Overcoming seed coat imposed dormancy in wild species of pigeonpea (Cajanus cajan L. Millsp.)

Abstract Occurrence of physical dormancy in the form of hard seed coat prevents proper utilisation and conservation of wild species of pigeonpea, which offers a source of many useful traits. Hence, in the present investigation attempt has been made to understand the variability in hardseededness and the pre-treatments to overcome it in 44 accessions comprising of 10 wild pigeonpea species ( Cajanus scarabaeoides, C. crassus , C. platycarpus , C. cajanifolius, C. lineatus , Rynchosia minima , R . bracteata , R rothii, R rufescens and R. aurea ). The level of hardseededness varied from 36–100%, with an average of 76.5%. Likewise, the time to initiate germination (T1), achieve 50% germination (T50) and mean germination time (MGT) varied between 16.18-249.9h, 94.7-607.7h and 37.5-153.2h, respectively. Overall, all the treatments reduced hardseededness and improved germination over the control, with partial incision on seed coat (PSCI) being the best treatment for all the species recording 70–98% germination, except for R. aurea (30%) and C. cajanifolius (59%). The hot water treatment (HWT) for 30 and 60 minutes was the best treatment for C. cajanifolius recording germination of 66–70% as compare to 11% in control. The sulphuric acid scarification (SAT) for 2 m was the best pre-treatment for overcoming dormancy and improving germination in R. bracteata , R. rothii and R. rufescens . The result indicated a significant inter and intra species variation in the effectiveness of pre-treatments in overcoming physical dormancy, suggesting that the optimum pre-treatment for overcoming hardseededness should be standardised for each accession. Also the dormancy breaking pre-treatments not only reduced hardseededness and improved final germination percent but it also reduced time for T1, T50 and MGT, suggesting that use of such pre-treatments before sowing could result into higher, uniform and rapid germination.