Development and implementation of a sequence-specific PCR marker linked to a gene conferring resistance to anthracnose disease in narrow-leafed lupin (Lupinus angustifolius L.)

Anthracnose caused by Colletotrichum gloeosporioides is the most serious disease of lupins (Lupinus spp). A cross was made between cultivars Tanjil (resistant) and Unicrop (susceptible) in narrow-leafed lupin (L. angustifolius). Analysis of disease reaction data on the F₂ population and on the resultant F₇ recombinant inbred lines suggested that Tanjil contained a single dominant gene (Lanr1) conferring resistance to anthracnose. The parents and the representative F₂ plants were used to generate molecular markers liked to the Lanr1 gene using the MFLP technique. A co-dominant MFLP polymorphism linked to the Lanr1 gene was identified as a candidate marker. The bands were isolated, re-amplified by PCR, cloned and sequenced. The MFLP polymorphism was converted into a co-dominant, sequence-specific, simple PCR-based marker. Linkage analysis by the computer program MAPMAKER indicated that the marker was 3.5 centiMorgans (cM) from the gene Lanr1. This marker is currently being implemented for marker assisted selection in the Australian National Lupin Breeding Program.     

Genetic analysis of the accumulation of COR14 proteins in wild (Hordeum spontaneum) and cultivated (Hordeum vulgare) barley

The cold-regulated (COR14) protein of 14 kDa is a polypeptide accumulated under low-temperature conditions in the chloroplasts of barley leaves. In H. vulgare the COR14 antibody cross-reacts with two proteins, with a slightly different relative molecular weight around the marker of 14.4 kDa, referred to as COR14a and COR14b (high and low relative molecular weight, respectively). In a collection of H. spontaneum genotypes a clear polymorphism was found for the corresponding COR proteins. While some accessions showed the same COR pattern as cultivated barley, in 38 out of 61 accessions examined the COR14 antibody cross-reacted with an additional coldregulated protein with a relative molecular weight of about 24 kDa (COR24). The accumulation of COR24 was often associated with the absence of COR14b; the relationship between the COR14b/COR24 polymorphism and the adaptation of H. spontaneum to different environments is discussed. By studying COR14 accumulation in cultivated barley we have found that the threshold induction-temperature of COR14a is associated with the loci controlling winter hardiness. This association was demonstrated by using either a set of 30 cultivars of different origin, or two sets of frost-tolerant and frost-sensitive F1 doubled-haploid lines derived from the cross Dicktoo (winter type) x Morex (spring type). These results suggest that the threshold induction-temperature of COR14a can be a potential biochemical marker for the identification of superior frostresistant barley genotypes.     

A molecular marker linked to the mollis gene conferring soft-seediness for marker-assisted selection applicable to a wide range of crosses in lupin (Lupinus angustifolius L.) breeding

To broaden the gene pool of domesticated commercial cultivars of narrow-leafed lupin (Lupinus angustifolius L.), wild accessions are used as parents in crossing in lupin breeding. Among the progenies from wild × domesticated (W × D) crosses, the soft-seediness gene mollis is the most difficult domestication gene to be selected by conventional breeding methods, where molecular marker-assisted selection (MAS) is highly desirable. MAS in plant breeding requires markers to be cost-effective and high-throughput, and be applicable to a wide range of crosses in a breeding program. In this study, representative plants from an F8 recombinant inbred line (RIL) population derived from a W × D cross, together with four cultivars and four wild types, were used in DNA fingerprinting by microsatellite-anchored fragment length polymorphisms (MFLP). Two co-dominant MFLP polymorphisms were identified as candidate markers linked to the mollis gene, and one of the candidate markers was selected and converted into a co-dominant, sequence-specific PCR marker. This marker, designated MoLi, showed a perfect match with phenotypes of seed coat permeability on a segregating population consisting of 115 F8 RILs, confirming the close genetic linkage to the mollis gene. Validation tests showed that the banding pattern of marker MoLi is consistent with all the 25 historical and current commercial cultivars released in Australia, and is consistent with mollis genotypes in 119 of the 125 accessions in the Australian L. angustifolius core collection. Marker MoLi provides a cost-effective way to select the mollis gene in a wide range of W × D crosses in lupin breeding.     

Development of molecular markers using MFLP linked to a gene conferring resistance to Diaporthe toxica in narrow-leafed lupin ( Lupinus angustifolius L.)

Phomopsis stem blight (PSB) caused by Diaporthe toxica is a major disease in narrow-leafed lupin ( Lupinus angustifolius L.). The F(2) progeny and the parental plants from a cross between a breeding line 75A:258 (containing a single dominant resistance gene Phr1 against the disease) and a commercial cultivar Unicrop (susceptible to the disease) were used for development of molecular markers linked to the disease resistance gene. Two pairs of co-dominant DNA polymorphisms were detected using the microsatellite-anchored fragment length polymorphism (MFLP) technique. Both pairs of polymorphisms were isolated from the MFLP gels, re-amplified by PCR, sequenced, and converted into co-dominant, sequence-specific and PCR-based markers. Linkage analysis by MAPMAKER suggested that one marker (Ph258M2) was 5.7 centiMorgans (cM) from Phr1, and the other marker (Ph258M1) was 2.1 cM from Ph258M2 but further away from Phr1. These markers are suitable for marker-assisted selection (MAS) in lupin breeding.     

The use of microsatellite markers for detection of genetic diversity in barley populations

 A barley lambda-phage library was screened with (GA)n and (GT)n probes for developing microsatellite markers. The number of repeats ranged from 2 to 58 for GA and from 2 to 24 for GT. Fifteen selected microsatellite markers were highly polymorphic for barley. These microsatellite markers were used to estimate the genetic diversity among 163 barley genotypes chosen from the collection of the IPK Genebank, Germany. A total of 130 alleles were detected by 15 barley microsatellite markers. The number of alleles per microsatellite marker varied from 5 to 15. On average 8.6 alleles per locus were observed. Except for GMS004 all other barley microsatellite markers showed on average a high value of gene diversity ranging from 0.64 to 0.88. The mean value of gene diversity in the wild forms and landraces was 0.74, and even among the cultivars the gene diversity ranged from 0.30 to 0.86 with a mean of 0.72. No significant differences in polymorphism were detected by the GA and GT microsatellite markers. The estimated genetic distances revealed by the microsatellite markers were, on average , 0.75 for the wild forms, 0.72 for landraces and 0.70 among cultivars. The microsatellite markers were able to distinguish between different barley genotypes. The high degree of polymorphisms of microsatellite markers allows a rapid and efficient identification of barley genotypes. Received: 26 November 1997 / Accepted: 19 January 1998     

A strategy to develop molecular markers applicable to a wide range of crosses for marker assisted selection in plant breeding: a case study on anthracnose disease resistance in lupin (Lupinus angustifolius L.)

A key challenge in marker-assisted selection (MAS) for molecular plant breeding is to develop markers linked to genes of interest which are applicable to multiple breeding populations. In this study representative F₂ plants from a cross Mandalup (resistant to anthracnose disease) × Quilinock (susceptible) of Lupinus angustifolius were used in DNA fingerprinting by Microsatellite-anchored Fragment Length Polymorphism (MFLP). Nine candidate MFLP markers linked to anthracnose resistance were identified, then ‘validated’ on 17 commercial cultivars. The number of “false positives” (showing resistant-allele band but lack of the R gene) for each of the nine candidate MFLP markers on the 17 cultivars ranged from 1 to 9. The candidate marker with least number of false positive was selected, sequenced, and was converted into a co-dominant, sequence-specific, simple PCR based marker suitable for routine implementation. Testing on 180 F₂ plants confirmed that the converted marker was linked to the R gene at 5.1 centiMorgan. The banding pattern of the converted marker was consistent with the disease phenotype on 23 out of the 24 cultivars. This marker, designated “AnManM1”, is now being used for MAS in the Australian lupin breeding program. We conclude that generation of multiple candidate markers, followed by a validation step to select the best marker before conversion to an implementable form is an efficient strategy to ensure wide applicability for MAS.     

Identification and validation of a core set of informative genic SSR and SNP markers for assaying functional diversity in barley

A ‘core set’ of 28 simple sequence repeat (SSR) and 28 single nucleotide polymorphism (SNP) markers for barley was developed after screening six diverse genotypes (DGs) representing six countries (Afghanistan, Pakistan, Algeria, Egypt, Jordan and Syria) with 50 SSR and 50 SNP markers derived from expressed sequence tags (ESTs). The markers of the core set are single locus with very high quality amplifications, high polymorphism information content (PIC) and are distributed across the barley genome. PIC values for the selected SSR and SNP markers ranged between 0.32–0.72 (average 0.58) and 0.28–0.50 (average 0.42), respectively. To make the SNP genotyping cost effective, CAPS (cleaved amplified polymorphic sequence) and indel assays were developed for 23 markers and the remaining 5 SNP markers were optimized for pyrosequencing. A high coefficient of correlations (r = 0.96, P < 0.005) between the genetic similarity matrices of SSR and SNP genotyping data of the core set on diverse genotypes (DGs) and their similar groupings according to the geographical distribution in both SSR and SNP phenograms with high bootstrap values underline the utility and reliability of the core set. A comparative allelic and sequence diversity for SSR and SNP markers between the DGs and six elite parental genotypes (PGs) of mapping populations showed comparable diverse nature of two germplasm sets. However, unique SNPs and indels were observed in both germplasm sets providing more datapoints for analysing haplotypes in a better way for the corresponding SNP marker. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Construction of a genetic linkage map using MFLP and identification of molecular markers linked to domestication genes in narrow-leafed lupin (Lupinus angustifolius L.)

A mapping population of F(8)derived recombinant inbred lines (RILs) was established from a cross between a domesticated breeding line 83A:476 and a wild type P27255 in narrow-leaf lupin (Lupinus angustifolius L.). The parents together with the 89 RILs were subjected to DNA fingerprinting using microsatellite-anchored fragment length polymorphism (MFLP) to rapidly generate DNA markers to construct a linkage map. Five hundred and twenty two unique markers of which 21% were co-dominant, were generated and mapped. Phenotypic data for the domestication traits: mollis (soft seeds), leucospermus (white flower and seed colour); Lentus (reduced pod-shattering), iucundis (low alkaloid), Ku (early flowering) and moustache pattern on seed coats; were included. Three to 7 molecular markers were identified within 5 cM of each of these domestication genes. The anthracnose resistance gene Lanr1 was also mapped. Linkage groups were constructed using MapManager version QTXb20, resulting in 21 linkage groups consisting of 7 or more markers. The total map length was 1543 cM, with an average distance of 3.4 cM between adjacent markers. This is the first published map for a lupin species. The map can be exploited for marker assisted selection for genetic improvement in lupin breeding programs.     

Dry matter production and distribution of zinc in bread and durum wheat genotypes differing in zinc efficiency

Six bread wheat (Triticum aestivum cvs. Kiraç-66, Gerek-79, Aroona, ES 91-12, ES-14 and Kirkpinar) and four durum wheat (Triticum durum cvs. BDMM-19, Kunduru-1149, Kiziltan-91 and Durati) genotypes were grown under controlled environmental conditions in nutrient solution for 20 days to study the effect of varied supply of Zn (0 to 1 µM) on Zn deficiency symptoms in shoots, root and shoot dry matter production, and distribution of Zn in roots and shoots.Visual Zn deficiency symptoms, such as whitish-brown lesions on leaves, appeared rapidly and severly in durum wheats, particularly in Kiziltan-91 and Durati. Among the durum wheats, BDMM-19 was less affected by Zn deficiency, and among the bread wheats Kiraç-66, ES 91-12, Aroona and Gerek-79 were less affected than ES-14 and Kirkpinar.Under Zn deficiency, shoot dry matter production was decreased in all genotypes, but more distinctly in durum wheat genotypes. Despite severe decreases in shoot growth, root growth of all genotypes was either not affected or even increased by Zn deficiency. Correspondingly, shoot/root dry weight ratios were lower in Zn-deficient than in Zn-sufficient plants, especially in durum wheat genotypes.The distinct differences among the genotypes in sensitivity to Zn deficiency were closely related with the Zn content (Zn accumulation) per shoot but not with the Zn concentration in the shoot dry matter. On average, genotypes with lesser deficiency symptoms contained about 42% more Zn per shoot than genotypes with severe deficiency symptoms. In contrast to shoots, the Zn content in roots did not differ between genotypes. Shoot/root ratios of total Zn content were therefore greater for genotypes with lesser deficiency symptoms than for genotypes with severe deficiency symptoms (i.e. all durum wheat genotypes).The results suggest that the enhanced capacity of genotypes for Zn uptake and translocation from roots to shoot meristems under deficient Zn supply might be the most important factor contributing to Zn efficiency in wheat genotypes. The results also demonstrate that under severe Zn deficiency, Zn concentration in the shoot dry matter is not a suitable parameter for distinguishing wheat genotypes in their sensitivity to Zn deficiency.     

Genetic diversity among and within Iranian and non-Iranian barely (Hordeum vulgare L.) genotypes using SSR and storage proteins markers

The objectives of this study were evaluation of genetic diversity and marker–trait association of 64 barley (Hordeum vulgare L.) genotypes using hordeins and simple sequence repeats (SSRs) markers under optimal moisture and drought stress conditions. Moreover, to evaluate the response of barley genotypes to drought stress, five drought tolerance indices were calculated. SSRs and hordeins generated clear patterns with high polymorphism. SSRs and hordeins analysis provided us with useful information on the level of polymorphism and diversity in barley. Marker–trait associations were studied for 22 agronomic traits using 122 SSR markers (obtained from 14 primer pairs) and 51 hordeins bands in 64 barley genotypes under both normal and stress conditions. Phenotypic traits strongly associated with SSRs were also strongly associated with hordeins. Generally, we believed that at least some of these markers would be informative and validated and can be used in marker-assisted selection (MAS) under drought stress.     

Zinc efficiency of oilseed rape (t Brassica napus and t B. juncea) genotypes

Twenty five genotypes of oilseed rape (canola and mustard) were tested under varied supply of Zn (+Zn: 2 mg kg^–1 soil, -Zn: no Zn added) in two pot experiments in soil culture to determine the genotypic variation in tolerance to the Zn-deficient conditions, that is, to identify the Zn-efficient genotypes. On the basis of performance of genotypes in pot experiments, ten genotypes were tested in 1995 for their performance under varied supply of Zn (+Zn: 3.5 kg ha^–1, -Zn: no Zn added) on a Zn-deficient field in South Australia.Zn efficiency (ratio of shoot dry matter in -Zn to shoot dry matter in +Zn treatment and expressed in percentage) in pot Experiment 1 varied from 35% for 92-13 to 74% for Siren. Narendra, Dunkeld, Barossa, Oscar and Xinza 2 performed well under -Zn treatment. Zn efficiency in Experiment 2 varied from 32% for Wuyou 1 to 62% for Pusa Bold. Pusa Bold and CSIRO-1(mustard genotypes) were the most efficient in terms of dry matter production among all the oilseed rape genotypes tested. Root dry matter accumulation was significantly higher in Zn-efficient genotypes. Zn efficiency (ratio of seed yield in -Zn to seed yield in +Zn and expressed in percentage) in field experiment varied from 62% for Huashang 2 to 76% for Dunkeld. With few exceptions, the ranking of genotypes in pot and field experiments indicates similarity in their response to Zn deficiency. There looks to be genetic control over Zn concentration in tissues. Zn-efficient genotypes had lower Zn concentration in roots and higher Zn concentration in youngest fully opened leaf blades, indicating a better transport of Zn. This, together with a higher Zn uptake, appears to be the basis of expression of Zn efficiency.     

Discovery and assay of single-nucleotide polymorphisms in barley (Hordeum vulgare)

The least ambiguous genetic markers are those based on completely characterized DNA sequence polymorphisms. Unfortunately, assaying allele states by allele sequencing is slow and cumbersome. The most desirable type of genetic marker would be unambiguous, inexpensive to assay and would be assayable singly or in parallel with hundreds of other markers (multiplexable). In this report we sequenced alleles at 54 barley (Hordeum vulgare ssp. vulgare) loci, 38 of which contained single-nucleotide polymorphisms (SNPs). Many of these 38 loci contained multiple polymorphisms, and a total of 112 polymorphisms were scored in five barley genotypes. The polymorphism data set was analyzed both by using the individual mutations as cladistic characters and by reducing data for each locus to haplotypes. We compared the informativeness of these two approaches by consensus tree construction and bootstrap analysis. Both approaches provided similar results. Since some of the loci sequenced contained insertion/deletion events and multiple point mutations, we thought that these multiple-mutated loci might represent old alleles that predated the divergence of barley from H. spontaneum. We evaluated sequences from a sample of H. spontaneum accessions from the Eastern Mediterranean, and observed similar alleles present in both cultivated barley and H. spontaneum, suggesting either multiple domestication events or multiple transfers of genes between barley and its wild ancestor.     

Development of PCR-based markers on chromosome 5H for assisted selection of frost-tolerant genotypes in barley

Frost tolerance is an important trait for barley breeding. Field selection for this trait is not always efficient since, especially in Southern Europe, severe winter frost occurs erratically. Recent advances of cloned genes and molecular markers in barley provide molecular breeders with the means to develop new, simple PCR-based molecular markers, which can be used to select frost-tolerant genotypes quickly without stress simulation. This paper reports the development of two STS markers derived from the RFLP probes WG644 and PSR637, chosen as they are located on the long arm of homoeologous group 5 chromosomes of Triticeae, known to harbour the most important loci for frost tolerance. The two STS markers were validated together with one selected RAPD marker, OPA17, by separating two sets of winter and spring barley genotypes with different levels of frost tolerance. The ability of the developed markers to select segregant frost-tolerant and frost-susceptible genotypes was then investigated in a population of doubled haploid lines derived from a cross between a highly tolerant ('Nure') and a susceptible ('Tremois') genotype. In this population only two markers, OPA17 and Psr637 demonstrated their efficiency in dividing the phenotypes according to the parental alleles. These two markers mapped on the long arm of chromosome 5H, tightly linked to two frost tolerance QTLs. Two polymorphic bands of the WG644 STS were mapped: the former on the long arm of chromosome 5H (Wg644c) and the latter (Wg644b) on the long arm of chromosome 2H.     

Development of retrotransposon primers and their utilization for germplasm identification in Diospyros spp. (Ebenaceae)

Retrotransposons play an important role in plant genetic instability and genome evolution. Retrotransposon-based molecular markers are valuable tools to reveal the behavior of retrotransposons in their host genome. In this study, suppression polymerase chain reaction was used, for the first time, to develop retrotransposon long terminal repeat (LTR) and polypurine tract (PPT) primers in Japanese persimmon (Diospyros kaki Thunb.), which were then employed for germplasm identification by means of interretrotransposon-amplified polymorphism (IRAP), sequence-specific amplified polymorphism (SSAP) and retrotransposon-microsatellite-amplified polymorphism (REMAP) molecular markers. The results showed that 16 out of 26 primers produced expected amplifications and abundant polymorphisms by IRAP in 28 genotypes of Diospyros. Moreover, some of these primers were further successfully used in REMAP and SSAP analysis. Each type of molecular markers produced unique fingerprint in 28 genotypes analyzed. Among the primers/primer combinations, two IRAP primers and four SSAP primer combinations could discriminate all of the germplasm solely. Further comparative analysis indicated that IRAP was the most sensitive marker system for detecting variability. High level of retrotransposon insertion polymorphisms between bud sports were detected by IRAP and SSAP, and the primers/primer combinations with powerful discrimination capacity for two pairs of bud sports lines were further obtained. Additionally, possible genetic relationships between several Japanese persimmon were discussed. To our knowledge, this is the first report on the development of retrotransposon LTR and PPT primers in Diospyros, and the retrotransposon primers developed herein might open new avenue for research in the future.     

Genetic diversity and association analysis for salinity tolerance, heading date and plant height of barley germplasm using simple sequence repeat markers

The objective of this study was to investigate the genetic diversity of barley accessions.Additionally,association trait analysis was conducted for grain yield under salinity,heading date and plant height.For this purpose,48 barley genotypes were analyzed with 22 microsatellite simple sequence repeat (SSR) markers.Four of the 22 markers (Bmac316,scssr03907,HVM67 and Bmag770) were able to differentiate all barley genotypes.Cluster and principal coordinate analysis allowed a clear grouping between countries from the same region.The genotypes used in this study have been evaluated for agronomic performance in different environments.Conducting association analysis for grain yield under salinity conditions using TASSEL software revealed a close association of the marker Bmag749 (2H,bin 13) in two different environments with common significant alleles (175,177),whereas the HVHOTR1 marker (2H,bin 3) was only significant in Sakhar_Egypt with alleles size being 158 and 161.Heading date also showed an association with scssr03907 through the common significant specific allele 111 and EBmacO415 markers in three different agro climatic locations,whereas HVCMA,scssr00103 and HVM67 were linked to heading date in the Egyptian environment only.The plant height association analysis revealed significant markers Bmag770 via the significant allele 152 and scssr09398.     

Comparison of RAMP and SSR markers for the study of wild barley genetic diversity

Two molecular marker technologies, random amplified microsatellite polymorphism (RAMP) and simple sequence repeats (SSR), were used to determine genetic diversity of 27 accessions of the wild barley Hordeum vulgare ssp. spontaneum. 19 primer combinations were used to generate RAMP fragments and 16 SSR loci were analysed. A high level of polymorphism was found with both kind of markers as revealed by the mean polymorphism information content (PIC) values obtained: 0.838 and 0.855 for RAMP and SSR, respectively. Genetic dissimilarities between genotypes were estimated from RAMP and SSR data. A lack of correlation was found between both sets of data. This was reflected in the two dendrograms obtained which presented accessions clustered differently. The results suggest that both sets of markers reveal genetic variation induced by different mechanisms. The dendrogram produced from the RAMP dissimilarity estimates showed most of the groups related to the geographic origin of the accessions.     

Molecular Marker Analysis of Differentially Aged Seeds of Soybean and Safflower

Storage of seeds for extended periods causes a number of degradative changes related to the aging process such as decreased seedling vigor and reduced germination. In this study, molecular markers were used to study the aging process in seeds of two different plants species. Seeds of three differentially aged seed groups, including control (un-aged), naturally aged, and accelerated aging, from soybean (Glycine max) and safflower (Carthamus tinctorius) were evaluated for genetic variability using random amplification of polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), and simple sequence repeat (SSR) markers. For both plant species, naturally aged and accelerated aged groups clustered together with RAPD markers, whereas control and naturally aged seeds showed similarity in both AFLP and SSR profiles. Based on these findings, it can be concluded that observed changes in DNA profiles of seeds from different aged groups did not contribute to accumulation of genetic variations of the same magnitude. Therefore, seed of similar viability must be selected for molecular marker analysis for plant variety protection, among other comparative studies.     

Development of a sequence-specific PCR marker linked to the gene “pauper” conferring low-alkaloids in white lupin (Lupinus albus L.) for marker assisted selection

Seeds and plants of wild type Lupinus albus are bitter and contain high level of alkaloids. During domestication, at least three genes conferring low-alkaloid content were identified and incorporated into commercial varieties. Australian lupin breeders exclusively utilize one of these sweetness genes, “pauper”, in all varieties to prevent possible bitterness contamination via out-crossing. A cross was made between a sweet variety Kiev Mutant (containing pauper gene) and a bitter type landrace P27174, and the population was advanced into F₈ recombinant inbred lines (RILs). Twenty-four plants representing sweetness and bitterness were subjected to DNA fingerprinting by the microsatellite-anchored fragment length polymorphism (MFLP) technique. A dominant polymorphism was discovered in an MFLP fingerprint. The MFLP marker was converted into a co-dominant, sequence-specific, simple PCR-based marker. Linkage analysis by the software program MapManager with marker score data and alkaloid phenotyping data from a segregating population containing 190 F₈ RILs indicated that the marker is linked to the pauper gene at the genetic distance of 1.4 centiMorgans (cM). This marker, which is designated as “PauperM1”, is capable of distinguishing the pauper gene from the other two low-alkaloid genes exiguus and nutricius. Validation on germplasm from the Australian lupin breeding program showed that the banding pattern of the marker PauperM1 is consistent with the alkaloid genotyping on a wide range of domesticated varieties and breeding lines. The PauperM1 marker is now being implemented for marker assisted selection in the Australian albus lupin breeding program.     

Development and assessment of simple PCR markers for SNP genotyping in barley

Simple molecular marker assays underpin routine plant breeding and research activities in many laboratories worldwide. With the rapid growth of single nucleotide polymorphism (SNP) resources for many important crop plants, the availability of routine, low-tech marker assays for genotyping SNPs is of increased importance. In this study, we demonstrate that temperature-switch PCR (TSP) supports the rapid development of robust, allele-specific PCR markers for codominant SNP genotyping on agarose gel. A total of 87 TSP markers for assessing gene diversity in barley were developed and used to investigate the efficacy for marker development, assay reliably and genotyping accuracy. The TSP markers described provide good coverage of the barley genome, are simple to use, easy to interpret and score, and are amenable to assay automation. They provide a resource of informative SNP markers for assessing genetic relationships among individuals, populations and gene pools of cultivated barley (Hordeum vulgare L.) and its wild relative H. spontaneum K. Koch. TSP markers provide opportunities to use available SNP resources for marker-assisted breeding and plant genetic research, and to generate information that can be integrated with SNP data from different sources and studies. TSP markers are expected to provide similar advantages for any animal or plant species. M. J. Hayden and T. Tabone contributed equally to this work.     

<Emphasis Type="Bold">Zinc nutrition in wheat-based cropping systems</Emphasis>

Background

Zinc (Zn) deficiency is one of the most important micronutrient disorders affecting human health. Wheat is the staple food for 35% of the world’s population and is inherently low in Zn, which increases the incidence of Zn deficiency in humans. Major wheat-based cropping systems viz. rice–wheat, cotton–wheat and maize–wheat are prone to Zn deficiency due to the high Zn demand of these crops.

Methods

This review highlights the role of Zn in plant biology and its effect on wheat-based cropping systems. Agronomic, breeding and molecular approaches to improve Zn nutrition and biofortification of wheat grain are discussed.

Results

Zinc is most often applied to crops through soil and foliar methods. The application of Zn through seed treatments has improved grain yield and grain Zn status in wheat. In cropping systems where legumes are cultivated in rotation with wheat, microorganisms can improve the available Zn pool in soil for the wheat crop. Breeding and molecular approaches have been used to develop wheat genotypes with high grain Zn density.

Conclusions

Options for improving grain yield and grain Zn concentration in wheat include screening wheat genotypes for higher root Zn uptake and grain translocation efficiency, the inclusion of these Zn-efficient genotypes in breeding programs, and Zn fertilization through soil, foliar and seed treatments.