In maize, fertile pollen is formed on the basis of normal cytoplasm (CIT), and hereditary sterility of pollen is due to the presence

In maize, fertile pollen is formed on the basis of normal cytoplasm (CIT), and hereditary sterility of pollen is due to the presence of sterile cytoplasm (CIT). The dominant Rf gene restores fertility, and sterile cytoplasm exerts its effect only in combination with the recessive alleles of this gene (rfrf). Which parent plant should be crossed: 1) plants with the CIT (s) rfrf genetic system to restore its fertility; 2) a sterile plant with the CIT (s) rfrf genetic system to ensure its sterility?

1) A plant with the CIT (s) rfrf genetic system, to restore its fertility, must be crossed with a plant that has the CIT (s) RfRf or CIT (N) RfRf genetic system;
2) a sterile plant with the CIT (s) rfrf genetic system must be crossed with a plant that has the CIT (s) rfrf or CIT (N) rfrf genetic system to ensure its sterility.

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