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  • Author or Editor: W. B. Davis x
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This study was conducted to investigate the effects of mild mass selection for adaptation on the performance, genotypic variance, combining ability, S1 family-testcross correlation, and midparent heterosis of S1 families derived from a sweet corn (su) × tropical maize (Zea mays L.) composite (Composite 1R). Four cycles of random mating followed by 10 cycles of 10% stratified mass selection were conducted for earliness, plant and ear type, and freedom from pests. Selection significantly (P < 0.01) decreased plant height, ear height, percentage barrenness, and ear length, and significantly (P < 0.01) increased stalk breakage, earliness (Celsius heat units to 50% anthesis and silking), and kernel row number of both S1 families and their testcrosses. Juvenile plant height at 45 days after planting increased in testcrosses only. Percentage tip blanking and pericarp thickness did not change. For most traits, the greatest response occurred during the first five of 10 selection cycles. Cycle 10 testcrosses performed at least as well as elite check testcrosses for eight of 10 traits. The tropical parents improved combining ability for increased juvenile plant height and kernel row number, and decreased percentage of stalk breakage. As a result of selection, genotypic variance among S families decreased by >40% for heat units to 50% anthesis and silking, ear height, and percentage of barrenness, although for all traits measured, significant genotypic variation persisted following 10 cycles of mass selection for adaptation. S1-testcross correlations and percentage midparent heterosis tended to be consistent across selection cycles. Five cycles of mild stratified mass selection increased the adaptation of a temperate sweet corn × tropical maize composite to the temperate zone of the United States while maintaining significant genotypic variation.

Free access

Abstract

MN 13 and MN 150 are extra-early maturing cowpeas [Vigna unguiculata (L.) Walp.] adapted to northern regions possessing a continental climate. They reach the mature-green harvest stage at about 1000 heat units (10°C base, air temperature) under Minnesota conditions, and can be harvested in early August from a late-May sowing. Both lines appear to be tolerant to bacterial blight (Xanthomonas vignicola Burkh.), based on field observation.

Open Access

Abstract

Nitrogen uptake by two N-deficient turfgrass species was characterized by measuring N depletion from a complete nutrient solution. The uptake rate of both NO 3 and NH 4 + was enhanced up to 6-fold in N-deficient perennial ryegrass (Lolium perenne L.) compared to N-sufficient controls, reaching a maximum of about 0.3 and 0.4 g N/m2 per hr for NO 3 and NH 4 + , respectively. Deficiency-enhanced uptake exceeded uptake by controls for about 72 hr following resupply of N. Nitrogen uptake was enhanced to a similar degree by N deprivation in Kentucky bluegrass (Poa pratensis L.). Mowing had no effect on NO 3 uptake by N-deficient perennial ryegrass turf, whereas mowing inhibited uptake by N-sufficient turf by ≈60%. Deficiency-enhanced uptake was found to be the result of an increased capacity for N absorption (Imax) rather than an increased affinity for N (K m). Imax values increased from 0.24 and 0.73 mg N/g dry weight per hr for N-sufficient ryegrass turf for NO 3 and NH 4 + , respectively, to 1.44 and 2.68 mg N/g dry weight per hr for N-deficient turf. K m values increased slightly, from 14 μm for both N forms for N-sufficient turf to 24 and 39 μm for NO 3 and NH 4 + , respectively, for N-deficient turf.

Open Access

Abstract

Compared to no pruning, pruning of seedling roots of four tree species during transplantings from the seed flat to peat pots and of the peat-pot liners into gallon cans more than doubled the number of plants with acceptable root systems. Survival and growth were neither significantly nor adversely affected by root pruning done over a range of transplanting dates.

Open Access

Abstract

Root pruning and care during the first two nursery transplantings of 4 tree species significantly increased the percentage of plants with good root systems. The 4 species were Eucalyptus sideroxylon A. Cunn., red iron bark; Pinus radiata D. Don., Monterey pine; Pistacia chinensis Bunge., Chinese pistache; and Quercus ilex L., holly oak. The percentage of trees with good root systems decreased the longer seedlings stayed in the seed flat and in peat pot liners, particularly those not root pruned. In all but one case, the earlier plants were moved from the seed flat into peat pots and on into into gallon cans, the more the plants grew in caliper and height.

Plants root pruned during the early moves were larger than those not root pruned. However, root pruning at the later moves resulted in smaller plants than those moved earlier or than those moved at the same time but not root pruned. The combination of lengths of time in the seed flat and in the peat pot (time in the greenhouse) which resulted in the best combination of quality root systems and large plants was only 1/2 to 2/3 the time now common nursery practice (90-120 days).

Open Access

Abstract

The depletion of N applied to a moderately N-deficient Kentucky bluegrass (Poa pratensis L.) turf was measured using a soil sampling procedure. Nitrogen as either Ca(NO3)2 or (NH4)2SO4 was applied in solution at 5 g N/m2 and washed into the thatch and soil with an additional 0.3 cm of water. Both N forms were located primarily in the thatch and upper 1 cm of soil. The NO 3 was present in the soil solution, while the NH 4 + was mainly exchangeable (86%). The concentrations of NO 3 and NH 4 + in the soil solution were 452 and 56 μg N/ml, respectively, in the upper 1 cm of soil. Depletion of both NO 3 and NH 4 + from the turf was very rapid, with 70% to 80% of the applied N disappearing during the first 24 hr. Essentially all of the applied N was depleted by 48 hr. Results using (l5NH4)2SO4 indicate that ≈75% of the NH 4 + depletion is attributable to absorption by the turf. Similar results were obtained following fertilization of perennial ryegrass (Lolium perenne L.), tall fescue (Festuca arundinaceae Schreb.), and creeping bentgrass (Agrostis palustris Huds.).

Open Access

Abstract

Artificial infestation with egg masses to simulate severe natural second brood European corn borer, Ostrinia nubilalis (Hubner), infestation caused less stalk and stalk-associated damage in the resistant field corn inbred ‘B52’ Zea mays L. than in susceptible sweet corn inbreds. Relatively severe damage, however, occurred on and around the region of the primary ear in both ‘B52’ and the sweet inbreds. Because direct kernel damage is of paramount economic importance in sweet corn as opposed to field corn, forms of second-brood resistance in addition to that found in ‘B52’ should be sought in sweet corn improvement. For stalk tunneling and number of sheath and collar lesions the resistance of F1 and F2 progenies was intermediate between the resistance of ‘B52’ and the sweet inbreds. Although there were no parental differences in damage to the ear, F1 and F2 means showed some indication of resistance.

Open Access

Abstract

Ammonia volatilization from urea-N applied to Kentucky bluegrass ( Poa pratensis L. ‘Bensun’) was investigated using a chamber trapping procedure. Urea was spray-applied in a 0.2 cm depth at N of 5 g·m−2 with and without additional irrigation of 0.5, 1, 2, or 4 cm. Losses up to 36% of the applied N occurred when urea was applied without irrigation. Supplemental irrigation of as little as 1.0 cm reduced the loss to 3-8%, while a 4.0-cm irrigation further reduced losses to about 1%. Of the ammonia volatilized, most was lost in the first 24 hr. Maximum N loss was associated with the thatch layer, a zone having high urease activity.

Open Access

Abstract

The response of rabbiteye blueberry plants (Vaccinium ashei Reade) to rates and modifications of deep well water (pH 8.7) containing 0.695 dS·m-1 electrical conductivity (EC), a sodium adsorption ratio (SAR) of 29.7, and a bicarbonate concentration of 7.89 meq·liter-1 was compared to plants irrigated with rain and surface waters applied to 3 soils in a glasshouse-container study. Fresh weight increase and root fresh and dry weight were greater on plants irrigated with rainwater or pond water compared to plants irrigated with different rates of deep well water, or deep well water modified by the addition of gypsum or acidified with H2S04. Fresh weight increase, root fresh and dry weight, leaf fresh weight, and top:root ratios were higher on a loamy sand soil than on sandy loam or clay loam soils. Plant weight gain was positively correated with the percentage of sand, and negatively correlated with the percentage of clay and saturation-extract SAR. An increase in soil pH resulted from irrigation with deep well water which, along with its modifications, resulted in increased leaf Na and decreased leaf Ca and Mn, compared to rain or surface-water irrigations, which slightly lowered soil pH.

Open Access

Abstract

In field tests, the most effective film mulch in deterring insects and reducing insect damage to fruits was aluminum. The insects affected were aphids, brown stink bugs, aphid parasites, and Diabrotica spp. Mosaic virus diseases were reduced among aluminum-mulched squash (Cucurbita pepo L.) and cucumber (Cucumis sativus L.) plants. Plant growth, flowering, and fruiting were delayed in tomatoes (Lycopersicon esculentum Mill.) and southernpeas (Vigna unguiculata (L.) Walp.).

Open Access