Breeding for resistance to basal rot in Narcissus.

摘要

Basal rot of Narcissus caused by Fusarium oxysporum f. sp. narcissi frequently results in major losses in UK commercial bulb crops. Until recently, resistance breeding programmes have used as parents only tetraploid varieties, none of which have complete resistance to basal rot. The diploid species N. jonquilla, which has been reported to be completely resistant, was used as the pollen parent in crosses with two cultivars (Golden Harvest and St. Keverne) that display opposite extremes of field resistance, and the seedling progenies were clonally propagated. The hybrids were screened for resistance by planting bulbs in compost infested with chlamydospores of the pathogen and recording bulb survival one year later. Progeny from self-pollinated N. jonquilla were also propagated and tested to study the inheritance of resistance in an F1 generation from the diploid species. All of the N. jonquilla 'selfs' displayed similar, very high survival rates indicating homozygous resistance in this species. A continuous distribution of survival rates from 0 to 100% was observed in both the hybrid progenies but more lines with 100% survival were found when St. Keverne, a cultivar with high field resistance, was the maternal parent than when Golden Harvest, a more susceptible cultivar was used. A detached-scale puncture-inoculation technique was developed as a rapid in vitro assay for basal rot resistance in Narcissus. Varying amounts of rot were recorded for eight cultivars and five species that correlated well with their known resistance to basal rot.