Title:
|
Genetic studies of wide crosses between cultivated pea species, and the domestication of Pisum abyssinicum
|
Genetic maps were produced from wide crosses between the garden pea
Pisum sativum and the cultivated species P. abyssinicum, cultivation of which is
confmed to North-east Africa and Yemen. Crosses were made in two directions:
with P. abyssinicum as the female parent in ll2202 (P. abyssinicum) x ll2822
(P. sativum), and as the male parent in Kite (P. sativum) x ll2 (P. abyssinicum).
Parallel linkage maps were produced for the two populations. 454 markers were
mapped in the ll2202 x ll2822 F7 population, and 252 in the Kite x ll2 F6
population, using predominantly SSR (simple sequence repeat) and SSAP
(sequence-specific amplification polymorphism) markers. 152 markers are shared
between linkage maps; this figure represents more than 50% of the mapped
markers derived from the primer combinations that were used on both
populations.
A number of novel loci were associated with segregating traits derived from both
cross parents. Analysis in the ll2202 x ll2822 population found strong partial
resistance to infection by downy mildew (Peronospora viciae f. sp.pisi), in which
52% of trait variance was explained by a single locus on linkage group I. This
source of resistance is derived from the P. sativum parent.
Significant segregation distortion affected approximately half of the markers used
in the linkage maps; segregation ratios were found to be biased in favour of
maternal alleles in both populations, which may represent a fonn of partial
reproductive isolation between P. abyssinicum and P. sativum. Combined with
observed transgressive segregation of domestication traits in the wide crosses, this
suggests that these taxa do not have a shared domestication history.
|