Resistance to Penicillium allii in accessions from a National Plant Germplasm System Allium collection

Multiple Allium accessions (garlic, and wild and ornamental Allium species) were screened for resistance using Penicillium allii and A. sativum (positive control). Single accessions of A. aflatunense, A. atroviolaceum, A. stipitatum, and Allium sp. remained asymptomatic. Single accessions of A. roseum and A. senescens, two accessions each of A. acuminatum and A. ampeloprasum and a single accession of A. moly displayed lesion expansion rates not exceeding 22%, 26%, 46%, 50%, 61%, 67% and 67%, respectively, of positive controls. Single accessions of A. sativum var. ophioscordon and A. scorodoprasum displayed rates not exceeding 68% and 55%, respectively, of positive controls with deep wounding, but did not consistently differ with shallow wounding. Accessions of A. canadense, A. sativum or A. longicuspis did not differ, differed inconsistently, or differed insubstantially from positive controls. Lesion expansion rates for A. acuminatum, A. ponticum and A. scorodoprasum were significantly less than in positive controls, but their small bulbs often rotted completely. Results document publicly available germplasm possessing significant resistance to P. allii.

Research highlights
► Complete to partial resistance to Penicillium decay is documented.
► Resistant germplasm is distributed amongst several subgenera.
► Penicillium allii causes Penicillium decay of garlic in North America.