Abstract
Abstract Black Sigatoka (black leaf streak disease) is caused by the fungus Mycosphaerella fijiensisMorelet. This phytopathogen colonizes banana leaves, resulting in reduced photosynthesis and decreased productivity. Fungicide applications are useful to control black Sigatoka; however, they increase production costs and can have adverse environmental and health impacts. The cultivation of resistant cultivars is regarded as a more economically viable option. The objective of this study was to perform diploid phenotyping in a set of wild banana accessions to identify resistant genotypes. A total of 31 accessions (30 with AA genome and one with AB genome) were phenotyped based on the presence of disease symptoms using a scoring scale. The area under the disease progress curve (AUDPC), the disease severity index (DI), and the disease severity increase index (DII) were estimated. The DII variable proved to be efficient in identifying banana accessions with black Sigatoka resistance. Likewise, the selection index for ranking accessions with moderate black Sigatoka resistance allowed us to identify those genotypes with the highest quantitative resistance. Five diploid accessions (Krasan Saichon, Zebrina, Birmanie, Nº 118, and Tuu Gia) were found to be resistant to this fungal disease; eight accessions (PA Rayong, Pisang Cici, Malaccensis 1, 028003- 01, Microcarpa, Pisang Lidi, Lilin, and Malbut) were moderately resistant.
Highlights
Bananas and plantains are essential components of the human diet for millions of people in tropical and subtropical regions, impacting on social and economic issues (WEBER et al, 2017; ALAKONYA et al, 2018)
This study evaluated 31 banana diploid accessions belonging to Embrapa banana and plantain germplasm collection; all were AA-genome accessions, except for genotype IAC 1 (AB genome) (Table 1)
Heatmap analyses were performed based on the two selection strategies, (AUDPC + disease severity index (DI) and area under the disease progress curve (AUDPC) + DI + disease severity increase index (DII) (Figure 1)
Summary
Bananas and plantains are essential components of the human diet for millions of people in tropical and subtropical regions, impacting on social and economic issues (WEBER et al, 2017; ALAKONYA et al, 2018). Significant losses in bananas and plantains production were assigned to black Sigatoka, a disease caused by the fungus Mycosphaerella fijiensis M. This fungus was first described in 1963, in the Fiji Islands (CROUS et al, 2003), and in Brazil, the first reports date from 1998, when it was identified in plantations around the cities of Tabatinga and Benjamin Constant, in the State of Amazonas, close to the border with Colombia and Peru (GASPAROTTO et al, 2006). M. fijiensis propagation occurs through air-disseminated conidia, which are asexual spores, and through sexual ascospores (CHURCHILL, 2011; ONYLO et al, 2018)
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