Table 1: Phenotype and genotype of major lettuce mutants derived from natural and artificial sources.


Domestication of lettuceNaturalLoss 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[36]
Growth and developmentEMSDwarfs with reduced stature, shortened internodes, and loss of ability to produce or respond to GAdwf-1, dwf-2, dwf-3, dwf-4 [11, 12]
NaturalEarly floweringEf-1, ef-2, Ef-3, ef-4, Ef-5, Ef-6[1316]
NaturalMale sterilityms-1, ms-2, ms-3, ms-4, Ms-5, ms-6, Ms-7 [17, 18]
Natural, EMSChlorophyll deficiencycd-1, cd-2, cd-3, cd-4, cd-5, cd-6, cd-7[19, 20]
NaturalReduced gravitropic response in hypocotyls and inflorescence stemsweary[53]
Miniature lettuceEMSAbout one-half the diameter of normal crisphead lettuceDerived from crosses with dwf-1 mutant[21]
Herbicide toleranceNaturalTolerance to sulfonylurea, imidazolinone, and triazolopyrimidineA single incompletely dominant gene[2226]
Downy mildew resistanceNatural, γ ray, fast neutron, EMS, transposonComplete loss of resistance specificitiesdm1, dm3, dm7, dm5/8[32, 3440]