On heterosis, inbreeding depression and general combining ability in annual caraway (Carum carvi)

Abstract

Caraway (Carum carvi) is a medicinal and aromatic plant of the Apiaceae family with a long history of cultivation. To this day, improvements in yield and essential oil content are desirable. In the past, line breeding was used to increase essential oil content with the final intention of combining inbred lines to a synthetic variety by outcrossing. Outcrossing should overcome inbreeding depression and exploit heterosis vice versa. In this study, we wanted to detect whether and to what extent heterosis can be exploited in caraway. In a randomized complete block design with two years of growing and four repetitions per year and genotype, we compared 18 inbred lines with 18 corresponding F1 populations produced in a polycross. In addition to yield, we estimated the beginning of flowering, the end of flowering, maturity, height, thousand-grain weight, stalk attachment rate, shattering rate and essential oil content. Linear mixed models were used to compute variance components, heritability and best linear unbiased estimates. As major result, we detected the existence of better parent heterosis in caraway. To summarize, outcrossing led to a significant increase in yield, thousand-grain weight and height and to an earlier beginning of flowering, end of flowering and maturity. In two-year data, no effect of outcrossing on the essential oil content was observed, but single year data revealed slight effects. We found strong negative correlations between developmental traits and yield. Hence, selection of early developing genotypes seems highly recommendable. Results make us confident that improved annual varieties can be introduced soon.

Heterosis in horticultural crop breeding: combining old theoretical bases with modern genomic views

“…In particular, similar to what emerged in cereals, such as maize (Yang et al, 2017;Liu et al, 2020a;Birdseye et al, 2021), rice (Dan et al, 2014;Shen et al, 2015;Zhu et al, 2016) and wheat (Song et al, 2009), multiple morphological features associated with vegetative tissue also showed different levels of heterosis in vegetable F1 hybrids. These insights, which have been observed depending on the crop and developmental stage, from post-germination to final yield, were derived from Brassicaceae crops, such as Chinese cabbage (Kawamura et al, 2016;Fujimoto et al, 2018;Shiraki et al, 2023), cabbage (Jeong et al, 2017), cauliflower (Verma and Kalia, 2017), rapeseed or canola (Brassica napus L.) (Basunanda et al, 2010;Wolko et al, 2019;Wang et al, 2021;Hu et al, 2022); Solanaceae crops, such as tomato (Chandel et al, 2021;Rajendran et al, 2022), potato (Buso et al, 2003), and eggplant (Kaushik, 2019;Kumar et al, 2020); Apiaceae crops, such as carrot, coriander and caraway (Jagosz, 2011;von Maydell et al, 2021;Hanifei et al, 2022); and Leguminosae crops, such as common bean (Goncalves-Vidigal et al, 2008) and pea (Sharma et al, 2023).…”