On the problem of genetic polymorphism dynamics in Russian cultivars of garden pea (<i>Pisum sativum</i> L.)

Abstract

Background. Breeding new crops is associated with a risk of decrease (erosion) in genetic polymorphism. It is associated mainly with the fact that only a limited range of pre-existing cultivars and forms are used for breeding new cultivars. The Russian cultivars of garden pea (Pisum sativum L.) are characterized by a high level of phenotypic variability, while dynamics of polymorphism at DNA level is poorly investigated. Such an investigation is relevant from the point of view of the prospects for further breeding of the crop, and for planning strategies of polymorphism conservation in germplasm collections. Materials and methods. The material used in the study included 18 Russian cultivars bred before 1991, 22 Russian cultivars created later, 40 foreign cultivars, as well as 7 marker lines and wild-growing accessions. These lines were phenotyped and genotyped using DNA markers (14 CAPS, 8 SSR, one mitochondrial and one chloroplast). Variability level was measured as an average Jaccard coefficient resulting from pairwise comparison within each group. Additionally, we analyzed the published characteristics of cultivars included in the State Register in 1994 - 2019. Results. At the phenotypic level, the variability of grain cultivars increased, while a decrease was recorded for vegetable cultivars. A comparison with foreign cultivars has shown that their polymorphism was similar to those of Russian cultivars, except for the vegetable cultivars which are phenotypically less polymorphic than foreign ones. The DNA polymorphism demonstrated a similar tendency, although to a lesser extent. A low level of within-cultivar polymorphism was found. Productivity characteristics of cultivars included into the State Register in the early period (1995 - 2000) and those included later (2016 - 2019) do not differ significantly. Conclusions. There is no clear indication of genetic erosion in Russian cultivars of pea. We also found no reliable increase in the basic agriculturally important characters within the two decades.

Keywords

• germplasm collection
• molecular markers
• variability
• erosion