Adel Ahmed Elshafei

Identification of new TRAP markers linked to chlorophyll content, leaf senescence, and cell membrane stability in water-stressed wheat

In order to identify target region amplification polymorphism (TRAP) markers linked to three physiological traits in wheat (Triticum aestivum L.), the segregating F4 population from the cross between drought-sensitive (Yecora Rojo) and drought-tolerant (Pavon 76) genotypes was made. The parents and 150 F4 families were evaluated phenotypically for drought tolerance using two irrigation treatments [2.5 and 7.5 m3(H2O) m−2(soil)]. Using 40 different TRAP primer combinations tested for polymorphism in parental and F4 family genotypes, the results revealed that quantitative trait locus (QTL) for chlorophyll content was associated with TRAP 5, TRAP 14, and TRAP 20 and explained 18, 16, and 23 % phenotypic variation, respectively. The genetic distance between chlorophyll content QTL and TRAP 5, TRAP 14, and TRAP 20 were 12.3, 19.8, and 13.6 cM, respectively. QTL for flag leaf senescence was associated with TRAP 2, TRAP 3, TRAP 15, and TRAP 16 and explained 33, 27, 28, and 23 % phenotypic variations, respectively. The genetic distance between flag leaf senescence QTL and TRAP 2, TRAP 3, TRAP 15, and TRAP 16 were 9.4, 14.7, 18.1, and 17.3 cM, respectively. QTL for cell membrane stability was associated with TRAP 8, TRAP 9, and TRAP 37 and explained 27, 30, and 24 % phenotypic variation, respectively. The markers TRAP 8, TRAP 9, and TRAP 37 had genetic distances of 17.0, 10.0, and 9.0 cM, respectively. Therefore, these TRAP markers can be used in breeding for drought tolerance in wheat.

Mapping of QTLs associated with abscisic acid and water stress in wheat

A segregating F4 population from the cross between drought sensitive (Yecora Rojo) and drought tolerant (Pavon 76) genotypes was made to identify molecular markers linked to a wheat (Triticum aestivum L.) abscisic acid (ABA) content at two water regimes. The parents and 150 F4 lines were evaluated phenotypically for drought tolerance using two irrigation treatments [0.25 and 0.75 m3(H2O) m−2(soil)]. Forty different target region amplification polymorphism (TRAP) primer combinations, 98 different sequence-related amplified polymorphism (SRAP) primer combinations, and 400 simple sequence repeat (SSR) primers were tested for polymorphism among the parental genotypes and the F4 lines. Seven loci in the F4 lines treated with the drought stress were identified. Single quantitative trait loci (QTLs) were located on chromosomes 1B, 2A, 3A, 5D, and 7B and each of them explained from 15 to 31 % of phenotypic variance with a LOD value of 7.2 to 15.7. Five QTLs were located on chromosome 4A and six QTLs on chromosome 5A. In control (well-watered) F4 lines, two QTLs were mapped on chromosome 3B and one QTL on each chromosome 5B and 5D. Statistically the most significant groups of QTLs for the ABA content were identified in the regions of chromosomes 3B, 4A, and 5A mostly near to Barc164, Wmc96, and Trap9 markers. Therefore, these markers linked to QTLs for the drought-induced ABA content can be further used in breeding for drought tolerance in wheat.

Anther culture response in wheat (Triticum aestivum L.) genotypes with HMW alleles

The objective of this study was to develop a simple anther culture protocol for a range of Saudi wheat genotypes. Seven wheat genotypes were evaluated in anther culture on five different medium protocols for their ability to initiate callus and green plants. The estimates of significance for the effects of genotypes, and medium protocols used, and their interactions on callus induction, callus weight and shoot formation derived from anther explants indicated that the in vitro traits were significantly influenced by the genotypes, medium protocols, and their interactions. The percentage of explants that developed calli ranged from 0.41% (Lang) to 15.39% (Irena) averaged across the five medium protocols with an average 4.45%. The genotype Irena produced the highest average means of shoot formation (69.65%) across medium protocols. The genotype Yecora Rojo (13.73%) was significantly inferior to all other tested genotypes for shoot formation.

The genetic basis of spectral reflectance indices in drought-stressed wheat

Drought imposes a major constraint over the productivity of wheat, particularly in arid and semi-arid production zones. Here, the genetic basis of spectral reflectance indices was investigated in drought-stressed wheat by comparing, under two contrasting moisture regimes, the performance of an F6 recombinant inbred line (RIL) population bred from a cross between the drought tolerant cultivar Pavon76 and the sensitive cultivar Yecora Rojo. The parents and RILs were genotyped with respect to both a set of microsatellite (SSR) loci and a number of known drought-responsive genes. In all, 28 quantitative trait loci (QTL) controlling dry weight per plant, water content of the above-ground biomass, leaf water potential, canopy temperature, and spectral reflectance indices traits were identified. The loci were distributed over 11 chromosomes, belonging to each of the three wheat sub-genomes. There were important location-flanking markers Barc109 and Barac4 on chromosome 5B relating to dry weight per plant accumulation under the limited irrigation regime. The same region-harbored QTL associated with leaf water potential, canopy temperature, and ratio index under the limited irrigation regime. Linkage between the known drought-responsive genes and aspects of the drought response was established. Some of QTL were of substantial enough effect for their linked markers to be likely usable for the marker-assisted breeding of drought tolerance in wheat.

Identification of new SSR markers linked to leaf chlorophyll content, flag leaf senescence and cell membrane stability traits in wheat under water stressed condition

Segregating F4 families from the cross between drought sensitive (Yecora Rojo) and drought tolerant (Pavon 76) genotypes were made to identify SSR markers linked to leaf chlorophyll content, flag leaf senescence and cell membrane stability traits in wheat (Triticum aestivum L.) under water-stressed condition and to map quantitative trait locus (QTL) for the three physiological traits. The parents and 150 F4 families were evaluated phenotypically for drought tolerance using two irrigation treatments (2500 and 7500 m3/ha). Using 400 SSR primers tested for polymorphism in testing parental and F4 families genotypes, the results revealed that QTL for leaf chlorophyll content, flag leaf senescence and cell membrane stability traits were associated with 12, 5 and 12 SSR markers, respectively and explained phenotypic variation ranged from 6 to 42%. The SSR markers for physiological traits had genetic distances ranged from 12.5 to 25.5 cM. These SSR markers can be further used in breeding programs for drought tolerance in wheat.

Doubled haploid wheat lines with high molecular weight glutenin alleles derived from microspore cultures

ABSTRACT A doubled haploid (DH) production system for wheat using a microspore culture method produced seeds and subsequently regenerated haploid wheat plants derived from the F1 plants of two wheat populations (Irena × Ksu102 and Klasic × Ksu105). 68 DH were obtained from both populations. Field trials of these DH lines were conducted over two seasons. Genotypic differences were highly significant for all agronomic traits recorded. Sets of five gene- or allele-specific PCR markers were used for identification of genes encoding high molecular weight (HMW) glutenin subunits Ax1 and Ax2* at the Glu-A1 locus, Bx7, Bx7*, By8 and By17 at the Glu-B1 locus and Dx5, Dy10 and Dy12 at the Glu-D1 locus in wheat inbred lines. The method developed for providing DH lines and subsequent molecular analysis and quality could be useful for improving bread-making quality and developing new cultivars. Abbreviations: DH: doubled haploid; HMW: high molecular weight; HMW-GS: high molecular weight glutenins subunits; MAB: marker-assisted breeding