The germplasm accessions of cotton (Gossypium hirustum L.) may be a source of resistance to the tobacco budworm (TBW), Heliothis virescens, for improvement of the cultivated cotton varieties. However, detailed knowledge about the inheritance of cotton TBW resistance would help the breeder to more effectively plan strategies for incorporating TBW resistance into new cultivars. The objectives of this study were to compare the differences of TBW resistance among generations and to estimate broad-sense heritability between the resistant parent (T-119) and its inbreeding or backcross-inbreeding progenies, and to examine plant to plant genetic variability for TBW resistance.

Twenty-four random plants from each of 5 Fs generations (F(5), BC(1)F(5), BC(2)F(5), BC(3)F(5) & BC⁴F(5)), resistant parent (or backcross parent) T-119, susceptible parent Deltapine 16 (DPL 16), and commercial cultivar Deltapine 50 (DPL 50), were evaluated in three replicates in the greenhouse at the Crop Science Research Laboratory, Mississippi State, Mississippi. Soil type was a mixture of sandy clay loam, sand and peat moss. Resistance was evaluated with larvae weight per larvae after 7 days rearing on cotton leaf tissue. Mean resistance of T-119 (5.05 mg/larvae) was significantly different from any other genotypes (range 7.81 - 11.09 mg/larvae) and relatively high resistance were examined on generation of BC(3)F(5) (7.81 mg/larvae), which was significantly different from DPL 50 (9.67 mg/larvae). The low heritability estimates (22%-38%) and no apparent distinct resistance classes indicated a relatively complex inheritance. Plant to plant variability was significant on three of five F(5) generations, which were BC(1)F(5), BC(2)F(5) and BC(3)F(5), indicating that selection based on individual plants would be necessary. Generally, the percentage of resistant individual plants among each of different F(5) generations was increased by more backcrossing with T-119, with the exception of BC(2)F(5), but this increase may not be practical.