Genetic evidence for early flax domestication with capsular dehiscence

Abstract

Flax (Linum usitatissimum L.) is the earliest oil and fibre crop, but little is known about its domestication process. Attempt was made here to assess genetic relationships of 63 Linum accessions representing seven typical groups of cultivated flax and its wild progenitor, pale flax (Linum bienne Mill.), by using 49 informative expressed sequence tag-derived simple sequence repeat (EST-SSR) primer pairs. The seven groups were pale flax from Turkey, pale flax from other countries, and five groups of cultivated flax (landrace, fibre, oil, winter, and dehiscent). From these 63 samples, 366 polymorphic bands were detected, which likely represented 79 loci. These polymorphic bands had frequencies that ranged from 0.016 to 0.984 and averaged 0.284. Group-specific EST-SSR variation (Fst values) ranged from 0.339 to 0.373 and averaged 0.349 and pairwise group EST-SSR variation ranged from 0.067 to 0.507. A neighbor-joining clustering of these seven groups revealed that dehiscent flax clustered most closely to its wild progenitor, pale flax, followed by oil flax and fibre flax. Winter flax clustered most closely to oil flax and less to pale flax. These clustering patterns were essentially the same when individual samples were analyzed via neighbor-joining. These findings strongly suggest that capsular dehiscence was among the first flax traits modified by human after initial domestication, reflecting the importance that reducing capsular dehiscence likely played in early flax domestication.