Breeding for disease resistant dark-fire-cured tobacco in Malawi
Dark fire-cured tobacco (DFC) is the third most important tobacco type grown in Malawi after Burley and flue-cured. With Malawi Western, MW 86-57 and AWL 28 as the leading approved DFC varieties for production in Malawi, the local and regional requirements are well supplied despite the genetic deficiencies that come with them. Such genetic deficiencies include lack of resistance to root-knot nematodes (Meloidogyne sp.), fusarium wilt (Fusarium oxysporum), bacterial wilt (Ralstonia solanacerum), angular leaf spot (Pseudomonas syringae pv tabaci) and alternaria brown leaf spot (Alternaria alternata). In a country where farm-served seed is a common practice, including that of open pollinated tobacco varieties, development of male sterile varieties has become urgent in order to comply with good agricultural practices (GAP) and ensure seed integrity and traceability by discouraging tobacco seed recycling. Consequently, a breeding programme involving the transfer of resistant genes from the flue-cured and Burley environments through backcross breeding started in the early 1990s in order to develop multiple disease resistant parental breeding lines that would later facilitate the development of the first group of male sterile Malawi DFC hybrids with resistance to nematodes, Fusarium wilt, Bacterial wilt, Angular leaf spot and Alternaria brown leaf spot. This report summarises data of the recent development of the DFC tobacco improvement programme by assessing disease ratings, leaf yields and quality of the first promising group of the hybrids to emerge from this long term conventional breeding. Recent results showed that two of the several hybrids have expressed good resistance, albeit at varied levels, to nematodes, bacterial wilt, fusarium wilt, angular leaf spot and alternaria. Further breeding is continuing to build on the genetic gains that earlier breeding efforts have achieved so that more superior parental lines are harnessed for development of even better hybrids in the near future for use by growers in Malawi.