Multi-environment evaluation of combining ability and heterosis for root yield and attributing traits in ashwagandha [Withania somnifera (L.) Dunal]

Abstract

Ashwagandha (Withania somnifera), a vital medicinal crop, suffers from limited genetic diversity, which constrains its yield potential on a commercial scale. Exploiting combining ability and heterosis can serve as effective breeding strategies to enhance productivity and alkaloid content. A comprehensive study was conducted during Rabi 2022-2023, involving 60 hybrids, their parental lines and standard checks (JA-20, JA-134 and RVA-100), evaluated in a randomized block design across three diverse environments. Significant variability was observed for alkaloid content, dry root yield and its contributing traits. To refine parent selection, combining ability analysis was performed, revealing that both general combining ability (GCA) and specific combining ability (SCA) were significantly influenced by environmental interactions. Parents, including UWS-23, UWS-60, UWS-13, UWS-79, UWS-100, UWS-104, UWS-131, UWS-134, GP-49 and GP-51, exhibited significant positive general combining ability (GCA) effects for dry root yield, indicating the predominance of additive gene action. Among these, UWS-100 emerged as a promising general combiner for both dry root yield and total alkaloid content. Furthermore, specific cross combinations such as UWS-104 × UWS-60, UWS-132 × UWS-10, and UWS-92 × UWS-10 demonstrated high standard heterosis for dry root yield over the superior check variety JA-20 in environment E3. These hybrids also showed significant positive specific combining ability (SCA) effects, highlighting the role of non-additive gene action in trait expression. These findings highlight the potential of identified genotypes for use in hybrid breeding programs aimed 5at improving both yield and phytochemical composition in Ashwagandha. The integration of heterosis exploitation with combining ability analysis provides a strategic approach for developing superior Ashwagandha cultivars, offering significant scope for commercial cultivation and enhanced utility in the medicinal plant industry.