الفهرس 
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Abstract
Amr Ramadan Hussein Hassan: Biochemical Studies on Symbiosis between Plant and Mycorrhiza under Stress Conditions. Unpublished Ph.D. Thesis, Department of Agricultural Biochemistry, Faculty of Agriculture, Ain Shams University, 2016.
Salinity in soil and water is one of the major stresses which limit the crop production. Mycorrhization is one of the suggested means for stress alleviation. Because tomato (Solanum lycopersicum L.) is an important crop and is moderately sensitive to salinity, the present studies evaluate the effect of mycorrhizal symbiosis on tomato under salinity stress.
Cultivated tomato (Solanum lycopersicum L. cvs Castle Rock (CR) and Super Strain-B (SS) were grown in a pot experiment under greenhouse conditions to evaluate the mycorrhizal benefits under sterilized soil and salt stress and variable phosphorus concentration . Tomato seeds were sown in inoculated or not inoculated sterilized soil mixture with spores of the fungus Glomus intraradices and grown in nursery for 4 weeks, and grown under sodium chloride doses corresponding to 0, 50, and 100 mM NaCl, as well as phosphorus treatment levels at (0.2, 0.4, and 0.8 mM P). Fresh weight and dry weight were recorded at eight-week growth stage, along with electrolyte leakage test, and biochemical determination of photosynthetic pigments, proline, superoxide dismutase activity and mineral contents in leaves. Additionally, total fruit yield was recorded. Results showed that increasing phosphorus concentration positively contributed in photosynthe-tic pigments content with tendency to decrease proline, SOD and electroly-te leakage in both cultivars. Salt stress affects severely both tomato cultivars in terms fresh and dry weights reductions which were accompanied by increases in electrolyte leakage percentage, free proline and sodium contents and decreases in potassium contents. Also, salt stress negatively affects fruit yield in both cultivars. The studied tomato cultivars responded differentially to mycorrhizal inoculation. Mycorrhizal inoculation, in SS plants, counteracted salinity damage through positively effects on fresh and dry weights, as well as fruit yield, with improved K and Ca content and tendency to increase proline and SOD activity, and decrease Na and electrolyte leakage. Mycorrhizal CR plants showed decreases in shoot fresh weight, dry weights, photosynthetic pigments, electrolyte leakage, and sodium content, and increase in potassium content. Decreases in leaves sodium content and electrolyte leakage with increased potassium in inoculated CR plants might be helpful means to yield more fruit weight, compared to non-inoculated ones. It was clear that SS cultivar was more mycorrhizal dependent than CR cultivar with greater correlation with growth and fruit yield. Also, beneficial effects of mycorrhizal inoculation against salt stress were notable at 50 mM NaCl, rather than 100 mM NaCl.
In a field experiment conducted under dominant conditions of Ras Sedr, South Sinai, the two tomato cultivars were inoculated in nursery with either or both of mycorrhizal inoculum and Biovet , a plant growth-promoting rhizobacteria PGPR source, in addition to non-inoculated plants as control. Inoculated and non-inoculated seedlings were transplanted in Ras Sedr experimental research station, South Sinai, and irrigated with available underground water during growing and fruiting stages until harvested. Plants were sampled 30 days after transplanting for growth records and biochemical analysis, and at the end of the growing season for yield and fruit quality traits.
Results of the field experiment showed that Biovit single inoculation significantly improved growth and chlorophyll content of inoculated plants, compared to non-inoculated, in both cultivars. Also, Biovit single inoculation enhanced the activity of SOD-1 isoform in both cultivars, while dual inoculation stimulated SOD-1 in SS cultivar only. fruit yield of bioinoculated plants were significantly lower than untreated ones. It could be suggested that rhizosphere prolonged exposure to salinity may result in failure of the used bioinoculants to mitigate salt injury, because of effects on the used microorganisms and/or the limited tomato plants adaptability to such high levels of salinity. Single Biovit inoculation increased tomato fruit total acidity, total soluble solids, and radical scavenging capacity in CR cultivar, whereas increases in SS were not significant. Mycorrhizal inoculation increased lycopene and ascorbic acid content in fruits of both cultivars, while negatively affected radical scavenging capacity and carbohydrate content in fruits of both cultivars. It could be recommended that using mycorrhizal and/or Biovit inoculants under moderate salinity would improve production and fruit quality characteristics.
Key words: salt stress, tomato, mycorrhiza, electrolyte leakage, proline, photosynthetic pigments, SOD, mineral nutrients, antioxidative capacity.