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Abstract
Cercospora leaf spot, a disease incited by Cercospora cruenta Sacc., is one of the major foliage diseases of southernpeas (Vigna unguiculata (L.) Walp.) in several important U.S. production areas 3 . The disease is frequently a problem on fall crops where severe losses are occasionally observed. Cercospora leaf spot spreads very rapidly on susceptible cultivars, resulting in premature defoliation and reduced yields. Schneider 4 reported that C. cruenta caused yield reductions of 42% in Nigeria. Accessions of V. unguiculata resistant to C. cruenta have been reported by Verma and Patel (3) and Vakin 4 . Schneider (3) used resistant cultivars in his work. The lack of information about the inheritance of resistance and the agronomic or exotic nature of many of these lines limit their value as sources of Cercospora leaf spot resistances in horticultural breeding programs. The breeding line CR 17-1-34 has been released for use as a resistant parent in such programs. It is a horticultural type that carries one of the genes reported by Fery et al. (2) to condition a high level of resistance to Cercospora leaf spot.
The Agricultural Research Service of the United States Department of Agriculture announced the release of `Bettergreen' southernpea on 30 April 1991. `Bettergreen' is a cream-type cultivar that is homozygous for a newly discovered gene(s) conditioning a unique green cotyledon trait. `Bettergreen' can be harvested at the near-dry seed stage of maturity without loss of the seed's fresh green color. The color of the peas harvested upon reaching “dry-stage” maturity is light olive, and the color is present in both the seed coat and the cotyledons. The fresh peas are small (22 g per 100 peas), ovate to reniform in shape, and have excellent culinary quality. The dried peas have a smooth seed coat. `Bettergreen' is recommended for use as a home garden and fresh market cultivar for spring, mid-season, and fall plantings throughout the southeastern United States. It is particularly recommended for trial as a commercial processing cultivar for the frozen food industry.
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.
A root-knot nematode (Meloldogyne incognita) project was initiated in a field of infested sandy loam (EREC) in 1991 and continued. There were ten sweetpotato entries consisting of six cultivars (Beauregard. Excel, Georgia Jet, Jewel, Red Jewel, and Sumor), three advanced lines (W-270, W-274, and W-279) and PI 399161 which were selected for their diversity in disease reactions and other traits. Each entry was planted in the same plots each year to monitor effects of continuous cropping, disease reactions, yield and population shifts of the pathogen. Marketable yields were reduced each year for Georgia Jet and Red Jewel, but not for Beauregard. Internal necrosis in the storage roots was most severe for Beauregard. Several of the highly resistant entries, especially Sumor and W-279, performed well each year, including high yields, good quality. and little or no nematode reproduction. This study demonstrates the considerable economic benefits of a high level of durable resistance to root knot in sweetpotato.
The southern root-knot nematode (Meloidogyne incognita) is a major pest of bell peppers (Capsicum annuum) in the United States. Since none of the leading bell pepper cultivars grown in the U.S. exhibit adequate levels of resistance, a breeding program was initiated to incorporate the N root-knot nematode resistance gene into commercial bell pepper germplasm. A backcross breeding procedure was used. The donor parent of the N gene was the open-pollinated, pimiento pepper cultivar Mississippi Nemaheart, and the recurrent parents were the open-pollinated bell pepper cultivars Keystone Resistant Giant and Yolo Wonder. A large number of homozygous resistant BC6 populations were evaluated in field tests in 1995, and two lines (PA-440, an isoline of `Keystone Resistant Giant', and PA-453, an isoline of `Yolo Wonder') were selected for further field evaluation and seed multiplication in 1996. Results of replicated field and greenhouse tests conducted in 1996 indicate that root-knot nematode resistance has been incorporated successfully in `Keystone Resistant Giant' and `Yolo Wonder' backgrounds.
Abstract
In the article “‘Carolina Cayenne’ Pepper”, by R.L. Fery, P.D. Dukes, and W.L. Ogle [HortScience 21(2):330, April 1986], the authors wish to note the following: The 13th line under Description should be changed from “…are straight to slightly curved, 0.64 cm in…” to “…are straight to slightly curved, 1.63 cm in…”.
A two year study was conducted to evaluate the efficacy of insect resistance in sweetpotato cultivars from our breeding program in combination with an insecticide (fonofos) and/or a parasitic nematode (Steinernema carpocapsae). In the laboratory, use of the parasitic nematode resulted in 99% mortality of Diabrotica larvae. In both years, much higher control of damage by all insect classes was achieved by the use of resistant cultivars in combination with a nematode and/or fonofos treatment. Analysis of the first year's field data showed the parasitic nematode treatment gave good damage protection against the WDS (Wireworm, Diabrotica, Systena), sweetpotato flea beetle, but not grubs. In this same year, fonofos only gave good protection against WDS. In the second test year, fonofos gave good protection against WDS, but the nematode did not. High moisture conditions may have affected the efficacy of the parasitic nematode. Host plant resistance by sweetpotato cultivars appears to be less affected by variable field conditions and accounted for 64% of the total crop protection (compared to the check susceptible line).
Abstract
‘Colossus 80’ southernpea [Vigna unguiculata (L.) Walp] has been released by the U.S. Department of Agriculture and Clemson University as a replacement for ‘Colossus’, a widely adapted and popular home garden and fresh-market cultivar that was released by Clemson University in 1972 (8). ‘Colossus 80’ is highly resistant to Cercospora leaf spot (CLS), a disease incited by Cercospora cruenta Sacc. (= Mycosphaerella cruenta Latham) 5 . CLS is one of the most serious foliage diseases of southernpeas in the southeastern United States and infection of susceptible cultivars results in premature defoliation and reduced yields. The original ‘Colossus’ is highly susceptible to this disease. Fery et al. (7) reported reductions of 36, 25, 10, and 3% in total seed yield, pod number, seed number per pod, and average weight per 100 seed, respectively, in a naturally infected ‘Colossus’ planting.