Breeding tobacco resistant to cucumber mosaic virus in Taiwan

Summary

Breeding tobacco resistant to CMV using Holmes' resistant line was initiated in 1966. The resistance was controlled by five genes. N from N. glutinosa, rm₁ and rm₂ from Ambalema and t₁ and t₂ from T.I. 245. The genotype of Holmes' resistant line was assumed to be NNrm₁rm₁rm₂rm₂t₁t₁t₂t₂, which showed a few-small-late (FSL) lesion reaction to TMV. This reaction facilitates the selection of CMV resistant plants in a segregating population.

Hicks Broadleaf was crossed to Holmes' resistant line and backcrossed to the susceptible varieties Vam-fen-Hicks, Kutsaga 51 and T.T.4. Two resistant lines, 418 and 470, were selected and tested for their CMV resistance, yield and agronomic characters in 1976–1979. The % reduction of infection rate when compared with a check was 41.8% and 52.7% respectively. The two lines outyielded the check and had slightly higher value/kg leaf tobacco and lower % midrib. They were also taller and later maturing. Line 470 showed slight leaf-wilting in the early growth stage, which disappeared after topping.

Smoking tests showed that the two lines had better scores than check T.T.5. The nicotine and tar contents in the cigarette smoke stream proved that the leaf quality was acceptable. The lines 418 and 470 were registered as T.T.6 and T.T.7.