Peanut Kernel Shrivel (PKS) is a currently undiagnosed condition affecting peanut crops primarily in the Bundaberg growing region. It is a condition where kernels in pods on a plant approaching maturity cease filling normally, and fail to reach their full size resulting in reduced kernel size and high shell %, which reduces overall crop yield, quality/grading and price/Mt of farmer stock. Affected kernels are small and often develop a shrivelled testa with light tan colour. There are no aboveground symptoms as overall canopy growth (leaf and stem) from PKS affected plants appear healthy with no obvious signs of nutrient deficiency or disease.
Since 2011, the peanut industry in the Bundaberg region has seen a steady rate of decline in crop grade out due to the increasing impact of PKS. PKS is currently costing the industry more than $2.5M+ p.a., and Bundaberg growers are threatening to reduce peanut plantings if a solution to PKS is not found soon.
To date, efforts to detect its cause have been unsuccessful. Results from initial investigations showed no evidence to indicate abiotic (including water quality and nutritional status) or biotic (including insect, nematodes, viruses and bacteria) cause. Some recent research results have suggested some sort of pathogen (e.g., fungi) may be involved, and possibly be associated with some sort of toxin or excess hormone production.
Work to identify possible biotic factors, focused on fungi and bacteria, is currently underway. A total of 33 fungi and 14 bacteria morphotypes have been identified from 80 symptomatic and asymptomatic plants. DNA sequencing was used to identify fungal and bacterial isolates and those consistently isolated from PKS affected plants will be used to perform Koch’s postulates.
Once the cause(s) of PKS is established, the next step is to develop management strategies to minimize its incidence in commercial peanut crops.