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Environmental Influence on Weather Fleck Ratings for Maryland Tobacco Cultivars¹

The effects of air pollution, primarily ozone, on crop production along the East Coast of the United States have been reported by several researchers over the past 25 years. Cultivars differ in their response to air pollution, but information on cultivar response over multiple environments is lacking. Therefore, this study was conducted to obtain information on the genotypic response of five Maryland tobacco (Nicotiana tabacum L.) cultivars over several environments and considers possible environmental factors which may influence the occurrence of weather fleck (air pollution damage) under field conditions.

Five cultivars were evaluated for weather fleck in five environments from 1972 to 1979. Weather fleck is characterized by small necrotic lesions on the leaf surface usually 0.2 to 0.5 cm in diameter. Plants were scored on a scale of 1 to 5 (1 = no damage, 5 = severe damage). On the average, the weather fleck ratings ranged from 1.44 for ‘Md. 872’ to 2.40 for ‘Md. 609’. Year-to-year variations were significant with a range in ratings of 1.55 (Davidsonville, 1978) to 2.50 (Upper Marlboro, 1979). Also a differential response was observed for the cultivars over the five environments as indicated by the significant genotype x environment interaction. The most important factor contributing to the significant genotype x environment interaction appeared to be the variation in total amount and distribution of rainfall during the growing season. These results emphasize the importance of utilizing multiple environments for testing genetic material for weather fleck resistance.

Key Words: Air pollution • Genotype x environment interaction • Nicotiana tabacum L.

² Professor of agronomy, Univ. of Maryland, College Park

Received for publication February 20, 1981.