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- Author or Editor: P. D. Dukes x
- Journal of the American Society for Horticultural Science x
Abstract
Thirty random seedlings from each of 50 random parents of a sweet potato (Ipomoea batatas (L.) Lam.) mass selected population were evaluated in the greenhouse and their subsequent field performances were recorded. Simulated selection sequences were also studied. A sequence with mass selection first on maternal hill weight, high seed set, and high seed weight followed by a 50% culling level within families on the basis of low greenhouse seedling vigor resulted in average progeny field yields 45% above that of no selection. The results showed seed weight to be a potentially useful selection criterion for root yield. Individual seedling root weight in the greenhouse was not a good predictor of field yield.
Abstract
Three greenhouse tests to determine the reactions of sweet potato (Ipomoea batatas (L.) Lam.) breeding lines and their respective open-pollinated offspring to 2 species of root-knot nematodes were conducted. Resistances occurred in high frequency to both the southern root knot nematode (Meloidogyne incognita (Kofoid & White) Chitwood) and the Javanese (tropical) root knot nematode (M. javanica (Treub) Chitwood). Reaction to M. incognita was studied in 2 consecutive years with different sets of parental lines using an egg mass index. Estimated heritability (h2) in 1976 was 0.75 ± 0.23 and in 1977 was 0.57 ± 0.37. Three indices of reaction to M. javanica and respective h2 estimates were: Egg mass index, 0.69 ± 0.18; galling index, 0.78 ± 0.19; and necrosis index, 0.72 ± 0.20. Resistances to the 2 species were not correlated, indicating independent inheritance. Development of cultivars with high levels of resistance to each or to both of the above diseases is possible.
Abstract
The inheritance of resistance in cowpea to root knot incited by the root-knot nematodes Meloidogyne incognita (Kofoid & White) Chitwood, M. javanica (Treub.) Chitwood, and M. hapla Chitwood was determined in 3 separate greenhouse experiments. Each seed was inoculated at planting with about 2,000 eggs of the appropriate Meloidogyne species. In Experiment I, plants of parental, F1, F2, and F1 × P1 and F1 × P2 backcross generations of a cross between the resistant cultivar ‘Mississippi Silver’ and the susceptible breeding line CR 18-13-1 were tested for reaction to M. incognita. In Experiment II, plants of parental, some F1, and all F2 generations of a series of crosses involving CR 18-13-1 and the resistant lines ‘Colossus’, ‘Mississippi Silver’, ‘Iron’, and PI 353383 were evaluated for resistance to M. incognita. In Experiment III, plants of parental, F1, and 30 randomly chosen F3 lines of the ‘Mississippi Silver’ × CR 18-13-1 cross were evaluated in separate tests for reaction to M. incognita, M. javanica, and M. hapla. A single dominant gene determined resistance to M. incognita, M. javanica, and M. hapla; the same gene governed resistance in ‘Colossus’, ‘Mississippi Silver’, ‘Iron’, and PI 353383. The gene conditioned a high level of resistance, but it did not confer immunity. Roots of many resistant plants exhibited limited galling and supported some egg production by the parasites. We propose that this gene be designated Root-knot resistance and symbolized Rk.
Abstract
Advances attained by the sixth generation of mass selection in sweet potato (Ipomoea batatas (L.) Lam.) were assessed. The objective was to combine multiple resistances to pathogens, nematodes and insects with other desirable production and market qualities. Although progress from 6 single-year cycles of selection was encouraging, a change to 2-year cycles was indicated. Generation 6 contained high frequencies of flowering and seed set, attractive root shape, orange flesh, thin cortex, root specific gravities of about 1.02, acceptable yield, and resistance to fusarium wilt (Fusarium oxysporum f. sp. batatas (Wr.) Snyd. and Hans.), the southern root-knot nematode (Meloidogyne incognita (Kofoid and White) Chitwood) and the following soil insects: the southern potato wireworm (Conoderus falli Lane), the banded cucumber (Diabrotica balteata LeConte), the spotted cucumber beetle (D. undecimpuncta howardi Barber), the elongate flea beetle (Systena elongata (F.)), a white grub (Plectris aliena Chapin), and the sweet-potato flea beetle (Chaetocnema confinis Crotch).
Abstract
Two southernpea breeding lines, CR 17-1-34 and Ala. 963.8, highly resistant to a leaf spot incited by Cercospora cruenta Sacc. were crossed with susceptible cultivars. The F1 and F2 progenies of these crosses, the F1 of the backcrosses, and the parental lines were grown in field experiments in which natural Cercospora leaf spot epiphytotics were allowed to develop. The resistances in the two breeding lines were found to be conditioned by different genetic factors. Resistance in CR 17-1-34 was controlled by a single dominant gene and that in Ala. 963.8 by a single recessive gene. We propose that the dominant and recessive genes to be designated Cls1 and cls2 , respectively.
Abstract
Twenty-two sweet potato (Ipomoea batatas (L.) Lam.) breeding lines and 19 open-pollinated offspring from each were used to estimate the heritabilities of 7 measures of soil insect injury. Four measures of injury by the wireworm, Diabrotica spp., and Systena spp. (WDS) complex and h2 (± SE) were: percentage of roots injured, 0.45 ± 0.12; holes per root, 0.32 ± 0.09; severity index, 0.37 ±0.11; and damage score, 0.39 ± 0.17. Two measures of injury by the sweetpotato flea beetle, Chaetocnema confinis Crotch, and h2 were: percentage of roots injured, 0.40 ± 0.07, and tunnels per root, 0.25 ± 0.08. The h2 of percentage of roots injured by all insects was 0.51 ± 0.12. The percentage measures were more easily obtained and were as effective as the other measures under the conditions of natural infestation that occurred in this test. Further advances in selection for high levels of resistance to soil insects are possible within the breeding materials tested.
Abstract
A parent-offspring test of 21 sweet potatoes (Ipomoea batatas (L.) Lam.) and 25 open-pollinated offspring from each provided heritability estimates (h2 ± SE) for root fiber (0.47 ± 0.04), weight (0.41 ± 0.04, shape (0.50 ± 0.05), cracking (0.37 ± 0.04), and sprouting (0.37 ± 0.02). These characters were sufficiently independent to allow selection of one, or of any combination simultaneously, without adverse effects on the others.
Abstract
Soil insect root injury to resistant sweet potato [Ipomoea batatas (L.) Lam.] cultivars ‘Regal’ and ‘Southern Delite’ was compared to injury to ‘Jewel’ and ‘Centennial’ in trials with the resistant-standard W-13 and the susceptible-standard SC 1149-19. Injury by three groups of insects was evaluated: the wirewoom-Diabrotica-Systena complex (WDS), which includes the southern potato wireworm (Conoderus falli Lane), the tobacco wireworm (C. vespertinus Fabricius), the banded cucumber beetle (Diabrotica balteata LeConte), the spotted cucumber beetle (D. undecimpunctata howardi Barber), the elongate flea beetle (Systena elongata Fabricius), the pale-striped flea beetle (S. blanda Melsheimer), and S. frontalis Fabricius (a flea beetle); the sweet potato flea beetle (Chaetocnema confinis Crotch.); and a white grub (Plectris aliena Chapin). Relative control estimates were obtained by comparison to the susceptible standard. ‘Regal’ and ‘Southern Delite’ provided good control of all three insect groups with control of all insect injuries of 79.2% and 81.0%, respectively. ‘Jewel’ and ‘Centennial’ were resistant to the sweet potato flea beetle and sustained less damage by WDS than the susceptible standard, but would still be classed as susceptible to WDS. ‘Centennial’ was as susceptible to the white grub as SC 1149-19. The levels of resistance demonstrated for ‘Regal’ and ‘Southern Delite’ would provide growers an alternative to insecticides for the control of these insects.
This 2-year study was conducted to determine if soil insect damage could be reduced in sweetpotato [Ipomoea batatas (L.) Lam] by treatment with an insecticide (fonofos) and/or a parasitic nematode (Steinernema carpocapsae Weiser), in conjunction with sweetpotato cultivars that differed in susceptibility to soil insect damage. Analysis of field data for the first year showed that the parasitic nematode provided significant damage protection of sweetpotato from wireworms (Conoderus spp.), Diabrotica sp., Systena sp., and sweetpotato flea beetle (Chaetocnema confinis Crotch), but not from grubs (Plectris aliena Chapin; Phyllophaga ephilida Say). In this same test, fonofos used alone provided protection against wireworm-Diabrotica-Systena (WDS complex) damage. In the second test, the nematode did not provide soil insect protection for the WDS complex, but fonofos did reduce damage for these insects. Poor efficacy in the second test with the nematode probably was due to high rainfall, which saturated the soil. Resistant cultivars provided good protection for all three categories of damage. When used with the insect-susceptible check `SC 1149-19', the nematode or fonofos treatments provided better control for all insect categories in the first test. In both years, much higher control of damage by all insect classes was achieved by the use of resistant cultivars in combination with the nematode and/or fonofos treatment (64% higher crop protection than the susceptible check line). Chemical name used: O-ethyl-S-phenylethylphosphonodithioate [fonofos (Dyfonate 10G)].