Resistance of the white clover variety G49 and its parent lines to stem nematode (Ditylenchus dipsaci)

Abstract

Stem nematode (Ditylenchus dipsaci)infection of white clover variety G49 was compared to that of other white clover lines in two experiments. The G49 parent lines were also screened for infection in a third experiment. Symptoms of stem nematode infection were assessed at 8, 14, and 21 days after inoculation. The lower infection rate of G49 by D. dipsaci was not sufficient, as a stand-alone trait, to distinguish G49 from other existing lines. However, G49 had a significantly lower infection rate than Pitau so these can be distinguished for the purposes of a Plant Variety Right application. The variation among the parent lines of G49 indicated scope for further selection to improve resistance. Three techniques for applying inoculum to seedlings were compared; the best one uses 1 ml of nematode suspension placed over a 3-day-old seedling lying on the surface of peat-based potting mix which is then lightly covered.

Host status and reaction of Medicago truncatula accessions to infection by three major pathogens of pea (Pisum sativum) and alfalfa (Medicago sativa)

“…Mercer and Grant (1995) estimated that more than 75% of the Ditylenchus inoculum may be lost during host invasion. The problem of plants escaping infection for reasons unrelated to resistance can be minimized but rarely eliminated, so it is also important to establish the resistance status in M. truncatula by determining the percentage of plants with an RI < 1, as in certified alfalfa cultivars.…”

Evaluation of the effects of resistance to stem nematode (Ditylenchus dipsaci) in white clover (Trifolium repens L.) under sheep grazing and cutting

“…This pest is also important in other parts of the world, e.g. New Zealand (Williams and Barclay 1972) where Mercer and Grant (1995) carried out evaluations for resistance that allowed them to distinguish between morphologically similar lines.…”