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  • Author or Editor: F. P. Cuthbert Jr. x
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Abstract

Character associations in a sweet potato [Ipomoea batatas (L.) Lam.] population after 4 cycles of selection for resistance to soil insects and in a control population with no selection were studied by use of contingency tables of pairs of traits. Possible common factors were indicated for resistances to the sweet potato flea beetle and the wireworm-Diabrotica-Systena (WDS) complex. Selection changed the means and distributions of 6 of 13 unselected root and vine traits. None of these changes were directly associated with insect resistances, but that in root cracking was caused by the grading techniques. Two traits appeared genetically associated (cortex thickness and leaf-whorl color), and 2 appeared to be expressions of the same character change (flesh-color changes were also expressed as skin-color changes). The selected population had shorter internodes than the unselected. These changes in unselected traits were probably due to drift caused by small population sizes in the selected generations. No barriers to development of insect-resistant cultivars were detected.

Open Access

Abstract

Insect resistance in sweet potatoes (Ipomoea batatas (L.) Lam.) was more effective than fonofos, O-ethyl-S-phenylethylphosphonodithioate, in reducing insect injury to the roots. The most recent resistant line tested did not sustain economic injury from relatively high insect infestations even without the protection of an insecticide. Fonofos at 2.24 and 4.48 kg/ha did not prevent economic injury to the susceptible ‘Goldrush’.

Open Access

Abstract

The South Carolina Agricultural Experiment Station and the United States Department of Agriculture announce the joint release of ‘Charlestowne’ and ‘Roots’ turnip, Brassica campestris L. (Rapifera group), which are resistant to the turnip aphid, Hyadaphis erysiimi (Kattenbach).

Open Access

Abstract

The southernpea breeding line, CR 18-13-1, a source of nonpreference resistance to the cowpea curculio, was crossed with the susceptible breeding line, Fla. 589.06. The F1, F2, and backcross progenies of this cross and the parental lines were grown in outdoor screen-cage and field tests over a 3-year period. Large error variances were noted in all tests because of apparent plant-to-plant variation in number of curculios. Resistance was inherited in a partially dominant manner and broad-sense heritability estimates ranged from 0.0 to 19.1%. Selection in the seedling stage for low amounts of adult curculio feeding damage increased the frequency of resistant plants.

Open Access

Abstract

The results of 2 years of field tests indicate that the level of cowpea curculio (Chalcodermus aeneus Boheman) resistance found in 2 southernpea (Vigna unguiculata) breeding lines was more effective in reducing curculio injury than the currently recommended insecticide toxaphene. No evidence was obtained that the insecticide’s effectiveness could be increased by altering the plant type.

Open Access

Abstract

California Blackeye No. 5, a cultivar highly susceptible to the cowpea curculio (Chalcodermus aeneus Boheman), was crossed with Ala. 963.8, one of the best available sources of pod-wall resistance (inhibition of pod-wall penetration) to the curculio. Forty F7 progeny lines developed from random F2 plants and the parental lines were grown in a field naturally infested by the curculio and evaluated for pod-wall resistance and the following pod and seed characteristics: pod:seed (PS) ratio, pod diameter, pod length, pod weight, pod-wall fiber content, pod-wall thickness, weight per 50 seeds, interseed space, pod surface contour, and seed shape. Except for the PS ratio, none of the pod or seed characteristics were associated with resistance. The PS ratio was negatively correlated with pod-wall resistance and accounted for a significant portion of the variation in curculio penetration success. These findings suggest that pod-wall resistance can be efficiently evaluated by means of PS ratio measurements.

Open Access

Abstract

The cowpea curculio, Chalcodermus aeneus Boehman, is the principal insect pest of southernpeas, Vigna unguiculata (L.) Walp., in the southeastern United States. The insect is of considerable economic importance to the processing industry because the insect damage and contamination make the processed product unacceptable for human consumption. Curculio feeding scars also provide an entry point for much of the pod rot, caused by Choanephora cucurbitarum (Berk. & Rev.) Thaxt., in field plantings (3, 5). Cuthbert and Davis (2) and Chalfant et al. (1) delineated several factors that contribute to increased genetic resistance in V. unguiculata to the curculio. Subsequently, Cuthbert et al. (4) showed that these factors were complementary in effect. They suggested that the two factors which offered the greatest potential for use in development of resistant cultivars were non-preference and a pod factor that inhibits penetration through the pod wall by the adult insect. The breeding lines CR 17-1-13, CR 18-13-1, and CR 22-2-21 have been released for use as resistant parents in such programs. All are horticultural types with nonpreference or pod factor resistance to the cowpea curculio.

Open Access

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.

Open Access

Abstract

In the early 1970s, a study was begun to find resistance to feeding in muskmelon, Cucumis melo L., by banded cucumber beetles, Diabrotica balteata LeConte. Bitter seedlings were observed to be more susceptible to feeding than nonbitter seedlings. We noticed reduced damage levels in both bitter and nonbitter seedlings in 1974. Genetic study of resistant materials showed that in addition to the recessive form of the bitter gene, bibi, a 2nd recessive gene, cbl cbl, conditioned reduced seedling susceptibility. Subsequent tests involving spotted (Diabrotica undecimpunctata howardi Barber), striped [Acalymma vittata (Fabricius)], and banded beetles on leaf disks of several C. melo cultivare showed that homozygous double recessive, bibi cblcbl, plants were more resistant to all 3 species of cucumber beetles than nonbitter, bibi Cbl — and bitter Bi—Cbl— plants. This double-recessive resistance provides muskmelon breeders with germplasm which can be incorporated into breeding lines and hybrids.

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