Pulse-wheat rotation: pulse crops effects on wheat endophytic bacteria, and feedback on wheat yield
Crop rotation is a common cultivation strategy and the legacy of a previous crop on biotic soil properties could feedback on the productivity of the following crop due to the mutual influence existing between plants and their biological environment. Polymerase chain reaction and 454 GS FLX pyrosequencing of amplicons were used in this study to determine the effects of genotype and termination time of previous pulse crops on the productivity and endophytic bacterial community colonizing the roots of durum wheat. In 2008-09, when chickpea plants (late maturing plant) were terminated as early as yellow pea (In July), all three genotypes of chickpea passed a sol biota to durum wheat that formed endophytic bacterial community which was similar to that formed following yellow pea, an early maturing plant. These four endophytic bacterial communities were different from those formed in wheat roots following late-terminated chickpea crops. Additionally, late terminated pulse crops (September) led to the formation of endophytic bacterial communities highly dominated by Firmicutes. These communities were less diverse than those formed after early-terminated pulse crops, which were dominated by Actinobacteria. High durum wheat yield was associated with the production of fewer heads m-2 and with the abundance of endophytic Actinobacteria and Acidobacteria. In contrast, low grain yield was associated with the abundance of endophytic Firmicutes. The effect of termination time was weak in 2009-2010, which was probably overridden by the extremely high amount of precipitation received during this period. The results demonstrate an important biotic legacy of crop termination time in agro-ecosystems, by influencing the endophytic bacterial colonization on the following crop. Environmental conditions appear as a key factor for the expression of this effect of crop termination time in agroecosystems.
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