Abstract
Active nitrifiers and rapid nitrification are major contributing factors to nitrogen losses in global wheat production. Suppressing nitrifier activity is an effective strategy to limit N losses from agriculture. Production and release of nitrification inhibitors from plant roots is termed "biological nitrification inhibition" (BNI). Here, we report the discovery of a chromosome region that controls BNI production in "wheat grass" Leymus racemosus (Lam.) Tzvelev, located on the short arm of the "Lr#3Nsb" (Lr#n), which can be transferred to wheat as T3BL.3NsbS (denoted Lr#n-SA), where 3BS arm of chromosome 3B of wheat was replaced by 3NsbS of L. racemosus We successfully introduced T3BL.3NsbS into the wheat cultivar "Chinese Spring" (CS-Lr#n-SA, referred to as "BNI-CS"), which resulted in the doubling of its BNI capacity. T3BL.3NsbS from BNI-CS was then transferred to several elite high-yielding hexaploid wheat cultivars, leading to near doubling of BNI production in "BNI-MUNAL" and "BNI-ROELFS." Laboratory incubation studies with root-zone soil from field-grown BNI-MUNAL confirmed BNI trait expression, evident from suppression of soil nitrifier activity, reduced nitrification potential, and N2O emissions. Changes in N metabolism included reductions in both leaf nitrate, nitrate reductase activity, and enhanced glutamine synthetase activity, indicating a shift toward ammonium nutrition. Nitrogen uptake from soil organic matter mineralization improved under low N conditions. Biomass production, grain yields, and N uptake were significantly higher in BNI-MUNAL across N treatments. Grain protein levels and breadmaking attributes were not negatively impacted. Wide use of BNI functions in wheat breeding may combat nitrification in high N input-intensive farming but also can improve adaptation to low N input marginal areas.
Highlights
Active nitrifiers and rapid nitrification are major contributing factors to nitrogen losses in global wheat production
Some elite varieties released in 2000 as well as “SONORA-64” have Biological nitrification inhibition (BNI) capacity akin to Chinese Spring (CS). These results indicate that wheat breeding had no directional impact on the BNI capacity of root systems (SI Appendix, Fig. S3)
We have demonstrated the feasibility of enhancing BNI capacity in elite wheats by transferring a chromosome arm 3NsbS controlling BNI traits from wild grass as a wheat L. racemosus translocation chromosome (T3BL.3NsbS)
Summary
Active nitrifiers and rapid nitrification are major contributing factors to nitrogen losses in global wheat production. Excessive nitrifier activity and a rapid generation of soil nitrates plague modern cereal production systems This has led to shifting crop N nutrition toward an “all nitrate form,” which is largely responsible for N losses and a decline in agronomic nitrogen-use efficiency (NUE) [6, 7, 9,10,11]. Regulating soil nitrifier activity to slow the rate of soil nitrate formation should provide more balanced N forms (NH4+ and NO3−) for plant uptake (rather than nearly “all NO3−” at present), reduce N losses, and facilitate the assimilation of dual N forms This optimizes the utilization of biochemical machinery for N assimilation, improving stability and possibly enhancing yield potential [16]. The lack of cost effectiveness, inconsistency in field performance, inability to function in tropical environments, and the concerns related to the entering of SNIs into food chains have limited their adoption in production agriculture [6, 7, 19, 20]
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