Deciphering bacterial community variation during soil and leaf treatments with biologicals and biofertilizers to control huanglongbing in citrus trees

The aim of the current study was to gain a clearer understanding of the bacteria involved in different treatments to control huanglongbing in citrus trees. The treatments included additions in soil or on leaf. In soil, there were two treatments, one was addition of biofertilizer mainly consisting of Brevibacillus laterosporus, and another one was the addition of burnt lime. On leaf treatment, a plant immunity inducer, Atailing spray, which is a fermented fungal protein product, was used. Besides, there was an integrative treatment including the above additions both in soil and on leaf. The control treatments had no addition. The growth of infected citrus plants was significantly improved by these treatments. We sampled soil under crown circumference, rhizosphere soil and roots, stems and leaves of the citrus trees. Sequencing of the 16S rDNA marker using Illumina methods was applied to determine the bacterial community composition of the samples. The results showed that in the soil samples under crown circumference, treatments increased the relative abundance of the genera Bradyrhizobium and Norank_f__Acidobacteriaceae__Subgroup_1_ compared with the control. In the rhizosphere soil samples, treatments increased the relative abundance of the genus Burkholderia–Paraburkholderia compared with the control. Atailing spray influenced the relative abundance of the bacterial genus norank_f__Acidobacteriaceae__Subgroup_1_ in the rhizosphere soil, as well as Pseudomonas in citrus leaves. Furthermore, 6 months after the treatments, the relative abundance of Actinobacteria and Bacilli at the class level was significantly increased in citrus plant leaves in the group treated with Atailing spray, biofertilizer and burnt lime. Overall, certain bacteria were stimulated by treatments, and the leaf‐associated bacterial communities had important indicators for the health of the citrus endophytic environment. These results provided a theoretical foundation for the development of biological approaches for huanglongbing treatment.