Phytochemical screening, GC-MS profiling of invasive cocklebur (Xanthium strumarium)-insect-pathogen interaction and simulated volatile chemical signaling at Northeast China
Authors: Iqbal Mazher Farid , Feng Yu Long 
Published: January 2020

Invasive cocklebur (Xanthium strumarium) is characterized by its excellent genetic and ecological plasticity, ability to spread in agriculture crops. There is a dire need to locate useful management strategies to control this invasive weed at diversified latitudinal gradients. In ecology, there is weak evidence that the damage caused by the natural enemy varies with latitudes. Therefore, we investigated this evidence with the help of transect quadratic ecological sampling method which was conducted randomly at ten different sites of Northeast China. Overall, significantly high infestation of gall-forming insect (Epiblema strenuana) was observed onXanthiumleaves (21.16%) at 41.51279°N, followed by 40.2241°N latitude. Similarly, there was a significantly high abundance ofEpiblemainfestation (7.3) with high damage (3.88%) at 41.51279°N and 40.12749°N latitude. Likewise, the fungal abundance (5.6) of rust i.e.Puccinia xanthii(presenting 16.23% attack) was dominated significantly at 41.51279°N. Hence, high pathogen infection rate (8.97%) was detected at 40.2241°N. On the other hand growth parameters, i.e. plant height (cm), stem diameter (mm) vary with latitude and longitudinal trends. In our experiment, of plant natural enemy interaction provides the evidence-based indication theEpiblemaabundance, was diversified at 41.51279°N, andP. xanthiiinfection was most frequent at 40.22411°N latitudes. This study provides an evidence-based indication that natural enemy pressure varies with latitude, however this investigations gave valuable information that insect and phytopathological fungus having biological control potential againstXanthium strumariuminvasive weed. Secondly, phytochemical qualitative and chemical signaling through Gas Chromatography-mass spectrometry (GC-MS) executed the presence of flavonoids, phenols, saponins, alkaloids, terpenoids, nitrogen (N), sulpher (S), silicon (Si) containing compounds in both treated and controlled leaves that defend againstPuccinia xanthii. Fascinatingly, allX. strumariumpopulations collected from different latitudes possess similar compositions. In interaction mechanism, plant known to omit volatile organic compounds in response to attack of natural herbivores. The leave chemical profiling suggested that the influence of fungus attack on invasive weed brought different changes in chemical infrastructure of leave and these chemicals also play a vital role in the food web. After attack of these biological control agents, plants exhibits passionate compound reprogramming within the leaf naturally that act upon in defense systems.

Author summary

The study was conducted to observe the environmental impact on the trend of insect, invasive weed and pathogens.

There was a significant dominance of gall-forming insect on invasiveXanthiumweed at all locations.

Puccinia xanthiiinfected more than 16% plantation

Plant growth had significant variation at various longitudes and latitudes.

The abundance of insect was positively linked with different environmental factors andXanthiumplant.

The results of GC-MS suggested thatPuccinia xanthiiinfected (treatment) leaves covered maximum area (%) compared to control treatments due to breakdown of the chemical compounds that proved our hypotheses that volatile organic compounds altered infrastructures of the leave chemistry that led to activeness of plant defensive chemicals resulted invasion success.