Overcoming seed coat–imposed dormancy in wild species of Cajanus and Rhynchosia

Abstract

AbstractOccurrence of physical dormancy or hard seed coat prevents proper utilization and conservation of wild species of Cajanus and Rhynchosia, which offers a source of many useful traits. Hence, an attempt has been made to understand the variability in hardseededness and the pretreatments (hot air treatment for 3, 5, 7, and 14 days; hot air treatment for 30 and 60 min; sulfuric acid scarification for 2 and 5 min; partial incision on seed coat) to overcome it in 44 accessions of 10 wild pigeon pea species. The level of hardseededness varied from 36% to 100% with an average of 76.5%. Likewise, time to 1% germination or time taken to initiate germination (T1), time to 50% germination (T50), and mean germination time (MGT) varied between 16.18–249.9 h, 94.7–607.7 h, and 37.5–153.2 h, respectively. Overall, all the treatments reduced hardseededness and improved germination over the control, with partial incision on seed coat being the best treatment for all the species recording 70%–98% germination, except for Rhynchosia aurea (30%) and Cajanus cajanifolius (59%). The hot water treatment for 30 and 60 min was the best treatment for C. cajanifolius recording germination of 66%–70% as compared to 11% in control. The sulfuric acid scarification for 2 min was the best pretreatment for overcoming dormancy and improving germination in Rhynchosia bracteata, Rhynchosia rothii, and Rhynchosia rufescens. The result indicated a significant inter‐ and intraspecific variation in the effectiveness of pretreatments in overcoming physical dormancy, suggesting that the optimum pretreatment for overcoming hardseededness should be standardized for each accession. Also, the dormancy‐breaking pretreatments not only reduced hardseededness and improved final germination percent but it also reduced time for T1, T50, and MGT, suggesting that use of such pretreatments before sowing could result into higher, uniform, and rapid germination.