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Discovery of five additional hardness mutations in the puroindoline b gene sequence of hexaploid
wheat. C. F. MORRIS (1), M. C. Simeone (1), and M. Lillemo (2). (1) USDA-ARS Western Wheat
Quality Lab., Pullman, WA 99164; (2) Dep. Horticulture & Crop Sci., Agric. Univ. Norway, As, Norway.
Grain hardness in wheat results from the loss of puroindoline gene
function. In its natural, "wild-type" state, wheat grain is soft; hardness arises through the loss of
puroindoline a or b protein (null mutations), or the alteration of puroindoline b protein sequence (point
mutations). Currently, seven hardness mutations have been characterized and in all cases one puroindoline
is affected whereas the other remains wild-type. From this, a model of puroindoline gene function suggests
that both proteins are necessary to effect a full level of grain softness. These five new alleles have been
provided the molecular loci designations of Pinb-D1c through Pinb-D1g. Pinb-D1c
is relatively prevalent, whereas the other four alleles are represented by only eight known varieties and their
progenitors. The last three mutations all involve generation of a "stop" codon and a lack of puroindoline b
protein (nulls). A complete description of the molecular genetics of puroindoline grain hardness will be
presented with the progress of backcrossing all hardness alleles into a common background.
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