VIRUS TITER, MEMBRANE-PERMEABILITY AND LYSOSOMAL ACTIVITY DURING DEVELOPMENT OF TIP NECROSIS IN BEAN YELLOW MOSAIC-VIRUS-INFECTED BEANS

Percentage tip necrosis in bean (Phaseolus vulgaris) induced by bean y ellow mosaic virus (BYMV) infection increased between 16 and 24-degree s-C and decreased to near zero above 28-degrees-C. Plants that failed to develop tip necrosis at 32-degrees-C did so within 4 to 5 days when moved to 24-degrees-C. The development of tip necrosis appeared to be associated with virus multiplication. A tip necrosis-induCing substan ce (TNIS) might be responsible for the tip necrosis. TNIS was shown to induce cellular leakage from the infected plants, which might be cond ucive to tip necrosis, and was seemingly inhibited at a temperature hi gher than 28-degrees-C. The inhibition of tip necrosis in BYMV-infecte d plants coincided with an exponential increase of acid phosphatase ac tivity, suggesting that lysosomes are involved. Further investigation is being undertaken to isolate and characterize the potential TNIS and to identify the enzyme(s) which might be responsible for its degradat ion.