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Root Size Variability Among Several Cultivars and Breeding Lines of Maryland Tobacco¹

Lodging of Maryland tobacco (Nicotiana tabacum L.) during the harvesting season may result in lower yields. ‘Maryland 609,’ a cultivar released in 1965, appears more susceptible to lodging than other cultivars. A previous root study with Maryland tobacco has been conducted in the field using the cultivars ‘Catterton’ and ‘Wilson’. These cultivars differed in root growth over a 10-week period. Studies of this type, however, require considerable time and labor, and the number of plants one can study is often small. Therefore, a greenhouse study was conducted for 2 years with the following objectives: (a) determine if a simple, but reliable, method could be utilized in the greenhouse for measuring size of tobacco roots, and (b) to determine the amount of variability present among the various Maryland tobacco cultivars for size of roots.

Three cultivars (Wilson, Catterton, and Maryland 609) were used in the study during the first year. The number of entries was expanded to six cultivars (Wilson, Catterton, Maryland 609, ‘Maryland 59,’ ‘Maryland 64,’ and ‘Maryland 10’) and three breeding lines (‘M871,’ ‘M872,’ and ‘M881’) during the second year. All entries were grown in clay pots 20.3 cm in diam filled with Galestown loamy sand (Psammentic Hapludult; sandy, siliceous, mesic). Plants were sampled approximately 20, 35, and 50 days after transplanting. Green weight, volume displacement, and dry weight data were obtained on roots and tops.

From these results, green weight measurements appeared to be the most simple and reliable for determining size of roots. Wilson had the largest root system of all entries for both years. Maryland 609 had the smallest root system of the three entries during the first year, and was among the group with the smallest roots during the second year. Breeding line M872 had the second largest root system as the plants reached maturity. The amount of variability for root size found among the cultivars and breeding lines suggests that some progress could be made through selecting for increased root size under greenhouse conditions. This increased root size should aid in reducing lodging as the plant reaches maturity.

Key Words: Nicotiana tabacum L. • Top weight

² Associate professor and professor of agronomy, respectively, Univ. of Maryland.

Received for publication December 31, 1974.