Improve the quality of two cultivars of bean (Phaseolus vulgaris L.) with using Phosphate and Zinc biofertilizers

Introduction Bean (Phaseolus vulgaris L.) is one of the richest seeds in legumes. It has special importance in the diet because it contains 20-25 percent protein, 60 percent carbohydrates, vitamins, dietary fiber, antioxidants, trace minerals and amino acids containing Zinc (Zn) and Iron (Fe). Mycorrhizal fungi and plant growth promoting rhizobacteria (PGPR) such as Azotobacter spp., and Pseudomonas spp. are able to increase uptake of nutrient elements particularly when they are applied with others. P solubilizing fungus and bacteria facilitate uptake of slowly diffusing nutrient ions such as phosphorus (P), Zn, Fe and increase their availability usually by increasing volume of soil exploited by plants, spreading external mycelium, secreting organic acids, production of dehydrogenase and phosphates enzymes and reducing rhizosphere acidity. Despite the high nutritional value of bean, it contains some antinutritional factors that caused to decrease this nutritional value with reducing the digestion and absorption of protein, minerals and trace elements. The main is phytic acid (PA), phenolic acid, tannin and trypsin inhibitors. PA has the ability to form bonds with divalent cations such as Fe, Zn, calcium (Ca) and magnesium (Mg). The high chelating capacity of PA reduces strongly availability of these elements and causes disturbances in the human gastrointestinal system. PA, phenolic compounds, tannin, and trypsin inhibitors can form bond with protein, fiber, carbohydrates, polysaccharides and other macromolecules and hence reduce enzyme activities, absorption and digestion of proteins and minerals. The main objective of this farm study was to evaluate the effect of P and Zn bio-fertilizers on decrease of antinutritional factors and improve seed quality in two cultivars of bean in Chaharmahal-va- Bakhtiari province. Material & Methods This field experiment was carried out as a factorial based on a randomized complete block design (RCBD) with three replications. The treatments of this research consisted of two cultivars of Chiti bean (Talash and Sadri), four levels of P (P0: Control, P1: Chemical fertilizer on the basis of soil test, P2: 50 percent of recommended P + bio-fertilizer (P), and P3: bio-fertilizer (P)), three levels of Zn (Zn0: Control, Zn1: 50 kg ha-1 Zinc sulphate, and Zn3: bio-fertilizer (Zn)). Bio-fertilizer (P) treatment consisted of using inoculum of P solubilizing bacteria from Azotobacter chroococcum strain 5 and three species of mycorrhizal fungi from Glomus species (Glomus etunicatum, Glomus intraradices and Glomus mosseae). Bio-fertilizer (Zn) treatment consisted of using inoculum of Pseudomonas aeruginosa strain MPFM and Pseudomonas fluorescent strain 187. Grain inoculation (5%) was done in shadow and after drying, inoculated grains were immediately cultivated. Two g of mycorrhizal fungus was applied under the grain hole just prior to sowing. Chemical fertilizers were applied from TSP at a rate of 100 and 50 kg ha-1 in P1 and P2 respectively, 50 kg ha-1 ZnSO4.7H2O in Zn1. After harvesting, seeds were prepared to measure antinutritional factors after grounding and passing from 60 mesh sieve. Phytic acid was measured by Haug and Lantzsch (1983), phenolic acid and Tannin by Makkar et al. (1993) and trypsin inhibitors by Kakade et al. (1974). Statistical analysis was done with SAS statistical software. Duncan’s multiple range test was used to compare means. Results & Discussion The results revealed that there were not significant difference between two cultivars on studying factors. The least of these characteristics except of phytic acid (PA) were obtained from Sadri cultivar. The effect of P treatment was significant on studying parameters, in a way P2 treatment in comparison with control treatment caused to decrease PA (11.5%), phenolic acid (35%), Tannin (38%) and trypsin inhibitors (25%). The effect of Zn treatment was also significant on studying parameters. The minimum of studying factors were obtained from Zn1 and Zn2 treatments. The effect of interaction between P and Zn was significant on these anti-nutritional factors except the trypsin inhibitors. The least rate of PA, phenolic acid, tannin were obtained 3.90 g kg-1, 3.13 and 2.45 mg GAE g-1 sample respectively from P2Zn1 and the rate of trypsin inhibitor 4.70 mg TI g-1 sample from P2Zn2. In this study, the dual inoculation with phosphate and Zn bio-fertilizers caused to increase nutrient uptake and improve in seed enrichment especially nutrients with antioxidant capacity such as Zn and Fe. It can be done with increasing mycorrhizal symbiosis, root colonization phytosiderophores secretion, organic acids and chelated compounds production. Our results were similar to findings of other researches. Reducing in antinutritional factors related to production of enriched seeds with using phosphate and Zn bio-fertilizers. Conclusion The results of this research revealed that individual and dual using of phosphate and Zn bio-fertilizers caused to decrease antinutritional factors in two studied cultivars of bean. Microorganisms used in biological treatments caused to increase the availability and uptake of nutrient elements such as N, P, Fe and Zn. It can be done with increasing mycorrhizal symbiosis, root colonization and enhance secretion of siderophore compounds, organic acids and chelate compounds. Also, plant hormones and enzymes promoting growth increased with using of these bio treatments. Application of bio-fertilizers in this study caused to decrease antinutritional factors in both cultivars with increase of growth and nutrient uptake and seed bioenrichment with iron (Fe) and Zn Seed bio-enrichment with Fe, Zn and other nutrients caused to indirectly decrease in PA and other antinutritional factors. In this research, the best treatment was using of mycorrhizal fungi with Azotobacter inoculant and 50 kg ha-1 TSP and 50 kg ha-1 ZnSO4.7H2O, (P2Zn1 treatment).