RESPONSE OF RHIZOBACTERIAL COMMUNITY TO AGRONOMIC PRACTICES IN CHICKPEA FIELD, AND ITS EFFECTS ON PULSE-CEREAL ROTATION SYSTEM

In chickpea production located in prairie ecozone, late-maturing genotype combined with current fungicide application practices may negatively impact soil bacteria composition and their biological functions, which may further influence the structure and activity of the rhizobacterial community of a following durum wheat crop. In field experiment I, three fungicide treatments and one control were used to test the influence of toxic chemical compounds on chickpea rhizobacterial community. Results show that different fungicide application strategies negatively affect the composition of rhizobacterial communities. The richness of the bacterial communities significantly changed between the two experimental years, indicating that environmental factors further influence the effects of fungicide application on rhizobacterial growth. In field experiment II, one yellow pea and three chickpea cultivars were used to test the impact of different pulse genotypes on rhizobacterial communities. Results demonstrate that pulse crops selectively influence the composition of their associated rhizobacterial communities. It was confirmed by a greenhouse bioassay, as wheat showed higher biomass production after yellow pea and CDC Luna chickpea than after CDC Vanguard and CDC Frontier. In a two-year crop rotation field trial conducted in the same field as experiment II, durum wheat was planted after pulses to test the effect of different previous pulse crops on the root endophytic bacterial community in a following durum wheat crop. Results indicate that the richness and composition of durum wheat endophytic bacterial communities may change with pulse crops, and these changes correlated with wheat yield, under field conditions. The better yield of wheat after pulses may be related to the release of hydrogen gas by their root nodules, which augment the abundance of H2-oxidizing rhizobacteria. The latter show an ability to promote plant growth under tested in vitro conditions. Finally, this microbial study reveals that the cropping practices influence the diversity and composition of chickpea rhizobacterial community. Shifts in the functional groups of soil bacteria may affect the overall microbial activities with important ecological consequences for each particular cropping system. Therefore, agronomic decisions reinforcing the beneficial microbial communities and its biological functions could improve the soil quality and efficiency of Prairie cropping systems