Bio-organic fertilizer decreased strigol release, improved microbial community and reduced Orobanche cumana parasitism
Parasitic plants are globally present in diverse ecological habitats. The application of bio-organic fertilizer has been observed to enrich the rhizosphere microbial communities, thereby fostering improved crop productivity and quality. However, the influence of bio-organic fertilizers on Orobanche cumana Wallr., remains inadequately understood. The study aimed to investigate the relationship between the host rhizosphere microbial community and parasitism quantity in sunflower rhizosphere soil collected under different parasitism degrees of O. cumana. Additionally, the inhibitory effect of bio-organic fertilizers on O. cumana and the changes in micro-ecological mechanisms through potting and field experiments were explored. The results showed that the composition of rhizosphere bacterial community changed significantly with the increase of parasite number. In contrast, the fungal community did not change significantly when the number of parasites reached a threshold level. Through the co-occurrence network study, the parasitism of O. cumana led to the enrichment of Plectosphaerella, and the strain was a significant positively correlated with the number of parasites. Notably, the application of bio-organic fertilizers led to a substantial decrease in strigol synthesis and the parasitic infestation in O. cumana. Bio-organic fertilizers application significantly promoted the expression of Mn-SOD, GST, XTH9, ACC01 and NPR1 genes associated with plant resistance, and significantly increased the levels of the fruit ripening-related hormones ACC and tZTR. The application of bio-organic fertilizers resulted in a notable enhancement of the yield and crude protein content of sunflower grains. Additionally, the utilisation of bio-organic fertilizers led to a significant reduction in the abundance of potential pathogenic fungus Plectosphaerella in the field, while simultaneously increasing the abundance of potential beneficial fungus Chaetomium. Following the application of bio-organic fertilizers, the roots of O. cumana were found to be attached to fungi that could cause its decay. The isolated strain Fusarium solani L5 was observed to significantly reduce the number of O. cumana parasites. In summary, Streptomyces rochei D74 bio-organic fertilizers was found to be an effective way to reduce O. cumana parasitism and improve sunflower yield and quality. The results of this study further deepen our understanding of bio-organic fertilizers for the control of parasitic plants, and provide a reference for solving the agricultural obstacles caused by parasitic plants from the perspective of rhizosphere microbial community.