II. 22. Barley mutant with few roots.
Ib Linde-Laursen, Agricultural Research Department, Research Establishment Riso, DK-4000 Roskilde, Denmark. "R"
A weakly rooted, but otherwise normal-looking mutant (no. '2076/04-10')
was- found in a spike progeny of a field-grown M3 of the Danish variety
'Bomi' treated with EMS. When kernels from the mutant were germinated
on filter paper, the seedlings had one or at the most two roots one week
after sowing. At this state 'Bomi' generally has about seven roots.
The mutant was crossed with the mother variety 'Bomi'. The number of roots of simultaneously grown parents, F1, and F2 plants was counted six and sixty days after sowing. The first counting was made on seedlings grown on filter paper (Table 1). The seedlings were then transferred to pots, the upper half of which was filled with gravel. The pots were supplied continuously with water from below. For the second counting, the roots were washed free of gravel.
The table shows that the six-day-old plants can be divided into two groups, 'Bomi', the F1, and 76 F2 plants having more than three roots per plant, and the mutant ('2076/04-10') and 26 F2 plants having less than four roots per plant. At sixty days the number of roots had doubled, and the division of the plants into two groups by number of roots had become very distinct; all plants of the former group had more than ten roots, the plants of '2076/04-10' had one to six roots (average 2.9 + 0.16), and the F2 plants with few roots had two to seven roots (average 3.5 + 0.27). During and after stretching, the plants with few roots were liable to overturn.
The mutant character "few roots" is conditioned by a single recessive gene. This is shown by the number of roots of the F1 plants, and the 3:1 segregation (0.95>p>0.90) in F2 in plants with the normal number of roots to plants with few roots. It is proposed to designate the recessive gene fer. To the best of my knowledge, this is the first example in barley of a mutation interfering with the number of roots. Besides being of interest to geneticists, the mutant could be of interest to plant physiologists and plant pathologists.
