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- Author or Editor: R. W. Robinson x
- Journal of the American Society for Horticultural Science x
Abstract
Five hundred ninety accessions of Citrullus lanatus, obtained from 42 countries, were exposed to natural infection with Sphaerotheca fuliginea (Schlecht) Poll. Only one line, P.I. 269677 from Belize, was highly susceptible. The fungus attacked all aerial parts of plants of this line, including fruits. All other lines, including those from areas of the world where powdery mildew of watermelon commonly occurs, were resistant or tolerant to the race of the fungus prevailing in NY.
Abstract
Recommended rates of (2-chloroethyl)phosphonic acid (ethephon) application did not prevent staminate flower formation on summer squash (Cucurbita pepo L.) sufficient to permit hybrid seed production without defloration. The field experiments were conducted in commercial fields in which flower development occurred during warm long day conditions, which promote maleness in squash. A strongly female ‘Cocozelle’ inbred, a strongly male ‘Straightneck’ inbred and a very strongly male ‘Crookneck’ inbred were treated at several seedling stages with rates up to 600 ppm ethephon. Two applications of 400 to 600 ppm ethephon resulted in development of the fewest staminate flowers without significantly reducing seed yield or quality. The ‘Crookneck’ inbred was least responsive to ethephon.
Abstract
In greenhouse tests, domestic and foreign accessions of Cichorium endivia L. were susceptible to turnip mosaic virus (TuMV), the most common and often destructive virus occurring in late plantings of endive and escarole in the Northeast United States, whereas those of chicory (C. intybus L.) and C. pumilum Jacq. were resistant. Thus, chicory represents a valuable source of TuMV resistance for interspecific gene transfer to endive and escarole. Resistance was dominant in F1 plants of C. intybus × C. endivia.
Abstract
Lycopersicon esculentum Mill. cv. New Yorker, Solanum pennellii Corr. PI 246502, and 16 stable breeding lines of horticultural type derived from this cross were evaluated under saline (0.1 m NaCl) and control conditions. The breeding line population exhibited a much wider range of salt tolerance than that found in the cultivated species. Relative ability to regulate sodium accumulation in the leaves was significantly correlated with growth under saline irrigation. Absolute levels of foliar sodium or chloride accumulated under saline irrigation were not significantly correlated with plant growth. Regulation of ion accumulation was assessed as the ratio of foliar ionic content in saltgrown plants to foliar content in control plants, a value which we define as ion regulation index (IRI). A low index indicated regulation of accumulation of a particular ion. Regulation of ion uptake is interpreted as reflecting an effective homeostatic system. The homeostasis was attributed to tomato, and salt tolerance improvement occurred only if the requisite homeostasis was combined with other factors conferred by S. pennelli. Information regarding occurrence and possible mechanisms of this type of salt tolerance is reviewed.
Abstract
EM VII, EM IX AND MM 106 apple rootstocks were grown under greenhouse conditions in cans containing soil-incorporated simazine at concentrations of 0–6 ppm. In general, except for severity of foliar injury, the rootstocks responded similarly to simazine. Least foliar injury occurred on MM 106 rootstocks and the most injury on EM VII. Fresh weight increases indicated, however, that this difference may be of no practical significance.
Simazine levels of 1 and 2 ppm improved above-ground growth and increased total leaf nitrogen (N) but suppressed root growth. At concentrations of 3 ppm and higher, simazine suppressed both above-ground growth and root growth but markedly increased leaf N.
Abstract
Shoot growth and fresh wt of greenhouse-grown EM VII clonal apple rootstocks in 1970 were reduced by 1.5 ppm soil-incorporated dichlobenil. Concentrations of 6.0 ppm and higher prevented growth.
No leaf margin yellowing (LMY) was observed in 1970, but in 1971 it occurred following placement of 3 clonal rootstocks outdoors. EM VII produced the most shoot growth and EM IX the least. EM IX produced the least fresh wt increase, while those of EM VII and MM 106 were equivalent. EM VII had more LMY than the other 2 rootstocks.
The responses of the 3 rootstocks to several concn of dichlobenil were similar. Dichlobenil concn of 0.2 and 0.4 ppm increased fresh wt, largely due to stimulation of root growth. Concentrations of 0.8 ppm and more of dichlobenil suppressed growth.
Abstract
Lycopersicon and Solanum species and an F1 hybrid of L. esculentum × S. lycopersicoides differed in growth and concentration of elements in leaves in response to levels of NaCl in outdoor sand culture. S. lycopersicoides and its hybrid with the tomato were more sensitive to NaCl on the basis of reduction in dry matter accumulation than L. esculentum, L. peruvianum, or S. pennellii. The dry weights of S. lycopersicoides and the F1 grown without NaCl in the rooting medium were 6 times greater than the average of L. esculentum, L. peruvianum, and S. pennellii, but only 2 times greater when the plants were grown with 294 meq NaCl/liter of rooting medium nutrient solution. S. lycopersicoides and the F1 were fruitless. The average tops without fruit of all species had 10.9% dry weight when grown without NaCl while tops of plants grown with 294 meq NaCl/liter nutrient solution had 14.0% dry wight. NaCl in the rooting medium increased the concentration of Na less in the leaves of S. lycopersicoides and the F1 than the other species and increased the Cl concentration in the leaves of all species. S. lycopersicoides and the F1 had higher concentration of K, and lower Ca in the leaves than the other species. S. pennellii had higher concentrations of Fe and Mn in the leaves than other species.
Abstract
Genetic variation in foliar symptoms of B deficiency in the seedling stage of red beet was observed among inbred lines and commercial cultivars grown in sand culture in growth chambers. F1, F2 and backcross populations between the most susceptible and tolerant lines, tested at .001 ppm B, indicated that susceptibility was conditioned primarily by a single dominant gene. No linkage was established between this gene and the gene controlling red leaf color.
The most susceptible line was inherently more vigorous than the most tolerant line but this relationship was not evident among the other inbreds and cultivars tested.
Boron deficiency sumptoms on leaves of both tolerant and susceptible lines were significantly accentuated by reducing the Ca(NO3)2 content of the nutrient solution from 8 to 7 mEq/litre without altering B content. At both Ca levels the B content was greater in the tolerant than in the susceptible line. When supplied with adequate Ca but low B the susceptible line contained higher Ca, Na and P and lower Mg than the tolerant line.