Resistance of barley landraces and wild barley populations to powdery mildew in Jordan

Eleven barley (Hordeum vulgare L.) landraces and 12 wild barley (H. spontaneum) populations, collected from diverse eco-geographical regions of Jordan, were screened for resistance to powdery mildew. The average powdery mildew disease score (based on a 0 to 4 severity scale) wa

Association analysis of single nucleotide polymorphisms in candidate genes with root traits in maize (Zea mays L.) seedlings

Background: Root growth and development is not only critical for nitrogen acquisition in plants, but also to anchor the plant in the soil. Several genes involved in maize root development have been isolated. Identification of SNPs associated with root traits would enable the selection of maize lines with better root architecture that might help to improve N uptake, and consequently plant growth particularly under N deficient conditions. Results: In the present study, an association study (AS) panel consisting of 74 maize inbred lines was screened for seedling root traits in 6, 10, and 14-day-old seedlings. Allele resequencing of candidate root genes Rtcl, Rth3, Rum1, and Rul1 was also carried out in the same AS panel lines. All four candidate genes displayed different levels of nucleotide diversity, haplotype diversity and linkage disequilibrium. Nucleotide diversity was highest in the Rtcl gene (π=0.021), intermediate in Rum1 (π=0.011), lowest in Rth3 (π=0.007) and Rul1 (π=0.005) gene. When coding and non-coding regions within the genes were compared, nucleotide diversity varied across the genes. Gene based association analyses were carried out between individual polymorphisms in candidate genes, and root traits measured in 6, 10, and 14-day-old maize seedlings. Association analyses revealed several polymorphisms within the Rtcl, Rth3, Rum1, and Rul1 genes associated with seedling root traits. These significantly associated SNPs also affected putative functional sequence motifs, mostly transcription factor binding sites, and major domains in the genes. Conclusion: Several nucleotide polymorphisms in Rtcl, Rth3, Rum1, and Rul1 were significantly (P\u3c0.05) associated with seedling root traits in maize suggesting that all four tested genes are involved in the maize root development. Thus considerable allelic variation present in these root genes can be exploited for improving maize root characteristics. Target nucleotide polymorphisms for functional marker development were identified which might find application in marker-based selection strategies in breeding programs

Genetic architecture of plant height in maize phenotype-selected introgression families

This study aimed at developing, characterizing and evaluating two maize phenotypic-selected introgression libraries for a collection of dominant plant height (PHT)-increasing alleles by introgressing donor chromosome segments (DCS) from Germplasm Enhancement of Maize (GEM) accessions into elite inbred lines: PHB47 and PHZ51. Different backcross generations (BC1-BC4) were developed and the tallest 23 phenotype-selected introgression families (PIFs) from each introgression library (PHB47 or PHZ51) were selected for single nucleotide polymorphism genotyping to localize DCS underlying PHT. The result shows that most PIFs carrying DCS were significantly (α = 0.01) taller than the respective recurrent parent. In addition, they contained larger donor genome proportions than expected in the absence of selection or random mating across all BC generations. The DCS were distributed over the whole genome, indicating a complex genetic nature underlying PHT. We conclude that our PIFs are enriched for favourable PHT-increasing alleles. These two libraries offer opportunities for future PHT gene isolation and allele characterization and for breeding purposes, such as novel cultivars for biofuel production

Variation in the volatile constituents of wild and in vitro propagated Tanacetum sinaicum Del. ex DC through GC-MS chemical fingerprint

Tanacetum sinaicum (Asteraceae) is a rare perennial herb growing wild in the mountains of Southern Sinai (Egypt). It is a medicinal and endangered plant. So, this work aimed to develop an in vitro propagation method for the conservation of this highly threatened plant. Sterile seedlings were used as a source of explants which were cultivated on Murashige and Skoog (M&S) media supplemented with different combinations of growth regulators for callus formation and induction of shoots and roots. M&S media with 1 mg/L kinetin (Kn) showed direct shoot induction. For root induction, excised shoots were transferred to M&S medium supplemented with 1 mg/L naphthalene acetic acid (NAA). Moreover, n-hexane extracts of wild and in vitro propagated plants were analyzed for their volatile constituents by gas chromatography-mass spectrometry (GC-MS) which resulted in the identification of 38 and 27 constituents, accounting for 87.75 and 75.51 % of their total composition; respectively

Variation in the volatile constituents of wild and in vitro propagated Tanacetum sinaicum Del. ex DC through GC-MS chemical fingerprint

238-246Tanacetum sinaicum (Asteraceae) is a rare perennial herb growing wild in the mountains of Southern Sinai (Egypt). It is a medicinal and endangered plant. So, this work aimed to develop an in vitro propagation method for the conservation of this highly threatened plant. Sterile seedlings were used as a source of explants which were cultivated on Murashige and Skoog (M&S) media supplemented with different combinations of growth regulators for callus formation and induction of shoots and roots. M&S media with 1 mg/L kinetin (Kn) showed direct shoot induction. For root induction, excised shoots were transferred to M&S medium supplemented with 1 mg/L naphthalene acetic acid (NAA). Moreover, n-hexane extracts of wild and in vitro propagated plants were analyzed for their volatile constituents by gas chromatography-mass spectrometry (GC-MS) which resulted in the identification of 38 and 27 constituents, accounting for 87.75 and 75.51 % of their total composition; respectively

Genotypic variation and relationships between seedling and adult plant traits in maize (Zea mays L.) inbred lines grown under contrasting nitrogen levels

Genotypes with better root development have good nutrient acquisition capacity and may yield better under limited nitrogen (N) conditions and consequently can help reduce the N fertilization rate and hence mitigate some economic and ecological problems. This study focused on the genotypic variation among diverse maize inbred lines for seedling and adult plant traits under contrasting N levels. Seventy four lines were screened under high and low N levels in a climate chamber and in the field. High phenotypic diversity was observed for seedling and adult plant traits together with moderate to high broad-sense heritability estimates. Seedling total root length and root dry weight were significantly correlated with other root traits in maize. Of the adult plant traits evaluated in the field, the anthesis-silking interval and the leaf chlorophyll contents were significantly correlated with grain yield under both low and high N levels. In one location, the seminal root length was correlated with grain yield both under low and high N levels and the root dry weight was correlated with grain yield under high N. Selection indices based on secondary root traits along with grain yield could lead to an increase in selection efficiency for grain yield under N stress condition. By identifying lines with better root development, particularly lines with longer SRL, it may be possible to select inbred lines with higher grain yield particularly under low N condition

Association analysis of genes involved in maize (Zea mays L.) root development with seedling and agronomic traits under contrasting nitrogen levels

Genotypes with large and well distributed root system might have the potential to adapt to soils with limited nutrient availability. For this purpose, an association study (AS) panel consisting of 74 diverse set of inbred maize lines were screened for seedling root traits and adult plant root traits under two contrasting nitrogen (N) levels (low and high N). Allele re-sequencing of RTCL, RTH3, RUM1, and RUL1 genes related to root development was carried out for AS panel lines. Association analysis was carried out between individual polymorphisms, and both seedling and adult plant traits, while controlling for spurious associations due to population structure and kinship relations. Based on the SNPs identified in RTCL, RTH3, RUM1, and RUL1, lines within the AS panel were grouped into 16, 9, 22, and 7 haplotypes, respectively. Association analysis revealed several polymorphisms within root genes putatively associated with the variability in seedling root and adult plant traits development under contrasting N levels. The highest number of significantly associated SNPs with seedling root traits were found in RTCL (19 SNPs) followed by RUM1 (4 SNPs) and in case of RTH3 and RUL1, two and three SNPs, respectively, were significantly associated with root traits. RTCL and RTH3 were also found to be associated with grain yield. Thus considerable allelic diversity is present within the candidate genes studied and can be utilized to develop functional markers that allow identification of maize lines with improved root architecture and yield under N stress conditions

Genome-wide association mapping in a diverse spring barley collection reveals the presence of QTL hotspots and candidate genes for root and shoot architecture traits at seedling stage

Figure S1. Examples of scanned root images from individual plants. Figure S2. Concatenated split network tree for the collection of 233 accessions based on 6019 SNP markers. Figure S3. LD pattern along the individual chromosomes of barley. Figure S4. Schematic representation of the eight re-sequenced candidate genes models. (DOCX 3427 kb