Transgressive segregation in inter and intraspecific crosses of barley

Summary Six populations of F₂-derived lines of barley and their parents were evaluated for heading date, plant height, grain yield, bundle weight, and harvest index in a replicated experiment in the field. These data were used to estimate the minimum number of effective factor pairs segregating for each trait, the number of favorable factors contributed by each parent in a cross, and the frequencies and magnitudes of transgressive segregates.Heading date, plant height, and harvest index were controlled by three to four effective factor pairs, whereas grain yield and bundle weight were controlled by five or more.All three H. spontaneum strains used in our study contributed one or more useful genes for each of the traits, grain yield, heading date, plant height, bundle weight, and harvest index. Therefore, it seems that H. spontaneum can be a useful source of favorable genes for quantitative traits, especially for grain yield, which could be incorporated into barley varieties readily by backcrossing. Transgressive segregates for grain yield in the interspecific crosses may provide the basic materials for improving the productivity of cultivated barley varieties.Journal Paper No. J-9760 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, IA 50011. Project 2227. Supported in part by a grant from the Science and Education Administration-Cooperative Research, United States Department of Agriculture.     

Inheritance of groat protein percentage in Avena sativa L. × A. Fatua L. Crosses

Summary Gene action and heritability of groat protein percentage were determined in F₁, F₂, and F₃ generations of nine crosses between three Avena sativa L. cultivars and three A. fatua L. selections. Relationships among groat protein percentage, grain yield, and 100-seed weight also were evaluated. The three A. sativa parents were Dal (high grain yield and intermediate groat protein percentage), Goodland (low grain yield and high groat protein percentage), and Stout (high grain yield and low groat protein percentage). The three A. fatua parents were chosen for the study on the basis of vigorous plant growth and high groat protein percentage. The study was conducted at Madison, Wisconsin in 1979 and 1980.There was partial dominance towards low groat protein percentage. Narrow sense heritability estimates for groat protein percentage were low in Dal and Goodland crosses and intermediate in Stout crosses. In the F₂ generation, groat protein percentage was significantly higher in shattering than in nonshattering plants in 1979, but not in 1980. There were significant, positive correlations between groat protein percentage, 100-seed weight, and grain yield in F₁ and F₂ generations, but they were not large numerically. Relationships among these traits were either negative or nonsignificant in the F₃ generation. Although our results indicated that selection for higher groat protein percentage is possible when a low protein A. sativa cultivar is used, most of our simple cross progenies from A. sativa x A. fatua crosses had weak straw and were susceptible to crown rust (Puccinia coronata Cda. var. avenae Fraser and Led.).     

Inheritance of resistance to Didymella lycopersici Klebb. in tomato (Lycopersicon Mill.)

Summary The inheritance of the resistance to Didymella lycopersici was studied on F₃- and Bc₁-lines from interspecific crosses of L. esculentum with L. hirsutum and with L. hirsutum glabratum. The resistance is not monogenic and is inherited in dominant fashion. The high h² values based on line means offer possibilities to seleet efficiently for enhanced levels of resistance.     

Linkage of downy mildew resistance genes Pd 1 and Pd 2from Allium roylei Stearn in progeny of its interspecific hybrid with onion (A. cepa L.)

Summary Male meiosis of the interspecific hybrid between Allium roylei and A. cepa is undisturbed relative to its parents. Based on meiotic data, A. roylei is concluded to be a closer relative of A. cepa than A. fistulosum. Segregation ratios for downy mildew resistance among BC₁ and F₂ progenies from the F₁ between A. roylei and A. cepa indicate the presence of two dominantly inherited, weakly linked nuclear resistance genes, Pd ₁ and Pd ₂, in A. roylei (recombination frequency 0.32±0.03). Presumably Pd ₁ and Pd ₂are the first genes described in Allium residing in one linkage group. The prospects of exploiting A. roylei in onion breeding seem very promising.     

Wheat x pearl millet hybridization: consequence and potential

Summary Eight grain pearl millet (2n=14) accessions were crossed as male to hexaploid spring wheat cv. Fukuho (2n=6x=42). An average of 80% wheat pistils showed pearl millet pollen tube entry in the ovules, compared to 56% in wheat x maize cv. Seneca 60 cross. Of the 15 embryos, obtained through in vitro immature seed culture from wheat x pearl millet crosses, 3 plantlets were produced and grown to maturity. These three were of the somatic chromosome constitution 2n=42, 21 and 22, respectively. Haploid wheat plant (2n=21) apparently originated from pearl millet chromosome elimination during embryogenesis. The 22 chromosome plant had retained a single pearl millet chromosome at tillering stage, but this chromosome was eliminated from pollen mother cells prior to and also during gamete formation. The significance and potential uses of this wide cross is discussed.     

Genetical studies of embryo survival and embryo breakdown in Pelargonium × hortorum Bailey

Summary The 6×6×4 analysis of variance of the mean percentage embryo survival for six variegated cultivars of Pelargonium × hortorum Bailey, with mutant plastids in their germ layers, and for their isogenic green (G) clones, shows highly significant differences between females (81 to 91 per cent) and between plastid crosses (83 to 91 per cent). Between cultivar differences are attributed largely to additive effects corresponding to additive gene action, and between plastid differences to a lower survival after crosses with white (W) males than with green males. The relationship between overall fertility (% fertilization × survival) and plastid crosses is a stepwise decline in the order G×G>G×W>W×G>W×W (28 to 19 per cent) in which the white embryos growing in a white mother are approximately 30 per cent less fertile than the green embryos in a green mother. The non-surviving embryos are classified into empty, undeveloped and dwarf embryos and submitted to a 6×4 analysis of variance after summing through males. The significant heterogeneity between females is attributed largely to a difference between one cultivar-with a high frequency of dwarf and a low frequency of undeveloped embryos-and the other five cultivars. The absence of a significant plastid effect upon any stage of embryo breakdown indicates that the depressive effect of white plastids is spread evenly throughout development.     

Glucosinolate content in interspecific crosses of Brassica carinata with B. juncea and B. napus

Brassica carinata A. Braun is a highly productive oilseed crop in the Ethiopian highlands, but the seed has a high 2-propenyl glucosinolate content, which is undesirable. The objective of this study was to introgress, through interspecific crosses, genes for low 2-propenyl glucosinolate content from the B genome of B. juncea and C genome of B. napus into the B. carinata B and C genomes and thus develop low glucosinolate B. carinata. The cross [(B. carinata×B. juncea) ×B. carinata] yielded plants that contained only ～ 20 μmoles of 2-propenyl glucosinolate, which was an 85% reduction compared with levels in B. carinata seed. Plants of the [(B. carinata×B. napus) ×B. carinata] cross had normal high concentrations of 2-propenyl glucosinolate. Backcross plants of both interspecific crosses also contained 3-butenyl and 2-hydroxy-3-butenyl glucosinolates. The results of these crosses suggested that genes for glucosinolate synthesis were located on B genome chromosomes of B. carinata because B. napus C genome introgressions did not result in reductions of total glucosinolate contents. The total alkenyl glucosinolate content of one F₃ family of the B. juncea backcross was similar to that of the B. juncea parent. It was concluded that through further selection in this family, B. carinata plants could be identified that would be basically free of 2-propenyl glucosinolate, and have a low total alkenyl glucosinolate content.     

Preliminary Studies on the Intergeneric Hybridization Between Brassica napus with OguCMS and Orychophragmus violaceus

In the cross between B. napus with OguCMS x Orychophragmus violaceus, pre-fertilizationcompatibility was observed. An intergeneric hybrid was successfully obtained by usingovary culture. The hybrid status was confirmed by cytology, morphology, fertility,isozyme and miosis analysis. The seed setting rate was 0.0072%. An amphidiploid of thehybrid was also produced by the use of chromosome-doubling method with 0.1% colchicinestreatment. Obtaining this hybrid and its amphidiploid has important theoretical andutilization value.     

二倍体和四倍体球茎大麦及其种间杂种的C－带核型研究

二倍体和四倍体球茎大麦的核型相似,都有５组非常相似的中着丝粒染色体,一组近中着丝粒染色体和一组随体染色体。Ｃ－带带纹很少,大多数染色体只有一或两条着丝粒带,染色体４有１条中间带,随体染色体有次溢痕带,二倍体类型的带型表现出一定的多态性。根据带型特征,结合染色体形态,球茎大麦的７组同源染色体可以区分,依据四倍体球茎大麦的Ｃ－带带型,可以证明其同源多倍体的起源。在种间杂种中,球茎大麦的核仁消失,而栽培大麦的核仁依然存在,表现出典型的“核仁隐性”现象