A population genetic analysis of self- and cross-incompatibility in sugar beet (Beta Vulgaris L.)

Abstract

A population genetic model is proposed for the reproduction of self-incompatible inbred lines in which incompatibility is controlled by 1-4 loci. From theoretical considerations it was expected that: a) with the random matings of lines In, (obtained by self-pollination of n generations), some lines would be cross-incompatible (all the plants within these lines would be homozygous for S-genes) and the rest would be cross-compatible (retain heterozygosity for one or more S-genes); b) in the case of random matings of Unes InGm (obtained by self-pollination of n generations and by random pollination for m generations), some lines would be cross-incompatible (heterozygous for one S-gene) and the rest would be cross-compatible (retain heterozygosity for two or more S-genes); c) the relative proportion of sterile plants, obtained by random pollination of cross-compatible lines, would be related to the number of segregating S-loci and to the generation in which the lines are studied.Forty-four inbred lines of sugar beet derived from self-incompatible plants of a population were analysed. Comparisons of the observed values with the theoretically expected ones demonstrated that: a) of 18 In (I1-I4) lines, 6 were cross-incompatible (homozygous for S-genes) and 12 were cross-compatible having one S-locus segregating in 7 lines and two S-loci segregating in 5 lines; b) of 22 InG1 (I2G1 and I3G1) lines, one line was self-fertile, 7 lines were cross-incompatible (heterozygous for one S-loci) and 14 lines were cross-compatible (heterozygous for two S-loci).No line was found to have three or more segregating S-loci. The results of this population genetics analysis of self- and cross-incompatibility in sugar beet comply with diallel analysis data on sugar beet incompatibility and indicates that it is under the gametophytic control of two basic S-loci.

Self-incompatibility reactions in wild species of the genusBeta and their relation to taxonomical classification and geographical origin

“…Although self-incompatibility in sugar beet is gametophytically inherited (Owen, 1942;Maletsky & Weisman, 1978;Larsen, 1977), this study and earlier investigations (Weisman, 1982(Weisman, , 1986 have observed rejection of the pollen on the stigma, which normally is interpreted as a sporophytic trend (De Nettancourt, 1977). Up until today self-incompatibility in beets has been investigated mainly on seed-set.…”

Populations of weedy crop–wild hybrid beets show contrasting variation in mating system and population genetic structure

“…Gametophytic self‐incompatibility prevents selfing and reproduction with genetically related individuals in wild beet populations (Maletski and Weisman 1978; De Cauwer et al. 2010).…”

“…The species Cultivated beets, wild beets (mostly found along the coastline) and weed beets (defined as flowering individuals found within sugar beet fields) all belong to the same species, Beta vulgaris L. In the wild, B. vulgaris is strictly self-incompatible, with up to four gametophytic S loci, and has a purely outcrossing mating system that depends on wind pollination (Owen 1942;Maletski and Weisman 1978;De Cauwer et al 2010). However, the Sf gene introduced by breeders to maintain selfed, near-isogenic lines (type O) and produce male-sterile seed bearers can override self-incompatibility.…”

“…Another key reproductive parameter selected for in crops may account for the successful establishment of weed beets in sugar beet fields: the Sf gene, a Mendelian self-fertility factor widely used by breeders to produce inbred lines, found in cultivated beet germplasm ( Owen 1942 ). This factor behaves as a dominant gene, and allows the gametophytic self-incompatibility system to be circumvented ( Maletski and Weisman 1978 ). If inherited during crop–wild hybridization, self-fertilization is thus likely to confer a selective advantage for weed beets, at least in the first stage of field infestation when the density of bolting F1 crop–wild hybrids is low.…”

Outcrossing potential between 11 important genetically modified crops and the Chilean vascular flora

“…Sugar beet, B. vulgaris, is an obligate outbreeder with a complex self‐incompatibility system (Maletsky and Weisman, ), and its pollen is easily transported by wind and insects (Archimowitsch, ; Free et al ., ). As sugar beet is a biennial crop grown for its root, it is not expected to flower during the first year of growth and, therefore, root‐production areas are assumed to be exempted from such problems; however, a few volunteer plants were repeatedly reported in root‐production fields, either induced by low temperature during spring growth (vernalization), or due to the presence of a bolting gene in a small percentage of the certified seeds sown (Darmency et al ., ).…”