How many different types of gametes are produced from a plant with genotype yyss?

during the process of the gamete formation, the law of segregation is followed. All the alleles in the genotype are segregated from each other. Each allele of the genotype will be present in a separate type of gamete. The plant having the genotype 'yyss' will lead to the formation of the following gametes: ys,ys,ys,and ys.

These four gametes contains the different combinations of the alleles of the genotype, but because the plant is homozygous, the type of all these gametes will be same.

Hence, the answer is 'the four similar types of gametes will be formed'.