Drought is a severe environmental constraint to plant productivity and an important factor limiting barley yield. To investigate the initial response of barley to drought stress, changes in protein profile were analyzed using a proteomics technique. Three-day-old barley seedlings of sensitive genotype 004186 and tolerant genotype 004223 were given two treatments, one with 20 % polyethylene glycol and the second with drought induced by withholding water. After 3 days of treatments, proteins were extracted from shoots and separated by 2-dimensional polyacrylamide gel electrophoresis. Metabolism related proteins were decreased in the sensitive genotype under drought; however, they were increased in the tolerant genotype. Photosynthetic related proteins were decreased and increased among the three sensitive and three tolerant genotypes, respectively. In addition, amino acid synthesis and degradation related proteins were increased and decreased among the three tolerant genotypes. These results suggest that chloroplastic metabolism and energy related proteins might play a significant role in the adaptation process of barley seedlings under drought stress.

ABSTRACT. Identification of new sources of salt tolerance is particularly important to develop crop varieties suitable for saline soils. We evaluated 129 Pakistani and 58 exotic wheat landraces/ cultivars grown in Hoagland's hydroponic nutrient solution, under control (tap water equivalent to 10 mM salt) and salt stress (200 mM NaCl) conditions. Forty-four genotypes were also tested under 250 mM NaCl stress. High heritability and positive correlations suggested that number of tillers per plant, root length, root fresh and dry weights, and shoot fresh and dry weights are associated with salt tolerance and could be used as selection criteria. SSR markers revealed high genetic variation in the wheat genotypes. Twelve SSR markers (cfd 1, cfd 9, cfd 18, cfd 46, cfd 49, cfd 183, wmc 11, wmc 17, wmc 18, wmc 154, wmc 432, and wmc 503) were found to be associated with salt tolerance because they were amplified in tolerant genotypes only. Five markers, cfd 9, cfd 18, cfd 183, wmc 96, and wmc 405, were identified as most suitable to evaluate salt tolerance because they were associated with four or more salt tolerance traits studied. Cultivars Pasban 90, accessions 10790, 10828, 10823, and 4098805 from Pakistan and Sakha-92 from Egypt performed best at both stress levels.

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Flowering time in bread wheat (Triticum aestivum L.) is controlled by vernalization and photoperiod response, and earliness per se genes. The genetic basis of flowering time has not been investigated in Pakistani bread wheat. This study was, therefore, conducted to determine the allelic composition at Vrn-A1, Vrn-B1, Vrn-D1, Vrn-B3 and Ppd-D1a loci of 59 Pakistani spring bread wheat cultivars. These cultivars, along with 4 isogenic lines for vernalization genes were characterized with previously reported DNA markers designed for detecting allelic variation at 4 Vrn (Vernalization) and 1 Ppd (Photoperiod) loci. Spring habit Vrn-A1a allele was found in 36% cultivars either alone or with spring habit Vrn-B1 and Vrn-D1 alleles. Two wheat cultivars had the dominant Vrn-A1c allele, whereas none of the cultivars had Vrn-A1b. Spring habit Vrn-B1 was the most frequent allele (64%) present either alone or with Vrn-A1a, Vrn-A1c and Vrn-D1. Spring habit Vrn-D1 was found in 61% cultivars. Vrn-D1 was singly found in 25% cultivars and along with Vrn-B1 in 29% cultivars. Dominant Vrn-B3 was absent in all cultivars studied. All cultivars except Era had the photoperiod insensitive allele PpdD1a. We did not find any association between the flowering time and Vrn allelic composition of the studied cultivars. This indicated that the partial vernalization requirement of cultivars with Vrn-B1 and Vrn-D1 alleles is probably fulfilled during Pakistani growing season. Earliness per se and the photoperiod sensitive loci other than Ppd-D1 need to be investigated to further understand the genetic basis of flowering time in Pakistani wheat.

Background: Two-line hybrid wheat system using thermo-photo sensitive genic male sterility (TPSGMS) is currently the most promising approach for wheat heterosis utilization in China. However, during past 20 years only few TPSGMS lines were developed in hybrid wheat breeding, which has been the main limiting factor to create heterotic hybrids. Application of doubled haploid (DH) breeding provides a useful strategy to efficiently develop practically usable TPSGMS lines. Results: F 1 s and selected F 2 and F 3 sterile plants of eight crosses made from two commercial TPSGMS lines were used to produce DH lines. We developed a total of 24 elite DH sterile lines with stable sterility, good outcrossing and yield potential, resistance to yellow rust and powdery mildew, as well as desirable plant height (50-60 cm). These DH lines were developed within 4 years through at least 1 year of evaluation. The stability of male sterility was confirmed for most (20/24) of these elite DH sterile lines by multiple tests in two or 3 years. These lines are expected to be used in hybrid wheat breeding. The percentage of elite lines developed from the tested DH lines produced from filial generations was in the order of F 2 > F 3 > F 1. Conclusions: We demonstrate that coupling DH techniques with conventional breeding is an efficient strategy for accelerating the development of more practical wheat TPSGMS lines. Generation of DHs from F 2 generation appeared to be the better choice considering the balance of shortening breeding time and overall breeding efficiency.