Abstract:
The productivity of major field crops is highly compromised due to weed infestation.
Inefficient weed management practices and undue and excessive use of chemical
herbicides have drastically contaminated the environment and human health, in addition
to resistance development in weed species. Therefore, utilization of allelopathic plants
to explore phytochemicals as potent organic alternatives to such chemical herbicides
has become indispensable. The current study evaluates the comparative bio-herbicidal
potential of methanolic extracts of castor (Ricinus communis), artemisia Qrtemisia
santolinifolia), wheat (Triticum aestivum), and sorghum (Sorghum bicolor) to suppress
growth of major weeds, i.e., wild mustard (Sinapic arvensis), Italian ryegrass (Lolium
multiflorum), and carrot grass (Parthenlum hysterophorus). The results demonstrated
a concentration-dependent effect on weeds' growth. Overall, in vitro seed germination
was reduced from 60 to 100% in response to 5% (w/v) extract concentration. Significant
reduction in radicle length, hypocotyl length, and fresh biomass of the weeds was also
observed.A strong inhibitory effect was seen in in vivo pot experiments, revealing that
application of 10—20% methanolic extracts induced permanent wilting and substantial
reduction in the chlorophyll content of weeds along with 20—80% increase in oxidative
stress. Artemisia showed themost significant allelopathic effect, on account of highest
phenolic and flavonoid contents, followed by castor, wheat, and sorghum, against
S. arvensis, L. multiflorum, and P. hysterophorus, respectively. Phytochemical analysis,
through high-performance liquid chromatography (HPLC), also exhibiteda correlation
between extract's phytotoxicity and their antioxidant potential due to their major
constituents (rutin, quercetin, catechin, gallic acid, vanillic acid, syringic acid, ferulic
acid, p-hydroxy benzoic acid, p-coumaric acid, and sinapic acid), among thetotal of
13 identified in methanolic fractions. Comprehensive profiling of allelochemicals with liquid chromatography—mass spectrometry (LC-MS) determined 120, 113, 90, and 50
derivates of phenolic acids, flavonoids, and alkaloids, reported for the first time through
this study, demonstrating significant allelopathic potential of the targeted plant fractions,
which can be explored further to developa sustainable bio-herbicidal formulation.
