MORPHOLOGICAL-CHARACTERISTICS ASSOCIATED WITH LODGING OF TOBACCO

Production of crops worldwide may encounter varying amounts of damage due to lodging each year. A 2-yr study was conducted to determine if variability of morphological traits is related to various components of lodging resistance among tobacco (Nicotiana tabacum L.) cultivars, and to determine if an efficient method could be developed to screen for lodging resistance. Eleven cultivars, representing four types of tobacco, were evaluated. Top and root fresh weights, top/root ratios (TRR), and root densities were obtained from greenhouse studies. Stalk and flower head traits and three lodging traits were measured in field studies. Artificial wind was generated to induce lodging. Significant variation was observed among cultivars for all traits examined. Phenotypic correlations among the various root, stalk, and flower head traits were not significant (P less-than-or-equal-to 0.05), except for two flower traits: basal internode length and plant height/basal stalk diameter. No significant correlations between lodging and single morphological traits were found; however, correlations were highly significant among lodging traits. Multiple regression equations predicting severity rating indicated that TRR and basal stalk specific gravity (BSSG) explained 44% of the variation (severity rating = -2.36 + 0.66 TRR + 0.12 BSSG). Thus, lodging resistance could be increased by selection for larger root systems and lower BSSG. The amount of genetic variability present in the population and the relationship of TRR and BSSG to severity rating suggest that progress in developing lodging resistant material is feasible using artificial wind for screening.