Yellow Sigatoka screening - agronomic evaluation trial (October 2020)
Katie Robertson, Jeff Daniells, David East, and Carole Wright, Queensland DAF (Dec 2023)
The screening trial assessing new varieties’ resistance or susceptibility to the fungal leaf disease, yellow Sigatoka is now complete. Varying degrees of leaf spot resistance were observed among the Cavendish (highly susceptible), Lady Finger (intermediate resistance) and CIRAD hybrids (resistant).
An estimated $25-30 million per year is spent on controlling yellow Sigatoka leaf spot (Pseudocercospora musae) in Australian banana plantations. Identifying varieties with better resistance to the disease, provided they were otherwise commercially viable, would be of great benefit to the industry, by reducing input costs and reliance on fungicides.
Over the 2023 wet season, a yellow Sigatoka screening trial was conducted at the South Johnstone Research Facility. This was after the agronomic assessments on 15 varieties had been completed in the 2020 Variety Evaluation and the block was nurse-suckered.
Leaf disease control ceased a few months prior to nurse suckering to build up inoculum levels and ensure adequate disease pressure. Plants were assessed for severity of leaf spot disease on 3 occasions, at monthly intervals leading up to bunching.
The assessment consisted of determining the Youngest Leaf Spotted (10 or more mature necrotic lesions) (YLS), and the Youngest Leaf with greater than 33% of the leaf lamina destroyed by disease (YL33).
The Total number of Functional Leaves (TFL) was recorded if the disease was not present or had not progressed to the >33% necrosis severity level. For the purposes of this article, only the YLS and TFL data will be discussed.
Figure 1 shows four of the varieties had comparable disease severity to the very susceptible reference variety, ‘Williams’, which had an average YLS of 4.5. These included the TR4 resistant Cavendish ‘Asia Pacific #1’, along with the two tetraploid ‘High Noon’ selections (one with a ‘clean’ rachis [HNC] and one with a ‘dirty’ rachis [HND]) , and the Pendulous Lady Finger selection.
The other four Lady Finger varieties demonstrated slightly better resistance and were statistically similar to ‘Pacific Plantain’ (YLS = 6.2), which has a documented intermediate level of resistance to leaf spot. Overseas, the hybrid ‘CIRAD 925’ has demonstrated both yellow and black Sigatoka (Pseudocercospora fijiensis) resistance (Risède et al. 2019).
It was anticipated that the other three CIRAD hybrids may also possess this characteristic, which proved to be the case. Although no leaf spot was present, ‘CIRAD 925’ and ‘CIRAD 918’ only maintained around seven functional leaves throughout the assessments, with older leaves snapping due to petiole weakness, while ‘CIRAD L9’ and ‘CIRAD X17’ sustained over 10 functional leaves.
The common leaf fungi, Cordana leaf spot (Neocordana musae) and banana leaf speckle (Mycosphaerella musae), were likely present on all varieties, but more obvious along the leaf margins of the CIRAD hybrids due to the absence of yellow Sigatoka. ‘Dwarf Ducasse’ was included as the resistant reference variety and supported an average of 13 functional leaves with no yellow Sigatoka present.
References
Risède, J.-M., Achard, R., Brat, P., Chabrier, C., Damour, G., Guillermet, C., de Lapeyre., Lœillet, D., Lakhia, S., Meynard, P., Tixier, P., Tran Quoc, H., Salmon, F., Côte, F.-X. and Dorel, M. (2019). The agroecological transition of Cavendish banana cropping systems in the French West Indies. In The agroecological transition of agricultural systems in the Global South. Côte, F.-X., Poirier-Magona, E, Perret, S., Roudier, P., Rapidel, B., Thirion, M.-C, eds. (Agricultures et défis du monde collection, AFD, CIRAD, Éditions Quæ, Versailles). Pp. 107 – 126. https://agritrop.cirad.fr/592993/1/ID592993.pdf
More information
This research has been funded as part of the project Improved Plant Protection for the Banana Industry (BA16001), which is funded by Hort Innovation, using the banana research and development levy, co-investment from the Department of Agriculture and Fisheries and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.
