A field experiment involving cry1Ab transgenic rice (GM) and its parental non-cry1Ab rice (M) has been on-going since 2014.  The diversity of the bacterial communities and the abundance of the microbial functional genes which drive the conversion of nitrogen in paddy soil were analyzed during the growth period of rice in the fifth year of the experiment, using 16S rRNA-based Illumina MiSeq and real-time PCR on the amoA, nirS and nirK genes.  The results showed no differences in the alpha diversity indexes of the bacterial communities, including Chao1, Shannon and Simpson, between the fields cultivated with line GM and cultivar M at any of the growth stages of rice.  However, the bacterial communities in the paddy soil with line GM were separated from those of paddy soil with cultivar M at each of the growth stages of rice, based on the unweighted UniFrac NMDS or PCoA.  In addition, the analyses of ADONIS and ANOSIM, based on the unweighted UniFrac distance, indicated that the above separations between line GM and cultivar M were statistically significant (P<0.05) during the growth season of rice.  The increases in the relative abundances of Acidobacteria or Bacteroidetes, in the paddy soils with line GM or cultivar M, respectively, led to the differences in the bacterial communities between them.  At the same time, functional gene prediction based on Illumina MiSeq data suggested that the abundance of many functional genes increased in the paddy soil with line GM at the maturity stage of rice, such as genes related to the metabolism of starch, amino acids and nitrogen.  Otherwise, the copies of bacterial amoA gene, archaeal amoA gene and denitrifying bacterial nirK gene significantly increased (P<0.05 or 0.01) in the paddy soil with line GM.  In summary, the release of cry1Ab transgenic rice had effects on either the composition of bacterial communities or the abundance of microbial functional genes in the paddy soil.

Blast, a disease caused by Magnaporthe oryzae, is a major constraint for rice production worldwide.  Introgression of durable blast resistance genes into high-yielding rice cultivars has been considered a priority to control the disease.  The blast resistance Pik locus, located on chromosome 11, contains at least six important resistance genes, but these genes have not been widely employed in resistance breeding since existing markers hardly satisfy current breeding needs due to their limited scope of application.  In this study, two PCR-based markers, Pikp-Del and Pi1-In, were developed to target the specific InDel (insertion/deletion) of the Pik-p and Pi-1 genes, respectively.  The two markers precisely distinguished Pik-p, Pi-1, and the K-type alleles at the Pik locus, which is a necessary element for functional genes from rice varieties.  Results also revealed that only several old varieties contain the two genes, of which nearly half carry the K-type alleles.  Therefore, these identified varieties can serve as new gene sources for developing blast resistant rice.  The two newly developed markers will be highly useful for the use of Pik-p, Pi-1 and other resistance genes at the Pik locus in marker-assisted selection (MAS) breeding programs.