Roots of symptom-free leguminous cover crop and living mulch species harbor diverse Fusarium communities that show highly variable aggressiveness on pea (Pisum sativum)

Abstract

Leguminous cover crop and living mulch species show not only great potential for providing multiple beneficial services to agro-ecosystems, but may also present pathological risks for other crops in rotations through shared pathogens, especially those of the genus Fusarium. Disease severity on roots of subterranean clover, white clover, winter and summer vetch grown as cover crop and living mulch species across five European sites as well as the frequency, distribution and aggressiveness to pea of Fusarium spp. recovered from the roots were assessed in 2013 and 2014. Disease symptoms were very low at all sites. Nevertheless, out of 1480 asymptomatic roots, 670 isolates of 14 Fusarium spp. were recovered. The most frequently isolated species in both years from all hosts were F. oxysporum and F. avenaceum accounting for 69% of total isolation percentage. They were common at the Swiss, Italian and German sites, whereas at the Swedish site F. oxysporum dominated and F. avenaceum occurred only rarely. The agressiveness and effect on pea biomass were tested in greenhouse assays for 72 isolates of six Fusarium species. Isolates of F. avenaceum caused severe root rot symptoms with mean severity index (DI) of 82 and 74% mean biomass reduction compared to the non-inoculated control. Fusarium oxysporum and F. solani isolates were higly variable in agressiveness and their impact on pea biomass. DI varied between 15 and 50 and biomass changes relative to the non-inoculated control -40% to +10%. Isolates of F. tricinctum, F. acuminatum and F. equiseti were non to weakly agressive often enhancing pea biomass. This study shows that some of the major pea pathogens are characterized by high ecological plasticity and have the ability to endophytically colonize the hosts studied that thus may serve as inoculum reservoir for susceptible main legume grain crops such as pea.

Bacterivorous Nematodes Correlate with Soil Fertility and Improved Crop Production in an Organic Minimum Tillage System

“…In contrast, the root lesion severity was only reduced under minimum tillage with compost. These lesions were likely caused by soil inhabiting and pea pathogenic fungi that were commonly found in soils of the study site [14,30]. The negative correlation of root lesion severity and pea biomass production in this study suggests that soil health under minimum tillage with compost fertilization is overall increased.…”

“…Plants were harvested at BBCH 71 after a growth period of 80 days and aboveground dry matter (DM) after heating at 105°C for 24 h, the number of pods, and root fresh weight were determined. A root rot disease index (0-100) was calculated based on the assessment of external root lesions and lesion lengths were measured according to Šišić et al [30] and Pflughöft [31]. Pratylenchus penetrans was extracted from pea roots via mist chambers [26].…”

Confirmation of Fusarium root rot resistance QTL Fsp-Ps 2.1 of pea under controlled conditions

“…Dry pea ( Pisum sativum L.) production has increased substantially in the US since 2004 to 0.5 million hectares, primarily in the northern tier states of North Dakota and Montana [ 1 ] and in Canada since the turn of the century to 1.7 million hectares in 2016 [ 2 ]. The increase of dry pea cultivation in short rotation with cereal crops has been associated with an increase in root rot incidence in in North America [ 3 , 4 ], Europe [ 5 , 6 ] and New Zealand [ 7 ].…”

“…pisi ( Fsp ), F. acuminatum , F. avenaceum , F. culmorum , F. graminearum , F. sambucinum , F. equiseti , F. oxysporum , F. poae , F. redolens , F. sporotrichioides and F. tabacinum were found pathogenic to varying degrees on pea [ 5 , 11 ]. In North America, two species have been identified as the most serious production constraints, Fsp and F. avenaceum [ 3 , 5 , 11 – 13 ] as determined by field surveys, virulence tests and accompanying confirmation of the species using molecular tools [ 3 , 14 ]. F. avenaceum is the dominant species under reduced or no-tillage practices as it survives on the preceding crop residue [ 4 , 5 ] and dominates in the northern plains of North America [ 3 , 12 ].…”

“…In North America, two species have been identified as the most serious production constraints, Fsp and F. avenaceum [ 3 , 5 , 11 – 13 ] as determined by field surveys, virulence tests and accompanying confirmation of the species using molecular tools [ 3 , 14 ]. F. avenaceum is the dominant species under reduced or no-tillage practices as it survives on the preceding crop residue [ 4 , 5 ] and dominates in the northern plains of North America [ 3 , 12 ]. However, the importance of both species varies by year [ 12 ].…”