Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/31/2001
Publication Date: 7/1/2002
Citation: GUTIERREZ, O.A., CAMPBELL, M.R., GLOVER, D.V. STARCH PARTICLE VOLUME IN SINGLE- AND DOUBLE-MUTANT MAIZE ENDOSPERM GENOTYPES INVOLVING THE SOFT STARCH (H) GENE. CROP SCIENCE. 2002. V.42.P.355-359. Interpretive Summary: Starch particle volume in maize is important in the processing industry because larger granules may improve performance attributes and milling efficiency. The purpose of this research was to compare starch particle volumes of normal maize inbreds, with those of their respective single and corresponding double endosperm mutant combinations. Eighteen public maize inbreds and their single and double endosperm mutant types were planted in replicated trials at two locations in 1995 and one in 1996. Mutants included the so- called ¿amylose-extender¿, ¿dull¿, ¿waxy¿, ¿sugary-2¿, and ¿soft starch¿ types alone and in pair combinations with soft starch. Starch was extracted from mature kernels and examined for particle volume using a laser-based, particle size analyzer. Starch particle volumes were greater in all inbred conversions containing the soft starch trait than in their respective normal inbreds. Starch particle volumes of all double-mutant soft starch combinations were greater across all inbreds than their respective single-mutant counterparts. These results demonstrate that the soft starch trait masks or overrides the expression of the other mutant traits. The masking or overriding nature of the soft starch trait further enhances its usefulness for increasing starch particle volume in combinations with other endosperm starch mutants utilized to develop specialty starches with value-added traits. This research also demonstrated that the genetic variation present among maize inbreds could be useful in breeding for increased starch particle volume.
Technical Abstract: Starch particle volume in maize (Zea mays, L.) is of interest to processors since larger granules may improve performance attributes and milling efficiency. The recessive soft starch (h) locus increases granule size compared with normal (+/+) genotypes. The objective of this study was to compare starch particle volume of normal maize inbreds, their near-isoline conversions to single-endosperm mutant genotypes and corresponding double-mutant combination genotypes including the h locus. Eighteen inbreds and their near-isogenic conversions to amylose-extender (ae/ae), dull (du/du), waxy (wx/wx), sugary-2 (su2/su2), h/h, ae/ae h/h, du/du h/h, su2/su2 h/h, and wx/wx h/h, were planted in two environments in 1995 and one in 1996. Starch was extracted from mature kernels collected from each plot and examined for starch particle volume. Starch particle volume was greater in all lines containing the h locus than in the respective normal inbred. Starch particle volume was greater for all inbred double-mutant h/h genotypes than for their respective single-mutant counterparts. Results demonstrate that the h allele is epistatic to the ae, du, wx and su2 alleles for increasing starch particle volume. Starch particle volume for single-mutant genotypes, averaged across inbreds and environments, ranked from the smallest to the largest as follows: du/du, ae/ae, su2/su2,+/+, wx/wx, and h/h. The respective ranking of the double- mutants was: du/du h/h, su2/su2 h/h, ae/ae h/h, and wx/wx h/h. This study demonstrated that the genetic variation among maize inbreds could be useful in breeding for increased starch particle volume.