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- Author or Editor: Philip D. Dukes x
Greenhouse experiments were conducted to determine the inheritance of the high level of southern root-knot nematode [Meloidogyne incognita (Kofoid & White) Chitwood] resistance exhibited by `Carolina Hot' cayenne pepper (Capsicum annuum L.) and to compare the genetic nature of this resistance to that exhibited by `Mississippi Nemaheart.' Evaluation of parental, F1, F2, and backcross generations of the cross `Mississippi Nemaheart' × `California Wonder' confirmed an earlier published report that the `Mississippi Nemaheart' resistance is conditioned by a single dominant gene. Evaluation of parental, F1, F2, and backcross generations of a cross between highly resistant and highly susceptible lines selected from a heterogeneous `Carolina Hot' population indicated that the resistance exhibited by `Carolina Hot' is conditioned by two genes, one dominant and one recessive. Evaluation of the parental and F2 populations of a cross between `Mississippi Nemaheart' and the highly resistant `Carolina Hot' line indicated that the dominant resistance gene in `Mississippi Nemaheart' is allelic to the dominant resistance gene in `Carolina Hot.' Comparison of the data that were collected on the parental lines in the latter cross demonstrated the superior nature of the resistance exhibited by `Carolina Hot.' The presence of the second resistance gene in `Carolina Hot' probably accounted for the higher level of resistance. The ease and reliability of evaluating plants for resistance to root-knot nematodes and the availability of a simply inherited source of resistance makes breeding for southern root-knot nematode resistance a viable objective in pepper breeding programs. This objective should be readily obtainable by the application of conventional plant breeding methodologies.
A series of greenhouse and field studies were conducted to determine the inheritance of the green cotyledon trait exhibited by the recently released southernpea `Bettergreen' and to elucidate the genetic relationship between the green cotyledon trait and the green testa trait exhibited by `Freezegreen'. Evaluation of parental, F1, F2, and backcross populations of the crosses `Bettergreen' × `Carolina Cream' and `Bettergreen' × `Kiawah' indicated that the green cotyledon trait is conditioned by a single recessive gene. Evaluation of parental and F2 populations of the cross `Bettergreen' × `Freezegreen' indicated that this gene is neither allelic to nor linked with the gt gene that conditions the green testa trait in `Freezegreen'. The color of seeds harvested from plants homozygous for both the green cotyledon and green testa genes was superior and more uniform than the color of seeds harvested from either `Bettergreen' or `Freezegreen' plants. We propose that the newly discovered gene be designated green cotyledon and symbolized gc. Seeds containing embryos homozygous for the gc gene are easily identified. The ability to select in the seed stage should greatly facilitate efforts to backcross the gc gene into cream-, pinkeye-, and blackeye-type cultivars.
Abstract
‘Carolina Cream’ is a new southernpea [Vigna unguiculata (L.) Walp.] cultivar that was approved for release in July 1982 by the Agricultural Research Service of the USDA. It is well-adapted for production throughout the southeastern United States, where it can be expected to produce excellent yields of high quality, cream-type peas. Major attributes of the new cultivar are its excellent culinary quality and its resistances to the cowpea curculio (Chalcodermus aeneus Boehman), the major insect pest of the southernpea, and Cercospora leaf spot [Cercospora cruenta Sacc. (= Mycosphaerella cruenta Latham)], a major foliage disease of the crop. Cercospora leaf spot on southernpea also can be incited by Cercospora canescens Ell. & Martin.
Four sweetpotato [Ipomoea batatas (L.) Lam.] clones were evaluated for metribuzin tolerance in greenhouse and field experiments. W-262 exhibited metribuzin response similar to the highly tolerant clone Tinian (U.S.P.I. 153655). SC 1149-19 was highly sensitive to metribuzin, and the commercial cultivar Jewel was intermediate in tolerance. Due to its more desirable horticultural characteristics and higher yields, W-262 is superior to Tinian as a source of metribuzin tolerance in sweetpotato breeding. Chemical name used: 4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one (metribuzin).