Response of intermediate ripening tobacco (Nicotiana tabacum) cultivars to frog eye (Cercospora nicotianae) and alternaria leaf spot (Alternaria alternata) in the medium growing areas of Zimbabwe
2022
Shava, Justify Gotami
Alternaria leaf spot (Alternaria alternata) and Frog eye leaf spot (Cercospora nicotianae) are foliar diseases of tobacco (Nicotiana tabacum) which occur mainly in mature tobacco. Hence, the diseases are often associated with maturity of cured tobacco leaf at the tobacco sales floor in Zimbabwe. Where they occur, they can result in significant reductions in yield and quality of cured tobacco leaf. A study was carried out in Trewaney, Mashonaland West province in Zimbabwe to investigate the response of newly developed ten flue cured tobacco varieties to the two foliar diseases Alternaria leaf spot (Alternaria alternata) and frog eye leaf spot (Cercospora nicotianae). The experiment was laid out as a randomized complete block design (RCBD) with three replicates. Standard agronomic practices in tobacco farming were followed and disease assessments were done 18 weeks after planting. Significant differences (p<0.05) for resistance to alternaria leaf spot were observed with the experimental hybrid T60 showing the highest resistance to the disease with a disease score of 1.6 under a 0–6 disease scale that ranges from 0 (no disease) to 6 (severely affected). However, there were no significant (p>0.05) differences among the varieties for frog eye leaf spot resistance, yield (kg/ha) and quality as measured by the grade index, however, K 326 showed the highest resistance to frog eye leaf spot. All the varieties, however, showed resistance to the two diseases. It was concluded that K 326 was the source of the resistance to frog eye leaf spot in all the experimental hybrids evaluated and that T60 had the highest Alternaria leaf spot resistance obtained from its parents which are both classified as resistant to the disease.
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