Brassicaceae cover crops reduce Aphanomyces pea root rot without suppressing genetic potential of microbial nitrogen cycling

Abstract

Aims Brassicaceae cover crops can be used to suppress soil-borne pathogens. The aim was to investigate the effect of different brassicas with different glucosinolate profiles on the development of Aphanomyces pea root rot in subsequent pea plants, and the genetic potential of free-living N 2 -fixing bacteria and ammonia oxidising bacteria (AOB) and archaea (AOA) performing key soil ecosystem services. Methods The Brassicaceae species Brassica juncea and Sinapis alba and non-Brassicaceae species Secale cereale were grown for 11-weeks in Aphanomyces euteiches infested soil at low and high nitrogen (N) fertiliser doses. After removing both shoots and roots of the cover crops, peas were grown as a bioassay to evaluate Aphanomyces pea root rot development. Soil was sampled before harvesting the cover crops and at the end of the bioassay. Volatile compounds were collected in the root-soil environment before harvesting the Brassicaceae cover crops to determine the concentration of isothiocyanates. The abundance of genes involved in N 2 -fixing bacteria and ammonia oxidation in AOA and AOB were assessed. Results Pea root rot disease severity was reduced in Brassicaceae grown soil at the high N fertiliser dose. This was associated with increased growth of the cover crops. The growth of Brassicaceae did not suppress the abundance of N-cycling microbial communities, but rather increased the AOB at the end of the bioassay, most likely due to increased N availability. The disease suppressive effect was higher with S. alba than with B. juncea, and this coincided with a more diverse composition and higher concentration of aliphatic ITCs released from S. alba roots. Fewer nodules were formed after the Brassicaceae crops, especially Sinapis alba. Conclusions Brassicaceae cover crops, particularly S. alba, can be used to control soil-borne pathogens without major side effects on the genetic potential of beneficial soil microorganisms involved in N cycling. However, less nodule formation after brassicas indicates an effect on rhizobium activity.

Prokaryotic Communities at Different Depths between Soils with and without Tomato Bacterial Wilt but Pathogen-Present in a Single Greenhouse

“…Nitrosospira , Denitratisoma , and Dyella are also involved in the nitrogen cycle in soil environments ( 9 , 36 , 37 ). The suppressive effect on plant disease has been discussed for bacteria that participate in the nitrogen cycle and the nitrogen they release has been found to affect microbial community structures in soil ( 7 , 14 ). Therefore, bacteria that play a role in the nitrogen cycle in soil may be involved in the control of bacterial wilt.…”

Comparison of Prokaryotic and Eukaryotic Communities in Soil Samples with and without Tomato Bacterial Wilt Collected from Different Fields

“…Azoarcus and Azospira , as Rhodocyclacea members, are generally involved in nitrogen cycling in soil environments. Bacteria involved in soil nitrogen cycling affect the suppression of plant diseases, and their release of nitrogen influences the microbial community structure ( 8 , 16 ). An Aquihabitans species was recently isolated from a freshwater environment, and its ecology has yet to be examined in detail ( 21 ).…”

Beheersing van bodempathogenen via bodemgezondheidsmaatregelen : Een overzicht van de beschikbare kennis voor een selectie van akkerbouwgewassen met hun bijbehorende bodemziekten

“…Kan zich ook goed ontwikkelen in gronden met een lage temperatuur, waardoor groenbemesters die tot de peulvruchten behoren waarschijnlijk bij kunnen dragen tot de instandhouding van de ziekte. In Zweden reduceerde gele mosterd (Sinapis alba) als groenbemester wortelrot veroorzaakt door A. euteiches sterk, mits de mosterd zich goed ontwikkelde (hoge N-dosis) (Hossain et al, 2015). Een biotoets voor het vaststellen van een bodembesmetting is beschreven en wordt toegepast in Frankrijk (Gangneux et al, 2014), maar ook in België en Oostenrijk wordt een standaard biotoets door conservenindustrie toegepast (Clarkson et al, 2014), maar die is voor de praktijk in Nederland vooralsnog niet beschikbaar.…”