Sugary Enhancer Research Articles

Sugary1 and Sugary Enhancer1 Sweet Corn Inbreds with Resistance to Northern Leaf Blight

Sugary1 and Sugary Enhancer1 Sweet Corn Inbreds with Resistance to Northern Leaf Blight

GENETIC VARIABILITY FOR EATING QUALITY ATTRIBUTES IN SWEET CORN.

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.

EVALUATION OF SWEET CORN LINES FOR RESISTANCE TO NORTHERN LEAF BLIGHT AND THE SUGARY ENHANCER (SE) GENE.

In regions of sweet corn production in the U.S. and overseas epidemics of northern leaf blight (NLB) caused by the foliar pathogen Exserohilum turcicum are common. NLB can significantly decrease yields, and ear quality of susceptible and moderately susceptible sweet corn hybrids. Thirty-four BC2F7 sweet corn inbreds have been created from several crosses between field corn lines with various Ht resistance genes (Ht1, Ht2, Ht3, and HtN) and three high quality sweet corn inbreds homozygous for the sugary enhancer (se) gene. These gene when homozygous in sweet corn kernels increases sugar content at harvest and improves fresh ear quality and consumer appeal. Seedlings of the 34 different inbreds with either the Ht1, Ht2, Ht3, or HtN gene were inoculated with race 0 and 1 of E. turcicum, evaluated for lesion size, amount of leaf necrosis and hypersensitivity response to compare levels of NLB resistance in different genetic backgrounds. To ascertain which of these lines also contain the se gene, kernels from 20 DAP (days after pollination: typical fresh harvest maturity) and mature dry ears were freeze-dried, ground into powder, extracted and quantified for sugar content using a gas chromatograph. The lines with the best resistance to NLB and containing the se gene have been selected for release to breeders for the development of superior sweet corn hybrids.

Prediction of Sweet Corn Phenology in Subtropical Environments

AbstractLimited information on phenology of sweet corn (Zea mays L.) grown in subtropical regions is available to processors wishing to manage harvest scheduling. This study was conducted to investigate developmental characteristics of both standard sugary (su) and mutant endosperm sugary enhancer (se), and shrunken‐2 (sh2) sweet corn in subtropical Australia. Field experiments were conducted at three locations with numerous times of planting so that a broad range of environments were encountered. Models of daily rate of development for the period sowing to kernel maturity (720 g kg−1 moisture) were derived by an iterative optimization procedure. Development rate was related to mean daily temperature and photoperoid. Temperature was the most important factor affecting rate of development. The temperature response was best described by a broken linear function. Various photoperiod functions fitted as multipliers to the temperature response did not improve goodness‐of‐fit. Cultivars were classified into three maturity groups based on analysis of covariance. Developmental characteristics appeared independent of genetic background as the response of the three sh2 cultivars was not significantly different from a tropical su type, and the se cultivar ‘Sweet Champion’ did not differ significantly from the majority of su types. Only su cultivar ‘Terrific’ differed significantly from both of these groups. Base temperatures (range from 5.4–6.4°C) were lower than the value traditionally quoted for sweet corn (10°C). Optimum rates of development occurred at temperatures ranging from 30.8 to 33.8° C. The models accurately predict the duration of sowing to maturity and were shown to be a practical tool for harvest date prediction of both standard and mutant endosperm sweet corn in subtropical environments.

Characteristics of α-Amylase during Germination of Two High-Sugar Sweet Corn Cultivars of Zea mays L.

The role of the scutellum and the aleurone in alpha-amylase production in the high-sugar sweet corn cultivars Illini X-tra Sweet (shrunken-2, sh2) and Illinois 677a (sugary, sugary enhancer; su se) was compared to that in the starchy (Su) hybrid Funks G4646 with the use of alpha-amylase enzyme assays, isoelectric focusing, electron microscopy, and laser scanning confocal microscopy. The scutellum of Illinois 677a had low levels of alpha-amylase activity compared to that of Funks G4646 through 10 days after imbibition, and the aleurone of Illini X-tra Sweet had negligible activity. On the isoelectric focusing gels, the Illinois 677a scutellum had fewer alpha-amylase isozymes at 7 days compared to the Funks G4646 scutellum. The Illini X-tra Sweet aleurone had no alpha-amylase isozymes. Funks G4646 scutellar epithelial and aleurone cells contained abundant rough endoplasmic reticulum, polysomes, and dictyosomes at 5 and 7 days, respectively. The scutellar epithelial cells of Illinois 677a contained fewer of these structures by 5 days, and the Illini X-tra Sweet aleurone contained mostly lipid bodies through 7 days. Few cytoplasmic membranes and little RNA were detected with laser scanning confocal microscopy in the Illini X-tra Sweet aleurone compared to Funks G4646 at 7 days. These data suggest that the scutellum of Illinois 677a and the aleurone of Illini X-tra Sweet have impaired abilities to produce alpha-amylase.

Sweet Corn Cultivars Respond Differentially to the Herbicide Nicosulfuron

Twelve sweet corn (Zea mays L. var. rugosa Bonaf.) cultivars were tested for response to nicosulfuron at rates of 0, 18, 36, and 72 g a.i./ha. Weight of marketable ears indicated that five cultivars were intolerant to the herbicide. Three of the cultivars that were intolerant contained the shrunken-2 endosperm mutant (sh) and two contained the sugary enhancer endosperm mutant (se). Cultivars that were most tolerant of nicosulfuron contained the sh, gene. Incorporation of terbufos insecticide before planting led to decreased marketable yield when nicosulfuron was applied at 36 g·ha in all cultivars tested. Chlorpyrifos insecticide incorporated before planting did not affect tolerance to nicosulfuron. Neither soil-applied insecticide affected yield when nicosulfuron was not applied. Chemical names used: 2-[[[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfony]-N,N-dimethyl-3-pyridinecarboxamide (nicosulfuron); S-[[(1,1-dimethylethyl)thio]methyl] O,O-diethylphosphorodithioate (terbufos); O,O-diethyl O-(3,5,6-trichloro-2-pyridyl)phosphorothioate (chlorpyrifos).

Field Performance of Sweet Corn Seed Bio-primed and Coated with Pseudomonas fluorescens AB254

In field experiments, bio-priming and coating with Pseudomonas fluorescens AB254 consistently protected sweet corn (Zea mays L.) seeds from preemergence damping-off caused by Pythium ultimum Trow. The bio-priming seed treatment was evaluated under various disease pressures and with seeds of three sweet corn genotypes: shrunken-2 supersweet (sh-2), sugary enhancer (se), and sugary (su). While no damping-off occurred in the su sweet corn, bio-priming protected sh-2 and se sweet corn seeds at a level equivalent to that obtained by treatment with the fungicide metalaxyl. Biopriming increased seedling height of all three sweet corn genotypes at 4 weeks post-planting. Coating of sweet corn seeds with P. fluorescens AB254 provided an equivalent degree of protection from damping-off under all but the most severe conditions.

Identification of Maize Inbreds with High Levels of Maltose in Endosperm of Germinating Seeds

Maltose appears in germinating seeds due to enzymatic hydrolysis of starch, but is absent or scant during development, except for endosperm of the sugary-1 (su-1) maize inbred IL677a and some related inbreds (Carey et al., 1984; Shaw and Dickinson, 1984). Mature dry seeds of these inbreds still contain some maltose (2% to 4%). IL677a is also the source of sugary enhancer (se), which increases endosperm sucrose (Ferguson et al., 1978). We attempted to learn whether the unknown biochemical change causing maltose accumulation in developing endosperm also operates during germination. Entries included the starchy (Su) inbred B73, IL451b and ‘Seneca Scout’ (both su-1), and the su1se inbreds IL677a and IL731a, which accumulate maltose during development (Shaw and Dickinson, 1984). Endosperms were dissected from seeds germinated in the dark under sterile conditions at 30C and moistened with 0.1 mM CaCl2, with 10 to 15 endosperms per sample, except for five to eight at 6 days due to limited seed supplies. Dissected tissue was kept on ice until ethanol extraction, and maltose was determined by gas chromatography (Shaw and Dickinson, 1984). Results of analyses sometimes varied; thus, data are presented as means over duplicates. Maltose was consistently higher in IL677a than in the other inbreds (Fig. 1) and increased rapidly early in germination when the others had none or only trace amounts, reaching the highest level (27 mg/endosperm) on the 4th day. An analysis of variance indicated the difference between IL677a and the other inbreds was highly significant

FIELD PERFORMANCE OF BIO-PRIMING FOR PROTECTION OF sh2 SWEET CORN FROM PREEMERGENCE DAMPING-OFF CAUSED BY PYTHIUM ULTIMUM.

Shrunken-2 supersweet (sh2) sweet corn is susceptible to preemergence damping-off caused by Pythium ultimum, especially when planted into cold soil. Bio-priming, a seed treatment which combines the establishment of a bioprotectant on the seed with preplant seed hydration, was developed to protect seeds from damping-off.In a series of field experiments conducted in Montana's Bitterroot and Gallatin Valleys, bio-priming or seed bacterization with Pseudomonas fluorescens AB254 protected sweet corn from P. ultimum damping-off. Bio-priming corn seed with P. fluorescens AB254 was comparable to treatment with the fungicide metalaxyl in increasing seedling emergence. Seedlings from bio-primed seeds emerged from the soil more rapidly than from nontreated seeds and were larger at three weeks postplanting. Seeds of sh 2 and sugary enhancer (se) sweet corn, as well as that of several sh 2 cultivars, were protected from damping-off by bio-priming.

Characterization of sugary-1 (su-1) sugary enhancer (se) Kernels in Segregating Sweet Corn Populations

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.

Single-kernel Analysis for the Presence of the sugary enhancer (se) Gene in Sweet Corn

Abstract This paper presents the methodology for the extraction and quantitative analysis of the sugars from single kernels of maize (Zea mays L. var. saccharata Bailey). Concentrations of sorbitol, fructose, glucose, sucrose, and maltose were determined for individual kernels of sweet corn inbreds homozygous for the endosperm carbohydrate mutants sugary (su) and sugary enhancer (se) by gas chromatographic analysis. The extraction procedure was efficient and precise. Single-seed sugar analysis of kernels from the inbreds IL451b (su) and IL677a (su se) revealed that genetic differences between the inbreds was the primary source of phenotypic variation in kernel sugar content. Differences between ears of the same inbred was also a significant source of variation, whereas, in most instances, kernel-to-kernel variation on ears was not. Fifty-eight percent of the variation in the predominant corn sugar, sucrose, was attributed to genetic differences between the two inbreds. Analysis of the observed and predicted distribution in a mature-dry F2 kernel population for sucrose content indicated that single-kernel analysis can isolate the action of the se gene in segregating populations. This procedure can be used to simplify the incorporation of se into elite inbreds, map its chromosomal location, and uncover other potentially useful alleles that modify corn endosperm carbohydrate metabolism.

Sugary (su) and sugary enhancer (se) Sweet Corn Inbreds with Resistance to Maize Dwarf Mosaic Virus

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.

Sugar characteristics of sweet corn populations from a sugary enhancer breeding program

Endosperm sugars and sorbitol were determined on 18 sweet corn (Zea mays L.) populations from a breeding program undertaken to transfer the sugary enhacer (se) gene into diverse sugary (su) backgrounds. Three subpopulations of IL677a, the source of se, and six su Se inbreds were included for comparison. Mature dry kernels of between two and four successive generations of these populations were analyzed. Immature kernels at two developmental stages (21 and 35 days after pollination) were also analyzed for one generation.

Effects of Two Maize Endosperm Mutants on Kernel Maturity, Carbohydrates, and Germination1

The shrunken‐2 (sh2) and sugary enhancer (se) genes which modify endosperm carbohydrates in maize (Zea mays L.) show promise as a means of improving quality for human consumption. A major factor limiting their use is the associated low germination of the seed and low seedling vigor. This research was undertaken to measure germination of sh2 and se hybrids as compared to their respective standard counterparts, Sh2 and Se, when seed was harvested at successive stages of maturity, and to examine germination differences as related to corresponding carbohydrate fractions. Hybrids were hand pollinated on the same day, and ears were harvested at approximately weekly intervals on six successive dates beginning 32 days after pollination. Kernel weight, moisture, reducing sugars (RS), total sugars (TS), water soluble polysaccharides (WSP), total soluble carbohydrates (TSC), water insoluble polysaccharides (WlP), tal non‐structural carbohydrates (TNC), cold and warm temperature germination, and seedling vigor were determined for seed at each harvest. Although the sh2 gene markedly increased kernel sugars and reduced kernel weight, seed of the hybrid, sh2 (2 ✕ 3), had satisfactory cold.temperature germination when harvested after mid‐September, when its moisture content was approximately 50%. Seed of the hybrid, se (8 ✕ 10), also higher in sugar than its standard counterpart, germinated satisfactorily at cold‐temperature when harvested at a moisture content of 60%. Cold‐temperature germination was negatively associated with kernel moisture, RS, TS, WSP, TSC, and TNC and positively associated with WlP. It usually was not significantly related to kernel weight. Root, shoot, and total seedling length were positively correlated with cold temperature germination. These results indicate that germination at low temperatures simulating those in the field can often be satisfactory for hybrids carrying the sh2 or se genes.

Release of Six Illinois Sweet Corn Inbreds with the Sugary Enhancer (se) Gene

Abstract Six sweet com (Zea mays L.) inbreds homozygous for the genes sugary (su) and sugary enhancer (se) have been developed at the Illinois Agricultural Experiment Station. The se gene is a recessive modifier of the su genotype (2) and results in increased kernel sugar content, sweetness, and tenderness (3). Kernels with the su se genotype contain amounts of sugar comparable to those found in lines homozygous for the shrunken-2 (sh2) gene but without a concomitant reduction in phytoglycogen (water-soluble polysaccharides) content (4). The high level of phytoglycogen found in su and su se cultivars contributes to their tender, creamy texture.

Reserve carbohydrates from kernels of sugary and sugary enhancer maize

Mature seeds of ‘sugary’ ( su) and ‘sugary-sugary enhancer’ ( su-se) maize inbreds were compared with respect to amount and properties of starch and glycogen. Sugars and sorbitol were also determined. Sucrose and maltose were elevated in the su-se seeds, starch was reduced and phytoglycogen was within the range expected for an su line. The se trait did not result in altered structure of the starch or phytoglycogen. Hence, it is unlikely that the observed increase in maltose resulted from premature action of amylases on starch and phytoglycogen during seed maturation.

Illinois Sweet Corn Inbreds with the su se Genotype1

Abstract Eleven maize inbreds homozygous for genes sugary (su) and sugary enhancer (se) were developed as a consequence of studies to characterize the effect of se with su on car bohydrates in the kernels (2, 3, 4). These inbreds should provide useful germplasm for the development of sweet com hybrids with superior culinary quality.

Postharvest Levels of Sugars and Sorbitol in Sugary Enhancer (su se) and Sugary (su Se) Maize1

Abstract Five sugary enhancer (su se) inbreds were compared with 2 sugary (su Se) inbreds of maize (Zea mays L.) for postharvest changes in sugars and sorbitol. The level of sucrose, the predominant sugar, was 17 to 26% of dry weight for the su se inbreds, and 8 and 9% for the su Se inbreds at the time of harvest. The su se inbreds lost about the same proportion of their sucrose as the su Se inbreds during 48 hours storage at 30°C, but storage at 2° slowed or prevented the loss in both genotypes. The sucrose content of su se inbreds after 48 hours storage at 30° was still greater than that of freshly harvested su Se inbreds. For the other sugars and sorbitol, the effect of the se gene was minimal during storage. In general for both genotypes, fructose decreased and maltose increased during either storage condition. Sorbitol decreased during cool storage and increased during warm storage.

Analysis of Endosperm Sugars in a Sweet Corn Inbred (Illinois 677a) Which Contains the Sugary Enhancer (se) Gene and Comparison of se with Other Corn Genotypes

The endosperm sugars of a new corn (Zea mays L.) mutant, sugary enhancer (se), were analyzed by gas-liquid chromatography and were compared with sugars of other genotypes. Illinois 677a, a sugary (su) inbred containing the se gene, was high in sucrose and was distinguished from all of the other genotypes by its high maltose content. During kernel development, the maltose content of IL677a increased to 3.28% dry weight at 40 days postpollination and remained high at the dry mature stage, whereas ;Silver Queen,' a high quality sugary (su) hybrid not possessing the se gene, showed no such trend in maltose accumulation. Sucrose, fructose, and glucose decreased during kernel development in ;Silver Queen' and IL677a from 19 days postpollination until the dry mature stage. The slow drying characteristic and the reduced starch content previously reported for maturing seeds of IL677a may be related to the maltose accumulation reported here.

The genetics of sugary enhancer (se), an independent modifier of sweet corn (su)

The genetics of sugary enhancer (se), an independent modifier of sweet corn (su)