Diurnal Alternating Temperature Improves Germination of Some Wild Potato (Solanum) Botanical Seedlots

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Abstract

Potato has about 100 wild species relatives that are multiplied in the form of botanical seed populations by genebanks and distributed for use in research and breeding, so understanding factors that affect seed germination is valuable. This is especially true for problematic seedlots that have slow and low (“trickle”) germination even when subjected to germination techniques that give optimal results in most other seedlots in the genebank. Twelve seedlots with trickle germination even after at least 2 years of storage and 2 robustly-germinating positive control seedlots encompassing 9 species were germinated in petri plates, and subjected to day/night = 10 h/14 h = 20C/6C alternating temperature (AT) trials along with constant room temperature (RT) controls, in the spring of 2015 and 2016. When Relative Area Under the Germination Progress Curve (RAUGPC) was calculated, normal germinating seedlots’ germination in AT was not significantly different from RT control. Some species’ seedlots’ RAUGPC germination in AT was nearly zero, some were about 50% of RT control, and some in AT germination had RAUGPC double or even triple that of RT control. In a separate trial in 2017, four seedlots most responsive to AT were shown to germinate significantly better in constant cold than their RT controls, but not as well as seeds germinated under AT. Also in 2017, two seedlots known to be very dependent on gibberellin pretreatment were tested. RT germination without gibberellin had RAUGPC of only 13% of RT control, but AT without gibberellin pretreatment increased this to 65%, showing AT substantially substitutes for gibberellin pretreatment in these seedlots. AT could be a useful application to all seed germination assays in the genebank if it facilitated a better assessment of the potential viability of trickle-germinating seedlots. But one would need to identify and exclude those seedlots for which alternating temperature greatly depresses germination.

Keywords

Germination US Potato Genebank 

Abbreviation

USPG

US Potato Genebank

Resumen

La papa tiene cerca de 100 especies silvestres en la familia, que se multiplican en forma de poblaciones de semilla botánica por los bancos de germoplasma, y son distribuidas para su uso en investigación y mejoramiento, de manera que es valioso el entendimiento de los factores que afectan la germinación de las semillas. Esto es especialmente cierto para lotes de semilla problemáticos que tienen germinación lenta y baja (“a cuentagotas”), aún cuando se expongan a técnicas de germinación que dan resultados óptimos en la mayoría de los otros lotes de semilla del banco. Doce lotes de semilla con baja germinación aún después de por lo menos dos años de almacenamiento, y dos lotes como testigo positivo de germinación robusta que incluían nueve especies, se germinaron en cajas Petri, y se les sometieron a ensayos con un régimen de luz día/noche de 10/14 hs, 20 °C/6 °C de temperatura alternada (AT), junto con testigos a temperatura ambiente constante (RT), en la primavera de 2015 y 2016. Cuando se calculó el área relativa bajo la curva de progreso de la germinación (RAUGPC), la germinación de los lotes de semilla de germinación normal en AT no fue significativamente diferente del testigo RT. El RAUGPC de germinación de algunos lotes de especies en AT fue cerca de cero, algunos fueron de cerca de 50% del testigo RT, y algunos en germinación AT tuvieron un RAUGPC el doble o aún el triple que el testigo a RT. En un ensayo por separado en el 2017, se sembraron cuatro lotes de semilla de mejor respuesta a AT y germinaron significativamente mejor en frío contante que sus testigos a RT, pero no tan bien como las semillas germinadas bajo AT. También en el 2017, se probaron dos lotes de semilla de los que se sabía que eran muy dependientes de los tratamientos de giberelina. La germinación a RT sin giberelina tuvo un RAUGPC de solamente 13% del testigo RT, pero en AT sin el pretratamiento de giberelina lo aumentó a 65%, mostrando que AT substituye substancialmente el pretratamiento con giberelina en estos lotes. La AT pudiera ser una aplicación útil para todos los ensayos de germinación de semilla en el banco de germoplasma si se facilita un mejor análisis de la viabilidad potencial de los lotes de germinación lenta. Pero necesitaríamos identificar y excluir aquellos lotes de semilla para los cuales la temperatura alternante deprime grandemente la germinación.

Notes

Acknowledgements and Perspectives

This study demonstrates how various threads can be drawn together over a long time into a single experiment. In 1985, Mrs. Jean Smejkal, technician at USPG identified similar trickle-germinating seedlots that were used in our 1986 experiment. She also first identified the S. acaule seedlots which, in 1999, we documented as being highly dependent on GA to sprout, providing the ideal materials in the current study for testing for stimuli that substitute for GA. In 1996, discussions about seed germination with Dr. Joe Pavek, USDA/ARS, potato breeder from Aberdeen Idaho suggested that AT might improve the germination of wild “trickle” germinating seedlots. We thank these colleagues and Mrs. Renee Sauer, USPG technician, for her assistance in finally putting the potential of AT to a systematic test.

Disclaimer

Specification of particular brand names does not imply an endorsement by USDA or that they are necessarily superior to other comparable products.

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Copyright information

© The Potato Association of America 2018

Authors and Affiliations

  1. 1.USDA/Agricultural Research ServiceUS Potato GenebankSturgeon BayUSA

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