Title: Morphological, biochemical, and molecular characterization of exotic brassica germplasm
Abstract:
Oilseed rape (Brassica napus L.) is an important oilseed crop. We examined the diversity of germplasm expressed at three distinct levels (i.e., morphological, biochemical, and DNA levels). For this study, the Bio resources Conservation Institute provided 150 B. napus L. accessions with three check varieties. During the current study, 7-day-old seedlings of hydroponically grown B. Napus were exposed to different biotic and abiotic stresses including AgNO3, Cinnamic acid, and Pseudomonas syringae under light and dark regimes. The germplasm was grown in field conditions for data collection for 15 quantitative and nine qualitative agro-morphological traits. The fatty acid composition of exotic Brassica napus accessions’ seed oil was evaluated using GC MS to find out the suitability of extracted oils for edibility. GC-MS analysis was carried out for accessions number 24189, 24192, 24250, 24894, 24903, 24907 and three standards i.e. Abasine, Chakwal and Takwara. The result indicated that for 15 quantitative agro-morphological traits, the highest coefficient of variation was recorded for plant height and days to flowering initiation. For nine qualitative traits, most of the accessions have a spatulate leaf, brown color seeds, yellow flowers, and erect silique attitude. The best adoptable genetically diverse exotic Brassica germplasms were selected, i.e., accessions 24178, 24881, 24199, 24214, 24242, and 24192. Based on biochemical analysis for high oil content and high oleic acid content, Chakwal, Sarsoon, and accession 24192 were selected. For high oleic and linoleic acids, accession 24181 performed best, for low erucic acid accessions 24177 and 24195. Based on molecular (SSR) markers, the top 50 selected genotypes were evaluated with 30 SSR markers. The 47 genotypes with three check varieties were clustered in six major groups; the coefficient of similarity ranged between 0.18 and 1.00. Based on SSR data, the germplasms accession 24178 and Abasin were the most diverse genotypes. These genotypes have the capacity and could be used in future breeding programs. High genetic variations were investigated through the SSR among the studied genotypes of Brassica napus L. Almost all accessions showed a similar overall trend for the highest of percentages of saturated long chain long-chain fatty acids, i.e., 1,4- Benzene di carboxylic acid, also known as Palmitic acid (50.65%- 81.33). Oleic acid (range 2.50%-22.82%) and (9E, 11E)- Octadecenoic acid also known as linolenic acid (range of 1%-3.31%) were also detected in all nine accessions. Erucic acid was also present in seven accessions with an abundance range of 1.32%-4.17% although it was not detected in Abasine and Takwara. Similarly, n Hexadecanoic acid was not detected in Abasine, Chakwal, and 24192. 9-Octadecenoic acid was not detected in accession 24192, 24250, 24903, 34907, and Chakwal. Erucic aid content ranged from 1.72% to 4.17% of the total fatty acid composition, with lowest value of 1.72% (<2%) in accession number 24189 making it highly desirable for use in edible oil, although all accessions showed less than 5% erucic acid content making them preferably suitable for industrial purposes. the effect of different concentrations of nutrients was analysed by growing the B. Napus seedlings in 1 X, 0.5 X, 0.25 X of Hoagland solution. It was noted that the roots of dark-grown seedlings exuded remarkably higher quantities of IAA and phenolics as compared to the control. However, under the effect of 200mM cinnamic acid, the growth rate of seedling was improved with the inhibition of secondary metabolites in light condition, while, higher concentration of nutrients (1 X Hoagland solution) positively influenced the release of secondary metabolites by roots. The effect of 200Mm of AgNO3 and P. syringae was adverse on B. Napus as both inhibited the level of overall exudation of flavonoids and phytoalexins in seedlings grown in the dark. Heavy metals and salt stress adversely affected the growth parameters (GP, SL, RL, FW, DW, RWC, VI, RSR, SWR, RWR). While, SSR is a good technique for evaluating intraspecific genetic diversity, it is recommended for future studies that modern techniques may be applied for the investigation of a high level of genetic diversity among brassica and other crop plants
