Total Non-Structural Carbohydrates in Winter Wheat Populations Segregating for Snow Mold Tolerance

Evaluation of wheat (Triticum aestivum L.) for tolerance to snow mold (caused by Typhula idahoensis Remsberg) is difficult because of the irregular occurrence and distribution of the disease in the field. Some wheat genotypes tolerant to snow mold are known to accumulate high levels of total non-structural carbohydrates (TNC), a trait that could be utilized for rapid screening of snow mold tolerance. The objective was to determine the heritability of TNC and the correlation of TNC with survival under disease pressure in two hard red winter wheat populations segregating for snow mold tolerance. Whole-plant TNC content (excluding roots), grain yield, and survival were measured in experiments planted near Tetonia, ID, an area prone to snow mold in wheat. Two experiments consisted of BC₁F₆ and BC₁F₇ lines derived from two crosses, ‘Manning’*2/‘Survivor’ and ‘Blizzard’*2/‘Sumner’. The third (mixed) experiment consisted of selected lines from each cross. In 1992–1993, conditions were excellent for the occurrence of snow mold infection, but no obvious snow mold damage occurred in 1993–1994. Heritability estimates of TNC measured before snowfall were 64.7% for the Manning population, 82.6% for the Blizzard population, and 87.0% for the Mixed population. Heritability estimates for winter survival were nonsignificant because of differences in snow mold infection between the 2 yr. Correlation of fall TNC levels with spring 1993 survival was r = 0.55 (P < 0.01) in the Manning backcross population, nonsignificant for the Blizzard population, and r = 0.48 (P < 0.01) in the Mixed population, suggesting that accumulation of TNC is moderately correlated to snow mold tolerance. Levels of TNC in the fall had no significant line × year interaction. Selection based upon TNC would advance a population toward higher TNC levels and may indirectly increase tolerance to snow mold in some populations. This research was funded in part by the Idaho Wheat Commission and the Pakistan Participant Training Program. Idaho Agric. Exp. Stn. Manuscript no. 95728.