Phosphate solubilization potentials of soil Acinetobacter strains

Many phosphate solubilizing microorganisms (PSM) require external pyrroloquinoline quinone (PQQ) for strong phosphorus (P) solubilization in vitro. The objective of this study was to isolate efficient and PQQ-independent PSM. A total of 21 PSM were isolated from the rhizosphere soil of wheat and maize grown in the pots. Acinetobacter strains were the only PQQ-independent and most effective solubilizers of tricalcium phosphate containing agar. The mean P dissolved in liquid cultures of Acinetobacter strains in a 5-day incubation ranged from 167 to 888 μg/ml P. The pH dropped to below 4.7 from 7.8 in six isolates, which produced gluconic acid in concentrations ranging between 27.5 and 37.5 mM. There was a linear regression between soluble P and gluconic acid concentrations in the bacterial cultures (P < 0.05; R ² = 0.59). Inoculation with Acinetobacter sp. WR922 significantly (P < 0.05) increased wheat (Triticum aestivum L.) P content by 27% at 15 days after emergence (DAE) and dry matter by 15% at 30 DAE compared to the control. The plant P content in inoculated plants at 30 DAE was linearly correlated with soluble P of the bacterial cultures (P < 0.05; R ² = 0.69). Gluconic acid production directly affected phosphate solubilization in vitro, which in turn influenced plant P content of inoculated plants in PQQ-independent P-solubilizing Acinetobacter strains.     

Evaluation of dietary protein and lipid requirements of two-banded seabream (Diplodus vulgaris) cultured in a recirculating aquaculture system

The objective of this study is to investigate the effects of dietary protein and lipid levels on the growth performance and bioeconomic benefits of two-banded seabream (Diplodus vulgaris) juveniles, a candidate species for aquaculture sector. Eight experimental diets were formulated with four protein (50, 45, 40 and 35 %) levels for each of the two lipid levels (15 and 10 %). Triplicate groups of juvenile fish with an average initial body weight of ~3.64 g were reared in a recirculating aquaculture system and hand fed twice a day until satiation for a period of 60 days. In the experiment, no difference in survival rate was found between the different groups. Relative growth rate (RGR), specific growth rate (SGR), feed conversion ratio (FCR) and daily feed intake were not significantly affected by increasing protein and/or lipid treatments in this present study. However, the RGR, SGR and FCR values showed slightly better efficiency in the experimental group (35/15) fed with lower protein content (35 %) and higher lipid level (15 %) compared with those fed other diets. According to bioeconomic analyses results, the diet with the 35 % protein and 15 % lipid generated the best profit. The results suggest that two-banded seabream can be accepted as a promising alternative species for the aquaculture industry and optimum growth of two-banded seabream fingerlings can be obtained when they are fed a diet containing 35 % crude protein and 15 % crude lipid.     

Genetic variability among Turkish pop, flint and dent corn (Zea mays L. spp. mays) races: Morphological and agronomic traits

32 Turkish corn accessions representing different climatic, geographic and topographic areas in Turkey were identified. Genetic variation and its pattern in three corn races (pop, flint and dent) included 32 accessions were investigated using 25 morphological and agronomic traits. Vegetative, ear and kernel related traits were significantly varied both among races and accessions within races. Variance component due to races and accessions within race were statistically significant, but the variance components due to accessions were generally made up large component of total variance and ranged from 17.17% in kernel length to 82.75% in tassel length. There were also strong and mostly positive correlations between studied agronomic traits as well as between agronomic traits and isoenzyme loci. These correlations were explained by the traditional farming practices and enzyme specificity with flint accessions since the enzyme systems such as Alcohol dehydrogenase (locus 1), Malate dehydrogenase enzyme (loci 2–3) and 6-phospho-gluconate dehydrogenase (locus-1) are generally considered to be the characteristics of flint corn race. Canonical discriminant function analysis with twenty-five morphological and agronomic traits revealed that first two canonical discriminant variables explained 68% of total variation among accessions. Two Canonical variables, in which kernel related traits were heavily weighted, correctly classify the three corn races – indicating that Turkish corn accessions maintained their racial characteristics with agronomic and morphological traits. This revised version was published online in August 2006 with corrections to the Cover Date.