Development of a SCAR marker associated with salt tolerance in durum wheat (Triticum turgidum ssp. durum) from a semi-arid region

Potential of tetraploid wheats in plant breeding: A review

Domestication syndrome, selection pressure, and modern plant breeding programs have reduced the genetic diversity of the wheat germplasm. For the genetic gains of breeding programs to be sustainable, plant breeders require a diverse gene pool to select genes for resistance to biotic stress factors, tolerance to abiotic stress factors, and improved quality and yield components. Thus, old landraces, subspecies and wild ancestors are rich sources of genetic diversity that have not yet been fully exploited, and it is possible to utilize this diversity. Compared with durum wheat, tetraploid wheat subspecies have retained much greater genetic diversity despite genetic drift and various environmental influences, and the identification and utilization of this diversity can make a greater contribution to the genetic enrichment of wheat. In addition, using the pre-breeding method, the valuable left-behind alleles in the wheat gene pool can be re-introduced through hybridization and introgressive gene flow to create a sustainable opportunity for the genetic gain of wheat. This review provides some insights about the potential of tetraploid wheats in plant breeding and the genetic gains made by them in plant breeding across past decades, and gathers the known functional information on genes/QTLs, metabolites, traits and their direct involvement in wheat resistance/tolerance to biotic/abiotic stresses.

Abscisic Acid-Stress-Ripening Genes Involved in Plant Response to High Salinity and Water Deficit in Durum and Common Wheat

In the dry and hot Mediterranean regions wheat is greatly susceptible to several abiotic stresses such as extreme temperatures, drought, and salinity, causing plant growth to decrease together with severe yield and quality losses. Thus, the identification of gene sequences involved in plant adaptation to such stresses is crucial for the optimization of molecular tools aimed at genetic selection and development of stress-tolerant varieties. Abscisic acid, stress, ripening-induced (ASR) genes act in the protection mechanism against high salinity and water deficit in several plant species. In a previous study, we isolated for the first time the TtASR1 gene from the 4A chromosome of durum wheat in a salt-tolerant Tunisian landrace and assessed its involvement in plant response to some developmental and environmental signals in several organs. In this work, we focused attention on ASR genes located on the homoeologous chromosome group 4 and used for the first time a Real-Time approach to "in planta" to evaluate the role of such genes in modulating wheat adaptation to salinity and drought. Gene expression modulation was evaluated under the influence of different variables - kind of stress, ploidy level, susceptibility, plant tissue, time post-stress application, gene chromosome location. ASR response to abiotic stresses was found only slightly affected by ploidy level or chromosomal location, as durum and common wheat exhibited a similar gene expression profile in response to salt increase and water deficiency. On the contrary, gene activity was more influenced by other variables such as plant tissue (expression levels were higher in roots than in leaves), kind of stress [NaCl was more affecting than polyethylene glycol (PEG)], and genotype (transcripts accumulated differentially in susceptible or tolerant genotypes). Based on such experimental evidence, we confirmed Abscisic acid, stress, ripening-induced genes involvement in plant response to high salinity and drought and suggested the quantification of gene expression variation after long salt exposure (72 h) as a reliable parameter to discriminate between salt-tolerant and salt-susceptible genotypes in both Triticum aestivum and Triticum durum.

Analysis of Genetic Diversity and Development of a SCAR Marker for Green Tea (Camellia sinensis) Cultivars in Zhejiang Province: The Most Famous Green Tea-Producing Area in China

Camellia sinensis (L.) O. Kuntze is one of the most important non-alcoholic beverage crops in Asian and African countries. In recent years, many green tea cultivars have been released and played an important role in improving the production and quality of tea trees. The objectives of this study were to assess the genetic diversity of the eighteen main green tea cultivars in Zhejiang Province-the most famous green tea-producing area of China-using start codon-targeted (SCoT) markers and to develop a specific sequence-characterized amplified region (SCAR) marker for application in cultivar diagnosis. Thirty-one SCoT primers produced 264 loci, 226 of which were polymorphic. The genetic similarity coefficients among these green tea cultivars ranged from 0.587 to 0.814, indicating that a high level of genetic diversity was present. Both a UPGMA dendrogram and a PCoA plot grouped the tea cultivars into three groups. The partitioning of groups in the UPGMA and PCoA was similar, and much of the clustering was highly consistent with the classification of tea cultivars according to their genetic backgrounds. A unique SCoT band, SCoT4-1649, specific to the tea cultivar 'Yingshuang,' was transformed into a SCAR marker. This SCAR marker is highly useful for the identification and germplasm conservation of green tea cultivars.