and the resistant lines. In addition, out of 340 RAPD primers tested, six produced polymorphic RAPD bands between the susceptible and the resistant lines. The genetic linkage of the polymorphic markers was tested on segregating F2 population (123 plants) derived from crosses between stripe rust-susceptible Triticum durum wheat, cv D447, and a BC3F9 resistant line carrying Yr15 in a D447 background. A 2.8-kb fragment produced by the Nor RFLP probe and a 1420-bp PCR product generated by the RAPD primer OPB13 showed linkage, in coupling, with the Yr15 gene. Employing the standard maximum-likelihood technique it was found that the order OPB131420–Yr15–Nor1 on chromosome 1B appeared to be no less than 1000-times more probable than the closest alternative. The map distances between OPB131420–Yr15–Nor1 are 27.1u2005cM and 11.0u2005cM for the first and second intervals, respectively. The application of marker-assisted selection for the breeding of new wheat cultivars with the stripe rust resistance gene is discussed.

Genetic distances revealed by morphological characters, isozymes, proteins and RAPD markers and their relationships with hybrid performance in oilseed rape (Brassica napus L.)

Genetic distances (GDs) based on morphological characters, isozymes and storage proteins, and random amplified polymorphic DNAs (RAPD) were used to predict the performance and heterosis of crosses in oilseed rape (Brassica napus L.). Six male-sterile lines carrying the widely used Shaan2A cytoplasm were crossed with five restorer lines to produce 30 F1 hybrids. These 30 hybrids and their parents were evaluated for seven agronomically important traits and their mid-parent heterosis (MPH) at Yangling, Shaanxi province in Northwest China for 2xa0years. Genetic similarity among the parents based on 34 isozyme and seven protein markers was higher than that based on 136 RAPDs and/or 48 morphological markers. No significant correlation was detected among these three sets of data. Associations between the different estimates of GDs and F1 performance for some agronomic traits were significant, but not for seed yield. In order to enhance the predicting efficiency, we selected 114 significant markers and 43 favoring markers following statistical comparison of the mean values of the yield components between the heterozygous group (where the marker is present only in one parent of each hybrid) and the homozygous group (where the marker is either present or absent in both parents of each hybrid) of the 30 hybrids. Parental GD based on total polymorphic markers (GDtotal, indicating general heterozygosity), significant markers (GDsign, indicating specific heterozygosity) and favoring markers (GDfavor, indicating favoring-marker heterozygosity) were calculated. The correlation between GDfavor or GDsign and hybrid performance was higher than the correlation between GDtotal and hybrid performance. GDsign and GDfavor significantly correlated with plant height, seeds per silique and seed yield, but not with the MPH of the other six agronomic traits with the exception of plant height. The information obtained in this study on the genetic diversity of the parental lines does not appear to be reliable for predicting F1 yield and heterosis.

Quantitative trait loci analysis for the developmental behavior of Soybean (Glycine max L. Merr.)

Quantitative trait loci (QTLs) identified so far in soybean were mainly derived in the final stage of plant development, which did not apply to the exploitation of genetic effects that were expressed during a specific developmental stage. Thus, the aim of this study was to identify conditional QTLs associated with yield traits at a specific developmental interval of soybean plant. The 143 recombinant inbred lines developed from the cross of soybean cultivars ‘Charleston’ and ‘Dongnong 594’ were used for the developmental QTLs analysis of pod number in the main stem and plant height by composite interval mapping method combined with mixed genetic model. The results indicated that the number and type of QTLs and their genetic effects for the two agronomic traits were different in a series of measuring stages. A total of 10 unconditional QTLs in 6 linkage groups and 5 conditional QTLs in 3 linkage groups were identified for the pod number of the main stem, while 13 unconditional QTLs in 7 linkage groups and 12 conditional QTLs in 6 linkage groups were identified for plant height. Many QTLs that were detected in the early stages were different from those detected at the later stages. Some QTLs existed only at one stage and others existed across two or three stages. Five marker intervals (satt509-satt251, sat_099-sat_113, sat_113-OPAW19_4, satt457-OPC10_85, sat_095-OPBA08_5) were proven to be associated both with the development of pod number in the main stem and the development of plant height. The present study suggested that the development of pods and plant height in soybean were governed by time-dependent gene expression.

RAPD polymorphisms in spring wheat cultivars and lines with different level of Fusarium resistance

Abstract. Random amplified polymorphic DNA (RAPD) markers have beenn used to characterize the genetic diversity among 35 spring wheat cultivars andn lines with different levels of Fusariumn resistance. The objectives of this study were to determine RAPD-based geneticn similarity between accessions and to derive associations betweenn Fusarium head blight (FHB) and RAPD markers.n Two bulked DNA from either highly resistant lines or susceptible lines weren used to screen polymorphic primers. Out of 160 screened primers, 17 primersn generated reproducible and polymorphic fragments. Genetic similarity calculatedn from the RAPD data ranged from 0.64 to 0.98. A dendrogram was prepared on then basis of a similarity matrix using the UPGMA algorithm, which corresponded welln with the results of principal component analysis and separated the 35 genotypesn into two groups. Association analysis between RAPD markers and the FHB indexn detected three RAPD markers, H191000,n F2500 and B12400, significantlyn associated with FHB-resistant genotypes. These results suggest that an collection of unrelated genotypes can be used to identify markers linked to ann agronomically important quantitative trait like FHB. These markers will ben useful for marker-assistant breeding and can be used as candidate markers forn further gene mapping and cloning.

Genetic relationships of tetraploid Elymus species and their genomic donor species inferred from polymerase chain reaction-restriction length polymorphism analysis of chloroplast gene regions

The genetic relationships of 38 individuals from 13 Elymus tetraploid species, two Pseudoroegneria species and one Hordeum species were examined using polymerase chain reaction-restriction length polymorphism analysis of chloroplast gene regions. The 13 Elymus species contain SH and SY genomes with either a single spikelet or multiple spikelets per rachis node. The Pseudoroegneria and Hordeum species contain an S genome with single spikelet per rachis node and an H genome with multiple spikelets per rachis node, respectively. Four chloroplast gene regions, trnD-trnT intron, trnK [tRNA-Lys (UUU) exon1]–trnK [tRNA-Lys (UUU) exon2], trnC-trnD, and rbcL were amplified with specific primers and subsequently digested with up to 16 different restriction enzymes. Interspecific variation was detected in the four regions. A dendrogram based on similarity matrices using the unweighted pair group method with arithmetic average algorithm separated the 38 individuals into two distinct groups: the Elymus and Pseudoroegneria species as one group and Horduem as a second group. This result corresponded well with previous findings, and strongly suggested that a Pseudoroegneria species is the maternal donor to tetraploid Elymus species. Unlike previous studies using nuclear genes, the chloroplast DNA used in this study could not clearly separate the SY-genome species from SH-genome species. No clear separation between the species with a single spikelet per rachis node and the species with multiple spikelets per rachis node was found. Intra-specific variation was detected for the species studied. These observations provide molecular evidence for the highly diverse nature of the Elymus gene pool based on morphological characteristics.

Microsatellite polymorphism and genetic differentiation in three Norwegian populations of Elymus alaskanus (Poaceae)

Abstract.u2002Variation at seven microsatellite loci was investigated in three local E. alaskanus populations from Norway and microsatellite variation was compared with allozyme variation. The percentage of polymorphic loci was 81%, the mean number of alleles per polymorphic locus was 5.7 and expected heterozygosity was 0.37. An F-statistic analysis revealed an overall 48% deficit of heterozygotes over Hardy-Weinberg expectations. Gene diversity is mainly explained by the within population component. The averaged between population differentiation coefficient, Fst, over 7 loci is only 0.13, which accounts for only 13% of the whole diversity and was contrary to allozyme analysis. The mean genetic distance between populations was 0.12. However, a χ2 -test showed that allele frequencies were different (pu2009<u20090.05) among the populations at 5 of the 7 loci. In comparison with the genetic variation detected by allozymes, microsatellite loci showed higher levels of genetic variation. Microsatellite analysis revealed that population H10576 possesses the lowest genetic variation among the tested three populations, which concur with allozyme analysis. The dendrogram generated by microsatellites agreed very well with allozymic data. Our results suggest that natural selection may be an important factor in shaping the genetic diversity in these three local E. alaskanus populations. Possible explanations for deficit heterozygosity and incongruence between microsatellites and allozymes are discussed.

Genetic diversity of Brassica napus L. Germplasm from China and Europe assessed by some agronomically important characters

SummaryThe genetic diversity and relationships among 63 rapeseed accessions, including 34 Chinese, 22 Czech, 2 Swedish, 2 German, one French and 2 Canadian accessions, were evaluated by nine agronomically important characters in the field at Yangling, Shaanxi, China. Significant differences between Chinese and European group in plant height, setting position of the first primary branch, number of siliques of the terminal raceme, thousand seed weight and seed yield per plant were detected. There were significant variations in nine agronomic characters among the tested rapeseed accessions. Ward’s minimum variance cluster analysis based on Mahalanobis distances on the raw data of nine agronomic characters clearly separated the European accessions from the Chinese ones. However, the Chinese accessions with erucic acid free and/or low glucosinolates could not be separated from those Chinese accessions with both high erucic acid and glucosinolates. In general, cluster analysis of the 63 accessions based on the selected agronomic characters was consistent with known pedigree information and geographic origin, as well as the previous RAPD results of these accessions. The European rapeseed could be important germplasm resources for enriching the genetic background of Chinese rapeseed, and vice versa.

Functional properties of a new low-molecular-weight glutenin subunit gene from a bread wheat cultivar

Some allelic forms of low-molecular-weight glutenin subunit (LMW-GS) can greatly influence the end-use of wheat flours, understanding the function of each allele of LMW-GS is important to wheat quality breeding. A LMW-GS gene XYGluD3-LMWGS 1(AY263369) has been cloned from bread wheat cultivar Xiaoyan 6. The deduced protein contained nine cystine residues, one more than that in all other LMW-GSs reported previously, indicating that it is either a new gene or a new allele of a known LMW-GS gene. In this study, the gene was expressed in E. coil in large scale for the testing of its functional property. Reactive Red 120-Agarose resin was used efficiently to purify the expressed LMW-GS proteins from bacteria, with the lactic acid–sodium lactate buffer (pH 4.5) which contained low concentration SDS as elution solution. The purified protein (belonging to the LMW-m family, MW about 35 KDa) was supplemented into a base flour, the results of 10xa0g dough mixing test indicated that incorporation of the LMW-GS increased the strength of the dough, with significant increases in mixing time (MT) and peak width (PW), and decrease in breakdown in resistance (RBD) compared with the control. In addition, the dough with incorporation of the LMW-GS had more glutenin macropolyeric protein than the control, suggesting that the LMW-GS participated in forming larger glutenin polymers, and greatly contributed to dough strength. The changes in mixing parameters and the amount of glutenin macropolyeric protein were related to the quantity of incorporating subunits.

Identification of QTL underlying the resistance of soybean to pod borer, Leguminivora glycinivorella (Mats.) obraztsov, and correlations with plant, pod and seed traits

Soybean (Glycine max L. Merr.) pod borer (Leguminivora glycinivorella (Mats.) Obraztsov) (SPB) results in severe loss in soybean yield and quality in certain regions of the world, especially in Northeastern China, Japan and Russia. The aim here was to evaluate the inheritance of pod borer resistance and to identify quantitative trait loci (QTL) underlying SPB resistance for the acceleration of the control of this pest. Used were the 129 recombinant inbred lines (RILs) of the F5:6 derived population from ‘Dong Nong 1068’ × ‘Dong Nong 8004’ and 131 SSR markers. Correlations between the percentage of damaged seeds (PDS) by pod borer and plant, pod and seed traits that were potentially related to SPB resistance were analyzed. The results showed highly significant correlations between PDS by pod borer and plant height (PH), maturity date (MA), pod color (PC), pubescence density (PB), 100-seed weight (SW) and protein content existed. Soybeans with dwarf stem, light color of pod coat, small seeds, lower density of pubescence, early maturity and low content of protein seemed to have higher resistance to SPB. The correlated traits had potential to inhibit egg deposition and thereby to decrease the damage by SPB. Three QTL directly associated with the resistance to SPB judged by PDS at harvest were identified. qRspb-1 (Satt541–Satt253) and qRspb-2 (Satt253–Satt314) were both on linkage group (LG) H and qRspb-3 (Satt288–Satt199) on LG G. The three QTL explained 10.96, 9.73 and 11.59% of the phenotypic variation for PDS, respectively. In addition, 12 QTL that underlay 10 of 13 traits potentially related with SPB resistance were found. These QTL detected jointly provide potential for marker assisted selection to improve cultivar resistance to SPB.