Submitted to: European Conference on Grain Legumes Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/1/2004
Publication Date: 6/1/2004
Citation: Weeden, N., Moffet, M., Mcphee, K.E. 2004. The domestication of pea: an analysis of polygenic characters in the abyssinicum pea supports a semi-independent domestication of this taxon. In: Proceeding of the 5th European Conference on Grain Legumes, June 7-11, 2004, Dijon, France. p. 157. Interpretive Summary: Pisum sativum L. comprises several different subspecies including the subspecies, P.s. subsp. abyssinicum. The abyssinicum pea was traditionally grown in the are that is now Ethiopia. It has been proposed that the abyssinicum pea followed an independent and narrow path of domestication due to its isolation from other pea production areas in the world. Several distinctive traits characteristic of primitive and domesticated germplasm were studied in abyssinicum accessions to determine its similarity to Pisum sativum ssp. elatius and Pisum sativum ssp. sativum. Segregation among progeny from crosses between P.s. sativum and P.s. ssp. abyssinicum show that abyssinicum pea has a combination of primitive and domesticated traits. These results indicate that the abyssinicum pea diverged several thousand years ago and after the loss of pod dehiscence and increase of seed size.
Technical Abstract: The abyssinicum pea [Pisum sativum ssp abyssinicum (A. Braun) Govorov] is a subspecies that was grown as a crop over a century ago in what is now Eritrea and Ethiopia. The extremely narrow and divergent genetic base of P. s. ssp. abyssincum relative to both domesticated pea (P. s. ssp. sativum) and the wild progenitor (P. s. ssp elatius) suggests that the abyssinicum pea has been isolated from the two other taxa for some time and has gone through a relatively recent genetic bottleneck. A possible semi-independent domestication of this taxon has been previously proposed. An analysis of the genetic basis of traits segregating in progeny derived from (Pisum sativum ssp. sativum x P. s. ssp abyssinicum) indicates that the abyssinicum pea is a combination of primitive and domesticated characters. Primitive characters include the presence of anthocyanins, black pigmented hilum, intermediate growth habit, and small root/shoot ratio. Domesticated traits include indehiscent pod, medium seed size, early blooming, broad leaflets, and lack of seed dormancy. The abyssinicum pea also possesses a set of traits (serrate leaflets, one pair of leaflets per leaf, several specific molecular markers) that uniquely define it taxonomically. Plant height, leaf size and shape, flowering time and root/shoot ratio all displayed polygenic inheritance in the populations studied. Two major genes were found to influence plant height, and these appeared to be the same as two identified as affecting height in P. s. ssp. elatius x P. s. ssp sativum populations. One of these genes (gibberellin 3-oxidase) also appeared to influence leaf size and total root area. The difference in total root area between the Abyssinicum pea and cultivated pea was also influenced by a gene on linkage group II. The genotype for flowering genes in abyssinicum pea was determined to be Lf, Sn, hr, E, with a fifth locus appearing to be responsible for the relatively early flowering node for this genotype. The results of our analysis of traits influenced by more than one locus paralleled that of single gene characters in that P. s. ssp. abyssinicum was found to be fixed for a mixture of P. s. ssp. elatius and P. s. ssp. sativum alleles, as well as possessing certain 'unique' alleles not identified in the other two taxa. The loci controlling the polygenic traits analyzed are distributed over six of the seven linkage groups. These results support the hypothesis that the abyssinicum pea diverged from the typical cultivated pea germplasm several thousand years ago after the loss of pod dehiscence and increase in seed size but before fixation of many other traits found in modern cultivars.