Effect of Temperature on the Expression of Necrosis in Soybean Infected with Soybean mosaic virus

Abstract

Soybean mosaic virus (SMV) causes mosaic symptoms in susceptible soybean [Glycine max (L.) Merr.] cultivars and stem‐tip necrosis (STN) in some soybean cultivars carrying resistance genes. The objective of this study was to examine the effect of different temperature regimes on the expression of SMV‐induced STN. Three soybean isolines, ‘Essex’ (rsv, mosaic to SMV strains G1 and G7), V94‐3971 (Rsv1, resistant to G1 and necrotic to G7), and V262 (Rsv1‐n, necrotic to G1 and mosaic to G7), were inoculated with G1 and G7 and maintained in growth chambers with a 12‐h photoperiod and constant temperatures of 10, 15, 20, 25, 30, 32, 33, and 35°C. The STN in V262 induced by G1 and in V94‐3971 by G7 developed at 10, 15, 20, 25, and 30°C, on 44, 41, 14, 8, 8 days after inoculation (DAI), respectively. No STN reaction was induced by either strain at 35°C. Further study demonstrated that STN was induced 7 DAI at 32°C in V262 by G1 and in V94‐3971 by G7, but mosaic symptoms developed in both genotypes at 33°C. However, STN was induced in V262 7 DAI by G1 and in V94‐3971 14 DAI by G7 at an alternate temperature of 33°C day/20°C night. Stem‐tip necrosis was also observed in V262 8 DAI by G1, but not in V94‐3971 by G7 at an alternate temperature 35°C day/20°C night. Essex exhibited mosaic symptoms when infected with G1 and G7 at all temperatures tested, and virus was detected by enzyme‐linked immunosorbent assay (ELISA). Stem‐tip necrosis is a SMV strain‐specific, thermosensitive response associated with SMV resistance genes.