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Stem nematode effects on lucerne cultivars

R.B. Wynn-Williams and R.G. Purves

Crop Research Division, DSIR, Private Bag, Christchurch, New Zealand

Stem nematode (Ditylenchus dipsaci (Kuhn) Filipjev) is a major problem in many lucerne (Medicago sativa L.) growing areas in New Zealand and Australia but some well adapted cultivars have good resistance to the pathogen. A range of cultivars, with known and differing levels of resistance, was sown to test their performance over a number of years on two nemotode infested sites.


On 10 December, 1981 ten cultivars were sown 6 weeks after cultivation began in a run-out lucerne stand on a Claremont silt loam south of Timaru, N.Z. (Trial 1). In November 1981, eight cultivars were sown on a Templeton silt loam at Lincoln, N.Z. (Trial 2). Both trials were randomised complete block designs with four replicates.

Results and discussion

All cultivars established satisfactorily in both trials and initial yields were high. Later yields of nematode-susceptible cultivars declined to less than 2.0 t/ha per cut (Table 1). The stem nematode-resistant cultivars Nova, Washoe, CRD Otaio and AS13R produced significantly higher yields.

Table 1. Mean dry matter yield per cut (t/ha].

Nova, Washoe, CRD Otaio and AS13R are also resistant to bacterial wilt (Corynebacterium insidiosum McCulloch) CRD Otaio is also resistant to blue green lucerne aphid (Acyrthosiphon kondoi Shinji), pea aphid (A. pisum Harris) and spotted aphid (Therioaphis maculata Buckton).

The only anomalous result was the apparent tolerance of the normally susceptible Wairau in the Lincoln trial. The possibility of pathogenicity differences between nematode races is being investigated.

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