Reciprocal compatibility within the genus Pisum L. as studied in F₁ hybrids. 3. Crosses involving P. abyssinicum A. Br.

A greenhouse experiment of crossing eight accessions of peas (Pisum L.), representing their different taxa and divergent lineages, with each other and to self has been carried out, aimed at evaluating reproductive barriers inside this genus which may be of importance for pre-breeding. The results of crosses involving the cultivated pea, P. sativum L. subsp. sativum, and Pisum fulvum Sibth. et Smith has been published earlier, while this paper presents those of crosses involving Pisum abyssinicum A. Br. (accession VIR2759 from Ethiopia). It was crossed, in both directions, with seven accessions representing P. fulvum (1 accession), P. sativum L. subsp. elatius (Bieb.) Schmalh. s.l. (5 accessions) and the cultivated pea, P. sativum subsp. sativum (1 accession). The average number of hybrid seeds per cross (crossing efficiency) was evaluated and the reciprocal F₁ hybrids were analysed for pollen and seed fertility and some quantitative traits. Two crossing combinations produced no hybrid seeds. Male and female fertilities of F₁ hybrids with P. abyssinicum were on average low but better than of the hybrids with P. fulvum analysed earlier. Both fertilities were on average better in hybrids with representatives of the evolutionary lineage AC of P. sativum than with those of the lineage B. In most cases differences in the fertilities were registered between reciprocal hybrid classes supposedly due to the conflict of the nucleus and plastids. Two hybrid classes produced no seeds. In one of them a hybrid plant was found which inherited paternal plastid (but maternal mitochondria); its male fertility was elevated to the level of the reciprocals but did not restore seed fertility. Surprisingly, the F₁ hybrids of P. abyssinicum resulting from pollination by accession 721, a tall climber from Mt. Carmel, showed fully fertile pollen, indicating their relatedness. These data show that crossability of the Abyssinian pea with all other peas is very poor (with one exception in one direction only), supporting its specific status in frame of the biological species concept.