Abstract
Leaf trichomes may protect plants against herbivorous insects, and may increase tolerance to drought and UV-radiation. The perennial herb Arabidopsis lyrata (Brassicaceae) is polymorphic for trichome production and occurs in a glabrous and trichome-producing form. In addition, there is quantitative variation in trichome density among trichome-producing plants. To examine the genetic basis of glabrousness, we conducted controlled crosses with plants originating from two natural populations in Sweden (one polymorphic for trichome-production, and one consisting of glabrous plants only). In addition, we estimated the heritability of trichome number from parent-offspring regressions for plants originating from the polymorphic population. Crosses between glabrous plants resulted in glabrous offspring only, whereas crosses between glabrous and trichome-producing plants, and crosses between trichome-producing individuals, resulted in either all trichome-producing offspring or both phenotypes. In segregating crosses between trichome-producing plants, the ratio of glabrous:trichome-producing offspring did not deviate significantly from 1:3, while in segregating crosses between glabrous and trichome-producing individuals the ratio did in most cases not deviate from 1:1. Within- and between-population crosses gave similar results. The heritability of trichome number estimated from regression of offspring on mid-parent was high (h2 +/- SE, 0.65 +/- 0.15). The results suggest that glabrousness is inherited in a simple Mendelian fashion, with the allele coding for trichome production being dominant over that for glabrousness. They further indicate that glabrousness is due to a mutation at the same locus in both populations.
Highlights
The genetic basis of adaptive traits determines how they can be moulded by selection, but is still poorly known
The results suggest that glabrousness is inherited in a simple Mendelian fashion, with the allele coding for trichome production being dominant over that for glabrousness
The production of trichomes may be beneficial for several reasons, but can be associated with a cost: In environments where trichomes do not confer an advantage, glabrous plants may be able to allocate more resources to growth and reproduction (A, GREN and SCHEMSKE 1993; BERGELSON 1994; MAURICIO and RAUSHER 1997; MAURICIO 1998)
Summary
Karkkainen, K. and A, gren, J. 2002. Genetic basis of trichome production in Arabidopsis lyrata. — Hereditas 136: 219–226. To examine the genetic basis of glabrousness, we conducted controlled crosses with plants originating from two natural populations in Sweden (one polymorphic for trichome-production, and one consisting of glabrous plants only). We estimated the heritability of trichome number from parent-offspring regressions for plants originating from the polymorphic population. To investigate the inheritance of glabrousness and whether the genetic basis of glabrousness in A. lyrata is consistent across populations in Sweden, we conducted crosses between glabrous and trichome-producing plants originating from two natural populations separated by about 32 km (one polymorphic for trichome-production, and one consisting of glabrous plants only). A, gren from parent-offspring regressions for plants originating from the polymorphic population
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