Study of extremophile plant extracts as botanical herbicides

Weeds are defined as harmful plant pests affecting agriculture worldwide. They cause huge economic losses which can rise up to 34% in major crops by lowering yields and competing with crops for nutrients, light, and water. For these reasons, a great interest has been shown on plant extracts as sources of allelochemicals used for weed management. In this context, our study aimed to assess, for the first time, the herbicidal effect of ten extremophile plant extracts in order to develop botanical herbicides.
Aerial plant materials were grounded and macerated with methanol for 24H. Methanol was then eliminated using a rotavapor. The yield of plant extracts varied between 5.29% and 29.71% following the species. Cynara cardunculus crude extract exhibited the best activity in terms of visual effect after spraying on weeds. Moreover, a formulation was carried out to improve their efficiency. The results showed that formulated C. cardunculus has completely punctured Trifolium incanatum and has inhibited growth of Phalaris minor and Sylibum marianum.
We have observed that C. cardunculus crude extract induced oxidative stress in the treated plants and consequently disturbed the physiological and biochemical functions of the plant cells. A fractionation of C. cardunculus crude extract was then carried out. Five fractions were obtained and tested on T. incanatum. Among these fractions, F2 formulated at 20 g/L showed a very similar effect to a commercial bioherbicide. It caused the total death of T. incanatum 9 days after spraying. Based on bioassay-guided fractionation, five compounds were identified which can be employed in developing new types of bioherbicides for controlling weeds on crops.
The strong weed suppressive ability of F2 formulated therefore offers interesting possibilities as an effective natural environment-friendly approach for weed management. Trials are ongoing in order to optimize the acclimatization and the growth of extremophile plants.