Bacterial wilt (Ralstonia solanacearum) resistant flue-cured hybrids - current Malawi situation
In Malawi, flue-cured tobacco production is negatively affected by both aerial and soil borne diseases. Bacterial wilt (Ralstonia solanacearum) is one of the major soil borne diseases that attack the crop, reducing cured leaf yield and quality. Currently the country has no flue-cured tobacco varieties resistant to bacterial wilt. ARET started a breeding program to develop bacterial wilt resistant flue-cured tobacco varieties with high cured leaf yield and acceptable quality. From 2014 to 2017 ARET evaluated eight advanced bacterial wilt resistant flue-cured tobacco lines alongside one popular variety, KRK 26 and a local check, AFH 4. The trials were laid out in randomized complete blocks and replicated three times. Data was collected on leaf yield, disease reaction and cured leaf quality (colour and grade outturn) and analysed using analysis of variance (ANOVA). Means were separated using the least significant difference (LSD). Three year results on bacterial wilt incidence (%) did not show any significant differences among the test lines. GRH11-9 with 21.4 % and GRH with 30.7 % gave values less than the acceptable threshold level. Nematode reaction showed significant differences (P ≤ 0.05) among the lines. GRH11-9 and GRH11-10 gave the same mean score, 3.3 better than AFH 4 showing moderate resistance. Yield performance was similar between the test lines and the two checks, KRK 26 and AFH 4. GRH11-2 and GRH11-31 gave yields >2000 kg/ha just like AFH 4. Yield ranged from 1594 kg/ha to 2166 kg/ha. Results on colour distribution (%) of cured leaf also showed no significant differences between the test lines and the checks, demonstrating that the test lines had the same leaf quality as the checks. In terms of leaf grade distribution GRH11-5 and GRH11-31 produced significantly higher proportions (P ≤ 0.001) of first quality leaf, together with the two checks, 34.0 % and 32.3 %, respectively.