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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

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

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

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

Two breeding lines of sweet potato [Ipomoea batatas (L.) Lam.] were released in 1975. They possess unusual combinations of disease and insect resistances with other useful characteristics. Both lines originated from mass selection for multiple disease and soil insect resistances in a sweet potato population incorporating a wide gene base. Both lines flower and set seed without any special treatment; traits of particular value in breeding

Open Access

Abstract

Application of systemic fungicides to sweet potato (Ipomoea batatas (L.) Lam.) increased the total number of healthy seed harvested 50% by increasing pod set, number of seed per pod and the proportion of healthy seed. Insecticides aldicarb and naled gave dramatic responses and increased the number of seedlings obtained per parent plant 2- to 5-fold. Insect damage appeared to be an important cause of low seed set and low seed quality in sweet potato.

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

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 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