Effects of Drought Stress and Bio-fertilizer Inoculation on Quantitative and Qualitative Characteristics of Marian Thistle (Silybum marianum L.)

IntroductionMarian thistle (Silybum marianum L.) is a medicinal, herbaceous and annuals plant belongs to the Asteraceae family which is used to treat liver disease. The essential oil of Marian thistle seeds is the type of flavonolignans (phenols family) that forms 1.5 to 3% of its seeds weight. The important flavonoids found in the seeds of this plant are silybin, silychristin and silydianin is known as silymarin compounds, that is yellow. Increasing the desired compounds of medicinal plants is possible by cultivation techniques manipulation such as irrigation, fertilization or photo-bioreactor systems. Water deficient is the most important factors limiting the growth and yield of medicinal crops, especially in arid and semi-arid regions. Bio-fertilizers as an alternative in some cases and in most cases as a complement to chemical fertilizers can help to ensure the sustainability of agricultural production systems. Han et al. (2006) in the study of the effect of phosphate solubilizing bacteria (PSB), Bacillus megaterium var. phosphaticum and potassium solubilizing bacteria (KSB), Bacillus mucilaginosus in nutrient limited soil planted with pepper and cucumber stated that Rock P and K applied either singly or in combination did not significantly enhance soil availability of P and K. PSB was a more potent P-solubilizer than KSB, and co-inoculation of PSB and KSB resulted in consistently higher P and K availability than in the control. Rock P with inoculation of PSB increased the availability of P and K, the uptake of N, P and K by shoots and roots, and the growth of both pepper and cucumber. Similar but less pronounced results were obtained when rock K and KSB were added concomitantly. Combined together, rock materials and both bacterial strains consistently increased further mineral availability, uptake and plant growth, suggesting their potential use as fertilizer. The present study was designed to evaluate the effect of bio-fertilizers inoculation and drought stress on quantitative and qualitative characteristics of Marian thistle.
Materials and methodsThis experiment was conducted in a split plot based on randomized complete block design with three replications, at the Research Farm of Zabol University, during growing season of 2012 and 2013. Main plots consisted of irrigation with 50, 70 and 90% field capacity and subplots including plant nutrition with nitroxin, supernitroplus, rich phosphate II, mycorrhiza and non-use of bio-fertilizer. Plant traits such as seed yield (kg.ha-1), the number of capitols per plant, the number of seeds per capitol, 1000-seed weight (g.plant-1), essential oil percentage, plant organic matter percentage, proline percentage and protein percentage of Marian thistle were measured. For statistical analysis, analysis of variance (ANOVA), Duncan’s multiple range test (DMRT) and simple correlation analysis were performed using SAS version 9.2 (SAS Institute Inc., Cary, NC, USA).
Results and discussionIn this experiment, the effects of drought stress, bio-fertilizer and their interactions on all studied traits were significant at the 1% probability level. The highest grain yield (1300.00 kg), the number of capitols per plant (12.00 no.), 1000-seed weight (23.27g), plant organic matter percentage (95.00%) and protein percentage (17.19%) belong to treatment of irrigation with 90% field capacity and nitroxin bio-fertilizer. The maximum number of seeds per capitol (87.67) were obtained by irrigation with 90% field capacity and mycorrhiza bio-fertilizer. Irrigation with 70 and 90% field capacity and nitroxin bio-fertilizer application were explained the maximum and minimum of essential oil percentage (3.72%) and proline percentage (0.04%), respectively. The number of capitols per plant was the most important component in determining grain yield. The use of bio-fertilizers damped the effect of drought stress and improved qualitative and quantitative characteristics of Marian thistle.
ConclusionInoculation with nitroxin bio-fertilizer compared to the others could further amend drought stress and improved the quantitative and qualitative characteristics of Marian thistle. Thus, it appears that in order to achieve sustainable agriculture instead of chemical fertilizers is recommended.