Pyramiding of the dep1-1 and NAL1NJ6 alleles achieves sustainable improvements in nitrogen-use efficiency and grain yield in japonica rice breeding

Rice is one of the most important cereal crops in the world, and a substantial increase in grain yield is necessary for food security. However, high yields of semidwarf modern rice varieties are heavily dependent on the application of mineral nitrogenous fertilizer (Tilman et al., 2002;Sun et al., 2014). Nitrogen (N)-insensitive sponses associated with reduced N-use efficiency (NUE) is a major characteristic of the green revolution varieties (GRVs), in which the growth-inhibiting protein SLENDER RICE1 (SLR1) accumulates (Li et al., 2018). Unfortunately, increasing the level of N fertilizer use to reach the full yield potential of GRVs is subject to diminishing returns, quite apart from its deleterious effect on the environments (Rahn et al., 2009;Liu et al., 2015). Therefore, there is an urgent need to develop new rice GRVs that increase NUE while maintaining their high yields. Recently, several genes (e.g., DEP1, OsNRTl.lB, OsNRT2.3b, ARE1 and GRF4) responsible for improved NUE have been identified in rice (Sun et al.. 2014;Hu et al., 2015;Fan et al., 2016;Wang et al., 2018;Li et al., 2018). More importantly, boosting the activity of the transcription factor GRF4 overcomes the ability of SLR1 to prevent the GRF4-GIF1 interaction, which in turn promotes the coordinated expression of the genes involved in N assimilation and carbon fixation and consequently enhances the NUE of rice GRVs, thereby improving our ability to grow crops sustainably (Li et al., 2018). However, current understanding of the genetic basis for improving NUE remains at the level of identification of a number of quantitative trait loci (QTLs), without any understanding of the nature of the gene products.

INTERCROPPING TEA PLANTATIONS WITH SOYBEAN AND RAPESEED ENHANCES NITROGEN FIXATION THROUGH SHIFTS IN SOIL MICROBIAL COMMUNITIES

Intercropping with eco-friendly crops is a well-known strategy for improving agriculture sustainability with benefits throughout the soil community,though the range of crop impacts on soil microbiota and extent of feedbacks to crops remain largely unclear.This study evaluated the impacts of different intercropping systems on soil bacterial community composition,diversity,and potential functions in tea gardens.Intercropping systems were found to be significantly influenced soil microbiota.Within the three tested intercropping systems(tea-soybean,tea-rapeseed and tea-soybean-rapeseed),the teasoybean-rapeseed intercropping system had the most dramatic influence on soil microbiota,with increases in richness accompanied by shifts in the structure of tea garden soil bacterial networks.Specifically,relative abundance of potentially beneficial bacteria associated with essential mineral nutrient cycling increased significantly in the tea-soybean-rapeseed intercropping system.In addition,soil microbial functions related to nutrient cycling functions were significantly enhanced.This was in accordance with increasing relative abundance of nitrogen cycling bacteria,including Burkholderia spp.and Rhodanobacter spp.Based on these results,it is proposed that intercropping tea plantation with soybean and rapeseed may benefit soil microbiota,and thereby promises to be an important strategy for improving soil health in ecologically sound tea production systems.