Abstract

The study was conducted to determine the morphological, physiological and genetic variability in soybean varieties as influenced by fertilizer application. Sixteen (16) varieties of soybean: NCRI Soy 16, TGX 1831-32F, TGX 1921-4F, TGX 1485-ID, TGX 1908-3F, TGX 1835-IE, TGX 1987-62F, NCRI Soy 8, TGX 1956-IF, TGX 1802-IF, TGX 1448-2F, TGX 1844-4E, TGX 1885-8F, CAMEROON LATE and TGX 1923-2E. Two (2) fertilizer rates (0 and 300 kgN/ha) of NPK 15-15-15 fertilizer were used for the study.;The study was a 2 x 16 factorial experiment laid in a randomized complete block design (RCBD). The experimental field measured 63 x 7.4 m consisting of 96 plots of 3 x 1.8 m each. 1 m space was giving between plots. Soil samples were collected from these experimental plots for pre planting soil analysis. Data on morphological, physiological and genetic parameters were collected from the soybean varieties. Data were subjected to analysis of variance (ANOVA), correlation, regression and cluster analyses. From the results, Plant height varied significantly with soybean variety and ranged from 8.81 in NCRI SOY 8, to 13.39 in TGX 1923 - 2E at 3WAP. At 3WAP, the stem girth ranged from 0.018 in TGX 1440- IE to 0.088 in TGX 1831 -32F. At 5WAP, leaf length ranged from 7.13 cm in TGX 1844 - 4E to 13.16 cm in TGX 1923 - 2E. Leaf length of TGX 1923 - 2E was significantly (P < 0.05) longer than those; of other varieties at 5WAP. At 7WAP, stem girth ofsoybean varieties ranged from 0.137 ciii in TGX 1485 - ID to 0.333 cm in CAMEROON LATE and TGX 1923 - 2E. Number of leaves per plant differed significantly with soybean variety at 7WAP. CAMEROON LATE followed by TGX 1923 - 2E was significantly leafier compared to other varieties at 7WAP. Leaf area index (LAI) of the varying soybean varieties ranged from 4.91 in TGX 1831 - 32F to 11.04 in TGX 1921 - 4F at 9WAP. All the parameters assessed increased significantly (P< 0.05) with increase in sampling date. At harvest, dry matter of soybean varieties ranged from 6.54 in TGX 1831 - 32F to 17.20 in TGX 1844 - 4E. The number of pods per soybean plant differed significantly (P<0.05) and ranged from a mean of 183 in TGX 1835 - IE to 53 in CAMEROON LATE. Eleven varieties had seed numbers that were lower than that ofCAMEROON LATE while four others had seed number that were not statistically different from that of CAMEROON LATE. Carbohydrate content ranged from 20.04 in TGX 1440 - IE to 25.22 in NCRI SOY 16. Protein contents ranged from 39.67 % in TGX 1923 - 2E to 36.63 % in CAMEROON LATE. Protein content of TGX 1923 - 2E was significantly higher than those of other varieties. Soybean varieties differed significantly (P<0.05) in the amount of mineral (calcium, potassium, magnesium, sodium and phosphorus) and phytochemical contents of the seeds. Chlorophyll a content of soybean ranged from 6.79 ug/g in NCRI SOY 8 to 11.42 ug/g in TGX 1921 - 4F. Total nitrogen ranged from 2.18 % in TGX 1448 - 2F to 3.45 % in TGX 1921 - 4F. There were significant differences (P<0.05) in DNA contents of soybean varieties ranging from 230.5 n/mcl in TGX 1485 -ID to 247.5 n/mcl in TGX 1923 -2E. DNA content of TGX 1923 -2E was significantly higher (P<0.05) than those of other varieties. In RAPD analysis, CAMEROON LATE and TGX 1923 - 2E are more closely related. Also, there was a clear distinction between NCRI soy 8 and TGX 1440 - IE and other varieties using RAPD analysis. The most genetically distant genotype was TGX 1440 - IE with similarity index of 67 %. The combination of RAPD and SSR markers indicated that CAMEROON LATE and TGX 1923 are more closely related than other varieties (similarity index 91 %). This result is similar to the RAPD marker analysis. This finding demonstrated the usefulness of both marker systems in accessing diversity and relatedness among glycine max gene pool; recommended the two markers system as accurate methods in determining genetic differences in soybean varieties.