Florida Staysweet Research Articles

Water extraction of plant tissues for analysis by ion chromatography1

High pressure liquid chromatography (HPLC)‐grade water was evaluated as an alternative extraction reagent to acid extraction of plant tissue. Green and red bell pepper fruit (Capsium annuum var. annuum L.), cultivar Pip; sweet corn internodes (Zea mays L.), cultivar Florida Staysweet; cabbage wrapper leaves (Brassica oleracea L. Capitata group), cultivar Solid Blue 770; peach leaves [Prunus persica (L.) Batsch], cultivar Coronet; and mixed leaves and stems of cotton (Gossypium hirsutum L.), cultivar Delta Pine 51; or okra [Abelmoschus esculentus (L.) Moench], cultivar Spineless Green Pod were extracted with HPLC‐grade water or 5 mM hydrochloric‐ (HCl), acetic‐, or citric‐acids. Ashed and fresh ground tissues were used for extraction with HCl. Cations and anions were determined by ion chromatography. In about 95% of occurrences, concentrations of ions in tissues extracted with HPLC‐grade water were equal to, or greater than, those extracted with acids. Therefore, extraction of plant tissues with HPLC‐grade water is recommended. Fewer waste disposal problems will also occur with water extraction of plant tissues.

Flavour Qualities of Frozen Sweetcorn are Affected by Genotype and Blanching

Peroxidase activity is used by the food processing industry as an indi- cator of adequacy of the blanching process and to predict off-flavour develop- ment in frozen food. Research reported herein showed that total peroxidase activity did not parallel flavour changes in frozen unblanched supersweet (sh2) or sugary enhanced (sullse) sweet corn genotypes. Frozen corn-on-the-cob of 'Florida Staysweet' (sh2), 'Merit' (standard sweet-sul) and 'Bodacious' (sullse), blanched and unblanched, was subjected to sensory evaluation and peroxidase analysis following frozen storage up to 12 months. Trained taste panellists rated the unblanched sh2 and sullse corn as acceptable up to 8 months of frozen storage. Kernels were cut from cobs after 0 and 12 months of storage. Proteins were extracted from acetone powders of kernels and separated by isoelectric focusing and native PAGE. Banding patterns differed according to genotype and storage duration. These results suggested molecular differences in peroxidase iso- zymes among the sweet corn genotypes which could be involved in off-flavour development. All genotypes contained a peroxidase isozyme having a molecular mass of 80 kDa and PI of 4-5. The sullse and sh2 genotypes produced an addi- tional peroxidase band of 13.8 kDa. An additional peroxidase isozyme (PI 5.4) appeared in extracts from the sul genotype after 12 months storage. Although changes in total peroxidase activity may not predict flavour changes in all geno- types, the presence or absence of certain peroxidase isozymes may be useful in predicting off-flavour development in sul frozen corn.

PEROXIDASE ACTIVITY DIFFERS IN SWEET CORN GENOTYPES

Increased peroxidase activity is used to predict development of off-flavor in frozen sweet corn. However, peroxidase activity was not indicative of flavor changes in frozen supersweet (sh2) or sugar enhanced (sul/se) sweet corn genotypes. These results suggested an inactivation or absence of certain peroxidase isozymes. Frozen `Florida Staysweet' (sh2), `Merit' (sul), and `Bodacious' (sul/se) kernels were cut from cobs after 0 and 12 months of storage. Proteins extracted from acetone powders were separated by isoelectric focusing (IEF) and Native-PAGE. Banding patterns differed according to cultivar and storage duration. All cultivars contained a peroxidase isozyme having a molecular weight of 99 kD and pI of 4.5. The sul/se and su2 cultivars expressed an additional peroxidase band of 17.9 kD. An additional peroxidase isozyme (pI 5.0) appeared after 12 months of storage in the sul cultivar. This isozyme did not appear in sul/se or sh2 and is a possible marker for predicting off-flavor in corn. This isozyme may also catalyze off-flavor reactions in sul corn genotypes. Although changes in total peroxidase activity may not predict flavor loss in all genotypes, certain peroxidase isozymes may be useful in predicting and catalyzing off-flavor reactions in sul corn cultivars.

Cell Death Patterns in Stalks of a “Supersweet” Sweet Corn Cultivar

Stalk No. Cell death ratingz Planting Developmental length expanded No. internodes Location date stage DAPy (cm) internodes 1 2–4 5–11 Overall Wilburton 18 May Late whorl 48 97 cx 4.7 b 0.0 c 0.0 b 0.0 c 0.0 c Tassel 59 147 ab 9.9 a 2.5 b 3.6 a 2.2 b 2.6 b Silk 69 140 b 9.6 a 3.6 a 4.0 a 4.0 a 4.0 a Mature silk 76 154 a 9.3 a 3.4 a 4.0 a 4.0 a 3.9 a Harvest 88 156 a 9.3 a 3.6 a 3.9 a 3.9 a 3.9 a Lane 15 June Late whorl 40 172 c 9.8 b 1.6 d 2.5 b 0.2 b 0.9 b Tassel 46 208 b 10.8 a 2.9 b 4.0 a 3.4 a 3.5 a Silk 54 217 a 10.8 a 2.2 c 3.9 a 3.9 a 3.8 a Mature silk 61 213 ab 10.4 a 2.1 c 3.9 a 4.0 a 3.8 a Harvest 68 208 b 10.5 a 3.4 a 4.0 a 4.0 a 3.9 a 17 July Late whorl 42 131 b 7.5 b 0.8 b 1.9 c 0.0 b 0.7 c Tassel 53 136 b 10.5 a 1.3 ab 3.3 b 3.9 a 3.3 b Dead pith tissue in split dent corn stalks (Zea mays L.) is white and fluffy (Pappelis and Williams, 1966), and it is easily colonized by fungal pathogens, especially Fusarium moniliforme Sheldon (Foley, 1962). In sweet corn, F. moniliforme produces metabolites toxic to plant and mammalian systems (Zummo and Scott, 1992). This fungus asymptomatically and systemically colonizes sweet corn tissues, including kernels (Bacon et al., 1992). Infection through nodes can result in colonization of ears if tissue subtending the inflorescence and shank are in advanced stages of senescence. Dent corn cultivars have some resistance to diplodia, gibberella, or fusarium stalk rots before silking, but they differ in susceptibility later (Koehler, 1960). Sweet corn cultivars are different from dent corn because they contain endosperm mutant genes controlling kernel sweetness (Courter et al., 1988). Planting later delays cell death in dent corn stalk internodes (Pappelis and Boone, 1966). Whether stalk cell death patterns in ‘Florida Staysweet’ sweet corn , an sh2 (shrunken-2) genotype, are similar to those in dent corn is unknown. Neither senescence rates nor causes that contribute to senescence in supersweet corn are well known. Our experiment was designed to determine if planting date affected senescence in stalk tissues in ‘Florida Staysweet’. On 18 May 1990 in Wilburton, Okla., and on 15 June and 17 July 1990 in Lane, Okla., seeds were sown with 0.23-m in-row spacing in single rows on beds with 0.9-m centers. Plantings were replicated four times. Fields were fertilized with ammonium nitrate (34N– 0P–0K), P2O5 (0N–46P–0K), and K2O (0N– 0P–60K) to bring nutrient levels to (in kg•ha) 100N–134P–134K. The principal water source was precipitation, but additional water was supplied weekly from tassel emergence through kernel filling by drip irrigation equivalent to 50 mm of precipitation per application. Beginning at the late whorl stage (collar of twelfth leaf present, ≈43 days after planting) and con-

ORGANOLEPTIC QUALITY OF MINIMALLY PROCESSED SUPERSWEET CORN

Supersweet corn with the shrunken-2 gene (sh2) has shown good quality after frozen storage. A study was undertaken to further evaluate the quality of supersweet corn (cv Florida Staysweet) unblanched or blanched then frozen. Samples were evaluated every 4 months for 12 months for peroxidase activity. sugar composition, water soluble polysaccharides and organoleptic qualities. Peroxidese activity changed in unblanched corn at each sampling date, which was consistently higher than in blanched corn. Sucrose and total sugars declined during storage. Sucrose was highest in blenched samples and reducing sugars were highest in unblanched samples. WSP content was low in all samples, but lower in blenched compared to unblanched samples. Taste panelists discerned differences between blanched and unblanched corn at 8 months when blanched samples were rated as more yellow than unblanched. However, no differences were found for taste between blanched and unblanched samples for taste at 12 months. These results indicate that sh2 sweetcorn maintained good eating quality for 12 months of frozen storage with or without blanching.

Insecticidal Control of Fall Armyworm in Florida Sweet Corn, 1992

Abstract Six raised beds on 6 ft centers prepared on 17 Aug included a fertilizer bottom mix of 1000 lbs/acre of 5-16-8 and 800 lbs/acre of 19-0-19 placed in a central band at bedding. Beds were fumigated with 220 lbs/acre of methyl bromide injected every 5 inches across the bed width and sealed immediately with white-faced, black polyethylene. On 5 Oct, two seeds per hole of the cultivar ‘Florida Staysweet’ were planted in two rows 10 inches apart in the center of each bed and later thinned to one plant per space. Manzate 200 was applied weekly with a plot sprayer at 100 psi to prevent leaf blight and rust. Each of two sets of 3, 240 ft rows was divided into two blocks, 50 ft long, with 100 row ft between blocks. Each row was randomly assigned one of 2 treatments or a control water-treatment in a RCB design. Spray applications were made weekly over 8 weeks beginning 30 Oct using a CO2 pressurized backpack sprayer manufactured by Weed Systems, Inc., Gainesville FL. At an operating pressure of 40 psi, the first 5 applications were calibrated at a rate of 30 gpa and the last 3 at 45 gpa. The surfactant, APSA-80 (80% Alkyl Aryl Alkoxylate) was added at the rate of 0.3% to the Larvin application. Armyworm counts and damage ratings were made one day prior to the first treatment and weekly thereafter by examining the whorl and the next 2 adjacent leaves before tasseling and all ears thereafter. The following numerical ranking system was used for damage ratings: 0: no damage, 1: windowing to 10%, 2: 11-30%, 3: 31-40%, 4: 41-50%, and 5: greater than 50%. Larvae observed during field evaluations were recorded. Plots were harvested on 21 Dec and 7 Jan. All the mature ears were collected and counted and weighed. The number of damaged ears was noted and ears weighed.

LEAKAGE AND MOBILIZATION OF STORAGE RESERVES DURING IMBIBITION OF SWEET CORN.

Interconversion and transport of seed storage reserves during imbibition may influence subsequent germination. Sweet corn (Zea mays L. cv. Florida Staysweet) seeds were imbibed in aerated distilled water for either 0, 3, 6,9,12, or 24 h intervals. Seed leachate electrical conductivity, leachate soluble carbohydrate concentrations, and seed moisture were quantified at each interval. Lipid, non-structural carbohydrate, and protein concentrations of embryo and endosperm tissue were quantified for each imbibition interval. After imbibition treatments, seed germination performance was evaluated at 10 and 25C. Leachate conductivity and seed moisture increased with duration of imbibition. Glucose and fructose were the major soluble carbohydrates found in the seed leachate. Embryo lipid and sucrose concentrations significantly increased within 6 h of imbibition, while endosperm lipid decreased. Endosperm sucrose concentration remained constant throughout the duration of imbibition. Germination percentage was not significantly improved at 10 or 25C during the course of imbibition. Conversely, time to germination decreased significantly at 10C within 3 h. Storage reserve mobilization during imbibition may be responsible for the decreased time to germination observed at 10C.

Treating Shrunken-2 Sweet Corn Seed with Fungicide Infused via Acetone

Experiments were conducted to determine if the fungicide imazalil infused into shrunken-2 sweet corn (Zea mays L. var. rugosa Bonaf.) seed via acetone could protect against soil- and seedborne fungi enough to improve germination and vigor. `Florida Staysweet' and `Crisp-n-Sweet 710' seeds were infused for 0.25 hours with 1% or 2% (w/w) imazalil-acetone (LA) solutions, air-dried, and subjected to a modified laboratory seedling growth cold test using sterile soil or soil inoculated with Fusarium moniliforme Sheldon. Both IA concentrations significantly reduced the incidence of diseased seedlings in soil inoculated with F. moniliforme when compared to nontreated controls. Neither treatment significantly reduced the incidence of seedborne fungi. Chemical name used: 1-[2-(2,4-dichlorophenyl)-2-(2-propenyloxy)ethyl-H-imidazole (imazalil).

SENESCENCE IN SWEETCORN

Fungi can colonize senescent sweet corn (Zea mays var. rugosa Bonaf.) tissue. Senescence levels of tissues can be rated. Effects of four planting dates on senescence of standard (su, cv. Merit), and supersweet (sh2, cv. Florida Staysweet) corn at fresh market and seed harvest were determined. Stalk senescence was affected by cultivar (sh2 < su) and planting date (earliest was lowest). Shank senescence was affected by cultivar (fresh market < seed harvest) and planting date (lowest for plants of the earliest and latest plantings). Cob senescence was not affected by cultivar, slightly lower at fresh market than seed harvest, and lower for plants of the later than earlier planting dates. In a second experiment senescence was rated during development of sh2 cultivars. Formation of reproductive structures increased senescence rate. Cultivar had little effect on stalk and cob senescence at fresh market harvest. The cv. `Honey'n Pearl' had the lowest shank senescence rating. Delayed senescence should be incorporated in to corn genotypes.

SEEDLING DEVELOPMENT OF SWEET CORN WITH LOW TEMPERATURE AND POTASSIUM

Five supersweet cultivars of corn (Zea mays L. var. rugosa) were planted in fields and growth chambers to compare potassium effects on seedling development at low temperatures. In fields, seeds were planted at Urbana, IL, in 1991 when soil temperatures were 15C(April) and 23C(June). Potassium chloride(KCl) was banded at 0, 45 or 90 kg KCl/ha. After 32 days `Illini Gold', `Florida Staysweet', and `Crisp'n`Sweet' were more developed than `Honey'n`Pearl' and `How Sweet It Is' as indicated by emergence, height, leaf area and number, and weight in April. However for June, cultivar differences were observed only for emergence. KCl had no effect on any cultivars. In chambers, seeds were planted in trays(6×22×30 cm) of vermiculite mixed with 0, 5 or 10 g KCl/tray at 17 and 26C. After 15 days, cultivar responses at both temperatures were similar to those at the April field planting except at 26C where none differed for emergence. KCl only affected seedlings at 26C when 10 g/tray slowed development. Thus more differences were found between cultivars at lower than higher temperatures, and potassium did not improve seedling development at low temperatures.

ROLE OF SEED STORAGE RESERVES IN OSMOCONDITIONING OF SWEET CORN

Interconversions of seed storage reserves during osmoconditioning (controlled imbibition of water) may influence seed performance under suboptimal conditions. Sweet corn (Zen mays L. cv. Florida Staysweet) storage reserve changes were examined during osmoconditioning in relation to seed germination performance. Seeds were osmoconditioned in two experiments using distilled water (duration 3, 6, 9, 12, and 24 h) and polyethylene glycol 8000 solutions (0, .5, and 1.0 MPa for 12, 24, 48, 72 and 96 h). Germination performance was evaluated at 10 and 25C, and seed moisture, carbohydrate, and protein concentrations were quantified at each water potential x duration combination. Germination performance was not significantly improved by any treatment at 25C. Germination percentage at 10C was increased 10% for seeds osmoconditioned for 24 h in distilled water, and time to germination was decreased 50%. For seeds osmoconditioned 12 and 48 h at .5 and 1.0 MPa, respectively, germination percentage at 10C was increased 15%. Time to germination was reduced 50% for seeds osmoconditioned at .5 and 1.0 MPa after 48 and 96 h, respectively. Starch levels increased for seeds osmoconditioned at higher water potentials, but remained the same or decreased at lower water potentials.

Infusion of shrunken-2 Sweet Corn Seed with Organic Solvents: Effects on Germination and Vigor

Sweet corn (Zea mays L. var. rugosa Bonaf.) seed carrying the mutant endosperm gene shrunken-2 (sh2) are very susceptible to seed rot and pre- and post-emergence damping off. Experiments were conducted to determine if selected organic solvents were suitable carriers for fungicide infusion of sh2 sweet corn seed for improved germination and stand establishment. Seed of `Florida Staysweet' and `Crisp-n-Sweet 710' were immersed in acetone, cyclohexane, decahydronaphthalene (Decalin), dimethylsulfoxide (DMSO), ethanol, or xylene for 5 seconds, 0.25, 0.50, 1.0, 2.0, 4.0, or 8.0 hours, air-dried, and subjected to a cold-stress test. Total germination and percentage of normal seedlings in both cultivars were significantly decreased after 8 hours of immersion in acetone. Average seedling dry weight, however, did not decrease. DMSO was highly toxic to both cultivars. Ethanol increased seed mortality with increasing immersion times. Cyclohexane, Decalin, and xylene caused erratic responses in all measured variables as immersion time increased. In a second experiment, the effects of immersion time up to 4 hours in acetone on germination and vigor of 11 sh2 cultivars were compared. There was no correlation between cultivar germination or vigor and immersion in acetone. Results indicate acetone could be used to infuse fungicides into the seed of some sh2 cultivars without compromising seed germination or vigor. However, each sh2 cultivar must be screened individually to determine if it is a suitable candidate for organic solvent infusion of fungicides.

Control of Corn Earworm on Sweet Corn, 1991

Abstract On 11 Apr, Florida Stay Sweet' sweet corn was seeded into fine, sandy loam soil at the Wes Watkins A.R.E.C., Lane, OK. Plots were 12 ft long and 4 rows wide with 3 ft spacing between rows and 4-6 inch spacing between plants. Plot buffers were 8 ft long with two unplanted rows between plots. Plots were arranged in a randomized complete block design with four replications. Fertilizer and herbicides were applied at recommended rates. Overhead irrigation was initially used to establish plant stand, but was later replaced with a trickle irrigation system. All insecticide applications were made with a tractor-mounted PTO-driven air pressure sprayer calibrated at 35.0 gallons per acre. Three TX-18 spray nozzles per row were suspended from the boom with two nozzles at the level of the silks and one nozzle above the row. A single broadcast application of Javelin WG at 0.5 lbs per acre was made on 7 Jun to control larvae in the whorls. Eight insecticide applications were made on a two-day schedule on the following dates: 13, 15, 17, 19, 21, 24, 26, and 28 Jun. Plots were harvested on 1 Jul. Each ear was evaluated for CEW damage and categorized as undamaged, marketable, or unmarketable. Marketability was determined by measuring the depth of CEW penetration from the tip. Ears less than five inches in length after trimming all CEW damage from them were considered unmarketable. Each ear was also evaluated for pollination and categorized as complete (100% filled kernels), marketable (80-90% filled kernels), and unmarketable (less than 80% filled kernels).

Physiological Maturity and Vigor in Production of ‘Florida Staysweet’ Shrunken‐2 Sweet Corn Seed

Shrunken‐2 (sh‐2) sweet corn (Zea mays L.) exhibits relatively poor germination and seedling vigor. Early harvest is sometimes advocated for avoidance of seedborne fungi. Our objectives included studying the effect of maturity on seed vigor, defining physiological maturity, and optimizing vigor testing. Six crops of ‘Florida Stay sweet’ seed were produced in 1987 and 1988 and harvested 22 to 90 days after silking (DAS). Maximum kernel dry weight was obtained 43 to 47 DAS except for very late (mid‐June) plantings, which required 48 and 66 DAS. Decline in kernel moisture content was linear. Unreated seed, harvested 72 to 75 DAS from mid‐April plantings. produced an 80% stand in the field the following year. Harvest at maximum dry weight (43 to 47 DAS) produced final stands of 20% of lower. Delaying planting of the seed crop until mid‐May resulted in a decrease of maximum attainable field emergence to 50% in 1987 but not in 1988. Delaying planting until mid‐June lowered maximum attained field emergence to 30% in 1987 and 40% in 1988. laboratory germination test maxima preceded field emergence maxima by 12 to 26 d. Black layer formation preceded low vigor resulting from immaturity. The soil cold test, accelarated aging, and mean leachate conductance (ASA 610) were more highly correlated wiht final stand (median r = 0.87, 0.85, and ‐0.88, respectively) than was rolled‐towel germination (median r = 0.71). In conclusion, early harvest (45 to 60 DAS) resulted in seed with high germination and low vigor. Leaving the crop in the field as long as 80 to 90 DAS resulted in consistent production of relatively high vigor seed, as long as the crop was not planted very late (mid‐June).

Seed Maturity Influences Germination and Vigor of Two Shrunken-2 Sweet Corn Hybrids

The objective of this study was to examine seed maturity at harvest as it relates to seed vigor in two commercial shrunken-2 (sh2 J sweet corn hybrids (Zea mays L. var rugosa Bonaf., cvs. Florida Staysweet, Crisp N' `Sweet 710). Seed harvest began at 0.76 g H2O/g fresh weight in 1987 and at 0.70 g H2O/g fresh weight in 1988 and 1989, and was continued at gradually declining moisture levels until frost. In five different tests of seed performance, seed of `Florida Staysweet' (FLASS) harvested between 0.23 to 0.57 g H2O/g fresh weight in 1987 possessed the highest seedling vigor. In 1988 and 1989, maximum vigor was achieved by FLASS seed harvested from 0.40 to 0.60 g H2O/g fresh weight and `Crisp N' Sweet 710' (CNS) seed harvested from 0.45 to 0.65 g H2O/g fresh weight. Standard germination test, seedling growth cold test (SGCT), and seed leachate conductivity provided the most consistent results to `determine optimum seed maturity. Seed weight was not as reliable an indicator of seed vigor in 1988 and 1989 as it was in 1987, and endosperm and embryo weights did not correlate with seedling vigor in any year.

Control of Corn Earworm on Sweet Corn, 1990

Abstract On 19 Jun 1990, 'Florida Stay Sweet' sweet corn was seeded into fine, sandy loam soil at the Wes Watkins AREC, Lane, OK. Plots were 12 ft long and 4 rows wide with 3 ft spacing between rows and 6 in between plants. Plot buffers were 10 ft long and 2 unplanted rows were left between plots. A randomized complete block design was used with four replications. Fertilizer was applied according to soil test recommendations. Overhead irrigation was used to establish the plant stand initially, but was later replaced with trickle irrigation. Treatments with 2-day application schedules were sprayed on six dates: 9, 11, 13, 15, 17 and 20 Aug. Insecticide application on plots with 4-day application schedules had three applications made on 9, 13 and 17 Aug. Treatments were made using a tractor-mounted PTO-driven air pressure sprayer which delivered 16.7 gal/acre at 40 psi. Two TX-10 spray nozzles per row were suspended from the boom at the level of silks on both sides of plant. Harvests were made on 17 and 21 Aug. Each ear was evaluated for CEW damage by rating the tip (proximal 3.8 cm) and ear (excluding tip area) using a scale of 1-5 where 1 = no damage, 2 = slight damage (<20%), 3 = moderate damage (20-50%), 4 = heavy damage (50-75%) and 5 = severe damage (>75%). A rating system of 1- 5 was used to evaluate the degree of pollination on each ear, where 1 = complete pollination (100% full kernals) to 5 = no pollination. The percentage of ears with no damage was also calculated from these ratings.

Comparison of Moisture Determination Techniques over a Range of Sweet Corn Seed Maturities

Table 1. Mean seed moisture content of ‘Florida Staysweet’ and ‘Crisp N’ Sweet 710’ as measured by three moisture determination methods.’ Seed moisture content, an estimate of kernel maturity, is commonly used by the sweet corn industry to determine optimal harvest date. Depending on environmental conditions, moisture in sweet corn seed can drop rapidly. Therefore, a rapid determination of moisture content was necessary to study the effects of seed maturity at harvest on germination and vigor of shrunken-2 sweet corn. A moisture analyzer (model AVC-80; CEM Corp., Indian Trial, N.C.) consisting of a microwave drying oven, electronic balance, and a microprocessor was used. The microprocessor computes moisture content based on percent weight loss of the sample after it has been dried by microwave radiation. We compared the efficacy of such a moisture analyzer (MA) across a range of 40% to 70% moisture (fresh-weight basis) in shrunken-2 sweet corn seed to two standard methods used by the seed industry, the air-oven (AO) and Brown Duvel distillation (BD). The moisture range was selected based on the industry’s harvesting guidelines for shrunken-2 sweet corn seed, which maximizes field performance (50% to 55% moisture on fresh weight basis). Seed of two shrunken-2 commercial hybrids, ‘Florida Staysweet’ and ‘Crisp N’ Sweet 710’, was produced by controlled hand pollinations of field-grown parental inbreds in southern Minnesota. Four harvests from each cultivar, each within a single pollination date, were made as seed moisture reached ≈70%, 60%, 50%, and 40%. Moisture was determined using seeds cut to cob level from the

Comparison of yield, cob characteristics and sensory quality of six supersweet (sh2) corn cultivars grown in a subtropical environment

Yield and cob characteristics of 6 supersweet corn (Zea mays L.) cultivars, homozygous for the recessive shrunken-2 (sh2) allele, were compared at 3 separate planting dates, in 1987-88, at Bundaberg (lat. 25�S.), Queensland. Sensory quality of the 6 sh2 cultivars and a standard cultivar, homozygous for the recessive sugary (su) allele, were compared in a separate experiment. Marketable yield (total weight of cobs-in-husks with at least 125 mm usable kernels without damage or defects) declined between each of the plantings: midwinter, early spring, late spring. Marketable yield of the cultivar Sucro was consistently high (9.18-13.7 t/ha), whereas, that of Honey Sweet was low (2.88-5.43 t/ha). Total weight of unmarketable cobs (cobs-in-husks with 125 mm usable kernels or cobs-in-husks having at least 125 mm usable kernels, but with damage or defects) was highest for Honey Sweet and ranged between 5.31 and 9.18 t/ha. Marketable yields of the 6 sh2 cultivars were similar to those obtained in other warm climates but were lower than those in cooler climates. The cobs-in-husks of Honey Sweet and Sucro from the midwinter planting were marginally heavier than the preferred cob-in-husk range (310-360 g/cob) demanded on domestic markets; those of Snosweet, Candy Sweet and Florida Staysweet were within the range; and those of Sugar Sweet were significantly (P<0.05) lower. None of the cultivars at the 2 later sowing dates achieved this desirable weight range. Because of the higher yields and larger cobs produced in the midwinter planting, and the higher incidence of disease and heat stress encountered in the later plantings, it is proposed that sh2 cultivar production should be limited to a midwinter sowing in subtropical Bundaberg. Taste panel testing indicated preference for all sh2 cultivars over the standard su cultivar in terms of both general acceptability and texture (P<0.05), and the su cultivar was rated least sweet (P<0.05). Snosweet was rated highest in terms of both general acceptability and texture scores and was also rated the sweetest cultivar.

Dry matter yield, nitrogen absorption, and water uptake by sweet corn under salt stress

Abstract The response to salinity differs greatly among various plant species. This study was conducted to evaluate the effects of NaCl salinity on growth of corn in terms of dry matter production and nitrogen and water uptake. Dry matter yield and N and water uptake by sweet corn (Zea mays L; cv. “Florida Stay Sweet) under normal (control) and NaCl salinized (3, 6, and 9 bars osmotic pressures) nutrient solutions were investigated in a walk‐in growth chamber. The 7‐day old seedlings were grown for 14 days in complete Hoagland solution before starting salt treatments. Then, osmotic pressures of the nutrient solutions (except the controls) were raised 1 bar every day by adding 24 mmol, 1.404 g L‐1, NaCl until the desired (3, 6, and 9 bars) salinity levels were attained. The levels of the nutrient solutions in the pots were maintained at the 2‐liter mark by addition of deionized water. The added water to each pot was recorded and considered as water absorbed by plants. Thirty days after the completion of s...

Leaching of Metabolites during Imbibition of Sweet Corn Seed of Different Endosperm Genotypes1

Sweet corn (Zea mays L.) hybrids with high‐sugar genotypes shrunken‐2 (sh2) and the triple recessive combination of genes amylose extender (ae), dull (du), and waxy (wx) have had limited acceptance for commercial production due to an inherent problem of low seed quality. The seed are lighter in weight and more shrunken than normal, or the sugary (su) genotype, and they frequently give erratic stands and low seedling vigor. This study was conducted to determine leaching of metabolites during imbibition of the high‐sugar seed and whether excessive leaching was associated with genotypes and their inherent low seed quality. Commercial seed of hybrids ‘Iochief’ (su), ‘Florida Staysweet’ (sh2), and ‘Pennfresh ADX’ (ae du wx) were chosen to represent three sweet corn genotypes in this study. Leaching of metabolites during imbibition was determined by measuring electrical conductivity of the leachates and the amount of soluble protein in the leachate at various time intervals after imbibition. Conductivity of leachates was higher for seed of the high‐sugar genotypes than for su. At 24‐ and 48‐h imbibition, leachate conductivity for ae du wx seed was higher than the other two genotypes. Leaching of soluble protein during imbibition was also higher for seed of the high‐sugar genotypes than from seed of su. There were no significant differences in the amounts of soluble protein initially present in seed of the various genotypes when expressed as milligrams per gram of seed. When expressed as milligrams per seed, however, the high‐sugar genotypes had much less soluble protein than su due to their low seed weight. Protein leaching during imbibition appeared to be related to broken pericarps and high membrane permeability in the seed of sh2 and ae du wx endosperm genotypes. These studies suggest that seed pericarps and membranes in the high‐sugar genotypes may be more susceptible to damage during harvest and drying than su and that special care may be required for producing high quality seed of the high‐sugar genotypes.