One form of male sterility (Ms) in corn is maternally transmitted. Plants of a m

Question

One form of male sterility (Ms) in corn is maternally transmitted. Plants of a male sterile line crossed with normal pollen give male-sterile plants. In addition, some lines of corn are known to carry a dominant nuclear restorer allele (Rf1) that restores pollen fertility in male sterile lines. Another dominant restorer (Rf-2) has been found on a different chromosome. Either or both of the restorer alleles will restore pollen fertility in male sterile lines. A male-sterile plant is crossed with pollen from a plant homozygous for Rf-1. An F1 plant from this cross is used as the ovule donor, and crossed with pollen from a normal plant (rf/rf-1). What phenotypes are produced by this cross? O fertile females; sterile males sterile females; fertile males O fertile females; 1/2 fertile males: 1/2 sterile males O 1/2 fertile females; 1/2 sterile females; 1/2 fertile males; 1/2 sterile males O fertile females; fertile males

Explanation / Answer

ANS- fertile females; 1/2 fertile males; 1/2 sterile males

If we cross male sterile(Ms) with normal male sterile

IN F1 generation offsprings will be of 3:1 ratio, and since male sterile consists of dominant allele so male sterile containing dominant allele are 3(Aa genotype for example).

and this F1 generation pollen is considered as ovule donor and we cross this progeny with normal pollen containg dominant allele on another chromosome. Hence in F2 generation we get fertile females; 1/2 fertile males; 1/2 sterile males

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