The potential of winter annual cultivation of caraway (Carum carvi L.) under changing climate conditions: Exploring genetic resources and evaluating cultivation system and sowing density

Biennial and summer annual cultivation of caraway ( Carum carvi L.), both sown in spring, are severely affected by climate change. As intermediate alternative, winter annual caraway (sown in autumn) could stabilize yields by harnessing precipitation from autumn to early spring for germination and vegetative growth. To achieve high quality seeds from winter annual cultivation, new cultivars need to be developed. However, breeding is hampered by limited knowledge of genetic resources adaptable to winter annual cultivation. In a first trial, we screened 60 annual genotypes for winter survival rate and essential oil content. We identified 26 genotypes with a medium to high winter survival rate (>50% to 95%), which had biennial material in their breeding history. In a second three-year trial, we compared winter annual (sown in September) and summer annual cultivation (sown in March) with three different sowing densities (50, 100 and 200 seeds/m 2 ) using four different genotypes. We measured seed yield, essential oil content, thousand-grain weight, plant height, the beginning of flowering, the end of flowering, and maturity. In the first harvesting year, with low precipitation, winter annual cultivation yielded between 113 and 170 g/m 2 , whereas yields of summer annual cultivation were extremely low (<30 g/m 2 ). In the following years with standard to high precipitation and heavy rainfalls, no general advantage of winter annual cultivation was observed. Shattering of seeds was identified as notable issue during these years. In several comparisons, a higher sowing density resulted in higher yields without affecting essential oil content.