Answer:
2/3 of the progeny would be green
Explanation:
Lethal alleles means that their presence result in death of the organism
Assuming this Lethal allele is recessive --> a
This way, if there is AA or Aa the plant will survive, otherwise if there is aa the plant will not survive
Than, assuming AA is a progeny white and Aa is green
Aa x Aa
2/3 Aa - Green
1/3 - White
1/3 - plant will not survive
Crossing 2 green progeny with each other
Aa x Aa
2/3 - Green