Paul W. Bosland, Jaime Iglesias, and Steve D. Tanksley
Kimberly P. Harvell and Paul W. Bosland
J.F. Hancock, A. Lavín, and J.B. Retamales
Yayeh Zewdie, Paul W. Bosland, and Robert Steiner
The inheritance of capsaicinoid content was studied in five Capsicum pubescens Ruiz & Pav. genotypes using diallel analysis. General combining ability and specific combining ability effects were significant for all capsaicinoids studied, indicating additive and nonadditive gene actions are present. The association of high capsaicinoid contents with high positive general combining ability of the parents also indicates the predominance of additive gene action in capsaicinoid inheritance. Because of the predominant additive gene effect, recurrent selection would be a good breeding method to increase capsaicinoid level in the population studied. Heterosis was observed in hybrids for some of the capsaicinoids, suggesting that F1 hybrids could also be used to increase capsaicinoid content.
Paul W. Bosland and John J. Ellington
Accessions of Capsicum annuum L., a susceptible host, and C. pubescens (R. & P.), a resistant host, were grown in a replicated greenhouse study to test whether antixenosis (nonpreference), antibiosis, or both was the mechanism for resistance to green peach aphid [Myzus persicae (Sulzer)]. A plant choice experiment established that aphids preferred C. annuum to C. pubescens. A no-plant choice test was not undertaken; nevertheless, the aphid's reproductive rates were measured in leaf containment cages and were similar on both hosts. The mechanism of antibiosis was not indicated because fecundity was not reduced in the containment cages; however, other measures of antibiosis were not studied. These observations suggest that antixenosis may be functioning in C. pubescens.
Margaret D. Collins, Loide Mayer Wasmund, and Paul W. Bosland
An improved high-performance liquid chromatography (HPLC) method for analysis of capsaicinoids in dried Capsicum fruit powder, involving changes in extraction, mobile phase, flow rate, and excitation and emission spectra and resulting in reduced analysis time, increased sensitivity, and safety, is reported. Extraction of Capsicum fruit powder using acetonitrile proved to be the best capsaicinoid extractor in the shortest time interval. Solvents used for HPLC separation and quantification of capsaicinoids include methanol and water at 1 ml·min–1 flow rate. Instrument sensitivity is enhanced by altering the fluorescence detector excitation and emission wavelengths. Two analytical methods have been developed. One method determines total amount of heat units in 7 minutes, while the other provides total amount of heat units as well as separation of all present major and minor capsaicinoids in 20 minutes. These improved techniques provide inexpensive and rapid methods for quantitative and qualitative analysis of capsaicinoids in Capsicum fruit samples along with good sensitivity and no interference or confounding peaks.
Lisa M. Oelke, Paul W. Bosland, and Robert Steiner
Despite extensive breeding efforts, no pepper (Capsicum annuum L. var. annuum) cultivars with universal resistance to phytophthora root rot and foliar blight (Phytophthora capsici Leon) have been commercially released. A reason for this limitation may be that physiological races exist within P. capsici, the causal agent of phytophthora root rot and phytophthora foliar blight. Physiological races are classified by the pathogen's reactions to a set of cultivars (host differential). In this study, 18 varieties of peppers were inoculated with 10 isolates of P. capsici for phytophthora root rot, and four isolates of P. capsici for phytophthora foliar blight. The isolates originated from pepper plants growing in New Mexico, New Jersey, Italy, Korea, and Turkey. For phytophthora root rot, nine of the 10 isolates were identified as different physiological races. The four isolates used in the phytophthora foliar blight study were all determined to be different races. The identification of physiological races within P. capsici has significant implication in breeding for phytophthora root rot and phytophthora foliar blight resistance.