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Root Physiology of Less Fall Dormant, Winter Hardy Alfalfa Selections

Dep. of Agronomy, Purdue Univ., West Lafayette, IN 47907-1150

View larger version (42K): [in a new window]   Fig. 1. Minimum air and soil (10-cm depth) temperatures at the Agronomy Research Center during the 2 yr of the study. Dates of the first killing freeze (-4°C) were 5 Nov. 1998 and 15 Nov. 1999.

View larger version (48K): [in a new window]   Fig. 2. (A) Shoot height in autumn and (B) winter injury of alfalfa cultivars and germplasms. Six alfalfa cultivars; Vernal, Dart, G2852, Archer, Sutter, and CUF 101 with known fall dormancy and winter hardiness were compared to five experimental germplasms; 98-141, 98-157, 98-148, 98-142, 98-132. Shoot height was measured in mid-October and winter injury was assessed in April. Data were averaged over 2 yr. The least significant difference (LSD, P ≤ 0.05) is provided.

View larger version (26K): [in a new window]   Fig. 3. Relationship of shoot height in autumn to winter injury of alfalfa. Data are means averaged over both years. Responses of the germplasms 98-148 and 98-132, and the cultivar Dart are identified because these data points were positioned below the regression line. Asterisks (**) indicate significant quadratic relationship at P ≤ 0.01.

View larger version (57K): [in a new window]   Fig. 4. (A) Sugar and (B) starch concentrations of alfalfa taproots sampled in mid-October and early December. Six alfalfa cultivars; Vernal, Dart, G2852, Archer, Sutter, and CUF 101 with known fall dormancy and winter hardiness were compared to five experimental germplasms; 98-141, 98-157, 98-148, 98-142, 98-132. Data were averaged over 2 yr. Error bars represent one standard error of the mean (n = 8).

View larger version (55K): [in a new window]   Fig. 5. (A) Amino N and (B) buffer-soluble protein concentrations of alfalfa taproots sampled in mid-October and early December. Six alfalfa cultivars; Vernal, Dart, G2852, Archer, Sutter, and CUF 101 with known fall dormancy and winter hardiness were compared with five experimental germplasms; 98-141, 98-157, 98-148, 98-142, 98-132. Data were averaged over 2 yr. Error bars represent one standard error of the mean (n = 8).

View larger version (51K): [in a new window]   Fig. 6. RNA gel blot analysis showing steady state transcript levels of a cold acclimation-responsive gene in roots of six alfalfa cultivars and five experimental germplasms in October (H1) and December (H2). Twenty micrograms of total RNA was loaded per lane and blots were hybridized with a 32P-labeled cold acclimation-responsive cDNA (bN-1 12a3) whose steady state transcript levels were previously shown to be high in winter hardy cultivars. The alfalfa cultivars and germplasms are listed in order of decreasing fall dormancy and include: 98-141 (141); 98-157 (157); Vernal (Ver); 98-148 (148); Dart; 98-142 (142); G2852 (G28); 98-132 (132); Archer (Arc); Sutter (Sut); CUF 101 (CUF). The lower panel is an ethidium bromide stained gel showing RNA loading levels.