Inherent responses to root-zone salinity in nine alfalfa populations

Abstract

Steppuhn, H., Acharya, S. N., Iwaasa, A. D., Gruber, M. and Miller, D. R. 2012. Inherent responses to root-zone salinity in nine alfalfa populations. Can. J. Plant Sci. 92: 235–248. Alfalfa productivity can be enhanced by growing crops from cultivars tolerant of root-zone salinity. Rangelander, Keho, Bridgeview, Halo, CW054038, CW064027, Rugged, Bullseye and TS4002 alfalfa plants (respectively designated Ra, Ke, Br, Ha, C8, C7, Ru, Bu and T4) were grown in sand tanks irrigated with nutrient-sulphate solutions averaging 1.53 (nutrients only), 8.03 and 15.61 dS m−1 in electrical conductivity. Except for Br and C7, seedlings emerged equally under the 1.5 and 8.0 dS m−1 treatments, but decreased in the 15.6 dS m−1 treatment by percentages ranging from 3.1 through 29.5. Average shoot biomass among the populations respectively decreased by 49.6, 43.6 and 37.6% in the 1st, 1st+2nd, and 1st+2nd+3rd harvest-cuts as salinity increased from 1.5 to 8.0 dS m−1 and by 80.1, 73.2 and 67.1% from 1.5 to 15.6 dS m−1. At 1.5 dS m−1, the C7 plants consistently produced more shoot biomass than the T4, Bu, Ha, Ru, Ra, or Ke plants. At 8 dS m−1, the relative yields of the Ha plants (scaled by their 1.5 dS m−1 production) exceeded those from the other populations, although the Ha plants produced no greater actual shoot biomass than the C7 or the C8 plants.

Emergence, Forage Production, and Ion Relations of Alfalfa in Response to Saline Waters

“…Salinity causes a general delay in alfalfa emergence (Ashraf and Foolad, 2005;Assadian and Miyamoto, 1987;Steppuhn et al, 2012) and our results confirm that. Rapid emergence is favorable because it reduces the time for salts to accumulate in plant tissue (Assadian and Miyamoto, 1987).…”

“…The mean time to reach the E max ( t max ) tended to increase by 0.6, 1.6, 3.7, and 5.1 d for the respective EC iw increments from 3.1 to 7.2, 7.2 to 12.7, 12.7 to 18.4, and 18.4 to 24 dS m −1 , although only the 18.4 to 24 dS m −1 increase in t max was significantly different from the others. An approximately similar delay between salinity levels was found by Steppuhn et al (2012) in tolerant alfalfa cultivars (dormant type) wherein the time to reach E max increased from 0.7 to 2.18 d for the respective increments from 1.5 to 8.0 and 8.0 to 15.6 dS m −1 . However, they reported greater means of E max percentages (95.8, 97.3, and 89.9%), and greater t max (6.96, 7.68, and 9.86 d), respectively, at 1.5, 8.0, and 15.6 dS m −1 as compared with our results (Table 2).…”

“…If the emergence is considered an extension of germination, then we can compare emergence and germination (%). These temperature differences could have influenced the germination and thus the comparatively lesser emergence that we observed (compared with the data of Steppuhn et al [2012]). As was earlier reported by Ungar (1967), the temperature affected the seed germination when the salinity increased.…”

“…Means per subplot of the cumulative emergence on successive days after seeding were analyzed in a manner described by the Gompertz function using the equation specified by Steppuhn and Raney (2005) and Steppuhn et al (2012) as follows: …”

“…In alfalfa, the results of previous studies are inconclusive. Some studies have concluded that the ability of the plants to produce biomass is not necessarily related to germination (Al‐Niemi et al, 1992; Johnson et al, 1992; Rumbaugh and Pendery, 1990) and emergence (Steppuhn et al, 2012). However, other studies have demonstrated a positive correlation between germination at severe salinity (342 mM of NaCl) with regrowth potential under salt stress (greenhouse experiment) and also with production under field conditions (Scasta et al, 2012).…”