Seedling blight. I. Seed colour and soil in relation to pre-emergence blight of William Massey peas

Abstract

Using a local soil the emergence of samples of William Massey peas supplied by nineteen growers varied from less than 50 to more than 80 per cent. In tests of ten samples, those with cotyledons more uniformly green in colour germiwated best. The percentage emergence of green peas from a local soil was significantly higher than that of yellow peas from the same sample, that of yellow-green peas being intermediate. Low percentage emergence of the yellow peas was due partly to a fraction of seed of low vitality common to all colours and partly to a low degree of resistance to fungal infection. Emergence of a sample of peas sown in three different soils was 39, 60, and 83 per cent. Differences in the percentages were due mainly to the influence of the soil environment on the susceptibility of the yellow pea fraction to pre-emergence blight. Percentage emergence of yellow peas and green peas also appears to be inversely correlated with reputed soil fertility. The percentage emergence of a sample of peas can be varied significantly, by varying the soil in which the seed is sown during the first three days of germination. The fungus associated with pre-emergence blight in all soils that have been sufficiently tested is commonly referred to as Pythium ultimum Trow. In addition to the usual dusting methods, control of pre-emergence blight of peas may be improved by the use of resistant seed and where possible the selection of suitable soils for sowing such seed. Appendix I contains a note on the name Pythium ultimum (Trow).