Seed carbohydrate composition and its relation to another breeding important traits of garden pea (Pisum sativum L.) in Krasnodar region

Starch is the main pea ( P. sativum L.) seed carbohydrate in which the amylose to amylopectin ratio is controlled genetically. Recessive allele r of locus RUGOSUS determines an increase in the amylose fraction which leads to the wrinkled-seed character of vegetable peas. A high proportion of amylose in pea starch (more than 70 %) promotes a slow transition of sugars to starch and results in a longer period of technical ripeness. High-amylose starch determines the use of peas in dietary nutrition, and also as raw materials for biodegradable plastics and films. Pea diversity on amylose content is poorly studied, and no data about the relationship between this trait and other agronomically valuable parameters is available. This study is the first to report polymorphism of VIR Collection accessions (Vavilov Institute of Plant Genetic Resources, St. Petersburg, Russia) and breeding forms from Krymsk Experimental Breeding Station (Krasnodarskii krai, Russia) on carbohydrate composition under contrast weather conditions, and a relationship between the amylose content in seeds, smaller seed size and seed number per pod. The objectives of this work were to reveal garden pea polymorphism on starch carbohydrate composition, to seek for genotypes with high-amylose starch in mature seeds and to estimate the relationships between the seed starch composition and other valuable traits in pea plants. In 2015 and 2016, 39 vegetable pea specimens were tested in field trials in Krasnodarskii krai. Starch content in seeds was determined polarimetrically, and iodine-based calorimetry was used for amylose assessment. The biochemical traits were influenced by environmental conditions. In more favorable 2016 as compared to 2015, seed productivity per plant was 4.5 g higher, the starch accumulation decreased by 3.6 %, whereas the amylose content in starch increased by 1.6 % (р < 0.05). There was no statistically significant difference in amylose content detected between accessions of leafy ( Af ) and semi-leafless ( af ) morphotypes in contrast weather conditions of 2015 and 2016 which indicates that both types may be involved in breeding programs. In both years, the highest amylose proportion in starch was in accessions with smaller 1000 seed weight ( r = -0.34 in 2015, r = -0.32 in 2016; р < 0.05) and the largest seed number per pod ( r = 0.47 in 2015, r = 0.41 in 2016; р < 0.05). Starch and amylose contents correlated inversely ( r = -0.60 in 2015, r = -0.49 in 2016; р < 0.05). Varieties Grundy, Durango, and Gropesa were starch-rich with the high amylose level in starch and could serve as donor genotypes. Starch and amylose contents, as averaged over a two-year period, were 31.9 and 75.1 % (р < 0.05), respectively, for Grundy, 32.0 and 74.1 % (р < 0.05) for Durango, 35.1 and 75.4 % (р < 0.05) for Gropesa. Among the varieties studied, SV 0987 UC, Vinco, Omega, Gropesa, and Butana possessed the high amylose level in seeds (79.5, 72.2, 74.0, 75.4 and 72.4 %, respectively, as averaged over 2 years) and small-sized seeds (р < 0.05). Varieties Mucio and Olinda were high in amylose (77.5 and 71.4 %, respectively) in combination with more than 8 seeds per pod (р < 0.05).