Mutations in Lettuce Improvement

Table 1

Phenotype and genotype of major lettuce mutants derived from natural and artificial sources.

Function	Source	Trait	Gene	Reference
Domestication of lettuce	Natural	Loss of prickles from leaves and stems, less latex and tissue bitterness, reduced suckering, slow bolting, reduced seed shattering, and increased seed size and oil content		[3–6]
Growth and development	EMS	Dwarfs with reduced stature, shortened internodes, and loss of ability to produce or respond to GA	dwf-1, dwf-2, dwf-3, dwf-4	[11, 12]
	Natural	Early flowering	Ef-1, ef-2, Ef-3, ef-4, Ef-5, Ef-6	[13–16]
	Natural	Male sterility	ms-1, ms-2, ms-3, ms-4, Ms-5, ms-6, Ms-7	[17, 18]
	Natural, EMS	Chlorophyll deficiency	cd-1, cd-2, cd-3, cd-4, cd-5, cd-6, cd-7	[19, 20]
	Natural	Reduced gravitropic response in hypocotyls and inflorescence stems	weary	[53]
Miniature lettuce	EMS	About one-half the diameter of normal crisphead lettuce	Derived from crosses with dwf-1 mutant	[21]
Herbicide tolerance	Natural	Tolerance to sulfonylurea, imidazolinone, and triazolopyrimidine	A single incompletely dominant gene	[22–26]
Downy mildew resistance	Natural, γ ray, fast neutron, EMS, transposon	Complete loss of resistance specificities	dm1, dm3, dm7, dm5/8	[32, 34–40]