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  • Author or Editor: Alfred Jones x
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Previous work in this laboratory identified high levels of unreduced (2n) pollen in the tetraploid (4×) Ipomoea spp. Acc. 81.2. This work provided indirect evidence that 2n pollen was involved in the evolution of the 6x ploidy level of the cultivated sweetpotato (I. batatas). To further study the role of 2n pollen in sweetpotato evolution, we examined plants of Acc. 81.2. plants of five sweetpotato cultivars, and 100 randomly selected heterozygous sweetpotato seedlings. The 4× Acc. 81.2 was determined to be I. batatas. High levels of large 2n pollen were confirmed in Acc. 81.2, and low levels of 2n pollen were observed in `Sulfur' and in 16% of the sweetpotato seedlings. Presence of monad, dyad, and triad sporads confirmed that the large 2n pollen grains were the result of nonreduction in the sporad stage. These new findings are direct evidence that 2n pollen was involved in the evolution of the 6× ploidy level of sweetpotato. This is the first report of a 4× accession classified as I. batatas; it is also the first report of 2n pollen in 6× I. batatas The widespread presence of 2n pollen in sweetpotato suggests that the trait can be used to advantage in breeding programs to introgress genes from wild 4× Ipomoea spp. into cultivated 6× sweetpotato without adverse effects on genetic stability or fertility.

Free access

Abstract

A parent-offspring study of 40 sweetpotato lines grown in 6 environments provided heritability (%) estimates for 10 root characters as follow: weight, 41; number edible roots, 32; veining, 30; growth cracks, 51; flesh oxidation, 64; shape, 62; flesh color, 66; cortex thickness, 45; skin color, 81; and skin purpling, 74. In most cases the realized changes due to selection fit the predictions very well. The additive component of genetic variance was relatively more important than the non-additive for all traits except veining and number of edible roots. The study illustrates the usefulness of quantitative genetic approaches to sweetpotato breeding.

Open Access

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).

Open Access

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.

Open Access

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.

Open Access

Abstract

Fourteen sweet potato [Ipomoea batatas (L.) Lam.] clones were grown in fertilized and unfertilized tests at four locations during 2 years. Significant effects of genotype-environment interactions on yield components of sweet potato were found. Yields were generally higher in fertilized than in unfertilized tests, and number of roots was higher in fertilized tests for most grades except for canners and total number of roots. Rank correlations of stability of clones in fertilized and unfertilized tests were low for all traits measured. Implications of the results on testing and selection of sweet potato are discussed.

Open Access

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.

Open Access

Abstract

Root knot caused by the southern root-knot nematode (Meloidogyne incognita (Kofoid & White) Chitwood) is a serious disease of sweet potato (Ipomoea batatas (L.) Lam.) in most production areas of the U. S. and especially in the southern states (3). Considerable variation in pathogenicity of this obligate parasite on sweet potato was reported by Giamalva et al. (1) in 1963. In 1973, Martin and Birchfield (2) reported the discovery of a race of M. incognita that was highly virulent and reproduced abundantly on a sweet potato line, L4-73, that had been established as resistant to root-knot nematode populations commonly found in Louisiana. This strain of M. incognita, herein designated the “resistance breaking” (RB) race, was provided through the courtesy of Dr. W. J. Martin of the Department of Plant Pathology, Louisiana State Univ., Baton Rouge. These findings have caused considerable concern about the future of breeding for root knot resistance in sweet potato, since the existence of RB races makes the work much more difficult and complicated. A breeding line of sweet potato (W-51) was developed at the U. S. Vegetable Laboratory, in cooperation with Clemson University, that is resistant to both the common and the RB race of root-knot nematodes (M. incognita). It also carries resistance to fusarium wilt (Fusarium oxysporum f. sp. batatas (Wr.) Snyd. & Hans.) and the sweet potato flea beetle (Chaetocnema confinis Crotch.). W-51 is being released for use as a root knot resistant parent in sweet potato breeding programs.

Open Access

Abstract

Breeding lines and cultivars of sweet potato, Ipomoea batatas (L.) Lam were evaluated in the field during a 4 year period for resistance to the sweet potato weevil, Cylas formicarius elegantulus (Summers). Appreciable resistance occurred in lines from Louisiana, Nigeria, Asia, and the U.S. Vegetable Laboratory. Lines performed similarly with respect to resistance when evaluated in 2 or more years.

Open Access