Linkage analysis in tetraploid potato and association of markers with quantitative resistance to late blight ( Phytophthora infestans )

We have constructed a partial linkage map in tetraploid potato which integrates simplex, duplex and double-simplex AFLP markers. The map consists of 231 maternal and 106 paternal markers with total map lengths of 990.9 cM and 484.6 cM. The longer of the two cumulative map lengths represents approximately 25% coverage of the genome. In tetraploids, much of the polymorphism between parental clones is masked by `dosage' which significantly reduces the number of individual markers that can be scored in a population. Consequently, the major advantage of using AFLPs – their high multiplex ratio – is reduced to the point where the use of alternative multi-allelic marker types would be significantly more efficient. The segregation data and map information have been used in a QTL analysis of late blight resistance, and a multi-allelic locus at the proximal end of chromosome VIII has been identified which contributes significantly to the expression of resistance. No late blight resistance genes or QTLs have previously been mapped to this location. Received: 1 October 1997 / Accepted: 18 March 1998     

Identification and mapping of three flower colour loci of potato (S. tuberosum L.) by RFLP analysis

Summary The inheritance of flower colour in diploid potato (2 n = 2x = 24), was found to be controlled by three unlinked loci D, F and P. To determine the allelism with previously described loci and to dissect this oligogenic trait, a set of tester clones with well-defined genotypes was developed. By backcrossing the mapping population with these tester clones it was possible to obtain monogenic segregation ratios. These were required to detect linkage with RFLP loci and, despite distorted Mendelian ratios, the inheritance and mapping of the D, F and P loci could be unambiguously determined. Locus D, involved in the biosynthesis of red anthocyanins, was mapped on chromosome 2, while locus P, involved in the production of blue anthocyanins, was mapped on chromosome 11. Locus F, involved in the flower-specific expression of gene(s) accommodated by the D and P loci, was mapped on chromosome 10. The tester clones and the map position of the D, F and P loci may be of considerable value in simplifying the genetics of anthocyanin pigmentation.     

An integrated genetic linkage map for eucalypts using RFLP,RAPD and isozyme markers

An integrated genetic linkage map for E. nitens was constructed in an outbred three-generation pedigree. Analysis of 210 RFLP, 125 RAPD and 4 isozyme loci resulted in 330 markers linked in 12 linkage groups covering 1462 cM (n=11 in eucalypts). The 12th linkage group is comprised of only 5 markers and will probably coalesce with another linkage group when further linked loci are located. Co-dominant RFLP loci segregating in both parents were used to integrate linkages identified in the male and female parents. Differences in recombination frequencies in the two parents were observed for a number of pairs of loci, and duplication of sequences was identified both within and between linkage groups. The markers were distributed randomly across the genome except for the RFLPs in linkage group 10 and for some loci showing segregation distortion, which were clustered into three regions of the map. The use of a large number of co-dominant RFLP loci in this map enables it to be used in other pedigrees of E. nitens and forms a basis for the detection and location of QTL in E. nitens and other eucalypt species.     

马铃薯NOA基因的克隆及序列分析(英文)

以马铃薯(Solanum tuberosum)为实验材料,利用电子克隆和RACE技术,从马铃薯中克隆出NOA(nitric oxide associated factor)基因,命名为StNOA1,测序结果表明,其cDNA序列长度为1 929 bp,此片段包含一个长为1 632 bp的完整编码框.氨基酸序列比对分析表明,StNOA1与烟草(Nicotiana benthamiana),葡萄(Vitis vinifera),蓖麻(Ricinus communis),水稻(Oryza sativa),玉米(Zea mays)以及拟南芥(Arabidopsis thaliana)均有很高的同源性 (89.44%～63.56%).同AtNOA1一样,StNOA1也具有保守的GTP结合区.从结构分析结果推测,StNOA1和AtNOA1在功能上有一定的相关性,其也可能通过调节内源NO的释放参与到植物生长、发育、抗逆等过程中.     

Microtuberization in potato (Solanum tuberosum L.)

Twenty-two genotypes of potato (Solanum tuberosum L.) were induced to form microtubers under six in vitro culture conditions. Cultures maintained under a short photoperiod (10 h of 6–12 μmol m^–2 s^–1) and low temperatures (day 20°±2°C and night 18°±2°C) had both a higher yield (255 mg/plantlet) and a greater number (2/plantlet) of microtubers than those maintained under long days (16 h of 38–50 μmol m^–2 s^–1) combined with high temperatures (day 28°±2°C and night 25°±2°C) (yield 207 mg/plantlet; microtuber number, 0.9/plantlet), over a wide range of genotypes. After the plantlets had been cultured under long days for an initial period of 60 days, continuous darkness advanced microtuberization by 2–3 months in various genotypes. Under short-day and low-temperature conditions the addition of 6-benzylaminopurine increased microtuber yield from 255 mg/plantlet to 645 mg/plantlet and average microtuber weight from 115 mg to 364 mg. A similar pattern was observed under conditions of long days and high temperature, and continuous darkness and low-temperature. Microtubers produced under light had a greater number of eyes (maximum average: 5.96/microtuber) than those produced in the dark (maximum average: 3.50/plantlet). The genotype × cultural conditions interactions were significant indicating the importance of developing genotype-specific protocols to maximize microtuberization. Received: 17 September 1997 / Revision received: 12 December 1997 / Accepted: 1 January 1998     

Comparative mapping between potato (Solanum tuberosum) and Arabidopsis thaliana reveals structurally conserved domains and ancient duplications in the potato genome

A genetic map of potato (Solanum tuberosum) was constructed based on 293 restriction fragment length polymorphism (RFLP) markers including 31 EST markers of Arabidopsis. The in silico comparison of all marker sequences with the Arabidopsis genomic sequence resulted in 189 markers that detected in Arabidopsis 787 loci with sequence conservation. Based on conserved linkage between groups of at least three different markers on the genetic map of potato and the physical map of Arabidopsis, 90 putative syntenic blocks were identified covering 41% of the potato genetic map and 50% of the Arabidopsis physical map. The existence and distribution of syntenic blocks suggested a higher degree of structural conservation in some parts of the potato genome when compared to others. Syntenic blocks were redundant: most potato syntenic blocks were related to several Arabidopsis genome segments and vice versa. Some duplicated potato syntenic blocks correlated well with ancient segmental duplications in Arabidopsis. Syntenic relationships between different genomic segments of potato and the same segment of the Arabidopsis genome indicated that potato genome evolution included ancient intra- and interchromosomal duplications. The partial genome coveridge and the redundancy of syntenic blocks limits the use of synteny for functional comparisons between the crop species potato and the model plant Arabidopsis.     

Analysis of RFLP mapping inaccuracy in Brassica napus L.

 We identified sources of mapping inaccuracy during the construction of RFLP linkage maps from one F₂ population and two F₁ microspore-derived populations from the same cross of oilseed Brassica napus. The genetic maps were compared using a total of 145 RFLP marker loci including 82 loci common to all three populations. In the process, we identified a series of mapping events that could lead to ambigous conclusions. Superimposed restriction fragments could be mistaken as a single dominant restriction fragment in a F₂ population and, when analyzed as such, would yield inaccurate linkage information. Residual heterozygosity in parental lines resulted in complicated allelic assignment and yielded subsequent difficulties in linkage determination. Loose and spurious linkages occurred during mapping and were identified by comparing maps derived from different populations. LOD scores and χ² test of independence were compared for their capacity to detect loose linkages or generate spurious ones. Extreme segregation distortions towards the same parental allele also contributed to an additional source of spurious linkage. Small but significant segregation distortions resulted in reduced estimates of the recombination fraction. The use of the same ‘probe× enzyme’ combinations in doubled haploid populations allowed the identification of the correct allele assignment as well as loose and spurious linkages. A translocation between two homoeologous linkage groups was observed. The consequences of such a chromosomal event as a source of error in mapping applications are discussed. Received: 7 September 1996/Accepted: 25 October 1996     

马铃薯HMGR基因的克隆,序列分析及其表达特征

采用ＲＴ－ＰＣＲ技术,从马铃薯（Ｓｏｌａｎｕｍ ｔｕｂｅｒｏｓｕｍ Ｌ．）幼叶中克隆了一个约１．０ｋｂ的ｃＤＮＡ片段,序列分析结果表明,该ｃＤＮＡ与忆报道的马铃薯ＨＭＧＲ基因家族的三种类型基因具有较高核酸序列同源性,与ＨＭＧＲⅠ基因同源性为７７．０％,ＨＭＧＲⅡ基因为９３．２％,ＨＭＧＲⅢ基因为７７．１％。其中３’端非翻译区序列与ＨＭＧＲⅠ、ＨＭＧＲⅡ、ＨＭＧＲⅢ三种基因同源性分别为５０．２％,８     

RFLP mapping of the barley homeotic mutant lax-a

The lax-a homeotic mutant of barley has flowers in which lodicules are replaced by stamens (giving five stamens per flower). RFLP mapping of an F₂ population from a Bonus lax-a ¹ x H. spontaneum cross showed that the mutation was on the short arm of chromosome 7(5H), closely linked to the centromere. An additional F₂ population was used to show that the lax-a mutation gave the five-stamen phenotype in all flowers of 6-rowed spikes and that hoods were elevated and reduced in size in lax-a/Hooded double-mutant plants.     

Construction of an RFLP linkage map for cultivated sunflower

 An RFLP linkage map was constructed for cultivated sunflower Helianthus annuus L., based on 271 loci detected by 232 cDNA probes. Ninety-three F₂ plants of a cross between inbred lines RHA 271 and HA 234 were used as the mapping population. These genetic markers plus a fertility restoration gene, Rf ₁, defined 20 linkage groups, covering 1164 cM of the sunflower genome. Of the 71 loci 202 had codominant genotypic segregation, with the rest showing dominant segregation. Thirty-two of the 232 probes gave multiple locus segregation. There were 39 clusters of tightly linked markers with 0 cM distance among loci. This map has an average marker-to-marker distance of 4.6 cM, with 11 markerless regions exceeding 20 cM. Received: 17 June 1997 / Accepted: 19 June 1997     

Immobilization of the Solanum tuberosum epoxide hydrolase and its application in an enantioconvergent process

Five supports have been evaluated for the immobilization of the epoxide hydrolase from Solanum tuberosum (StEH) by adsorption. The highest immobilization yield (90-99%) and the maximum EH (epoxide hydrolase) activity (0.6 U g^-1 wet support) were obtained by ionic adsorption onto DEAE-cellulose. Although the activity recovered upon immobilization of StEH onto DEAE-cellulose was low, a notable stabilization factor of 6.9 at 65°C was obtained. In addition, the immobilized StEH showed a higher temperature for maximal activity (57°C) and the optimal pH (5.0) was shifted one unit towards the acidic region as compared to the free enzyme. Immobilized StEH was successfully reused in six consecutive hydrolytic kinetic resolutions of rac-pCSO without noticeable loss in activity. Finally, the sequential use of immobilized StEH with the immobilized EH from Aspergillus niger (AnEH) in a repeated batch reactor, operated for five cycles, enabled the enantioconvergent preparation of the corresponding (R)-diol, which was thus obtained with an ee of 89% and an overall yield of 100%.     

Molecular linkage mapping in rye (Secale cereale L.)

A rye linkage map containing clones from rye, wheat, barley, oat and rice genomic and cDNA libraries, known-function genes and microsatellite markers, was created using an F₂ population consisting of 110 F₂-derived F₃ families. Both co-dominant and dominant markers were added to the map. Of all probes screened, 30.8% were polymorphic, and of those polymorphic 79.3% were mapped. The current map contains 184 markers present in all seven linkage groups covering only 727.3 cM. This places a marker about every 3.96 cM on average throughout the map; however, large gaps are still present. The map contains 60 markers that have been integrated from previous rye maps. Surprisingly, no markers were placed between the centromere and C1–1RS in the short arm of 1R. The short arm of chromosome 4 also lacked an adequate number of polymorphic markers. The population showed a remarkable degree of segregation distortion (72.8%). In addition, the genetic distance observed in rye was found to be very different among the maps created by different mapping populations. Received: 10 January 2000 / Accepted: 26 May 2000     

Studies on Plant Regeneration from Mesophyll Protoplasts of Solanum tuberosum L.

Protoplasts from potato mesophyll of two strains (Solannum tuberosum L. cv. Xiao Yie Zi x Duo Zi Bia and Solanum tuberosum L. cv. Wu Meng 601) were induced to callus in culture medium of protoplasts. The callus derived from mesophyll protoplasts were transferred to MS medium with 2 mg/l ZT+0.1 mg/L IAA. Shoots regenerated from the callus were detected after 70 days of culture.The shoots which had grown to a height of 2–3 cm were transferred to MS medium with 0.05 mg/L NAA. Roots were coming out in a few days.Complete plantlets were achieved. Stern segments with 1–2 leaves were then transferred to a mixture of sterilized soil and grown, and produced tuber.     

Drought and chlorophyll fluorescence in field-grown potato (Solanum tuberosum)

Light interception, stomatal conductance and chlorophyll fluorescence were measured in potato ( Solanum tuberosum L.) grown either irrigated, or droughted from the time of plant emergence. Compared with the irrigated treatment, drought reduced both light interception and stomatal conductance. In both treatments, the yields of variable fluorescence in the dark- and light-adapted states (F_y/F_m and F'_v/F'_m, respectively) were negatively correlated with photosynthetic photon flux density (PPFD) and mirrored daytime changes in PPFD. Photochemical quenching was positively correlated with PPFD, but the dominant effect of F'_v/F'_m resulted in a decrease in the quantum yield of photosystem II (PSII) electron transport with increasing PPFD.
Drought had no significant effect on the functioning of PSII and the balance between photochemical and non-photochemical quenching was unaffected. Non-photochemical quenching was not increased by drought and the quantum yield of PSII electron transport was unaffected. It is concluded that, in leaves of droughted plants, excess energy, resultant of stomatal limitation of photosynthesis, was dissipated by photochemical quenching such as increased photorespiration.     

Cloning and Characterization of One Member of the Chalcone Synthase Gene Family from Solanum tuberosum L.

We have isolated a chalcone synthase gene 2 (ST-CHS2) from potato by rapid amplification of cDNA ends by PCR. CHS2 cDNA had high homology to tomato LET-CHS2 (98%), petunia PHCHSJ (94%), potato ST-CHS1B (92%), petunia PHCHSA (92%), and LET-CHS1 (90%) at the overall 389-amino acid level. Genomic hybridization analysis indicated that CHS genes of potato comprise a family of at least six individual members.     

马铃薯Alfin1-like锌指蛋白基因克隆与序列分析

利用紫花苜蓿盐胁迫相关锌指结构蛋白Alfin1基因cDNA序列,通过电子克隆在GenBank中对马铃薯同源EST序列进行查询比较和拼接,获得了1个含有完整编码区的cDNA序列,并通过RT-PCR成功获得了该序列.获得的全长cDNA序列中包含1个747 bp的最大读码框,编码248个氨基酸,将其命名为Stfin1.氨基酸序列分析表明存在典型的Cys4-His-Cys3锌指结构,与Alfin1一致性达93.09%.从结构分析结果推测Stfin1与Alfin1在功能上具有一定的相关性.     

A RFLP linkage map of Sorghum bicolor (L.) Moench

A RFLP linkage map of sorghum composed principally of markers detected with sorghum low-copy-number nuclear DNA clones has been constructed. The map spans 1789 cMs and consists of 190 loci grouped into 14 linkage groups. The 10 largest linkage groups consist of from 10 to 24 markers and from 103 to 237 cMs, and the other 4 linkage groups consist of from 2 to 5 markers and from 7 to 62 cMs. The map was derived in Sorghum bicolor ssp. bicolor by analysis of a F₂ population composed of 50 plants derived from a cross of IS 3620C, a guinea line, and BTx 623, an agronomically important inbred line derived from a cross between a zera zera (a caudatum-like sorghum) and an established kafir line. The restriction fragment length polymorphism (RFLP) frequency detected in this population using polymerase chain reaction (PCR)-amplifiable low-copy-number sorghum clones and five restriction enzymes was 51%. A minimal estimate of the number of clones that detect duplicate sequences is 11 %. Null alleles occurred at 13% of the mapped RFLP loci.     

Sheep linkage mapping: RFLP markers for comparative mapping studies

Restriction fragment length polymorphisms (RFLPs) detected using cDNA probes for conserved genes provide an important set of markers that anchor or link syntenic groups in a range of divergent mammalian species. DNA probes from sheep, cattle, pig, human and mouse were screened against sheep DNA samples and 24 new RFLP markers for sheep were identified. Among the loci tested, 22 had a homologue that has been mapped in humans. An RFLP for fibronectin (FN1) was linked to α-inhibin (INHA) at a distance of 5cM. The FN1 locus has been assigned to sheep chromosome 2q41–q44 and linkage between FN1 and INHA assigns INHA to the same chromosome in sheep. In addition to the new loci reported here, 28 RFLPs have been published previously by this group and these are collated together with RFLPs published from other laboratories. RFLPs have been reported for 86 loci in sheep. Fifty-four loci have been mapped to 16 different chromosomes.     

RFLP analysis of asymmetric somatic hybrids between Solanum tuberosum and irradiated S. brevidens

The nuclear genome composition of five asymmetric somatic hybrids, obtained by fusion of leaf protoplasts from Solanum tuberosum and gamma-irradiated leaf protoplasts from S. brevidens, have been analyzed at the molecular level. An analysis of 21 loci using linkage group-specific restriction fragment length polymorphism (RFLP) was included in the study. All five hybrids contained a complete set of the loci studied from S. tuberosum. The degree of elimination of alleles from the irradiated S. brevidens donor genome ranged from 10–65% in the five asymmetric hybrids analyzed. The detection of incomplete chromosomes, as well as non-parental bands in Southern hybridizations with RFLP markers, revealed extensive chromosome rearrangements in the asymmetric hybrids.