Mammoth Genotypes and Tobacco Management Regimes for Reduced Production of Downstalk Tobaccos 1

Demand for flue−cured tobacco ( Nicotiana tabacum L.) from basal leaf positions has decreased in recent years, and production systems which maximize higher quality, upstalk, leaf grades are needed. In this study we tested production regimes utilizing photoperiod−sensitive genotypes to prevent flowering and produce additional upstalk leaves as a substitute for discarded basal leaves. Normal and photoperiod−sensitive (mammoth) versions of four cultivars were grown in field experiments at two locations in 2 years. Apical meristems of mammoth genotypes were removed when plants had produced the same number of leaves as normal cultivars, four leaves more than normal in 1977, and two leaves more than noma1 in 1978. Mammoth genotypes allowed to produce the same leaf number as normal cultivars provided higher yields, with leaf quality equal or superior to the controls. Total alkaloids were lower than in normal cultivars in 1977, but equal in 1978. Reducing sugar contents were equal in both types in 1977, but significantly higher for mammoths in 1978. Permitting mammoth plants to produce four more leaves than normal, with the bottom four leaves removed from the plants and discarded, resulted in yield overcompensation with slight reductions in leaf alkaloids and increases in reducing sugars. Two additional top leaves on mammoth entries did not compensate adequately for yield reductions caused by discarding the bottom four leaves. Leaf alkaloids and sugar contents in the latter production regime did not differ from those of control cultivars. These regimes could reduce the production of downstalk tobaccos without significant yield reductions and would eliminate all premature flowering. The maintenance of apical dominance in mammoths would enhance axillary bud control.