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Strategies of nitrogen efficiency among landrace and domesticated sorghum cultivars
Abstract
Nitrogen (N) is the mineral element required in the greatest quantities and most often deficient in crop plants. Genetic diversity for N-use efficiency within the plant (NUE$\sb{\rm p}$, g dry weight per g N in plant material) has been demonstrated in sorghum (Sorghum bicolor (L.) Moench) which suggests further breeding improvement is possible. Some of the most NUE$\sb{\rm p}$ sorghums examined have been landrace cultivars, evolving from low fertility environments. Modern breeding programs, often with observation and selection only under environments of high fertility and little other stress, have been implicated as possibly reducing the level of NUE$\sb{\rm p}$. The objectives of this study were to compare the NUE$\sb{\rm p}$ of selected landraces ('M35-1', and 'SC 566') and domesticated grain sorghums ('Martin', 'CK60', and 'Dekalb E59+') under two levels of limited N (severe and moderate) conditions in the field. Morphological, physiological, and anatomical differences among these cultivars were characterized to isolate the factors which contributed to NUE$\sb{\rm p}$. The landrace cultivars had the highest NUE$\sb{\rm p}$ producing an average of 152.5 versus 123.7 g dry matter g N$\sp{-1}$ for the other cultivars. The domesticated cultivars were the most responsive to the increased availability of N from the severe to the moderate level of N stress, increasing total dry weight by 362% in comparison to 170% from the landrace cultivars. The most efficient landrace cultivar, M35-1, partitioned more dry matter into stalk tissue and maintained thicker leaves, than all other genotypes. The commercial hybrid, Dekalb E59+, was as efficient as SC 566 at moderate N stress and was the only cultivar to equal the leaf area produced by M35-1. Physiologically, instantaneous measurement of N-efficiency (CO$\sb2$ gain per unit leaf N) differed among cultivars, but did not predict season-long NUE$\sb{\rm p}$. Dekalb E59+ and M35-1 were the cultivars which most rapidly solubilized and remobilized N from older to younger leaves. Leaf N content was closely associated with stomatal conductance among the cultivars highest in NUE$\sb{\rm p}$, particularly Dekalb E59+, which also had a significantly lower dark respiration rate than all other cultivars. Anatomically, the most efficient landrace cultivar, M35-1, had the thickest leaves and had the largest cross-sectional phloem area. (Abstract shortened with permission of author.)
Subject Area
Agronomy|Botany|Plant propagation
Recommended Citation
Gardner, John C, "Strategies of nitrogen efficiency among landrace and domesticated sorghum cultivars" (1988). ETD collection for University of Nebraska-Lincoln. AAI8904487.
https://digitalcommons.unl.edu/dissertations/AAI8904487