A .   EMS induced N - suppresor mutant line B201 is partially resistant to TMV B .   Fast Neutron induced N - suppresor mutant is susceptible to TMV Fig 2: Two N - Suppresor Mutant Phenotypes .     A) The EMS induced mutant B201 is partially resistant to TMV .   This mutant develops both HR and mosaic symptoms on the same leaf .      B) The fast - neutron induced mutant is susceptible to TMV .   This mutant develops mosaic symptoms even though it contains the N transgenes . Wild - type NN phenotype 32°C Survivors Putative N - suppressor mutant phenotype Dead 24°C 3 days 3 days TMV Fig 1: Seedling Lethal Screen .   N resistance is inactivated at 32?C, which allows the virus to spread systemically .   After shifting to 24?C, seedlings with a functional N pathway undergo HR in every cell where virus is present, killing the plant .  

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