Effects of root‐ and stolon‐infecting fungi on root‐colonizing nematodes of white clover

Abstract

The effects on white clover ( Trifolium repens ) of different combinations of the nematodes Meloidogyne trifoliophila , Helicotylenchus dihystera and Heterodera trifolii and nine stolon-infecting and three root-infecting fungi were studied in a glasshouse experiment. The presence of the fungus Phytophthora megasperma alone increased ( P < 0·001) root-rot severity and reduced ( P < 0·001) plant growth. Other species combinations, such as Phoma nebulosa and Alternaria alternata , interacted and increased root-rot severity. Combinations of P. megasperma with Pythium irregulare , and P. nebulosa with Phoma medicaginis or A. alternata , increased M. trifoliophila populations. Several other fungi ( P. irregulare , P. nebulosa , Colletotrichum coccodes , Macrophomina phaseolina , P. medicaginis and Phoma sp.) interacted with the nematode M. trifoliophila causing severe root-knot symptoms. The results indicated that fungi and nematodes interacted to cause root and stolon rot and reduced yields, and that poor persistence of white clover in pastures is likely to be a problem with a complex etiology.

Plant-Mediated Systemic Interactions Between Pathogens, Parasitic Nematodes, and Herbivores Above- and Belowground

“…Information on the effect of AG pathogens on root-feeding nematodes is virtually absent. Stolon inoculation of white clover with the fungus Drechslera halodes significantly increased densities of the nematodes Helicotylenchus dihystera and Heterodera trifolii, and suppressed negative effects of the root pathogen Pythium irregulare on the nematode Meloidogyne trifoliophila (174). This contrasts with the general negative effects of root pathogens on these nematodes.…”

Disease complexes involving plant parasitic nematodes and soilborne pathogens

“…While there are far fewer reports of such phenomena, several hypotheses have been proposed. For example, Zahid et al . (2002) investigated a large and complex set of interactions between 12 species of root‐ and stolon‐infecting fungi and three species of root‐colonizing nematodes on white clover ( Trifolium repens ), an important forage crop for dairy herds in eastern Australia.…”

“…While there are far fewer reports of such phenomena, several hypotheses have been proposed. For example, Zahid et al (2002) investigated a large and complex set of interactions between 12 species of root-and stoloninfecting fungi and three species of root-colonizing nematodes on white clover (Trifolium repens), an important forage crop for dairy herds in eastern Australia. Although a good number of interactions were found between the various combinations of nematodes and fungi, the root-knot symptoms of Meloidogyne trifoliophila were commonly found to be increased in treatments containing the stolon-infecting fungus Drechslera halodes.…”

Detection of fungal 18S rRNA sequences in conjunction with marine nematode 18S rRNA amplicons

“…In particular, the level of interaction between nematodes and fungi (relevant to the present study) can be broadly grouped into 4 principal categories: (1) nematodes as fungal predators (Bakhtiar et al 2001); (2) fungi as predators or parasites of nematodes (Viaene and Abawi 2000); (3) etiological relations between nematodes and fungi (Zahid et al 2002); and (4) nematodes acting as vectors for fungal spores (Mendoza de Gives et al 1999). While such interactions occur frequently in the terrestrial environment, there are no reports as yet of fungal and nematode interactions from estuarine and marine environments.…”