Commercial storage of potatoes often relies on the use of sprout inhibitors to prolong storage and reduce spoilage. The compound 1,4-dimethylnaphthalene (DMN) has seen increase application as a sprout inhibitor in the potato industry as older chemistries are being phased out. The mode of action of DMN is poorly understood as is the sensitivity of potato tissues to this new class of inhibitor. During storage potato tubers transition from a state of endo-dormant to eco-dormant and it is not known if the DMN response is consistent across this developmental transition. RNA-seq gene expression profiling was used to establish if stored potato tubers (Solanum tuberosum cv La Chipper) have differential sensitivity to DMN as tubers age. DMN was applied at three different times during storage; just after harvest when tubers are in endo-dormancy, midwinter at early eco-dormancy, and in spring during late eco-dormancy when sprouting was prevented via exposure to cold storage temperatures. Changes in gene expression were lowest during endo-dormancy while midwinter and spring treatments exhibited a greater and more diverse expression response. Functional analysis of differential gene expression demonstrated gene sets associated with DNA replication, cell division, and DNA methylation are suppressed after DMN treatment. However, gene sets associated with salicylic acid, jasmonic acid, abiotic and biotic stress responses are elevated by DMN only after endodormancy terminates. Gene clusters associated with pathogenesis related proteins PR-4 and PR-5 are also upregulated in response to DMN. These results indicate that DMN sensitivity changes as potato tubers age and transition from endo-dormant to eco-dormant in storage and the overall response is a shift in gene classes that regulate growth and response to stress.

The compound 1,4-dimethylnaphthalene, originally isolated from dormant potatoes, is currently in use as a commercial sprout inhibitor. Growers and processors report a reduction in fungal infections in potatoes treated with DMN resulting in increased yields. To assess the effects of DMN on fungal growth a culture of Fusarium oxysporum was isolated from potato tubers and identified via DNA fingerprinting using the 18ITS ribosomal region. Growth of F. oxysporum was inhibited by 31% after four days of exposure to DMN but overall rate of spore germination was not affected by DMN treatment. The growth of additional fungi, including Alternaria alternata, Aspergillus niger, Epicoccum nigrum, Gnomoniopsis smithogilvyi, Phoma medicaginis, and Pythium ultimum was inhibited by DMN as was suppression of sporulation in A. niger. These results suggest that DMN is fungistatic at the application levels examined.

The shoot apical meristem (SAM) in plants is composed of totipotent cells that generate the major plant organs including leaves and flowers. Within the SAM synthesis and movement of auxin creates a hormonal flux. In production of leaf primordia, the hormonal flux alters a series small ribonucleic acids (RNAs) that impact the expression of homeotic genes. This results in the generation of a WUSCHEL/CLAVATA feedback loop that generate niches that result in the placement of leaf primordia. This placement of leaf primordia generates the overall phyllotaxis and nodal architecture that defines the major plant body. In perennial plants, seasonal cues alter primordia development resulting in shifts between true leaves and bud scales creating the overwintering meristem. How the transition between bud scales and leaf primordia occurs in unclear. Key Concepts The initiation of leaf primordia at nodes is regulated by an auxin gradient within the SAM. A series of homeotic genes are associated with both SAM formation and establishment of leaf primordia and leaf organ symmetry including Knotted1, WUSCHEL‐RELATED Homeobox 1 and CLAVAT‐type (CLV) homoeotic genes. Small RNAs play a critical role in the developmental processes associated with the SAM development. Auxin flux is directed by PIN1 transporter polarity controlled by MONOPTEROS . Responses to seasonal variation alter leaf primordia development.