Genetic Analysis of a Baculovirus, Autographa californica Nuclear Polyhedrosis Virus I. Isolation of Temperature-Sensitive Mutants and Assortment into Complementation Groups

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Abstract
Temperature-sensitive (ts) mutants were isolated from the baculovirus A. californica (alfalfa looper) MNPV, grown in Spodoptera frugiperda (fall armyworm) cells in the presence of N-methyl-N''-nitro-N-nitrosoguanidine. Of 567 plaque isolates screened, 27 were temperature sensitive (ts), representing a mutation frequency of 4.8%. Ten ts mutants were studied in detail; 6 failed to yield nonocclude virus at 33.degree. C (NOV mutants), whereas the other 4 produced nonoccluded virus but were restricted in formation of polyhedra at 33.degree. C (Poly mutants). One of the 6 NOV mutants failed to synthesize viral DNA. Reversion and leak frequencies were determined, and the mutants were assorted into complementation groups based on the yield of polyhedrin synthesis in cells coinfected with pairs of mutants at 33.degree. C, as measured by radioimmunoassay. For NOV mutants, complementation indexes were also based on virus yield and were consistent with those based on polyhedrin synthesis. Nine mutants were assorted into 5 complementation groups. One mutant remained unclassified.