Association of SSR markers and morpho-physiological traits associated with salinity tolerance in sugar beet (Beta vulgaris L.)

The conventional screening methods for salinity tolerance are time-consuming, labor-intensive and have low throughput screening rate. Molecular marker-quantitative trait association can be used to increase the efficiency of a breeding program, especially for salinity tolerance. This study was carried out to find marker-trait association using regression analysis between 13 morpho-physiological traits and 104 simple sequence repeat (SSR) markers (from 18 SSR primer pairs) on a set of 168 genotype from 12 extreme salt tolerant and sensitive crossing parents (14 samples in each parent) during 2011 and 2012. The morpho-physiological traits included Ca2+, Na+ and K+ in leaf, quality related traits in root, root yield, sugar yield and white sugar yield which were field evaluated under saline and non-saline conditions in 2 years. Results of analysis of variance revealed a significant difference between genotypes for most of the studied traits in both environments. High estimates of broad-sense heritability with relatively low genetic advance were observed for ECS and MS (in stress conditions) and for ECS and alpha-N in root (in non-stress conditions). The result of regression analysis showed that in 2011, five markers [(FDSB1007 (c-284 bp), KWS (a-234 bp), SB06 (c-180 bp), FDSB502 (f-293 bp) and FDSB1027 (a-211 bp)] and in 2012, nine markers [KWS (f-250), KWS (h-266), USD29 (b-153), BQ588629 (f-196), SB07 (c-278), Bmb3 (b-268), SB04 (d-200), SB15 (d-164) and Bvm3 (e-131)] had significant effect on at least one trait in both environments. Two SSR markers (FDSB502 and Bmb3) were significantly associated with the key traits contributed to salinity tolerance such as leaf Na+ and leaf K+ and the highest root quality-related traits suggesting these as the appropriate markers to improve salinity tolerance of sugar beet. The efficiency of such markers in breeding programs for developing sugar beet cultivars with high salinity tolerance requires further investigation.