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Abstract
Tandem mass selection in a sweet com (Zea mays L.) composite produced a 5-day gain in maturity, increased the percentage of plants with light-colored silks, and increased the number of kernel rows per ear. Although the differences in earworm resistance between generations were not statistically significant, they suggest a slight but steady increase through the first four cycles of selection. Because infestation of earworm [Heliothis zea (Boddie)] was very low in 1972, no selection was applied to the fifth generation for resistance, and the level of resistance based on mean larval weights and larval instars dropped. Tandem mass selection improved the sweet com population for certain agronomic characters, and maintained its level of earworm resistance.
Abstract
Mature green ‘Homestead’ tomatoes (Lycoperiscon esculentum Mill.) and 3 advanced breeding lines were treated with ethylene gas and some compositional parameters of the treated fruit were compared with those of control fruit. Tomato breeding line T3702j 2 showed a greater response to ethylene treatment than ‘Homestead’ and other advanced breeding lines carrying the crimson (og c) and high pigment-crimson (hp og c) genotypes. Ethylene treatment had negligible effects on the levels of soluble solids, dry matter, ascorbic acid, β-carotene, and lycopene in the genotypes studied. The mean pH of the treated samples was slightly higher than that of the control, but was not statistically significant in all cultivars or breeding lines every year. The data suggest that breeders should pay attention to the response of breeding lines and potential cultivars to ethylene-induced ripening.
Growth chamber studies were conducted to determine if inverse day/night temperature could control canopy height of sweetpotato without adversely affecting storage root yield. Four 15-cm-long vine cuttings of TU-82-155 sweetpotato were grown in rectangular nutrient film technique hydroponic troughs for 120 days. Two troughs were placed into each of six reach-in growth chambers and subjected to 24/18, 26/20, 28/22, 18/24, 20/26, and 22/28 °C, respectively. Growth chamber conditions included a 12/12-h photoperiod, 70% RH, and photosynthetic photon flux of 1000 μmol·m-2·s-1 at canopy level. Total and edible storage root yields were reduced by 50% among plants grown under cool days/warm nights regimes. Harvest index was similar among treatments except for the low value obtained at 22/28 °C. Canopy height was positively correlated with the change in temperature, and for every 2 °C decrease there was a 3.1 centimeter decrease in canopy height. Inverse day/night temperature effectively controlled canopy height but at the expense of storage root production.
Abstract
Harvesting mature-green tomatoesis common practice where they are grown commercially for the fresh market. Usually, the tomato fields are picked 4 to 6 times in a season, as the most mature fruits on the vine reach the mature-green stage. If mechanical harvesting becomes a reality for fresh market tomatoes, a once-over harvest will probably be used instead of the usual multiple pick. Yields will then be limited by the number of fruits mature enough at a given time to ripen off-vine and meet market standards for color. It will be imperative to grow a variety that has a concentrated set and whose fruits have good ripening ability when harvested prematurely.
Abstract
Carbohydrate analyses were made at harvest and after 7 days of postharvest storage at 65°F on sweet corn hybrid cultivars with endosperm mutant genotypes ae wx, ae du wx, and sh 2 and of standard sweet corn (su 1). Cultivars with the mutant genotypes contained from 1.5 to 2.0 times as much total sugar at harvest as the standard. They also lost more total sugar during the post-harvest period. Still, the hybrids with ae du wx and sh 2 genotypes contained significantly more sugars than the standard after the 7-day storage treatment. The mutant cultivars were low in water soluble polysaccharides but relatively high in starch. All cultivars had approximately the same amount of total carbohydrate. Moisture loss from the kernels during the storage period was significantly less in the mutant cultivars. Therefore, they maintained their fresh appearance longer, and they were slower than standard sweet corn to show kernel denting. Taste tests indicated a preference for the sweetness of the ae wx and ae du wx genotypes over the standard cultivars Golden Security and ‘Iobelle’ (Florida 104), but they were rated below the standards for pericarp toughness. These studies indicated that, with further refinement of certain horticultural and quality characteristics, the ae wx, ae du wx, and sh 2 endosperm mutant genotypes have a definite potential for improving the initial quality and the ability for maintaining good quality during normal post-harvest handling of fresh sweet corn.
The effect of inoculation with Azospirillum brasilense strain Cd on mineral concentration in sweetpotato, [Ipomeo batatas (L) Lam cv. TI-155] tissue and ionic composition of plant nutrient solution was investigated in a greenhouse study. In the field, inoculation of sweetpotato with Azospirillum spp. has been reported to enhance. sweetpotato yield. In this study, 48-h old broth cultures were used as inoculum at a population density of approx. 1 × 108 cfu/ml. The inoculum (0.20 L) was added to the reservoirs containing 30.4 L of a modified half Hoagland's plant nutrient solution at 28 days after the start of the experiment Results indicate that percent total nitrogen in sweetpotato foliage tended to be higher for the inoculated fibrous mat than in the fibrous mat for non-inoculated plants. The percent total nitrogen in storage roots for the non-inoculated treatment tended to be higher than in storage roots for inoculated plants. Inoculation resulted in a slight increase in foliar phosphorus concentration but had no effect on phosphorus concentration in sweetpotato storage and fibrous root samples. Inoculation tended to reduce foliar calcium concentration. Magnesium concentration in leaf tissue was not influenced by inoculation. Foliar potassium concentration tended to increase slightly. The effect of inoculation on potassium concentration in sweetpotato root tissue was not well-defined; potassium concentration tended to be higher in fibrous root tissue for the inoculated treatment. But in storage root tissue, potassium concentration was higher for the non-inoculated treatment than for the inoculated treatment. Inoculation did not affect foliar concentrations of any of the micronutrients measured. This study indicates no effect of inoculation on ionic strength of nutrients in solution reservoirs.
The effects of within-channel spacings (WCS; 13, 18, 25 cm) and between-channel spacings (BCS; 13, 25,38 cm) on yield and linear growth rate of sweetpotatoes [Ipomoea batalas (L.) Lam.] grown by use of the nutrient film technique (NFT) were evaluated. Storage root count, fresh and dry weights, and linear growth rate, expressed as root area, declined linearly in response to decreased BCS, while fresh and dry foliage weight decreased linearly and quadratically as spacing was reduced within the growth channels. Neither linear growth rate on a canopy area basis nor the edible biomass index was significantly affected by WCS or BCS.
Growth chamber experiments were conducted to study the physiological and growth response of sweetpotato [Ipomoea batatas (L.) Lam.] to either 50% or 85 % relative humidity (RH). Vine cuttings of T1-155 were grown using the nutrient film technique in a randomized complete-block design with two replications. Temperature regimes of 28/22C were maintained during the light/dark periods with irradiance at canopy level of 600 μmol·m-2·s-1 and a 14/10-hour photoperiod. High RH (85%) increased the number of storage roots per plant and significantly increased storage root fresh and dry weight, but produced lower foliage fresh and dry weight than plants grown at 50% RH. Edible biomass index and linear growth rate (in grams per square meter per day) were significantly higher for plants grown at 85 % than at 50% RH. Leaf photosynthesis and stomatal conductance were higher for plants at 85 % than at 50% RH. Thus, the principal effect of high RH on sweetpotato growth was the production of higher storage root yield, edible biomass, growth rate, and increased photosynthetic and stomatal activity.
Two sweetpotato [Ipomoea batatas (L.) Lam] genotypes (`Georgia Jet' and the breeding clone TI-155) were grown at 12-, 15-, 18-, and 21-h light/12-, 9-, 6-, 3-h dark cycles, respectively, to evaluate their growth and elemental concentration responses to duration and amount of daily lighting. Vine cuttings (15 cm long) of both genotypes were grown in rectangular nutrient film technique channels for 120 days. Conditions were as follows: photosynthetic photon flux (PPF) mean 427 μmol·m–2·s–1, 28C day/22C night air cycle, and 70% ± 5% relative humidity. The nutrient solution used was a modified half-strength Hoagland's solution. Storage root count per plant and per unit area, yield (in grams per square meters per day), and harvest index increased, while production efficiency (in grams per mole) decreased with increased daily PPF. Stomatal conductance for both genotypes declined with increased daily PPF. Leaves were smallest for both genotypes at the 21-h light period, while storage root yield declined as leaf area index increased. Except for a linear decrease in leaf N and K with increased light period, elemental concentration was not significantly influenced.