Citrus psorosis is probably caused by a bipartite ssRNA virus.

Isolate 90-1-1 Concordia (Argentina) of the citrus psorosis agent was graft-transmitted to citrus and mechanically transmitted to Chenopodium quinoa, which was used as a local lesion assay host. Infected citrus and C. quinoa plant lesions were used as starting materials for the purification of the psorosis-associated agent.

Alfalfa mosaic virus temperature-sensitive mutants. III. Mutants with a putative defect in cell-to-cell transport.

Forty-five mutants of alfalfa mosaic virus with a temperature-sensitive (ts) replication in tobacco leaf discs were assayed in cowpea protoplasts at 25 and 30 degrees . The extent of replication of 9 mutants at 30 degrees was less than 10% of that at 25 degrees, whereas the replication of 14 mutants was not affected at 30 degrees. Twenty-two mutants showed an intermediate ts behavior.

Bacteriophage SPO1 DNA polymerase and the activity of viral gene 31.

Bacteriophage SPO1 DNA-negative (D0) mutants were tested for the induction of viral DNA polymerase during Bacillus subtilis infection. Extracts from SPO1-infected bacteria exhibited enzymatic activity when representative mutants of seven out of the nine known D0 genes were employed. This activity was undetectable in cells infected with mutants in genes 28 and 31.

Alfalfa mosaic virus temperature-sensitive mutants. II. Early functions encoded by RNAs 1 and 2.

Mutants Bts 03 and Mts 04 of alfalfa mosaic virus (AIMV) have temperature-sensitive mutations in genomic RNAs 1 and 2, respectively. These mutants are defective in the production of viral minus-strand RNA, coat protein, and infectious virus when assayed in cowpea protoplasts at the nonpermissive temperature (30 degrees). To determine the temperature-sensitive step in the replication cycle, mutant-infected protoplasts were shifted from an incubation temperature of 25 degrees (permissive temperature) to 30 degrees at different times during a 24-hr incubation period.

Alfalfa mosaic virus temperature-sensitive mutants. I. Mutants defective in viral RNA and protein synthesis.

The replication in cowpea protoplasts of temperature-sensitive (ts) mutants of alfalfa mosaic virus (AIMV) was studied at the permissive (25 degrees) and the restrictive (30 degrees) temperature. Using the Northern blot hybridization technique, it was shown that at the restrictive temperature two RNA 1 mutants, Bts 03 and Bts 04, and two RNA 2 mutants, Mts 03 and Mts 04, were all defective in the synthesis of viral minus-strand RNA, whereas the synthesis of the plus-strand genomic RNAs 1, 2, and 3 and the subgenomic coat protein messenger, RNA 4, was relatively unimpaired. In Bts 04 inoculated protoplasts the RNA 4 produced at 30 degrees was translated into coat protein and viral RNA was encapsidated to give infectious virus.