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This article in CS

  1. Vol. 22 No. 2, p. 367-371
    Received: Mar 15, 1981

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Carbohydrate Composition of Alleles at the Sugary Locus in Maize1

  1. D. L. Garwood and
  2. S. F. Vanderslice2



Carbohydrate and starch compositions were determined for maize (Zea mays L.) endosperms homozygous for the sugary-Reference (su-Ref), Brawn-2 (su-Bn2), starchy (su-st), and amylaceous (su-am) alleles in the W64A inbred background to further ellucidate the nature of the su locus. Glucose, fructose, sucrose, water soluble polysaccharide (WSP), and starch contents were measured in kernels sampled 20 days after pollination, and the starch component was fractionated using Sepharose 2B-CL gel filtration. Kernel size and carbohydrate composition for the four alleles were in agreement with expectations based on observations of their mature kernel phenotypes. Sucrose was significantly higher in su-Ref kernels than in kernels of the other three alleles suggesting that they will not be useful in developing improved sweet corn types. Differences in glucose and fructose contents were small and probably do not reflect major effects of the alleles. WSP was highest in su-Ref and su-st kernels, intermediate in su-Bn2, and lowest in su-am. Starch content was highest in su-am kernels, intermediate in su-Bn2 and su-st, and lowest in su-Ref. Fractionation of su-am starch gave an elution profile similar to that of normal starch while profiles of su-Ref and su-Bn2 starches apparently contained only high and intermediate molecular weight branched components which may be more highly branched than amylopectin. Starch from su-st contained three components. The first two were branched similar to amylopectin, and the third was amylose. Thus, the su locus not only conditions the production of highly branched phytoglycogen (WSP), branched amylopectln, and amylose but also starch components of intermediate molecular weight and degree of branching. Based on the existence of multiple alleles which condition unique carbohydrate compositions, the su locus is hypothesized to be a regulatory locus.

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