EN
Seeds of pigeonpea are known to accumulate protease inhibitors (PIs), belonging to the Bowman-Burk inhibitor family. PIs are important for natural defense against phytophagous insect pests. Most insects attack crops at the early stages of seed development. Accumulation patterns of individual PIs and their relationship with each other were studied in developing seeds of 76 pigeonpea lines derived from BDN2 cultivar by ethyl methane sulfonate induced chemical mutagenesis. PIs extracted from these lines, collected between 10 and 40 days after flowering (DAF) and from mature seeds of BDN2 cultivar, were detected by using gel X-ray film contact print method. A total of 9 trypsin–chymotrypsin inhibitors were detected in mature seeds. All the nine PIs were capable of inhibiting proteases. Appearance of detectable levels of individual PIs started around 10 DAF. The PI-3 appeared early and was the most stable. It was accumulated in all the studied lines and was also detected in 84 % of the samples collected 10 DAF. In particular, 14 DAF, the individual PIs were accumulated and accumulation sequence was observed (PI-3, PI-2, PI-5, PI-7, PI-6, PI-4, PI-8, PI-9 and PI-1). Accumulation continued up to 40 DAF when seeds started hardening. Chemical mutagenesis could not produce any variation in the profile of individual PIs in the 76 studied lines in mature seeds. The process of accumulation of inhibitors is sturdy and mutagenesis fails to alter it. The robust mechanism is responsible for early appearance of PI-3. Early accumulated PIs in this study need further exploration for strengthening natural defense of pigeonpea against pests.