Laboratory drought resistance of pea breeding accessions in PEG-6000
Authors: Shevchenko L.M. 
Published: May 2023

The results on the laboratory drought resistance determined by germination of pea seeds in 8.6% PEG-6000 are presented. The depression of root and shoot growth processes was determined for seeds harvested in different years (2018–2020).
The study purpose was to evaluate the laboratory drought resistance of pea varieties and breeding material in PEG-6000.
Materials and methods. Seeds harvested in 2018–2020 were investigated. Fifty-nine pea (Pisum sativum L.) accessions (breeding varieties, breeding material, collection specimens) were tested. Pea seeds were germinated in 8.6% PEG-6000. Control seeds were germinated in distilled water. The germination temperature was 20°C. On day 7, the shoot and root lengths were measured in the control and experiment and the depression of root and shoot growth processes was evaluated.
Results and discussion. Across the study years, the depression of the «root length» trait in the pea accessions represented by varieties and breeding material varied -96.3% to 67.8%, and the depression of the «shoot length» trait was not negative in the study years, ranging 8.3% to 91.7%. The root length depression in the pea accessions ranged -52.1% to 67.8% in 2018, -96.3% to 67.7% in 2019, and -33.6% to 61.6% in 2020. The shoot length depression also varied significantly across the study years: from 22.3% to 88.7% in 2018, from 8.3% to 91.7% in 2019, and from 15.8% to 87.1% in 2020.
If we take into account the significant values of the coefficient of variation for the depression of root growth processes, it may confirm the fact that differences in the response to drought can be predicted from this trait. For the convenience of analysis of the obtained data, the accessions were ranked according to the depression of «root length» and «shoot length» traits. It should be noted that the coefficient of variation for the depression of the «shoot length» trait in 2018 and 2020 was high (23.0% and 28.3%, respectively) and very similar. In general, no stimulatory effect of PEG-6000 was observed for this parameter, unlike the «root length» trait in some accessions. Despite the fact that Zekon, Hotik and Mascara are varieties bred in Western Europe, they were among the best ones in this sample according to the depression level. Of the pea accessions bred at PPI NAAS, breeding line SL 15-95 was the best one; variety Ramonskiy 77, a leafy variety bred in the USSR, was highly resistant, judging from the depression of growth processes. It should be noted that in our experiments the depression level of growth processes in PEG-6000 was not associated with yield. Thus, the accession with the lowest rank sum, SL 15-95, gave an average yield of 1.86 t/ha in 2018–2020. At the same time, Rezonator, a variety with the rank sum of 261, produced 1.84 t/ha; Hotik with the rank sum of 89–1.90 t/ha. Ramonskiy 77 with the rank sum of 83 gave a yield of 1.49 t/ha, and Chekryhinskyi with the largest rank sum in the experiment (294) gave a yield of 1.33 t/ha.
The Spearman coefficient for the matrices of depression ranks showed high identity. Thus, the Spearman coefficient (rs) was 0.98 between the matrices for all study years. Hence, to determine the laboratory drought resistance by germination in PEG-6000, it is sufficient to replicate the experiment on seeds harvested in two years.
Conclusions. Thus, the obtained data on the depression of growth processes in the pea accessions in PEG-6000 are not mature and require further, more in-depth study.