Polymorphisms of α-amylase activity in barley landraces and cultivars from China

Summary -Amylase activity was assayed by measuring reducing power equivalent for 80 accessions of cultivated barley, Hordeum vulgare L., representing major barley growing areas of China. Replications were applied at two different levels of the experiment and enzyme activity was assayed on four consecutive days starting on the 6th day after germination. The area under the curve formed by connecting the four data points was integrated as the measurement of -amylase activity. The results established that there was extensive variation in -amylase activity in cultivated barley; about three-fold difference existed among accessions assayed. Comparisons were also made between six- and two-rowed, and between covered and naked barleys. The results showed that high -amylase activity was not necessarily associated with six-rowed type, and that covered barleys were slightly higher in -amylase activity than naked ones.     

Limited but specific variations of seed storage proteins in Japanese common wheat (Triticum aestivum L.)

The electrophoretic banding patterns ofgliadin in common wheat lines derived fromJapan were determined byacid-polyacrylamide gel electrophoresis. For the 107 wheat lines used in our study,27 different patterns were identified, 13corresponding to the -gliadin, 8 tothe , -gliadin and 6 to the-gliadin. The gliadin patterns ofJapanese wheat cultivars and landracesgreatly differed from the patterns of wheatlines from other countries, and thevariation seen in wheat lines from Japanwas limited to 46 patterns. Sevencollection or breeding areas in Japanshowed different frequencies in theirgliadin patterns. Combining the gliadinpatterns with high molecular weightglutenin subunit compositions, 67combinations were observed. One gliadinpattern consisting of -gliadinpattern F, , -gliadinpattern H and -gliadin pattern Dwas frequently found in many Japanese wheatlines, though the other patterns werelimited to only one or two wheat lines.     

Evaluation of methods for the assessment of malting quality in barley breeding

Summary Methods for assessing malting quality in barley breeding were evaluated for their precision, including variation between different batches, analysts and barley samples. The barley characters measured were grain moisture, ground grain moisture (two methods), grain weight, steep moisture, malt moisture (two methods), malt yield, malt nitrogen, malt soluble nitrogen, Kolbach index, malt diastatic power, malt -amylase, malt -glucanase, wort refractive index, hot water extract, extract yield, wort reducing sugars, wort total carbohydrates, wort -amino nitrogen and wort total nitrogen. The value of these measurements in barley breeding is discussed.     

Inheritance of late maturity α-amylase in wheat

Summary Two wheat cultivars that consistently show high levels of grain -amylase at harvest ripeness, in the absence of preharvest sprouting, were crossed with a control, low -amylase cultivar, and F₁, F₂ and BC₁ populations were developed. Grain of these populations was analysed for -amylase activity at harvest ripeness. Distribution and segregation patterns were consistent with control at a single locus with high -amylase the recessive allele. This mode of inheritance would make it extremely difficult to differentiate homozygous low -amylase lines from heterozygotes (low -amylase phenotype but carriers of high -amylase) and has important implications for wheat breeders. High -amylase, termed late maturity -amylase, was not linked with the awned inhibitor gene, B2, located on the long arm of chromsome 6B.     

Diallel analysis of yield components of snap beans exposed to two temperature stress environments

Ten snap beans (Barrier, Brio, Carson, Cornell 502, CT 70, HB 1880, Hystyle, Labrador, Opus and Venture) were selected for differential temperature tolerance and used as parents in a complete diallel mating design. The 45 F₁ hybrid lines (with reciprocals) and parents were screened at 32 C day/28 C night, and in a separate experiment, 16 C day/10 C night, during reproductive development in replicated controlled environments. Variation for yield under temperature treatments was observed among parents and hybrids, with certain hybrids exceeding parental performance. Significant (P 0.0001) general combining ability (GCA), and significant (P 0.05) specific combining ability (SCA) were observed for yield components including pod number, seed number, and seeds per pod. There was evidence that pod number and seeds per pod under temperature stress are under separate genetic control. Reciprocal effects and heterosis were not significant. GCA could not be predicted from parental performance. The breeding line Cornell 502 had the highest GCA under high temperature, and the cultivar Brio had the highest GCA under low temperature. The cross Brio × Venture was high yielding in both temperature treatments. Heat tolerance and chilling tolerance were associated in certain parents and hybrids. However, performance under high and low temperature treatments was not generally correlated in the parents and hybrids, indicating that these traits should be selected separately.     

Expression of late maturity α-amylase in wheat containing gibberellic acid insensitivity genes

Summary Two wheat cultivars, Spica and Lerma 52, which consistently produce high levels of -amylase during the later stages of grain development (late maturity -amylase), were crossed with a set of four near-isogenic lines carrying the tall (rht) allele or one of the dwarfing genes Rht1, Rht2 or Rht3 (GA-insensitive alleles). The F₁ and F₂ populations were developed and analysed for grain -amylase and plant height. The Rht3 gene exhibited the strongest influence on plant height and strongly inhibited new -amylase synthesis during the later part of grain ripening. By comparison, Rht1 and Rht2 had a less pronounced effect but still significantly reduced the expression of late maturity -amylase. These observations suggest that gibberellic acid is involved either directly or indirectly in this phenomenon. The implications of the effect of dwarfing genes on expression of late maturity -amylase are discussed in relation to cultivar improvement and to the identification and control of high -amylase germplasm.     

The inheritance and association of resistance to rust,common bacterial blight,plant habit and foliar abnormalities in Phaseolus vulgaris L.

Summary No antagonistic or synergistic interaction was found between isolates of Uromyces appendiculatus var. appendiculatus and Xanthomonas campestris pv. phaseoli when inoculated to the same plant. A single dominant gene was suggested to control resistance to three isolates of rust in the crosses Pompadour Checa × Chichara and Pompadour Checa × NE W-4. A two-gene model was confirmed for the reaction to the three rust isolates for the crosses Pompadour Checa × GN Tara and Pompadour Checa × San Cristobal; a dominant (Ur _p) gene determined resistance and was epistastic to a dominant gene (Ur _t) for susceptibility. (Ur _t) was expressed only in the presence of recessive (ur _p) alleles. The reaction to common bacterial blight was quantitatively inherited and an association was detected with plant habit but not with rust reaction and leaf variegation. Plants with leaf variegation and crippled growth, were detected in the progeny of the cross Pompadour Checa × GN Tara and were controlled by duplicate recessive genes (mutatorunstable genes) and three genes, acting additively, respectively. The developmental expression of the latter trait varied considerably. Linkage was detected between genes controlling the variegated and the crippling traits.Published as Paper No. 7839, Journal Series, Nebraska Agricultural Experiment Station. Research was conducted under project No. 20-036.     

Breeding implications of the relationship between competitive ability and pure culture yield in self-pollinated grain crops

Summary The relative efficiencies of pedigree and bulk breeding systems for selection of high yielding genotypes are shown to be dependent on the relationship between competitive ability in mixed culture and yield in pure culture. A critical statistic is the regression coefficient, , of competitive ability (defined as the yield of a genotype in mixed culture minus its yield in pure culture) on yield in pure culture. If is less than –1, competition in mixed culture so supresses genotypes which are high yielding in pure culture conditions that they are eliminated by natural selection in early generations; pedigree selection of the lowest yielding genotypes in the F₂ and F₃ is indicated. If is greater than –1, genotypes which are high yielding in pure culture survive even when they compete less well than low yielding genotypes, and bulk breeding is indicated. An example from two sets of 100 genotypes in pure and mixed culture was analysed and the estimate of fell between 0 and –1, but because exact simulation of a segregating population was not feasible the estimate was biased. The bias tended to give estimates of that were too close to zero.Agricultural Research Council Statistics Group, Department of Applied Biology, University of Cambridge England     

Inheritance of gliadin composition in bread wheat,Triticum aestivum L.

Summary The gliadin compositions of 101 selected lines from 2 crosses between varieties of T. aestivum were examined by applying starch-gel electrophoresis at pH 3.1. The gliadin patterns of these lines were recognized to be composed of sections of the parental patterns. In a wheat variety the gliadin pattern proved to be divisible into 6 or 7 sections, the configurations of which are inherited unaltered. Its gliadin composition, consequently, is determined by at least 6 genetic factors. The sections appeared to be identical to the gliadin fractions currently known as , , , and ; the gliadin proved to consist of 2 sub-fractions and the gliadin of 2 or 3 sub-fractions.Dedicated to Professor Dr H. Veldstra on the occasion of his retirement from the chair of biochemistry of the University of Leiden.     

Effect of genetic blends of dry beans (Phaseolus vulgaris) of different Plant architecture on apothecia production of Sclerotinia sclerotiorum and white mold infection

Summary The determinate Phaseolus vulgaris L. cvs Dark Red Kidney Charlevoix, and near-isogenic Great Northern Nebraska 1 were grown in blends with the indeterminate GN Nebraska 1 in white mold (Sclerotinia sclerotiorum) disease field nurseries. A critical difference between Charlevoix and indeterminate GN Nebraska 1 is that the latter has a greater leaf area closer to the soil surface, and this is associated with increased numbers of apothecia beneath the canopy and higher disease severity. White mold infection and apothecia number/m² beneath the canopy of the blends containing Charlevoix were significantly reduced in comparison with the severely infected, homogeneous, indeterminate GN Nebraska 1. A reduction of white mold infection for the indeterminate GN Nebraska 1 was not observed in blends grown under severe or moderate white mold incidence, but did occur under slight incidence in blends containing 65% and 75% Charlevoix.No significant difference for seed yield occurred between the blends and homogeneous cultivars planted in four experiments under severe, moderate, slight and zero white mold incidence, respectively, except in Experiment 1 under moderate white mold incidence, the blend of 50% indeterminate GN Nebraska 1 and 50% Charlevoix exceeded the yield of the indeterminate GN Nebraska 1. Mean weight of white (GN Nebraska 1) and red seed (Charlevoix) increased and decreased, respectively, in some blends due to the more vigorous growth of the indeterminate GN Nebraska 1.Published as Paper No. 5341, Journal Series, Nebraska Agric. Exp.t Station. Research was conducted un under Project 20–3.     

Functions of time for growth characters,their evaluation and approximation to examine differences between genotypes

Summary As a follow up to a previous paper on growth curves (Keuls & Garretsen, 1982) a procedure is described to derive functions of time for growth characters from elementary growth curves which are suited for statistical analysis.For each plot from the parameters , , of the second degree growth curves of type + (t–t) + (t–t)², corresponding functions of time (of harvest) are obtained for the derived growth characters: relative growth rate (of dry weight per plant), net assimilation rate, leaf area ratio, specific leaf area, leaf weight ratio. The elementary growth curves concern ln W, ln LA and ln LW, where W = dry weight per plant, LA = leaf area per plant, LW = leaf dry weight per plant.Only relative growth rate is a simple linear expression in t, i.e., + 2(t–t), where t represents average harvest time.The functions for the four other growth characters are approximated by quadratic functions in t, such that for each plot a curve is characterized by a triple of parameters f(t), f(t), % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaKabGfaammaalaaaba% Gaaiymaaqaaiaackdaaaaaaa!3946!\[\frac{1}{2}\]f(t), representing respectively mean, slope and curvature for that plot at time t The approximation of the function of time is given by f(t) + (t–t)f(t) + % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaKabGfaammaalaaaba% Gaaiymaaqaaiaackdaaaaaaa!3946!\[\frac{1}{2}\](t–t)²f(t).These sets of parameters per plot: (, , ) for ln W(t) etc.; (, 2, 0) for RGR(t) or (f(t), f(t), % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaKabGfaammaalaaaba% Gaaiymaaqaaiaackdaaaaaaa!3946!\[\frac{1}{2}\]f(t)) for the four other growth characters can be analysed by the MANOVA-procedure for 3 parameters as exemplified by Keuls & Garretsen (1982).     

Transient gene expression in transformed banana (Musa cv. Bluggoe) protoplasts and embryogenic cell suspensions

Summary In order to introduce currently-available genes with agronomical value into banana, two genetic transformation protocols have been optimized.Firstly, regenerable protoplasts isolated from embryogenic cell suspensions of the cultivar Bluggoe have been used for the introduction of several chimaeric uidA gene constructs by electroporation. With the inclusion of polyethylene glycol and heat shock, the frequency of transiently expressing protoplasts reached 1.8% as shown by an in situ -glucuronidase assay. A duplicated 35S promoter with an alfalfa mosaic virus leader sequence (pBI-426) induced the highest expression rate among the constructs tested.Embryogenic cell suspensions of cv. Bluggoe have also been bombarded with accelerated particles coated with a high expression uidA gene construct (pEmuGN) using a biolistic gun. After a partial optimization of the procedure, transient GUS assays reproducibly demonstrated the presence of 400 blue foci in 30 l of settled cell volume (approximately 25 mg cells). Selection and characterization of antibiotic-resistant transformed cultures is in progress.Abbreviations AMV alfalfa mosaic virus - GUS -glucuronidase - TGE transient GUS expression - uidA gene for -glucuronidase     

Relationship between allelic variation of Glu-1 and Gli-1/Glu-3 prolamin loci and gluten strength in hexaploid wheat

Summary Allelic variation of prolamin loci was examined in the F₂ from crosses between the hexaploid wheat varieties: Cajeme 71, Yécora 70, Ablaca, Anza, Pané 247 and Axona. Different allelic blocks for gliadins and LMW glutenin subunits were determined in Gli-1, Gli-2 and Glu-3 loci. A percentage of recombination of 1.5 ± 0.3 was determined between Gli-A1 and Glu-3 in the F₂ progeny of Yécora 70 x Axona. A significant positive association was found between gluten strength, measured by SDS-sedimentation volume, and the prolamins coded by Anza Gli-D1/Glu-D3 loci and Yécora 70 Gli-A1/Glu-A3 loci. Interactions between non homeologous loci Glu-1 and Gli-1/Glu-3 were also found.     

Inheritance of pod cross-section in beans (Phaseolus vulgaris L.)

Summary OSU 5062, a green bean line with a tendency for pods to become creasebacked (wider than deep) in cross-section, was crossed to near-round-podded cultivars Oregon 83 and Slenderette, oval-podded Bountiful, and flat-podded Roma, to further clarify the inheritance of pod cross-section. Differences among generations in pod cross-section index (PCS), calculated as pod width/depth, were small in the near-round x creaseback crosses (1.07 and 1.01 for Oregon 83 and Slenderette versus 1.20 for OSU 5062). Bountiful (0.63) and Roma (0.50) differed to a greater extent from 5062. Generation means of individual plant PCS of the F₁ and F₂ were almost identical, were almost exactly intermediate between parents, and strongly supported additive inheritance. Backcross data generally supported additive inheritance, but in some cases indicated degrees of dominance of higher PCS. A generation means analysis indicated additive gene action, but deviations from an additive-dominance model were significant in each cross.     

Evaluation of maize varieties for their potential as breeding populations

Summary A 7-variety diallel of synthetic varieties that have not had selection for yield improvement and a 10-variety diallel of synthetic varieties that either resulted from recurrent selection for yield improvement or from the introgression of exotic germ plasm into adapted varieties were evaluated in six environments for yield and five other agronomic traits. The specific objective was to determine the relative potential of the synthetic varieties as germ plasm sources for breeding programs.Recurrent selection improved population yield in BSSS CO, BSK CO, and Alph CO in the varieties and also in crosses with other varieties. BSSS(R)C6 and BSSS(HT)C7 yielded 11.4% and 16.1% more than BSSS CO, and the variety crosses of BSSS(R)C6 and BSSS(HT)C7 yielded 21.6% and 22.0% more than the variety crosses of BSSS CO. Recurrent selection also improved stalk-lodging resistance for BSSS(R)C6 and BSSS(HT)C7, but root lodging for BSSS(HT)C7 was significantly higher. BS15 had 61.0% higher yields than Alph CO, with 9.3% less stalk lodging. Average heterosis of the 10-variety diallel was 1120 kg/ha (19.6%) and ranged from 800 kg/ha (13.7%) for BSK(S)C5 to 1770 kg/ha (39.4%) for BS12(HI)C5. The heterosis expressed among individual variety crosses ranged from 4.3% for BSK(S)C5 x BSTE(FR)C1 to 37.6% for BSSS(R)C6 x BS12(HI)C5, which approached the yield of the two highest yielding single-cross checks.In the 7-variety diallel of unselected varieties, BSTE CO and Late Rootworm Synthetic were superior as varieties and in crosses for yield and stalk quality. Average heterosis for the 7-variety diallel was 950 kg/ha (18.5%). Stalk lodging was important in the performance of varieties with poor stalk quality.Although recurrent selection improved yield, development of superior breeding populations also will require selection for general agronomic performance. The performance of BS16 and the yields of BSTL and Teozea and their crosses suggest that exotic germ plasm should receive greater attention.Contribution from the Agricultural Research Service, U.S. Department of Agriculture, and Journal Paper No. J-8096 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50010. Project No. 1897.     

Lilium x ‘Black Beauty’—a potential bridging hybrid in Lilium

Summary Lilium Black Beauty, a rare intersectional hybrid previously reported sterile, was re-examined for pollen and ovule fertility. No pollen tubes were detected following incubation of styles pollinated with Black Beauty pollen. However, embryos varying in size from small globular to long boat-shaped and only rarely associated with endosperm, were found in 0.1–1.0% of the ovules in Black Beauty pistils pollinated with Oriental or Aurelian division lilies. Aseptic extraction and culture of these embryos on a nutritive medium resulted in growth, germination, and plantlets. It is apparent that with embryo culture, Black Beauty has unique value as a species bridge in that it accepts pollen of both Oriental and Aurelian lilies, two of the major commercial lily divisions.Scientific Journal Series Paper Number 9197 of the Minnesota Agricultural Experimental Station.     

Winter barley breeding in the Netherlands

Summary Various Dutch breeders have devoted themselves to winter barley breeding; the local variety Groningen Winter Barley used always to be the foundation material for breeding work. In the course of years 8 new varieties have been derived from it by line selection which demonstrates clearly the degree of variation.The varietal range (fig. 1) shows the peculiarity that the leading variety Vindicat has almost completely been superseded by Urania within some years. If ever, the slogan the Dutch farmer readily accepts new varieties applies here.Its sister variety Vinesco makes a favourable impression.The varieties of winter barley are now for 97 percent based on homebred material.     

Results of one cycle of recurrent selection in rye

A sufficiently variable rye population was subjected to one cycle of recurrent selection for combining ability in order to ascertain whether this complex property can be repatterned.Some hundreds of clones derived from this population were toperossed to an other unrelated variety used as tester. Through visual selection, more than half of these clones were rejected. The topcross progenies of the remaining clones were subjected to a comparative test whereby, as was to be expected, a considerable degree of variability was demonstrated. From the best 10% and the poorest 10% that is from those which surpassed the general average by at least 1.5 standard deviation units or remained below that average by at least 1.5 , narrowed populations were built up. This was done with the aid of reserve seed which in the year in which the top cross was made had been obtained from these clones, either through compulsory selfpollination or by allowing the clones to fertilize each other in isolation. The two subpopulations obtained through selection in opposite directions further indicated as high and low were crossed en masse with the same tester variety as the first time. In addition a large number of randomly taken individuals from the high synthetic were cloned and toperossed to this common tester. On testing the top crosses carried out en masse, the high synthetics clearly yielded more than the low ones. In one trial it was even found that the high synthetic surpassed our standard variety Petkus by approximately 20%. It is possible, therefore, to segregate a population into two fractions of different combining ability.The optimistie pieture to be derived from the foregoing trials unfortunately is shaded by the results of the individual test crosses pointing to a shift of the frequency distribution in a negative sense in regard to the original population. The influence of the year may be mentioned as a possible cause of this contrast and also the fact that in the original population a close visual selection had been practised while those obtained from the synthetic resulting after one cycle were derived from individuals which had been taken entirely at random.

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Samenvatting Een voldoende variabele roggepopulatic werd onderworpen aan één ronde van cyclisch herhaalde selectic op combinatie-geschiktheid ten einde na te gaan of deze complexe eigenschap kan worden vervormd.Enige honderden klonen voortgekomen uit deze populatie werden onderworpen aan een top-cross door een als tester gebruikt ander, onverwant, ras. Op grond van visuele selectie werd meer dan de helft van deze klonen afgekeurd. De proefkruisings-nakomelingschappen van de overblijvende klonen werden aan een vergelijkende toets onderworpen waarbij zoals viel te verwachten een aanzienlijke variabiliteit in opbrengstvermogen aan het licht trad. Uit de beste 10% en de slechtste 10%, d.w.z. die welke het algemeen gemiddelde met minstens 1,5 overschreden resp. daar minstens 1,5 beneden bleven, werden vernauwde populaties opgebouwd. Dit geschiedde met behulp van reservezaad dat in het jaar waarin de top-cross werd verricht van deze klonen was gewonnen, hetzij door gedwongen zelfbestuiving, hetzij door de klonen in isolatie aan onderlinge bestuiving over te laten. De op deze wijze verkregen twee in tegenovergestelde richting geselecteerde sub-populaties-aangeduid als high en low-werden en masse gekruist met hetzelfde tester ras als de eerste keer. Bovendien werd een groot aantal willekeurig uit het high syntheticum genomen individuen tot klonen gemaakt en onderworpen aan een top-cross door het zoëven genoemde tester ras. Bij de toetsing van en masse uitgevoerde proefkruisingen bleek de combinatie high x tester duidelijk meer op te brengen dan low tester. In een proef werd zelfs gevonden dat high x tester ons standaardras Petkus met ongeveer 20% overtrof. Het blijkt dus mogelijk een populatie te splitsen in 2 fracties van uiteenlopende combinatie-geschiktheid.Het optimistische beeld dat men uit de zo juist vermelde proeven krijgt wordt helaas verduisterd door de resultaten van de individuele proefkruisingen welke wijzen op een verschuiving van de frequentieverdeling in negatieve zin ten opzichte van de oorspronkelijke populatie. Als mogelijke oorzaken van deze tegenstelling kunnen worden aangewezen jaarinvloeden en tevens het feit dat onder de klonen uit de oorspronkelijke populatie een scherpe selectie op het oog werd toegepast terwijl die uit het na één cyclus verkregen syntheticum werden afgeleid van volkomen willekeurig genomen individuen.

     

The influence of cytokinins and ionic strength of Anderson's medium on shoot establishment and proliferation of evergreen azalea

Shoot-tip explants of evergreen azalea cv. Fuchsia grown on Anderson's medium and containing different cytokinins produced the highest proliferation rate on a medium containing thidiazuron (TDZ). TDZ concentrations ranging from 0.23 to 2.3 M resulted in both good bud-break rate (4 to 5) and shoot quality (> 0.5 cm in length). Adding 2.3 M zeatin to Anderson's medium containing 0.23 or 2.3 M TDZ increased the number of axillary shoots/explant. However, increasing the zeatin concentration to 4.6 M resulted in a reduced shoot proliferation rate. A medium containing 1.15 M TDZ and 2.3 M zeatin resulted in an 18-fold increase for 'Fuchsia' and a 9-fold increase for 'Hino Crimson' after 6 weeks of culture. It was found that explants grown on a half-strength Anderson's medium with 87.6 mM sucrose generally had better shoot proliferation rate and shoot quality than at higher ionic strength.     

The influence of modifier genes on the intensity and stability of self-incompatibility in cabbage

Summary Four inbred cabbage lines have been derived from a single parental plant through several generations of selfing. Two inbreds have been found homozygous for an S ₁ allele while the other two are each homozygous for S ₂. Each inbred is self-incompatible, cross-incompatible with the inbred carrying the same S allele, and fully cross-compatible with inbreds carrying the other S allele. The S ₁ and S ₂ pairs of inbreds were each found to consist of one inbred with very high self-incompatibility (mean seed set of 0.15–0.25 seeds per pod) and one inbred with less intense self-incompatibility (mean seed set of 1.25–1.70 seeds per pod). For the S ₁ pair, flower to flower and plant to plant variation in seed set per pod was much larger for the less incompatible inbred that for the highly incompatible inbred. Further, incompatibility expression of the less incompatible inbred was influenced by temperature variation while that of the highly incompatible inbred was stable under different temperature regimes. The F₁ between the two inbreds of high and low incompatibility with the common S ₁ allele behaved like the less incompatible parent. F₂ plants showed intermediate intensities of selfincompatibility as well as variation for both lesser and greater intensities than those exhibited by the parents. The variations of self-compatibility and the sensitivity to environmental differences are considered to be conditioned by genes which modify incompatibility expression of the S alleles.