Root Physiology of Less Fall Dormant, Winter Hardy Alfalfa Selections

Abstract

The physiological mechanisms causing fall dormancy (FD)‐induced differences in alfalfa (Medicago sativa L.) shoot growth in autumn and winter hardiness are not understood. The objective of this research was to examine root physiology of experimental germplasms selected for decreased FD that also were selected simultaneously for high winter hardiness. Dormant and semi‐dormant cultivars and germplasms had high root sugar concentrations that were positively associated with winter hardiness. Root amino N and protein levels in December were greater for germplasms selected for decreased FD and increased winter hardiness than for cultivars with comparable levels of winter hardiness. Among the five most fall dormant cultivars Vernal incurred the greatest amount of winter injury and it had lower root amino‐N concentrations when compared with three of the other four dormant cultivars and germplasms. Germplasm 98‐132 with an intermediate FD, incurred relatively low winter injury, similar to that of fall dormant Vernal, when compared with other intermediate dormancy cultivars and germplasms. This germplasm had root sugar concentrations that were similar to plants with FD ratings of 1 to 3. Creation of even less FD germplasms that possess high winter hardiness would facilitate our understanding of the physiological and molecular mechanisms controlling these two very important agronomic traits of alfalfa.

Autumn growth and its relationship to winter survival in diverse safflower germplasm

“…This suggested that in winter types sugar production is elevated, providing a potential cryoprotectant and needed carbohydrate for basal metabolism and spring regrowth. In perennial alfalfa (Medicago sativa L.) winter hardiness is associated with increased sugar concentration in roots and crowns in the autumn acclimation period (Haagenson et al 2003). Protein levels may also increase (Cunningham et al 1998), but not in all cases (Weishaar et al 2005).…”

“…This was necessary to prevent a skewing of the error variance derived in other environments. Of the 99 total experimental units analyzed over the three environments (Central Ferry and Pullman in 2002-2003, and Central Ferry 2003-2004 there were two missing values, each in a different replication. These were accession FO-4 at Central Ferry in 2002-2003and FO-2 at Pullman also in 2002-2003.…”

“…Of the 99 total experimental units analyzed over the three environments (Central Ferry and Pullman in 2002-2003, and Central Ferry 2003-2004 there were two missing values, each in a different replication. These were accession FO-4 at Central Ferry in 2002-2003and FO-2 at Pullman also in 2002-2003. Data were analyzed over environments using the SAS general linear models (GLM) procedure appropriate for the experimental design (SAS Institute, Inc. 1990).…”

Fall Dormancy and Harvest Stage Impact on Alfalfa Persistence in a Subtropical Climate

“…In particular, WSC accumulation is considered a primary factor for cold tolerance and the taproot concentrations in late autumn have been positively correlated with enhanced alfalfa winter survival (McKenzie et al, 1988; Castonguay et al, 1995; Dhont et al, 2002). In addition, Haagenson et al (2003b) documented positive relationships between winter survival, WSC concentration in taproots, and FD rating of several alfalfa entries.…”

Fall Harvesting of Alfalfa in North Dakota Impacts Plant Density, Yield, and Nutritive Value

“…However, studies indicate that inheritance of these two traits is independent (2), and this has led to newer variety releases with both a lower fall dormancy and improved winter hardiness. Genotypes with intermediate fall dormancy had relatively low injury compared with Vernal, a fall dormant cultivar (7). Ventroni et al (20) indicated that cutting frequency and fall dormancy of alfalfa are critical factors influencing both productivity and persistence; however, fall dormancy is not as critical as cutting frequency.…”