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  • Author or Editor: J. A. Juvik x
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Some of the primary physiological attributes of sweet corn eating quality that have previously been associated with consumer preference are kernel moisture content, pericarp tenderness (the force required to puncture the pericarp), sugar content and the concentration of phytoglycogen, a water soluble starch, and dimethyl sulfide (DMS), a volatile aromatic compound. This experiment was conducted to evaluate a set of 24 sweet corn inbreds with three endosperm mutations (4 sugary1, 7 sugary enhancer, and 13 shrunken2) for variation for these characteristics over two years on fresh ears harvested at 18 and 22 days after pollination (DAP). Significant genotypic variability was observed among inbreds, as well as between harvest stages for all the characteristics. Kernel moisture ranged from 69 to 79%, pericarp tenderness from 49 to 165 g/mm2, sugar content from 125 to 496 mg/g, phytoglycogen from 4 to 212 mg/g and DMS from 4 to 65 μg/g of dry matter at 18 DAP. From 18 to 22 DAP ears, averaged over the inbreds, were found to decrease 7% in kernel moisture, 25% in tenderness, 17% in sugar and 40% in DMS content, and increase 32% in phytoglycogen. Genetic differences among the inbreds accounted for most of the total variability for the attributes analyzed. This suggests that development of genotypes with improved eating quality can be accomplished.

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Abstract

Evaluation of progeny populations from crosses between tomato accessions (Lycopersicon spp.) with high and low alkaloid levels indicated that variation in α-tomatine content is controlled by the segregation of 2 co-dominant alleles at a single locus.

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Abstract

When larvae of Heliothis zea (Boddie) were caged on fruits of varying developmental ages from 3 accessions of Lycopersicon, the length of the larval stage and mortality were positively correlated with fruit α-tomatine content. Larval growth rates and adult weights of H. zea were found to be inversely correlated with fruit alkaloid content. Growth and survival of caged Spodoptera exigua (Hubner) were not related to the levels of tomatine in the fruit. However, a highly significant correlation exists between fruit cuticular toughness and S. exigua mortality. Compared to the processing tomato line VF145B-7879, lower H. zea and S. exigua survival rates were observed when the larvae were reared on the tougher, higher-alkaloid fruits of L. esculentum var. cerasiforme and L. pimpinellifolium accessions. These results indicate a possibility of enhancing cultivar resistance to these insect pests through the development of tough-fruited, high-α-tomatine genotypes.

Open Access

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.

Open Access

Approximately 200 sweet corn inbred lines were screened for two years for resistance to northern leaf blight, caused by Exserohilum turcicum, and Stewart's wilt, caused by Erwinia stewartii. Inbreds with the best levels of partial resistance to races 1 and 2 of E. turcicum included IL11d, IL676a, IL677a, IL685d, IL766a, IL767a and IL797a. Inbreds with the best partial resistance to E. stewartii included IL126b, IL676a, IL767a, IL772a, IL774g, IL797a, IL798a and M6011. Several of these resistant and moderately resistant inbreds had common ancestors; however, inspection of pedigrees suggested that resistance was derived from Puerto Rican, Bolivian, and other tropical sources and/or dent corn. Thus, many of the sweet corn inbreds may carry different genes for resistance and can be used for the development of populations with improved resistance.

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Dimethyl sulfide (DMS), the compound responsible for the characteristic “corny” aroma, and sugar are the principle chemical components of flavor in sweet corn. It was our contention that it may be possible to enhance the flavor potential of some high-sugar sweet corn hybrids by supplying increased amounts of N and S fertilizer to the crop to increase kernel DMS and sugar content. A factorial combination of two N (168, 310 kg/ha) and three S rates (0, 34, 101 kg/ha) was applied to six sh-2 sweet corn hybrids in a Plainfield sand. Kernel DMS and sugar levels were assayed over a period ranging from 20 to 29 days after pollination. In each case, kernel DMS and sugars decreased with increasing harvest maturity. In three hybrids, there was a positive response in kernel DMS to either N or both N-S. Kernel fructose and glucose concentrations tended to decrease as N fertilization rate increased, while sucrose levels remained relatively constant. In all hybrids, S fertilization had no effect on kernel sugars. The results indicated that it may be possible to increase kernel DMS potential in some genotypes by increased N fertilization, and to a lesser degree, from S application.

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Abstract

Twenty-seven accessions from 6 species of the genus Lycopersicon and 1 accession of Solanum pennellii were surveyed for content of the glycoalkaloid, α-to-matine. Significant variation in alkaloid content was found to exist among the accessions. L. esculentum cultivars were found to contain much lower concentrations of α-tomatine than accessions of L. esculentum var. cerasiforme, L. pimpinellifolium, and the L. peruvianum accession, LA 462.

Open Access

To identify qualitative and quantitative chemical variation in tomato fruit dry matter, crosses were made between the high soluble solids concentration (SSC) line LA 1501 (6.3% SSC when red-ripe) and the nearly isogenic commercial tomato cultivar VF 145B-7879 with a lower SSC (4.4% when red-ripe). Fruit samples from the parents and the reciprocal F1 hybrids were collected at 3-day intervals, from 25 to 52 days after anthesis, to evaluate the accumulation of various quality components throughout the development of the fruit from immature-green to red-ripe stage. Fructose and glucose concentrations, titratable acidity, pH, and percent dry weight (pulp and serum) were determined for each sample on a fresh basis. Fruit maturity was evaluated by puree color using Hunter `a' colorimeter values. Changes in most of the chemical constituents of the fruit were found to regress linearly with changes in fruit color. Regression of puree color against fruit SSC, and fructose, glucose, and total sugar concentrations described more of the observed variability in these components than days after anthesis, indicating that Hunter `a' colorimetric values provide a more precise measurement of fruit physiological age. The variation between the parents in fruit dry matter was found to be primarily due to differences in SSC. The ratio of fruit soluble to total solids concentration increased 23.7% in LA 1501 (from 61.6% to 85.3%) throughout ripening compared to-an increase of only 8.9% (from 66.3% to 75.2%) in `VF 145B-7879'. At the red ripe stage, LA 1501 possessed a 44% higher SSC than `VF 145B-7879'. Differences in fructose and glucose accounted for 41% of the variation in SSC between the two lines. An unidentified component(s) was responsible for the residual variation. Application of the genetic and physiological information generated from this study can be used to isolate and select for genes controlling accumulation of tomato fruit dry matter.

Free access

Two chromosomal segments from the wild tomato L. chmielewskii have been introgressed into the L. esculentum genome. Using molecular markers they have been mapped to the middle and terminal regions of chromosome 7 (7M and 7T, respectively). This study was conducted to further clarify the physiological influence of the introgressed segments on tomato soluble solids, and other fruit and yield parameters. Sixty-four BC2F5 recombinant inbreds were developed from a cross using LA1501 (L. esculentum line that contains both fragments from L. chmielewskii) as the donor parent, and VF145B (processing cultivar) as the recurrent parent. Recombinant inbreds were classified in four groups (++: inbreds without either of the fragments, 7M+: with only the 7M fragment, +7T: with only the 7T fragment and, 7M7T: with both fragments) based on RFLP information, and then compared to each other for all the parameters under study. Inbreds homozygous for the 7M fragment displayed greater soluble solids (26%) and higher pH (0.10) than the control group (++), through a physiological mechanism related to water uptake. The 7L fragment did not influence either soluble solids or pH, but was observed to significantly increase fruit yield by 11%. A gene or genes that increase yield without affecting soluble solids or pH may have potential in the development of commercial cultivars.

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