No description available.

Thesis (M.S.)--University of Delaware, 2009. / Principal faculty advisor: John L. Gallagher, College of Earth, Ocean, & Environment. Includes bibliographical references.

Thesis (M.S. in botany)--Washington State University, August 2009. / Title from PDF title page (viewed on Sept. 22, 2009). "Department of Biological Sciences." Includes bibliographical references (p. 138-139).

Soil salinity is a serious problem for farmers in irrigated agriculture. Soil salts cause reduced stands and yields because of toxic ion and osmotic problems for surviving seedlings. The tolerance to sodium chloride during germination and emergence was studied in three commercial cultivars of short staple cotton (Gossypium hirsutum L.). It is this stage of the life cycle that cotton is most sensitive to salts in the soil solution. The objectives of this study were to increase the tolerance to sodium chloride during germination and emergence and to determine the narrow sense heritability of this factor. Parental cultivars initially demonstrated 15% emergence at -1.2 MPa NaCl. Surviving salt tolerant plants were planted in the field and seeds from these plants were used as the germplasm for the next cycle of salt tolerance selection. Experiments were conducted to determine the relative salt tolerance of all plants at -1.2, -1.4, -1.6, and -1.8 MPa NaCl. Emergence of salt tolerant accessions from the first cycle of selection ranged from 3.1 to 25.8% in the first relative salt tolerance experiment. The average emergence of all accessions taken over all four salinity levels was 8.9% for first cycle plants. After a second cycle of selection for salt tolerance, the average emergence percentage increased to 13.0% over the four salinity levels. Emergence ranged from 0.7 to 32.6% in the second relative salt tolerance experiment. Narrow sense heritability of sodium chloride tolerance during germination and emergence was estimated at 0.38 using data from the first and second relative salt tolerance experiments.

The application of fertilizers and saline irrigation water have resulted in increased soil salinity and the removal of large land areas from crop production. One method to overcome the effects of soil salinity is to increase the salt tolerance of crops. The objective of this research was to investigate the physiological, genetic, and agronomic differences between alfalfa (Medicago sativa, L.) bred for increased salt tolerance and salt sensitive alfalfa. The materials used in these studies were the result of five cycles of selection for germination NaCl tolerance, AZST 1978 to 1982, and the source population, 'Mesa-Sirsa'. All salt-tolerant cycles and Mesa-Sirsa were evaluated for ability to germinate in NaCl, NaNO₃, KCl, KNO₃, mannitol and polyethyleneglycol (PEG) solutions ranging from -1.0 to -1.6 MPa of osmotic potential and a control of distilled water. Germination in the lower osmotic potentials of all germination medias was significantly higher with each succeeding cycle of selection for germination NaCl tolerance. Selection for tolerance to NaCl during germination also resulted in increased tolerance to the other salts as well as mannitol and PEG. Germination in mannitol was higher than in any of the salt solutions. This suggests that ion toxicity also inhibits germination. There was no significant difference between Mesa-Sirsa and AZST 1982, the most salt-tolerant cycle, in seed respiration in NaCl solutions or in uptake of tritiated NaCl solution during germination. Broadsense heritability of germination NaCl tolerance was estimated at 49%. All the Arizona Salt Tolerant cycles and Mesa-Sirsa were evaluated for several mature plant characteristics under non-saline field conditions. There were no significant differences among germplasm sources in forage yield, apparent photosynthesis, transpiration, or diffusive resistance. Seedlings of Mesa-Sirsa and AZST 1982 were grown in NaCl solutions ranging from 0 to 18000 ppm NaCl in the greenhouse. The plants were evaluated for several plant growth characteristics to determine whether selection for germination NaCl tolerance resulted in increased salt tolerance at more mature plant growth stages. There was no evidence that germination salt tolerance is related to salt tolerance at later growth stages in alfalfa. Salt tolerance during germination and later growth stages may be controlled by different physiological and genetic mechanisms.

No description available.

Seedlings were grown at five salinity levels in Hoagland's solution for 4 weeks. Transpiration, leaf diffusive resistance, leaf temperature and plant growth of the tomato (Lycopersicon esculentum Mill.) cultivars 'VF 145B' and 'VF 10' were examined at different levels of NaCl ranging from 0 to -12 bars. Salinity-reduced transpiration increased leaf diffusive resistance and increased leaf temperature for both cultivars. Shoot length, root length, shoot and root weight and leaf area were all lower for the two cultivars at increasing salinity levels. However, the two cultivars responded differently to salinity, with VF 10 showing better growth at the control and the -4 bar treatment than VF 145 B. At -9 and -12 bar treatment, the reverse was true. Selection of tomato for salt resistance should not be based on vigorous growth at non-saline conditions because different genes may control the salt tolerance ability of the plants at high salinity levels.

The performance of an alfalfa (Medicago sativa L.) population has been improved by recurrent selection for germination salt tolerance. However, recurrent selection may lead to increased inbreeding. Since alfalfa is subject to severe inbreeding depression, accumulation of inbreeding during the selection process may negatively affect performance. This experiment was designed to determine the effects of inbreeding on germination performance in alfalfa under saline and non-saline conditions. The germination performance of seed having three different levels of inbreeding as examined. No adverse effects of inbreeding were observed in non-saline conditions. Consistent (but nonsignificant) declining trends were observed in germination percentage in saline conditions as the level of inbreeding increased. Proportionately larger declines were observed between generations in germination speed and early seedling vigor. These results suggest heterozygosity in alfalfa may be maintained simultaneously while recurrent selection for germination salt tolerance is conducted. Moreover, reducing inbreeding during recurrent selection for germination salt tolerance may be more successful if germination speed index or early seeding vigor are used for the measurement.

No description available.

NaCl-induced and -repressed cDNA clones had previously been isolated by differential screening of a cDNA library, prepared from poly(A(^+)) RNA isolated from Distichlis spicata (salt grass) cell cultures grown in the presence of 260 mM NaCl (Zhao, et al., 1989). Eight of these cDNA clones have now been subcloned and/or sequenced and the predicted polypeptides compared with owl sequence data base. Three clones pDZ6.2, pDZVIII 1.2.1 and pDZIX 3.1 encode proline rich proteins, containing an amino acid repeat [PPKKDH(H)Y(Y)]. They have similar amino acid usage to proline-rich cell wall proteins, being rich in P, K, H and Y. The first 20 amino acid residues encode a putative leader sequence, supporting the proposed extracellular role as a cell wall protein. This N-terminal sequence (MPLLVALLLVLAVVAAAGAD) shares some similarity with die leader sequence of a soyabean proline-rich cell wall protein precursor and other extracellular proteins (the conserved residues are underlined). There is an increase in abundance of transcripts hybridising to the inserts from pDZ6.2 and pDZVUI 1.2.1 in response to either 520 mM NaCl or 100 µM ABA, but a decrease in response to 5 mM exogenous proline. It is suggested that the corresponding gene(s) are regulated at the level of either transcription or transcript stability, in response to elevated NaCl, with ABA as a mediator of (or part of) tills response. pDZ6.2 and pDZXI 3.1 have identical nucleotide sequences, whilst pDZVni 1.2.1 differs in three base paks within the putative open reading frame, suggesting that there may be at least two members of a multi gene family. A 68 bp OA repeat has been found in the 5' untranslated region of pDZ6.2 and a corresponding transcript identified by northern analysis using this OA sequence as a probe. Such nucleotide repeats can form triplexes (DNA) or hakpin loops (RNA), which is dependent on pH and ionic conditions. Therefore this OA repeat may play a role in the regulation of the gene corresponding to pDZ6.2 at the level of transcription or translation, possibly by attenuation of these processes, either by the formation of triplexes or hah-pins, or the binding of a protein to this GA region, at low ionic strength. However initial in vitro ttanscription experiments, to compare the transcriptional activity of pDZ6.2 and pDZVin 5.1.1 at different ionic strengths, proved inconclusive. An attempt was also made to identify the corresponding genomic region from D. spicata by anchored PGR.A fourth clone pDZ2.8L encodes a histone 2B protein, having 97.9% similarity to a wheat histone 2B. Its transcript abundance decreased in response to either 520 mM NaCl, 5 mM proline or 100 µM ABA. The sequences of the remaining clones either revealed no significant similarity to any known sequences or were assigned as being cloning artefacts .D. spicata cells accumulate proline within eight hours of exposure to 260 mM NaCl (Heyser, et al., 1989b). An unsuccessful attempt was also made to isolate a pyrroline-5- carboxylate reductase gene homologue from D. spicata, by heterologous probing of Southern blots with a soyabean cDNA pProCl and PCR.