A study looking for additional sources of resistance to the deadly fungal disease of banana, black Sigatoka, has identified 11 new accessions that are potential sources of resistance to Pseudocercospora fijiensis.
These accessions are from a collection of banana germplasm maintained by International Institute of Tropical Agriculture (IITA) at Sendusu, Wakiso District in Uganda.
They can be used to broaden the current narrow genetic base for ongoing efforts to breed bananas with resistance to the disease.
Black Sigatoka, caused by P. fijiensis, is one of the most devastating banana diseases. In commercial banana-growing systems, black Sigatoka is primarily managed using fungicides.
However, this method of controlling the disease is not feasible for resource-limited smallholder farmers. Therefore, developing banana varieties resistant to P. fijiensis remains one of the most effective ways to support smallholder farmers to protect their bananas, income, and food security.
Currently, breeding banana resistant to P. fijiensis is dependent on a narrow gene pool of resistance genes, mostly from the wild banana accession, Calcutta 4 and the edible Pisang Lilin banana. P. fijiensis can reproduce sexually in nature; thus, it can evolve, generating variants that can overcome existing sources of resistance.
There is a need to diversify the pool of resistance sources to ensure the durability of developed resistant cultivars. Therefore, the identification and introgression of new and effective P. fijiensis resistance genes into banana hybrids and cultivars is necessary.
The team evaluated 95 banana accessions under field conditions in Sendusu to identify additional sources of resistance. Eleven of these accessions responded to P. fijiensis infection in a similar manner to Calcutta 4, a cultivar widely used as a source of P. fijiensis resistance genes. Therefore, these 11 accessions could be used as parents in IITA and NARO’s banana program in East Africa.
IITA PhD student and the lead author, Janet Kimunye, explains “some of the accessions identified to be resistant to black Sigatoka like Tani, Truncata, Balbisiana, Long Tavoy, Pahang, Pisang KRA, and Malaccensis 0074, are diploids and can be useful for breeding programs.’’
Other accessions that grouped with Calcutta 4, like Pisang Lilin, Monyet, and Cacambou, allowed the pathogen to sporulate. Thus, their reaction is more appropriately described as intermediate or partial resistance characterized by typical but slow symptom progression up to necrosis.
“The resistance provided by these accessions needs to be stacked to develop cultivars with durable black Sigatoka resistance’’, Senior Pathologist at IITA, George Mahuku, recommends.
The study was drawn from IITA Uganda and Tanzania in collaboration with researchers from the Department of Plant Pathology, Stellenbosch University, University of Hohenheim, and the Laboratory of Tropical Crop Improvement, KU Leuven, Belgium.
This study was part of the project ‘Improvement of banana for smallholder farmers in the Great Lakes Region of Africa’, under the CGIAR Research Programme for Roots, Tubers and Bananas (CRP-RTB) framework.
The findings can be found in a paper ‘Sources of resistance to Pseudocercospora fijiensis, the cause of black Sigatoka in banana’ published in Plant Pathology on May 24.