Assessment of combining ability for targeted traits in periwinkle (Catharanthus roseus (L.) G. Don) through diallel analysis

Catharanthus roseus (L.) G. Don is a vital summer season perennial semi shrub and multipurpose drought resilient flower crop of the tropical region of the Indian subcontinent. This industrially dominant crop is primarily availed as border, bedding and pot culture in landscaping; and also cultivated for its anti-cancer alkaloid compounds enriched plant parts. Hence, the present study was focused to explore diversity. Six inbred lines of periwinkle were crossed in full-diallel fashion with an objective of identifying superior cross-combinations for high general, specific and reciprocal combining ability. The analysis of variance for combining ability was highly significant for growth and flowering traits indicated existence of both additive and non-additive gene actions. However some traits showed only additive effect due to non-significant general combining ability. The parental lines of Vi-13–2 and Vi-15–2 expressed superior general combining effects for flower yield and considered as good general combiners for crossing programmes. The cross combinations Vi-15–1 × Vi-14–3 and Vi-16 × Vi-15–2 exhibited significantly positive specific combining ability effects for flower yield and considered as good specific direct combiners. High specific direct cross combiners necessitate poor × good, good × good and poor × poor parental combinations and can be contribute additive × dominance, additive × additive, dominance × dominance and epistatic gene interactions. The specific reciprocal cross combiners identified as Vi-14–3 × Vi-29 and Vi-14–3 × Vi-13–2 with superior expression in the reciprocal magnitudes for various traits might be due to cytoplasmic effects. The current investigation is designed to identify the best performing inbred lines for ornamental utilization as well as lines that can be exploited as parents in subsequent crosses.