Yayeh Zewdie and Paul W. Bosland
Maria M. Jenderek and Yayeh Zewdie
Until recently, there has been no large-scale production of true seeds in garlic (A. sativum L. and A. longicuspis L.). The recent discovery of male fertile garlic accessions stimulated research on the genetics and breeding of garlic. However, there is no information regarding the phenotypic characteristics of garlic populations generated from true seeds. We evaluated the first generation of sexually derived families of garlic for bulb and clove weight, number of cloves per bulb, flower stalk height, number of leaves, plant height, and days required to achieve bulb maturity. Significant variations were observed within and among families for these important traits.
Yayeh Zewdie and Paul W. Bosland
Pungency, caused by the presence of capsaicinoids, is a major quality-determining factor in chile (CapsicumL. sp.) The inheritance of nordihydrocapsaicin, capsaicin, dihydrocapsaicin, isomer of dihydrocapsaicin, and homodihydrocapsaicin has not yet been determined. Generations mean analysis revealed that additive, dominance, and interaction effects were significant for capsaicin, dihydrocapsaicin, and isomer of dihydrocapsaicin in an interspecific hybridization of C. annuum L. × C. chinense Jacq. A simple additive-dominance model was sufficient to explain the genetic variation for nordihydrocapsaicin and homodihydrocapsaicin. Except dihydrocapsaicin and isomer of dihydrocapsaicin in the BCP1 family, the values of backcross families shift toward the recurrent parents. Because of the significant additive gene effect and the tendency of the values of the capsaicinoids at backcross families to shift toward the recurrent parents, repeated backcrossing and selection will increase and decrease (depending on the recurrent parent) the capsaicinoid content. Positive genetic correlations were observed between the capsaicinoids and the values ranged from 0.4 to 0.8. The estimated number of effective factors were 0.4 for nordihydrocapsaicin, 0.6 for homodihydrocapsaicin, 0.9 for isomer of dihydrocapsaicin, 1.1 for dihydrocapsaicin, 2.8 for total capsaicinoids, and 6.2 for capsaicin. Different gene actions and a different number of effective factors involved in the capsaicinoids inheritance imply that different genes are controlling the synthesis of each capsaicinoid.
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, Yayeh Zewdie, and Stephen H. Thomas
Yayeh Zewdie, Michael J. Havey, James P. Prince, and Maria M. Jenderek*
Garlic has been propagated exclusively by asexual means since time immemorial. The recent discovery of male fertile garlic accessions allowed studies on genetics and garlic improvement. Single nucleotide polymorphism (SNP) and random amplified polymorphic DNA (RAPD) based genetic linkage map was developed for garlic using a segregating population derived from one plant of PI 540316. Progenies segregated for male fertility and other morphological characters. Distortion of segregation was observed for most of the markers. This was expected due to the segregation of recessive deleterious alleles present in the garlic genome. The map contained 23 loci distributed on five linkage groups. It covered 319 cM with the average of 18 cM between loci. Linkage with the male fertility (Mf) locus was established with SNP marker AOB155 (26.7 cM).
Yayeh Zewdie, Michael J. Havey, James P. Prince, and Maria M. Jenderek
Garlic (Allium sativum L.) has been cultivated by asexual propagation since time immemorial. The discovery of male-fertile garlic accessions has opened a venue for genetic studies and improvement through sexual recombination. An S1 family of 84 plants was generated from a single male-fertile heterozygous plant from the U.S. Dept. of Agriculture Plant Introduction 540316 and used to identify the first genetic linkages in garlic based on single nucleotide polymorphisms, simple sequence repeats, and randomly amplified polymorphic DNAs. Thirty-seven markers formed nine linkage groups covering 415 centimorgans (cM) with average distance of 15 cM between loci; other 16 loci remained unlinked. A male fertility locus was placed on the map. This first genetic map of garlic is a seminal step toward the genetic improvement of garlic and eventual marker-assisted breeding.