The WF1 (White Flower 1) gene controlling the white color of petals and flowering time in lines from a mapping population of flax (Linum usitatissimum L.)

Flax (Linum usitatissimum  L.) is grown  in different  climatic zones  as both  a spring  and  winter  crop. Adaptation to different growing conditions produced genotypes with different growth  durations and degrees of photosensitivity. It was always of great importance for breeders to create varieties with rapid development, in particular, early-flowering ones. The evaluation of lines from the VIR flax genetic collection revealed  a wide intraspecific diversity in the duration of growth  phases,  the number of leaves on the stem  (physiological indicator  of early flowering), and the degree of photosensitivity. Line gc-109, early flowering under the long-day conditions, but greatly photosensitive, was found to possess the wf1 (white flowers) gene, associated with early flowering and a small number of leaves. This line was crossed to the late-flowering but low-photosensitive line gc-375, which had reddish purple flowers. The analysis of segregation in F₂ held under  the long (19 hours) and short (12 hours, daylength at the equator) day conditions showed that  the number of leaves on the plant stem was associated with the flowering time and controlled by close genetic systems only under the long-day conditions. In addition, no relationship between the flowering time and petal color was found under  the short-day  conditions. Thus, different groups  of genes  are active in different light schedules. More than 200 lines of the 6th generation of inbreeding were obtained from the plants of the hybrid population. Their field testing under  the long-day  conditions showed that  although the majority of the lines with white petals  flowered early and had a small number of leaves, some of them bloomed later and were leafier. On the contrary, the early flowering and less leafy lines appeared among the lines with colored flowers. Therefore, it is reasonable to assume  that a crossover between the gene  participating in the control of early flowering, which came from the gc-109 line, and its wf1 gene occurred  in meiosis of F₁. The linkage between the genes  controlling  early flowering and white petals  suggests that flower color can serve as a marker of early flowering in the selection of early breeding material.

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