Two protease inhibitors from Cajanus cajan seeds have been purified to homogeneity by trichloroacetic acid (TCA) solubilisation, ion-exchange and gelfiltration chromatography followed by preparative polyacrylamide gel electrophoresis. One of the inhibitors, Cajanus trypsin-chymotrypsin inhibitor (CTCI), inhibits both bovine trypsin and chymotrypsin while the other, Cajanus trypsin inhibitor (CTI), inhibits only bovine trypsin. The two inhibitors contained no carbohydrate and had an isoelectric point of 6. CTCI and CTI had average molecular weights of 15000 and 10500, respectively. The purified inhibitors in solution were stable to heat at 80°C for 15 min and pH 7-10. In the pH range 3-5, 80% of the activity was retained. Autoclaving totally destroyed the inhibitor activity. CTCI had two sites for trypsin binding and one site for chymotrypsin binding while CTI had only one site for trypsin binding. The inhibitors were very specific towards mammalian serine proteases and did not inhibit other proteases or serine proteases of bacterial origin.

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Detached mungbean (Vigna radiata L.Wilczek) leaves were inoculated with a conidial suspension of a local isolate (TI-1) of the powdery mildew pathogen (Erysiphe polygoni DC) under controlled environment conditions. Based on the latent period and severity of the infection, a rating scale of 0-5 was used to classify the host pathogen interactions. Reactions 0, 1 and 2 were considered resistant and referred to as R0, R1 and R2 while 3, 4 and 5 were classified as susceptible (S). RUM lines (resistant to powdery mildew) and their derivatives are crossed with several susceptible (reaction types 3-5) genotypes and the inheritance of the resistance was studied in the F1, F2 and F3 generations. The results showed that powdery mildew resistance in mungbean is governed by two dominant genes designated as Pm-1 and Pm-2. When both Pm-1 and Pm-2 were present, an R0 reaction was observed after inoculation with TI-1. The resistant reaction was R1 when only Pm-1 was present and R2 in the presence of Pm-2. In the absence of both Pm-1 and Pm-2, susceptible reactions 3, 4 and 5 were observed.

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