ALBERT

Notes: 2.5 cm long stem segments of Populus nigra L. did not root when cultured in water or in auxins alone but rooted in glucose. The number of rooted segments and roots produced on them increased with rising glucose concentrations up to 0.5%, but decreased with higher concentrations. An addition of 1.0 mg/1 IAA inhibited rooting at 0.01 % glucose, was ineffective at 0.1 % and stimulative at higher concentrations of glucose which were inhibitory when used alone. The results show that the auxin effects on rooting are influenced by the nutritional status of the stem cutting of a species, and that a proper balance of the two is necessary for root development.

Notes: Rooting on 2.5 cm long stem segments of Salix tetrasperma was optimal when cultured in 5.0 mg/I IAA in combination with 1.0 % glucose at 30°C, and in combination with 0.1 % glucose at 15°C. 5-Fluorodeoxyuridine (FUDR), actinomycin-D and cycloheximide all inhibited rooting and the inhibitory effect in each case increased with concentration. 5-Fluorouracil (FU), on the other hand, was ineffective. The results show that auxins probably act as a triggering agent for the synthesis of specific enzyme proteins that are required for the initiation of root primordia at the transcriptional level and that a correct balance of auxin and nutrition which may vary with the environmental conditions, is necessary for optimal rooting.

Notes: The effectiveness of GA3 in inducing floral-bud initiation in Impatiens balsamina under non-inductive photopcriods varies considerably at different parts of the year and appears to be determined by the prevailing temperature conditions. The period of floral-bud initiation is shortest in October and February and increases both with decreasing temperatures in November and with increasing temperatures in August and September. Floral buds do not initiate in March and April, during which time the temperature increases considerably subsequent to the start of experiment.

Notes: This paper deals with the effect of 100 mg/1 each of GA3 TIBA and IAA singly and in combination with each other on stem elongation, development of lateral branches and floral bud initiation in Impatiens balsamina plants exposed to 8-, 16- and 24-h photoperiods. GA3 enhances stem elongation, the enhancing effect decreasing with IAA as well as with TIBA during 8-h but increasing during 16- and 24-h photoperiods. It decreases the number of lateral branches, the decrease being greatest during 16-, less during 8- and the least during 24-h photoperiods. The time taken for floral buds to initiate with and length of branches during 16-h photoperiods.During 8-h photoperiods, IAA delays the initiation of floral buds, while GA3 hastens it when used together with TIBA or IAA or both. GA3 increases the number of floral buds on the main axis but decreases it on lateral branches, while TIBA decreases the number on the main axis but increases it on lateral branches. IAA reduces the number of floral buds on the main axis only when used alone, but on both the main axis as well as on lateral branches when used together with GA3 and TIBA. Floral buds were not produced on lateral branches when plants were treated with GA3, TIBA and IAA all together.GA3 and TIBA induced floral buds even under non-inductive photoperiods, the number of buds and reproductive nodes being less in TIBA- than in GA3-treated plants during 24-h photoperiods. The time taken for floral buds to initiate with GA3 and TIBA during noninductive photoperiods is much longer than that during 8-h inductive photoperiods with or without GA3 or TIBA application. IAA completely inhibits the GA3- and TIBA-caused induction during 24-h, but only delays it and reduces the number of reproductive nodes and floral buds during 16-h photoperiods.

Notes: Stem cuttings of Populus nigra were treated with 10 and 100 mg/1 each of IAA., IBA, 2,4-D and NAA at one month intervals and observations were recorded for the morphophysiological status of the branches, their starch content and their rooting response. — The first phase characterized by delayed, short and scarce roots and the high starch content of cuttings coincided with the onset of winter dormancy in November lasting through February. It was followed by a phase of vigorous rooting and low starch content of cuttings coinciding with the renovation of growth activity in February lasting through October, except in April and May when rooting was more or less completely nullified. — The poor rooting in winter was caused by low activity of hydrolyzing enzymes not mobilizing starch into soluble sugars; and profuse rooting during active growth period by high activity of hydrolyzing enzymes caused by endogenous auxin, resulting in mobilization of reserved food materials necessary for the initiation and development of roots. The low rooting in April and May is ascribed to the fact that bulk of the mobilized food was used up in the growth of sprouted branches leaving very little for rooting when these cuttings were planted. — The seasonal changes in the effectiveness of exogenously applied auxins also appear to be related with the level of endogenous auxin. In June endogenous auxin was high due to high meristematic activity, the exogenously applied auxins raising it to supra-optimal levels that were inhibitory. On the other hand, in October exogenously applied auxins enhanced rooting by raising it to an optimal level as the production of endogenous auxin had been decreasing gradually due to lowering temperatures. — The results demonstrate that auxin effect on differential rooting with season in this plant is determined by the physio-morphological status of the branches that govern the production of endogenous auxin and is mediated primarily through its effect on mobilization of reserve food materials caused by enhanced activity of hydrolytic enzymes.

Notes: Clubroot disease caused by Plasmodiophora brassicae is one of the major diseases of Brassica crops, often devastating to the cultivation of cruciferous crops in temperate regions. In a previous study (Moriguchi et al. 1999) identified three major quantitative trait loci (QTLs) for clubroot resistance, each in a separate linkage group, in a population derived from a cross between a clubroot-susceptible inbred cabbage line, Y2A and a resistant inbred kale line, K269. In this study, the original random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP) markers were converted into sequence-characterized amplified region (SCAR) markers to facilitate large-scale marker-assisted screening of clubroot resistance in cabbage breeding. Of 15 RAPD markers closely linked to the three QTLs, nine SCARs were developed as dominant markers after cloning and sequencing. In addition, two RAPD markers were converted into co-dominant cleaved amplified polymorphic sequence (CAPS) markers, and one RFLP marker out of three tested was converted to a dominant SCAR marker. The effect of selection for resistance by the improved markers was evaluated in progeny plants in the F2 and F3. A total of 138 F2 plants were genotyped with nine SCARs and 121 well-distributed makers consisting of 98 RAPD, 19 RFLP, two isozymes, and two morphological markers in order to estimate the level of resistance and the proportion of undesirable alleles from the kale in non-target areas in each of the F2 populations. An F2 plant, YK118, had kale alleles at QTL1, QTL3 and QTL9. Three F2 plants, namely, YK107, YK25 and YK51 had kale alleles at only QTL1, QTL3 and QTL9, respectively. These F2 plants were selected for their low proportion of alleles derived from kale in non-target regions. YK118, like the resistant kale parent, expressed very high resistance to three field isolates of Plasmodiophora brassicae, whereas the mean disease index in the F2 and F3 plants carrying only single QTLs was intermediate. The QTLs showed no differential response to the isolates. These plants with improved resistance will be useful as parental inbred lines for F1 hybrids.

Notes: Most genes for resistance to barley leaf scald map either to the Rrs1 locus on the long arm of chromosome 3H, or the Rrs2 locus on the short arm of chromosome 7H. Other loci containing scald resistance genes have previously been identified using lines derived from wild barley, Hordeum vulgare ssp. spontaneum. A single dominant gene conditioning resistance to scald was identified in a third backcross (BC3F3) line derived from an Israeli accession of wild barley. The resistance gene is linked to three microsatellite markers that map to the long arm of chromosome 7H; the closest of these loci, HVM49, maps 11.5 cM from the resistance gene. As no other scald resistance genes have been mapped to this chromosome arm, it is considered to be a novel scald resistance locus. As the Acp2 isozyme locus is linked to this scald resistance locus, at 17.7 cM, Acp2 is assigned to chromosome 7H. Molecular markers linked to the novel scald resistance gene, designated Rrs15, can be used in breeding for scald resistance.