Investigation the effects of effective microorganisms (EM) and humic acid application on some morphophysiological and biochemical characteristics in almond (Prunus dulcis Mill.) rootstocks under salinity stress conditions.

Hatami, Elnaz (2019) Investigation the effects of effective microorganisms (EM) and humic acid application on some morphophysiological and biochemical characteristics in almond (Prunus dulcis Mill.) rootstocks under salinity stress conditions. Doctoral thesis, University of Mohaghegh Ardabili.

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Abstract

Research aim:Salinity is one of the increasing problems in the world and it covers a large part of our country, so identifying efficient adaptation methods against abiotic stresses is a major challenge. Having complete information about morphophysiological and biochemical indicators can be an important criterion for isolating salinity resistant plants. In order to select new salinity resistant strains and to identify the morphophysiological and biochemical markers associated with these conditions, the effect of different levels of salinity and effective microorganisms and humic acid treatments on these indices of two-year seedlings of 2 hybrids almond and a seedling rootstocks were evaluated at the Faculty of Agriculture, Department of Horticulture of the University of Mohaghegh Ardebili during 2014-15. Research method: a pot experiment was carried out in two independent designs on two bio-fertilizers, as a factorial based on a RCBD design with 3 replications. First two-year seedlings of two hybrids of peach and almond (GF677 and GN15) and seedling almond rootstocks were divided into two groups. The first group were treated with effective microorganisms concentrations contains EM0: control, EM1: 10 ml per liter, EM2: 20 ml per liter and EM3: 30 ml per liter and the second group were treated with humic acid concentrations contains HA0: control, HA1: 2.5 kg ha-1, HA2: 5 kg ha-1 and HA3: 7 kg ha-1. These bio-fertilizers were applied for 60 days, once a week, with irrigation water and soil application on the rootstocks. From the beginning of July, for 60 days, the pots were irrigated with different levels of NaCl (S0: control, S1: 60 mM NaCl, S2: 120 mM NaCl and S3: 180 mM NaCl) once each 2 days. In order to evaluate these conditions, on the studied almond rootstocks, main stem length growth, number of stems, stem diametergrowth, number of leaves, viability percentage, specific leaf area, root volume, root dry weight / stem dry weight ratio, proline, soluble carbohydrates, starch, protein, peroxidase and catalase enzymes activity, chlorophyll a, b and total chlorophyll, electrolyte leakage, relative water content of leaves, leaf water potential, nutrient elements such as sodium, chlorine, potassium, calcium, nitrogen and potassium / sodium ratio of leaf and root, stomatal conductivity, photosynthesis rate, transpiration and leaf stomatal index traits, were measured. Findings: Analysis of variance of data showed that the effect of year and its interactions with salinity and EM treatment on main stem length growth, root volume, root dry weight / stem dry weight ratio, proline, leafcalciumand electrolyte leakage and in the treatment of humic acid on specific leaf area, root chloride, leaf and root potassium, root nitrogen and the rootpotassium / sodiumratio, stomatal conductivity, photosynthesis rate and leaf transpiration were statistically significant. The simple effects of treatments in all studied traits except the effect of humic acid on stem number, trunk diameter, root volume and leaf starch content were statistically significant. The interactions between treatments were statistically significant, and only the tripleeffects of rootstock, humic acid and salinity on stem number, trunk diameter and leaf starch were not statistically significant.The results showed that the growth factors were decreased with increasing stress in all three studied rootstocks, but the GF677 and seedlings almond had higher growth and viability characteristics and growth reducing was low in these. The amount of proline, electrolyte leakage, peroxidase and catalase enzymes activity, sodium chloride and leaf chlorophyll and root and leaf stomatal index increased with increasing salinity stress in all three tested rootstocks, but the GF677 and seedling rootstock had the lowest proline content, electrolyte leakage, sodium and chloride in leaf and root and stomatal index and highest activity of antioxidant enzymes. With increasing salt stress levels, chlorophyll a, b and total chlorophyll content, leaf relative water content, leaf water potential, potassium concentration, calcium, nitrogen and potassium / sodium ratio of leaves and roots, decreased in all three rootstocksbut these indices were higher in the GF677 and seedling almond.The amount of soluble carbohydrates in the test for effective microorganisms increased up to 60 mM NaCl and in the test for humic acid up to 120 mM NaCl increased and then decreased and the highest level was related to the GF677 and seedling almond. The amount of leaf starch in the test for effective microorganisms decreased to the same level of salinity and then increased and the highest level was related to the GN15. In the experiments of effective microorganisms, stomatal conductivity and transpiration increased up to 120 mM NaCl and photosynthesis rate increased up to 60 mM NaCland then decreased and highest of these indices were related to the GF677. However, in the humic acid biofertilizer experiment, the rate of these three photosynthetic indexes decreased with increasing salinity stress in each of the three studied rootstocks, especially in the GN15.By increasing the concentration of effective microorganisms treatment up to 30 ml per liter and humic acid treatment up to 2.5 and 5 kg ha-1, all morphophysiologicaland biochemical indices were improvedin all three rootstocks under salinity, especially at the GF677. So, vegetative indices, soluble carbohydrates, protein, activity of catalase and peroxidase enzymes, chlorophyll a, b and total chlorophyll, potassium, calcium, nitrogen concentrationand potassium / sodium ratio of leaves and roots, relative water content of leaves, leaf water potential, stomatal conductivity, photosynthesis rate and leaf transpiration were increased compared to the control and the amount of starch, electrolyte leakage, sodium and chloride concentration in leaves and roots and leaf stomatal index decreased compared to the control. The amount of proline was reduced by the application of effective microorganisms biofertilizer but the application of humic acid biofertilizer failed to reduce the upward trend of proline synthesis and increased the amount of this amino acid by increasing the level of humic acid. Conclusion:Among the traits tested, the specific leaf area, root volume, root dry weight / stem dry weight ratio, protein, peroxidase and catalase enzymes activity, leaf nitrogen, potassium / sodium content, electrolyte leakage, leaf water potential and stomatal conductivity were good markers to study salinity tolerance of almond rootstocks. Application of biofertilizers improved all studied indices in each of the three studied rootstocks and the best result in the effective microorganisms expriment was related to the GF677, the level of 30ml per liter of effective micronutrients and 0 mM of salinity. The best result in the humic acidexpriment was obtained from the combination of GF677, 2.5 and 5 kg ha-1 of humic acid and 0 mMof salinity. Based on this, the GF677 hybrid was tolerant to salt stress conditionsandseedling almond and GN15 were placed in the next positions, respectively.

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