Effects of inoculum concentration, leaf age and wetness period on the development of dark leaf and pod spot (Alternaria brassicae) on oilseed rape (Brassica napus)

Experiments were done under controlled environment and glasshouse conditions to study the effects of inoculum concentration, leaf age and wetness period on the development of dark leaf and pod spot (Alternaria brussicae) on oilseed rape (Brassica napus). On leaves of potted oilseed rape plants (cv. Bienvenu) inoculated with A. brassicae conidial suspensions, the severity (number of lesions cm^-2) of dark leaf spot increased as inoculum concentration increased from 80 to 660 spores ml^-1and as leaf age increased from 4 to 14 days. On pods on detached racemes of spring oilseed rape (cv. Starlight), the incidence of dark pod spot (% of pods diseased) increased as inoculum concentration increased from 80 to 10⁴spores ml^-1. Increasing inoculum concentration above 10⁴spores ml^-1did not increase the incidence but did increase the severity of dark pod spot. A minimum wetness period of 4 h was needed for infection of oilseed rape leaves (cv. Envol) by A. brussicue at 18°C and disease severity increased with increasing wetness period up to 12 h. The length of dry interruptions after 3–8 h of initial wetness affected the severity of dark leaf spot. A second wetness period increased the severity of dark leaf spot if the dry interruption was ≤ 6 h and if the first wetness period was ≤ 8 h. The incubation period of A. brassicae decreased from 3.5 to 2.5 days as inoculum concentration increased from 80 to 660 spores ml^-on leaves (cv. Bienvenu) at 17–25°C and from 3.8 to 1.0 day as inoculum concentration increased from 80 to ≥2 ≥ 10³spores ml^-1on pods (cv. Starlight) at 18°C.     

A RFLP-based linkage map of mustard [Brassica juncea (L.) Czern. and Coss.]

 A genetic linkage map of Brassica juncea was constructed based on restriction fragment length polymorphism (RFLP) detected by anonymous cDNA markers from B. napus, using a segregating F₁-derived doubled haploid (DH) progeny from a cross between a canola-quality mustard line (J90-4317) and a high-oil-content mustard line (J90-2733). The RFLP probes consisted of 229 cDNA probes from B. napus and a B. napus tandem repeat sequence, RDA2. The map consisted of 343 marker loci arranged in 18 major linkage groups plus five small segments with two to five marker loci, covering a total map distance of 2073 cM. Twenty-four percent of the markers were dominant in nature. Sixty-two percent of the marker loci were duplicated, and the majority were involved in inter-linkage group duplications, illustrating that complex duplications and subsequent rearrangements occurred after allopolyploidy. Deviation from the Mendelian segregation ratio for a DH population was observed for 27% of the markers. Two-thirds of these markers with a skewed segregation were clustered in 6 linkage groups and two unassigned segments. The overall average marker interval of the B. juncea map reported here was 6.6 cM, which would provide a marker density satisfactory for efficient use of the map in breeding applications, such as tagging of important agronomic traits and marker-assisted selection. Received: 14 May 1996 / Accepted: 11 October 1996     

The relative importance of glucosinolates and amino acids to the development of two aphid pests Brevicoryne brassicae and Myzus persicae on wild and cultivated brassica species

This paper describes an experiment to investigate the relative importance of glucosinolates and the availability of free amino acids in the phloem to the feeding behaviour and development of the specialist brassica aphid, Brevicoryne brassicae (L) (cabbage aphid) and the generalist, Myzus persicae, (Sultzer) (peach potato aphid). Aphid development was determined on brassica species and cultivated brassica varieties. Analysis of individual glucosinolates in the wild brassica species identified significant differences in their profiles and in their concentrations present in freeze dried leaves. Multiple regression analysis showed a significant correlation ( ) between the intrinsic rate of increase of B. brassicae and glucosinolate concentrations; four glucosinolates, 2-OH-3-butenyl, and 2-propenylglucosinolate, 3-methoxyindolyl and 4-pentenylglucosinolates accounted for 79% of the variation. The intrinsic rate of increase of M. persicae was less correlated, though still significant ( ); 3-indolyglucosinolate and 3-butenylglucosinolate accounted for 47% of the variation. Regression analysis also showed a correlation between phloem amino acid concentrations and the intrinsic rate of increase of B. brassicae ( ) but not of M. persicae. The concentration of the important amino acids tyrosine, alanine, leucine and glutamic acid, accounted for 43% of the variation in intrinsic rate of increase. Leaf water potential of the Brassica species showed no relationship with the intrinsic rate of increase of either B. brassicae or M. persicae.     

Characterization of progenies of Triticum aestivum- Psathyrostachys juncea derivatives by using genomic in-situ hybridization

Using genomic in-situ hybridization (GISH) technique, 7 translocation-addition lines, 6 transloca-tion and translocation-addition lines, 2 ditelosomic addition lines and 1 translocation line were identified from Triticum aestivum L.-Psathyrostachys juncea (Fisch. ) Nevski intergeneric hybrids, of which translocation-addition and translocation and translocation-addition lines were not found in other reports. No substitutions and disomic additions were detected in the hybrids and breakages occurred in all P. juncea chromosomes studied. Results have shown that the improved GISH technique is a rapid and economical method for use in this field.     

油菜游离细胞培养及易再生的体细胞无性系的建立

以芥菜型油菜(Brcssica juncea)下胚轴来源的愈伤组织为材料,进行悬浮细胞振荡培养,得到游离的单细胞。这些细胞作浅层液体静置培养,可获得高频率的愈伤组织。在附加有水解乳蛋白200毫克/升、BA 2—3毫克/升及GA,0.1—1毫克/升的MS培养基上,这些愈伤组织分化了芽。分化的芽在无激素或附加有0.01—0.1毫克/升IAA或NAA的MS培养基上长出根,从而发育成完整植株。当对游离细胞获得的再生植株的茎切段愈伤组织,再经上述程序进行细胞培养时,发现愈伤组织诱导率及愈伤组织分化频率均远远高于原供体,从而建立了B.juncea易再生的体细胞无性系。     

Population fluctuations of cabbage aphid,Brevicoryne brassicae (L.) (Hom.: Aphididae) and its natural parasitism rate on different canola cultivars

The cabbage aphid, Brevicoryne brassicae is one of the most destructive pests in Cruciferaceae or Brassicaceae plant family around the world. According to this pest rapid resistance to insecticide, using the resistant cultivars should be evaluated. In the present study, the different canola cultivars resistance against the cabbage aphid and the population fluctuations in canola fields and also the natural parasitism are evaluated in Shahre-rey region. To evaluate the population fluctuations and its natural parasitism on the RGS003, SLMOO46, Karag2, Licord, Sarigol, Opera, Ocapi and Talaei canola cultivars were cultivated in four replications using the complete randomised block design. The population fluctuations studies showed that the pest is active during the canola growth period in studied region, but the peak of population and damage is found in 6 May month. The results showed that natural parasitism percentage of cabbage aphid on different canola cultivars has not significant difference, but the parasitism amount in different sampling dates was significantly different, so that the natural parasitism maximum observed in date 29 April. These results showed that the different canola cultivars have significant effects on cabbage aphid and parasitoids activity amount. Using the present results, the recognised cultivars in integrated pest management programmes can be used to grow the laboratory aphids as the parasitoids hosts.     

Floral structure, breeding system and fruit-set in the threatened sub-shrub Tetratheca juncea Smith (Tremandraceae)

Tetratheca juncea Smith (Tremandraceae) has undergone a range contraction of approx. 50 km in the last 100 years and is now listed as a vulnerable sub-shrub restricted to the central and north coast regions of New South Wales, Australia. There are approx. 250 populations in a 110 km north-south distribution and populations are usually small with fewer than 50 plants/clumps. The reproductive ecology of the species was studied to determine why seed-set is reportedly rare. Flowers are bisexual, odourless and nectarless. Flowers are presented dependentally and there are eight stamens recurved around the pistil. Anthers are poricidal, contain viable pollen and basally contain a deep-red tapetal fluid that is slightly oily. Thus flowers are presented for buzz pollinators, although none were observed at flowers during our study. The species was found to be facultatively xenogamous with only one in 50 glasshouse flowers setting seed autogamously, i.e. without pollinator assistance. Field studies revealed fertile fruit in 24 populations but production varied significantly across sites from exceedingly low (0.6 fruits per plant clump) to low (17 fruits per plant clump). Fruit-set ranged from 0 to 65 %, suggesting that pollen vectors exist or that autogamy levels in the field are variable and higher than glasshouse results. Fruit production did not vary with population size, although in three of the five populations in the south-west region more than twice as much fruit was produced as in populations elsewhere. A moderately strong relationship between foliage volume and fruit : flower ratios suggests that bigger plants may be more attractive than smaller plants to pollinators. A review of Tetratheca pollination ecology revealed that several species are poorly fecund and pollinators are rare. The habitat requirements for Tetratheca, a genus of many rare and threatened species, is discussed.     

Recombination between chloroplast genomes of Trachystoma ballii and Brassica juncea following protoplast fusion

We document here the presence of a recombinant plastome in a cytoplasmic male sterile (CMS) line of Brassica juncea developed from the somatic hybrid Trachystoma ballii + B. juncea. Restriction endonuclease digestion of the chloroplast (cp) DNA has revealed that the recombinant plastome gives rise to novel fragments in addition to the parent-specific fragments. Analysis of the 16S rRNA region by Southern hybridization shows no variation between B. juncea, T. ballii and the CMS line. The rbcL gene region of the recombinant plastome is identical to that in T. ballii. Analysis with probes for psbA and psbD using single and double DNA digests indicates that the hybridization patterns of the recombinant plastome are identical to those of the parents in digests obtained with some restriction enzymes, while novel bands hybridize to probes in other digests. In the psbA region, a B. juncea-specific PstI site and a T. ballii-specific EcoRI site are found in the recombinant plastome. The psbD region of the recombinant plastome contains a B. juncea-specific HindIII site and T. ballii-specific BamHI and HpaII sites. These results indicate the occurrence of intergenomic recombination between the chloroplasts of T. ballii and B. juncea in the somatic hybrid from which the CMS line was developed. The recombined plastome appears to be a mosaic of fragments specific to both parents and the recombination event has occurred in the single-copy regions. These recombinational events have not caused any imbalance in the recombinant plastome in terms of chloroplast-related functions, which have remained stable over generations. Received: 3 March 1998 / Accepted: 5 August 1998     

Genetic Transformation of Brassica juncea var. tsatsi Induced by Ri T-DNA of Agrobacterium rhizogenes

Hairy roots of mustard (Brassica juncea var. tsatsi) cv. "Paoye' were obtained from in vitro inoculation of reversely inserted petioles with Agrobacteriurn rhizogenes strain LBA9402 harbouring the agropine-type Ri plasmid (pRi1855). The root inducing rate was 100%. Transformed roots grew rapidly on hormone-free MS medium and showed typical hairy root phenotype. Transformed plantlets regenerated from hairy roots on MS medium supplemented with BA 8.0 mg/L and NAA 0.6 mg/L. Opine analysis evidenced the integration and expression of TR-DNA, PCR analysis and Southern hybridization confirmed the integration of TL-DNA including 862 bp rol B sequence in the transformed plants.