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Don R. La Bonte and John A. Juvik

A single-kernel, sugar analysis technique was used to study the genetic relationship between morphological and metabolic traits previously associated with expression of the sugary enhancer (se) endosperm mutation in a su-1 sweet corn (Zea mays L.) background. Analysis of sucrose and total carotene content in su-1 kernel populations segregating for se showed that light-yellow kernel color was a reliable phenotypic indicator for kernels homozygous for the se gene. High levels of kernel maltose was not always indicative of su-1 se kernels in mature (55 days after pollination) kernel populations. Characteristic high levels of percent moisture in su-1 se kernels at 28 and 35 days post-pollination were identified as an expression of high sugar content. Kernels homozygous for su-1 se were also found to weigh less at maturity than su-1 Se kernels, and se was found to be partially expressed in a heterozygous condition.

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John A. Juvik, Gad G. Yousef, Tae-Ho Han, Yaacov Tadmor, Fermin Azanza, William F. Tracy, Avri Barzur, and Torbert R. Rocheford

This study was conducted to identify the chromosomal location and magnitude of effect of quantitative trait loci (QTL) controlling sweet corn (Zea mays L.) stand establishment and investigate the impact of dry kernel characteristics on seedling emergence under field conditions. Genetic and chemical analysis was performed on two F2:3 populations (one homozygous for su1 and segregating for se1, the other homozygous for sh2 endosperm carbohydrate mutations) derived from crosses between parental inbreds that differed in field emergence and kernel chemical composition. A series of restriction fragment-length polymorphism (RFLP) and phenotypic markers distributed throughout the sweet corn genome were used to construct a genetic linkage map for each population. F2:3 families from the two populations were evaluated for seedling emergence and growth rate at four locations. Mature dry kernels of each family were assayed for kernel chemical and physiological parameters. Composite interval analysis revealed significant QTL associations with emergence and kernel chemical and physiological variables. Improved emergence was positively correlated with lower seed leachate conductivity, greater embryo dry weight, and higher kernel starch content. QTL affecting both field emergence and kernel characteristics were detected in both populations. In the su1 se1 population genomic regions significantly influencing emergence across all four environments were found associated with the se1 gene on chromosome 2 and the RFLP loci php200020 on chromosome 7 and umc160 on chromosome 8. In the sh2 population the RFLP loci umc131 on chromosome 2 and bnl9.08 on chromosome 8 were linked to QTL significantly affecting emergence. Since seedling emergence and kernel sugar content have been shown to be negatively correlated, undesirable effects on sweet corn eating quality associated with each emergence QTL is discussed. Segregating QTL linked to RFLP loci in these populations that exert significant effects on the studied traits are candidates for molecular marker-assisted selection to improve sweet corn seed quality.

Open access

John A. Juvik and Cleora J. D'Arcy

Abstract

Maize dwarf mosaic virus (MDMV), an economically serious viral disease of sweet corn (Zea mays L.) in the United States and other countries of the world, is transmitted primarily by aphid vectors. Early infection by the virus in sweet com can cause stunted growth, delayed maturity, reduced yield, and poor ear quality (11). To provide public and private breeders with germplasm to help alleviate this problem, the Illinois Agricultural Experiment Station announces the release of nine sugary (su) sweet corn inbreds with improved resistance to maize dwarf mosaic virus. These newly developed inbreds have been designated IL793a, IL794a, IL795a, IL796a, IL796b, IL797a, IL798a, IL799b, and IL800a.

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Adamson D. Wong, John A. Juvik, David C. Breeden, and John M. Swiader

Extensive variability was found among 24 currently available commercial sh2 hybrids of sweet corn (Zea mays L.) for yield and yield components, and for the chemical components of eating quality. The primary source of variation was explained by genotypic differences, with the environmental effects due to planting locations having a minor influence. Kernel sugar concentrations, however, had a highly significant level of genotype by environment interaction. The extensive genotypic variability among the sh2 hybrids indicated that allelic variation at other loci is profoundly influencing sucrose and total sugar levels in freshly harvested sweet corn. In each case, the kernel chemical components of quality decreased from 20 to 29 days after pollination (DAP). Mean performance of sh2 hybrids for yield, yield components, and kernel quality parameters was in all cases equal or better than the hybrids homozygous for the su1 endosperm mutation. In addition, there were no strong negative relationships between yield and some of the important chemical components of kernel quality, suggesting that it may be feasible to develop superior sh2 hybrids with acceptable yield potential and improved eating quality targeted for the different sweet corn markets.

Free access

Bernardo Ordás, Rosa A. Malvar, Amando Ordás, and Pedro Revilla

. Rocheford, T.R. 2003 QTL influencing kernel chemical composition and seedling stand establishment in sweet corn with the shrunken2 and sugary enhancer1 endosperm mutations J. Amer. Soc. Hort. Sci. 128 864 875 10.21273/JASHS.128