Waterlogging Tolerance at Germination in Field Pea: Variability, Genetic Control, and Indirect Selection

Abstract

In the Eastern Gangetic Plain of South Asia field pea (Pisum sativum L.) is often grown as a relay crop where soil waterlogging (WL) causes germination failure. To assess if selection for WL tolerance is feasible, we studied the response to WL stress at germination stage in a recombinant inbred line (RIL) population from a bi-parental cross between WL-contrasting parents and in a diversity panel to identify extreme phenotypes, understand the genetics of WL tolerance and find traits for possible use in indirect selection. The RIL population and the diversity panel were screened to test the ability of germination under both waterlogged and drained soils. A total of fifty, most waterlogging tolerant and sensitive, genotypes from each of both the RIL and the diversity panel were further evaluated to assay testa integrity/leakage in CaSO4 solution. Morphological characterisation of both populations was undertaken. A wide range of variation in the ability to germination in waterlogged soil was observed in the RIL population (6 - 93%) and the diversity panel (5 - 100%) with high broad-sense heritability (H2 > 85%). The variation was continuously distributed indicating polygenic control. Most genotypes with a dark coloured testa (90%) were WL tolerant, whereas those with a light coloured testa were all WL sensitive in both the RIL population and diversity panel. Testa integrity, measured by electrical conductivity (EC) of the leakage solute, was strongly associated with WL tolerance in the RIL population (rG = -1.00) and the diversity panel (rG = -0.90). Therefore, testa integrity can be effectively used in indirect selection for waterlogging tolerance. Response to selection for WL tolerance at germination is confidently predicted enabling the adaptation of the ancient model pea to extreme precipitation events at germination.