‘Banana variety mixtures’ a hope to controlling Black sigatoka damage in Uganda
August 20th, 2012
Black sigatoka disease, caused by Mycosphaerella fijiensis, is second most devastating disease of banana and plantain. It is spread through air-borne conidia and ascospores. The disease decreases photosynthesis, reduces fruit size and induces early maturation in susceptible banana cultivars thus leads to yield reductions that may exceed 50% (Rodriguez-Garcia et al., 2010). Currently, recommended control methods for Black sigatoka include use of fungicides but their effects on the environment are a cause for concern as quarantine restrictions are difficult to enforce.
Farmers in Nakaseke, Kabwohe and Bunyaruguru reported a variation in host resistance to Black sigatoka within and among farms, sites, as well as in the different varieties of bananas during household surveys and focus group discussions that were conducted. When these farmers’ fields were assessed, there was variation in the intensity of Black Sigatoka on the different banana cultivars under the different geographical locations. Banana cultivars in Kabwohe had higher Index of non- spotted leaves (INSL) of 84, followed by Bunyaruguru with 71- 79 and Nakaseke with 49.1- 78. Nakitembe, Enyeru and Kibuzi varieties had higher INSL values in Kabwohe and Bunyaruguru and very low values in Nakaseke. Average Leaf damage of 1-5% was observed on all cultivars in three sites. According to the on-farm trials established in Nakaseke and Bunyaruguru, variation in host response to sigatoka among cultivars across sites was significant . In Nakaseke, Km5 ,FIA17 were resistant while Enyeru, Musakara, M9, Gross Mitchel were less affected . In Bunyaruguru Km5, FIA 17 were resistant, Enzirabahima ,Kibuzi, Nakinyika, Nakabururu, Gross Mitchel and M9 were tolerant . The rest were susceptible. Disease intensity differed among cultivars and sites and was lower in Bunyaruguru with 0-5% damage compared to 1-15% in Nakaseke .The high INSL-value observed in Gross Mitchel which is a susceptible check may be as a result of the effect of having planted a diversity banana varieties together that lowered the disease incidences and intensity.
The variability of Black sigatoka intensity observed among cultivars and across sites may be influenced by a number of factors like soil fertility, genetic variability, climatic conditions and plantation management style. These preliminary findings indicate that growing mixtures of different banana cultivars is a likely option for control of Black sigatoka. This gives hope to poor farmers who cannot afford fungicides but also to us all who desire a healthy environment.