Factors affecting the incidence of internal deviations in Brussels sprouts (Brassica oleracea L. var. Gemmifera DC.)

Summary A study was made on the incidence of internal deviations in buttons of Brussels sprouts. Sprouts picked in the autumn showed an only slight degree of internal necrosis, in contrast to those picked in the winter. Large sprouts were more sensitive than smaller ones. No clear direct effect of nitrogen and planting distance could be established. Low temperatures in the winter are considered to be the main causal factor of this type of necrosis. Very distinct differences in sensitivity between varieties and strains were found. probably resistant varieties may be bred by selection.

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Samenvating Onderzoek werd uitgevoerd over het voorkomen van inwendige afwijkingen in spruitkool. In spruiten geplukt in de herfst kwam weinig inwendige necrose voor, in tegenstelling tot de in de winter geplukte spruiten. Grote spruiten waren gevoeliger dan kleine. Er kon geen direct van stikstof en plantafstand worden vastgesteld. Lage temperaturen in de winter zijn waarschijnlijk de belangrijkste oorzaak van het optreden van de gevonden necrose. Tussen rassen en selecties werden zeer duidelijke verschillen in gevoeligheid gevonden. Misschien kunnen door selectie resistente rassen worden gekweekt.

     

Identity tests of ms-genes of Brussels sprouts (Brassica oleracea L. var. Gemmifera DC.) and cauliflower (B. oleracea var. Botrytis L.)

Summary Research was carried out on the identity of ms-genes of Brussels sprouts and cauliflower.It was concluded that these genes are not identical and act independently.The consequences for the detection of plants with fertility restoring plasm are discussed.A method is outlined to produce lines with a high percentage of male sterile plants by accumulation of ms-genes.     

The effect of alternating temperatures on the self-incompatibility of some clones of Brussels sprouts (Brassica oleracea L. var. Gemmifera (DC.) Schulz)

Summary The influence of temperature on self-incompatibility of six S-homozygous clones of Brussels sprouts was studied. The clones were treated with constant temperatures of 14°, 17° and 20°C and alternating day and night temperatures of 17/14°, 20/14°, 23/14° and 26/14°C. To determine the degree of incompatibility the mean number of pollen tubes per style after selfing was calculated.The clone with the weak S-allele S-5 was less self-incompatible in the 23/14° and 26/14°C treatments than in the other treatments. The other clones with the weak S-alleles S-15 and S-45 remained sufficiently self-incompatible during all treatments. The clone with the rather strong S-39 showed the highest level of self-incompatibility at 26/14°C.In the two weakly self-incompatible clones with S-5 and S-39 a clear difference in self-incompatibility was found between young and old flowers. The strongly SI clones with S-39 showed no difference and in the two clones with S-15 the differences were small and significant in one case only.     

Dominance relationships between S-alleles in the stigmas of Brussels sprouts (Brassica oleracea var. Gemmifera)

Summary Partial dominance between S-alleles in the stigma was found to be common in 412 plants of Brussels sprouts in which two S-alleles could be detected. Amongst a further 168 plants in which only one S-allele could be detected, 5 plants showed the detected allele to be completely dominant to the other allele present, but further examples are expected. Dominance relationships are given for 34 pairs of S-alleles representing 16 different S-alleles. The most recessive S-alleles in the stigma appear to be S5, S14, S15 and S45, while the most dominant are S23, S29, S35, S36 and S39. The significance of dominance between S-alleles in connection with the breeding system of Brussels sprouts is discussed, and an explanation proposed for the high frequency of S2 based on its unusual dominance behaviour.     

Classification of S-alleles by their activity in S-heterozygotes of brussels sprouts (Brassica oleracea var. Gemmifera (DC.) Schultz)

Summary Over a period of many years, data on dominance relationships of S-alleles in Brussels sprouts were collected at URL and IVT. The level of activity of S-alleles in heterozygotes was assessed on the basis of the number of pollen tubes that penetrated into the stigma. 209 out of 210 possible combinations between 21 S-alleles were used for this investigation. The S-alleles were grouped separately for activity in pollen and style on the basis of their sensitivity to lose activity in S-heterozygotes. Besides S-allele interaction per se, activity was found to be influenced by environment and genetic background.Results suggest that in stigma, co-dominance is the normal pattern and that deviations are caused by factors other than S-allele interaction as such.In pollen, only three truly recessive alleles were found. Besides several combinations with mutual weakening in pollen, examples of independent weakening were found.     

Inheritance of head splitting in cabbage (Brassica oleracea L. var. capitata L.)

Summary The inheritance of head splitting was probed by studying two moderate inbred lines of early-splitting and late-splitting cabbages, their F₁, F₂ and backcross progenies under field condition. It was concluded that there were at least 3 gene pairs for controlling head splitting. Gene action was mostly additive but partial dominance for early splitting was detected. Narrow sense heritability was estimated as 47%.     

Effect of temperature on the expression of cytoplasmic male sterility in cultivated barley (Hordeum vulgare L.)

Twenty‐three cytoplasmic male sterile BC₁F₁ barley lines were exposed to varying temperature treatments (TTs) to examine the effect of temperature on the stability of the expression of cytoplasmic male sterility (cms). The TTs used for this test were: (i) controlled low‐temperature treatment of 16°C (CL), (ii) controlled medium‐temperature treatment of 21–24/16–17°C day/night (CM) and (iii) ambient glasshouse‐temperature treatment of 24–41/16–17°C day/night (AG). The expression of cms was found to be variably influenced by temperature and by the genetic background of the cms recipient lines. Ten cms lines exhibited consistently complete male sterility over TTs, indicating that these lines are completely under cms genes control, while other lines showed partial revision to fertility across different TTs with profound influence of warm temperatures (CM and AG) in breaking down the cms in barley.     

Analysis of genic male sterility in Brassica oleracea

Summary The male sterility system MS-1 of Brassica oleracea was studied in order to elucidate if nucleo-cytoplasmic interactions determine this system. Crosses of male sterile MS-1 genotypes with heterozygous MS-5 genotypes gave fully fertile F₁ progenies. Selfing of seven F₁ plants resulted in five F₂ populations showing a 9:7 segregation ratio and two a 3:1 ratio for fertile and male sterile plants. Two F₂ progenies deviated from the expected 9:7 or 3:1 segregation ratios for fertile and male sterile plants. Thermosensitivity and distortion of the meiosis are suggested as the causal factors underlying the deviation of the segregation ratios. It was concluded that nuclear factors determine the male sterility in the MS-1 system, because the presence of a nucleocytoplasmic interaction in this system should have given only a 3:1 segregation ratio for fertile and male sterile plants in the F₂ generation.     

Inheritance of stalk rot resistance in cauliflower (Brassica oleracea var. Botrytis L.)

Summary The inheritance of resistance in cauliflower to stalk rot (Sclerotinia sclerotiorum (Lib.) de Bary) was investigated in population from six generations of six crosses. Disease incidence was recorded on 4 parents, 6 F^s ₁, 6 F^s ₂ and 12 back-crosses in a screenhouse under artificially created epiphytotic conditions. Resistance to stalk rot in this set of parents was found to be polygenic and under the control of recessive genes and due primarily to additive gene action. A breeding strategy emphasizing recurrent selection should lead to improvement in resistance.     

Investigations into the breeding system of cauliflower Brassica oleracea var. botrytis (L.)

Incompatibility reactions of 21 varieties of summer, autumn and winter type cauli-flowers were assessed by

1. (a)
   comparing the seed sets per siliqua from separate inflorescences of the same plant which were self-pollinated and mixed-pollinated with self and Brussels sprout pollen,     
   
   

Routine large-scale electrophoresis for plant breeding. An example with F1 seeds of Brussels sprouts (Brassica oleracea var.gemmifera)

Summary A routine method of large-scale electrophoresis is proposed for use in plant breeding. The method can be applied both with research and teaching and does not require sophisticated apparatus. A skilled laboratory technician can thus handle 768 samples a day. Within a series of electrophoretic investigations the individual electrophoresis can be stopped at any time, while the other investigations in the series continue.     

Variation of flowering time in inbred brussels sprouts and cabbage (Brassica oleracea L.)

Summary Differences in time of flowering between two parent lines of F₁ varieties of Brassica oleracea could significantly affect both the total seed yield and the proportion of sibs in the hybrid seed crop.The results for the time to flower of an incomplete diallel show that even in relatively inbred material of brussels sprouts there is potential to select for altered flowering time. Results obtained from a set of highly inbred cabbage lines which were given three temperature regimes in early spring show that between line variation is complicated by different responses of some of the lines to the environments.     

Inheritance of internal pigmentation in green cabbage (Brassica oleracea var. Capitata L.)

Summary Internal anthocyanin pigmentation (IP) in otherwise normally green cabbage occurs in a number of Oregon State University breeding lines. Extracted pigment, tested for spectral absorption and for color reactions with lead acetate and aluminium chloride, was similar but not necessarily identical to pigment extracted from red cabbage cultivar Redman. When IP line R52 was crossed with normal green line C70, the F₁, F₂ and backcross progenies indicated that IP at the intensity found in R52 was determined by a single factor in homozygous condition, with intermediate levels of IP expressed by the heterozygous genotypes. Modifying factors also appear to influence the level of IP. In the cross R52 (IP)×R51 (normal green), expression of IP in the F₁ was much reduced. The F₂ failed to fit the expected 3 IP: 1 green ratio due to an excess of green plants, but instead, closely fit a 9:7 ratio. This may have resulted from incomplete expression of IP because of modifiers, rather than from the effects of a second major gene. An allele at the A (anthocyanin) locus of B. oleracea is tentatively proposed and designated A ^IP or a ^IP pending further identification.Oregon Agricultural Experiment Station Technical Paper No. 4690.     

Effect of temperature on the occurrence of male sterility in onion (Allium cepa L.)

Summary Experiments were made to ascertain whether sex expression in the onion depends on temperature.Some populations were found to be largely male sterile at about 14°C and much less so at 20°–23°C. In other populations this phenomenon did not occur. Besides all the fertile populations produced less and worse pollen at 14°C.The first-mentioned temperature influence may be an essential factor in searching for an explanation for the partially male sterile plants found by various research workers, and for the unexpected segregations for male sterility when A-, B- and C-lines are propagated.     

A mutation affecting curd colour in cauliflower (Brassica oleracea L. var. Botrytis DC)

Summary A single gene mutation in cauliflower resulted in the production of an orange coloured curd when heterozygous, and a stunted orange curd when homozygous. The orange heterozygote has commercial potential.     

Increased atmospheric humidity post pollination: A possible aid to the production of inbred line seed from mature flowers in the Brussels sprout (Brassica oleracea var. Gemmifera)

Summary In two highly self incompatible inbred lines of Brussels sprouts the effect of increased atmospheric humidity post pollination was examined immediately following 1) hand pollination of green buds and open flowers, and 2) blowfly pollination of open flowers. Data were obtained for mean number of seeds set per pollination, mean number of fruits setting seed, and mean number of seeds produced per fruit which set for both varieties. Measured as number of seeds produced per minute spent pollinating, it was clear that open flower pollination followed by high humidity conditions was a much more efficient method of producing inbred line seed (46 seeds/minute) than green bud pollination (27 seeds/minute).     

Preliminary Study of the Characteristics of Several Glossy Cabbage(Brassica oleracea var. capitata L.) Mutants

To determine the characteristics and potential practical applications of glossy cabbage(Brassica oleracea var. capitata L.) mutants, five different glossy mutants were studied. The amount of epicuticular wax covering the mutant leaves was only approximately 30% that of the wild-type(WT) leaves. The wax crystals of WT plants were columnar and linear, while they were granular and rod-shaped in the mutants. Additionally, in WT cabbage, the primary wax components were alkanes, alcohols, fatty acids, ketones, and aldehydes. There was a significant decrease in the abundance of alkanes and ketones in the wax of the mutants. The glossy-green trait of the mutants may be the result of an inhibited alkane-forming pathway. Higher rates of chlorophyll leaching and water loss demonstrate that the mutant leaves were more permeable and sensitive to drought stress than the WT leaves. Growth curve results indicated that the growth rate of mutant-1 and mutant-3 was slower than that of the corresponding WT cabbage, resulting in shorter plants. However, the growth rate of mutant-2 was not influenced by the lack of coating wax. An investigation of the agronomic traits and heterosis of the glossy cabbage mutants indicated that all five mutants had glossy-green leaves, which was a favorable characteristic. The F1 plants derived from crosses involving mutant-2 exhibited obvious heterosis, suggesting the observed glossy-green trait is controlled by a dominant gene. Therefore, mutant-2 may be useful as a source of genetic material for future cabbage breeding experiments.     

Glossy-leaf in collard (Brassica oleracea L. var. Acephala D.C.): An incomplete dominant

Glossy-leaf in the collard variety Green Glaze is incompletely dominant to waxy foliage normal in other varieties; the suggested gene symbol is Go. The phenotype is similar to that controlled by a recessive gene in Brussels sprout. Further loci may be involved in other glossy-leaved forms reported in B. oleracea and such genes would form a useful series of markers in a breeding programme.     

Thiocyanate in forage kale (Brassica oleracea L.)

Summary An improved technique has been used for the determination of thiocyanate ion (^-SCN) released on enzymatic hydrolysis of kale (B. oleracea) inbred lines and F₁ hybrids. Considerable heritable variation has been found. Grazing trials have shown a relationship between ^-SCN in the crop and in the blood plasma of grazing sheep.