3.5 Correlation network
Correlation network analysis indicated that positive correlation occurred within prokaryotic or eukaryotic groups in microbiota of aerial parts and roots. In aerial tissues, positive correlation was observed among endophytic bacterial genera, while negative correlation occurred among fungal genera (Fig. 4a). For example, unidentified fungal OTU_673 and OTU_702 showed strong negative correlations to several fungal taxa. Meanwhile, positive correlation could be also observed between prokaryotic or eukaryotic members. In roots, bacterial or fungal members in the community were more connected (Fig. 4b). Concatenated negative correlations were observed between prokaryotic and eukaryotic members, which suggested intensive antagonism between bacteria and fungi in roots. These findings indicate denser inter-kingdom interactions in the roots rather than in the aerial tissues.
Network analysis of endophytic bacterial communities suggested a minor effect of radiation on the topology of endophytic bacterial network. The network of endophytic bacterial communities in aerial tissues showed similar connectance and modularity across control and three radioactive treatments (Table 1). Meanwhile, the root bacterial communities showed higher connectance in control and similar modularity in control and radioactive environments. Simultaneously, radiation showed a strong effect on the topology of endophytic fungal correlation network. Higher modularity and lower connectance were observed in all radiation levels compared to control regardless of the tissue type (aerial tissues or roots) (Table 1).