Germination and Emergence Response of Common and Tepary Beans to Controlled Temperature1

Abstract

AbstractSoil temperature strongly influences the germination and emergence of common beans (Phaseolus vulgaris L.) and tepary beans (Phaseolus acutifolius A. Gray). The purpose of this investigation was to identify accessions of both species that could potentially germinate and emerge under cool soil conditions, and to determine an optimum germination temperature for tepary beans. Germination of 129 common and 18 tepary bean accessions was initially evaluated at 10°C. The 10 earliest common and the five earliest tepary beans to germinate were entered into an emergence test at three temperatures (12, 14, and 16°C). The common beans emerged 1 day earlier than the teparies at 12 and 14°C, while the teparies emerged 1 day earlier at 16°C. The most cold‐tolerant common bean at emergence was PI 165‐426, while accessions G40034 and PI 319‐443 displayed the highest cold tolerance among the tepary beans. Subsequently, tepary beans were compared to common beans for germination response over six temperatures from 10 to 35°C. In general, tepary and common beans took approximately the same time to germinate except at 35°C where teparies germinated faster. A scarification experiment was undertaken with the same six temperatures as above to determine any effects of the seedcoat on tepary bean germination. Scarification generally resulted in an earlier germination response, but the effect was small. Both germination experiments indicate that the optimum temperature range for teparies is 25 to 35°C, whereas it is lower, 20 to 30°C, for common beans.