Effect of Nonanal, Citral, and Citrus Oils on Germination of Conidia of Penicillium digitatum and Penicillium italicum

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Abstract
Suspensions of nonanal in 1% water agar stimulated germination and swelling of conidia of P. digitatum Sacc. (33% at 500 .mu.l/l, 5 days, control 0%) and P. italicum Wehmer (35% at 500 .mu.l/l, 3 days, controls 4.5%). Nonanal was the most active of the C6-C12 aldehydes studied. Decanal and dodecanal were very effective in causing swelling of spores. Citral was about as stimulatory as nonanal. Mixtures of citral and nonanal were more stimulatory to germination, or induced more swelling, than either compound alone. Suspensions of oils (1000 .mu.l/l in 1% water agar) from orange, lemon, lime, grapefruit and tangerine, which contain these compounds along with many related compounds, were more stimulatory than nonanal, citral or mixtures, and germination was more rapid. [This study has relevance to the etiology of blue- and green-mold storage disease in citrus.].