In agricultural field, biological control is being used to overcome pests and use of chemicals is being discouraged. Biological invasion has gained a lot of attention of experts in recent decades. The spread of invasive alien pests has caused serious economic losses, ecological and environmental troubles and biodiversity losses as well as they exhibit dangerous impacts human health and safety1. Therefore, development of management to overcome the allelopathic and competitive effects of invasive alien species has become a major goal of scientists.
Mikania micrantha (Asteraceae) is a perennial herb and native to Central and South America2. The vine has been reported among the top 100 worst invasive species and as one of the top 10 worst weeds in the world3. Its habitat includes broad range of farming systems and forest lands, banks of streams and rivers, roadsides and railway tracks2. M. micrantha has caused serious economic damage, less output, biodiversity loss and negative environmental impacts4.
To control and manage these serious outcomes researchers are investigating a crop (sweet potato) to check its potential against threatening vine. Sweet potato (Ipomoea batatas) is a viatl locally grown cash crop native to the American tropics. It was studied to inhibit M. micrantha growth in Yunnan (Province in China). These experiments were performed in sweet potato fields where M. micrantha occurred5.
The allelopathic effects of water extracts and soil incorporation from leaves of three sweet potato cultivars (SP1, SP0 and SP9) on the sprout seedling growth of M. micrantha were investigated under laboratory and greenhouse circumstances. Researchers found that sweet potato exhibited greater competitive ability than M. micrantha. M. micrantha significantly suppressed plant height, branch, leaf, stem node, adventitious root and biomass of this weed.In addition, sweet potato also demonstrated higher levels of nutrient uptake than M. micrantha6. Moreover, the number, biomass, length, set rate, germination of seeds, sexual and asexual seedling populations and mortality of M. micrantha were significantly suppressed by sweet potato competition7.
Among three cultivars, SP1 had the strongest inhibition effect and the next highest impact was from SP0 and SP9 exhibited the lowest effect. The best control was observed for root biomass, followed by total biomass, whereas; the lowest impact was on aboveground biomass. The strong correspondence between results for both leaf water extracts and leaf soil incorporation demonstrated that compounds produced by sweet potato have allelopathic effects on M. micrantha.8 Moreover, the synthetical allelopathic indices of leaf soil incorporation of three cultivars on M. micrantha were generally higher as compared to leaf water extracts. Therefore, it can be claimed that synergism has the huge potential between competition and allelopathy which can be used to reduce weed infestations.
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26 May, 2019