Effect of plant growth promoting substances from rhizo- and cyano -bacteria on sugar beet growth, yield and yield quality in saline soil

The production of plant growth promotors [indole acetic acid, gibberellic acid and abscissic acid] by rhizobacteria and cyanobacteria has been taken as a main criterion in the selection of the microbial strains used in this study. A field experiment was conducted at Sahl El Hussinia Station, El Sharkia Governorate, during the winter season of 2008/2009 to investigate the effect of rhizobacteria and cyanobacteria either individually or in combination on growth, yield and yield quality of sugar beet under salinity stress. Soil biological activity in terms of dehydrogenase activity was significantly affected by the biological treatments. The dehydrogenase recorded its highest value when the combined inoculum of rhizobacteria and cyanobacteria was applied. Inoculation with rhizobacteria and/or cyanobacteria in saline soil alleviated the salinity effects on the sugar beet and enhanced photosynthesis [leaves chlorophyll content], proline and phenoic accumulation in roots, along with, increasing the concentrations of N, P and K and decreasing Na[+] concentrations in roots. This physiological positive response of the plant growth promoting rhizobacteria and/or cyanobacteria resulted in significant increases in sugar beet root yield and yield quality [TSS, sucrose and purity%]. Best results were obtained by the combined mixture of bacteria and cyanobacteria followed by the individual treatments of either. This investigation pointed out that plant growth promoting substances secreted by rhizobacteria [PGPR] and cyanobacteria could be used as a good tool to alleviate salinity stress and promote sugar beet productivity and yield quality as it provides an ceo-friendly biological approach under saline soil conditions

Influence of beneficial microbes and proline treatments on sugar beet under nitrogen limitation in saline-sodic soil

A field experiment on sugar beet [Beta vulgaris L.] yield and yield quality under saline-sodic soil conditions was conducted at Sahl El Hussinia Res. Station, El Sharkia Governorate, Egypt, during the winter season of 2008/2009. The influence of cyanobacteria and N[2]-fixing bacteria were compared either individually or in combination to supplementation with proline amino acid under two levels of mineral nitrogen fertilization [50 and 75% of nitrogen recommended dose]. Soil enzymatic activities [dehydrogenase and nitrogenase], total bacterial counts, total cyanobacteria counts and total nitrogen fixing bacteria counts were enhanced by the biofertilizers compared to proline treatment and controls, particularly when the combined inoculum of cyanobacteria and N[2]-fixing bacteria was applied in the presence of 75% N. In addition, inoculation with cyanobacteria and N[2]-fixing bacteria, either individually or in combination with 75%N, led to a slight decrease of pH and EC values of saline soil, while there was an increase in the availability of NPK as compared with control plots. Proline and biofertilizers showed a significant positive impact on some physiological properties of plants drown at 75% nitrogen level, such as chlorophyll in leaves, proline and phenolic compounds in roots. The highest responses for these traits were in proline-treated plots followed by the combined inoculation of cyanobacteria and N[2] fixing bacteria, while, there was no significant difference in root yield productivity between proline treatment and the combined inoculum of cyanobacteria and N[2] fixing bacteria with 75% nitrogen fertilizer. The combined inoculation positively increased N, P and K uptake and decreased the uptake of Na in roots. Also, the combined inoculum of cyanobacteria and N[2] fixing bacteria with 75% nitrogen led to a significant increase in shoot and root dry weight as well as root yield quality [sucrose and purity]. Results suggest that the beneficial effect of the cyanobacteria and N[2] fixing bacteria on sugar beet growth, yield and yield quality was attributed to the biologically active substances produced by these microbial strains besides the nitrogen fixation of the diazotrophs which compensate the reduction of the costly and the environmentally polluted mineral nitrogen fertilizers in the new reclaimed saline-sodic soil