Intraspecific variation in the ultraviolet colour proportion of flowers in Brassica rapa L.

In Brassica rapa L., intraspecific variation in the ultraviolet (UV) colour proportion invisible to humans but visible to insect pollinators, was investigated by UV‐photographing. After digitization of each photograph, the UV‐absorbing area (UVA) and total flower area (FA) were evaluated by means of image analysis. The ratio of UVA to FA represented the UV colour proportion (UVP). Nested anova indicated that the proportion of the variance caused by the genotypic effect was largest for UVP, and anova indicated that the F‐value for UVP was larger than that for FA. These results indicate that UVP is very stable within a genotype. That is, there was almost no additional variation caused by plants and branches. In contrast, UVP varies widely between genotypes with respect to FA. The large differences in the UVP of B. rapa flowers are likely to be distinguishable by insect pollinators, which might use these differences as visual cues in their foraging flight.     

Cytogenetics of Brassica juncea×Brassica rapa hybrids and patterns of variation in the hybrid derivatives

Interspecific hybridization is an important tool to elucidate intergenomic relationships, transfer characters across species and develop synthetic amphidiploids, and it has been widely applied for improving Brassicas. The objective of the present study was to create genetic variability in Brassica through interspecific hybridization. Crosses between Brassica juncea (AABB, 2n= 36), and Brassica rapa (AA, 2n = 20) vars toria, yellow sarson, and brown sarson were attempted, and the hybrid derivatives were advanced to the F4 generation. Hybrids were obtained from the crosses B. juncea× toria and B. juncea× yellow sarson. The F₁ plants were vigorous and intermediate to the parents in many morphological traits. The meiotic study of AAB hybrids showed 10 II + 8 I in the majority (71.8%) of cells analysed. A maximum of 12 and a minimum of seven bivalents were also observed in a few cells. The occurrence of multivalent associations (trivalents to pentavalents) at diakinesis/metaphase I and a bridge‐fragment configuration at anaphase I were attributed to homoeology between A and B genomes. A high percentage of plants resembling B. juncea was observed in the F₂ generation. Transgressive segregation in both directions was found for plant height, primary branches, main raceme length, siliquae on main raceme, siliqua intensity, seeds per siliqua and seed yield. There were significant differences for the 14 characters in the F₄ derivatives. Moderate to high estimates of phenotypic and genotypic coefficients of variation, broad‐sense heritability, and expected genetic advance were found for seed yield, 1000‐seed weight, siliquae per plant, seeds per siliqua and days to flowering. Intergenomic recombination, reflected as wide variation in the hybrid progenies, permitted the selection of some useful derivatives.     

Combination of resistance to Verticillium longisporum from zero erucic acid Brassica oleracea and oilseed Brassica rapa genotypes in resynthesized rapeseed (Brassica napus) lines

Resynthesized (RS) forms of rapeseed (Brassica napus L.; genome AACC, 2n = 38) generated from interspecific hybridization between suitable genotypes of its diploid progenitors Brassica rapa L. (syn. campestris; genome AA, 2n = 20) and Brassica oleracea L. (CC, 2n = 18) represent a potentially useful resource to introduce resistance against the fungal pathogen Verticillium longisporum into the gene pool of oilseed rape. Numerous cabbage (B. oleracea) accessions are known with resistance to V. longisporum; however, B. oleracea generally has high levels of erucic acid and glucosinolates in the seed, which reduces the suitability of resulting RS rapeseed lines for oilseed rape breeding. In this study resistance against V. longisporum was identified in the cabbage accession Kashirka 202 (B. oleracea convar. capitata), a zero erucic acid mutant, and RS rapeseed lines were generated by crossing the resistant genotype with two spring turnip rape accessions (B. rapa ssp. olerifera) with zero erucic acid. One of the resulting zero erucic acid RS rapeseed lines was found to have a high level of resistance to V. longisporum compared with both parental accessions and with B. napus controls. A number of other zero erucic acid RS lines showed resistance levels comparable to the parental accessions. In the most resistant RS lines the resistance and zero erucic acid traits were combined with variable seed glucosinolate contents. Erucic acid‐free RS rapeseed with moderate seed glucosinolate content represents an ideal basic material for introgression of quantitative V. longisporum resistance derived from B. oleracea and B. rapa into elite oilseed rape breeding lines.     

油菜花发育同源异型基因BAP2的克隆及序列分析

拟南芥(Arapidopsis)同源异型基因AP2对花分生组织和花器官的发育具有重要的表达调控作用。根据AP2基因信息利用同源序列法分离了油菜(Brassicarapa)的AP2基因(BAP2,GenBank登陆号:AF941097),并且比较了正常油菜与无花瓣油菜BAP2基因序列的差异。研究结果表明,BAP2基因的DNA序列长度为2138bp,包含9个内含子,外显子区与AP2基因的同源性达90%以上;推导的氨基酸序列为433aa,具有完整的核定位信号区和高度保守的AP2结构域,推测与AP2基因具有相似的功能。正常油菜和无花瓣油菜的BAP2基因序列仅有2处碱基存在差异,这2处碱基均位于内含子区,推导的氨基酸序列则完全一致,因此初步认为白菜型油菜花瓣缺失突变与BAP2基因无关。     

果洛地区芜菁栽培试验

在青南海拔高度近4000m的地区种植芜菁产量在8133-12333kg/hm^2之间，其块茎产量与燕麦干草产量基本一致。试验结果表明当地引进训化品种优于引进品种，紫芜菁优于白芜菁。作为多汁饲料适宜在青南牧区推广种植。     

Effect of temperature on primary infection by Plasmodiophora brassicae and initiation of clubroot symptoms

A study was conducted to assess the effect of temperature on infection and development of Plasmodiophora brassicae in root hairs of Shanghai pak choi (Brassica rapa subsp. chinensis) and on initiation of clubroot symptoms. Ten‐day‐old seedlings were grown in liquid‐sand culture, inoculated with resting spores and maintained in growth cabinets at 10, 15, 20, 25 and 30°C. Seedlings were harvested at 2‐day intervals, starting 2 days after inoculation (DAI) and continuing until swelling of the tap root was observed (maximum 28 days). Roots were assessed for root hair infection (RHI), stage of development of infection (primary plasmodia, zoosporangia, release of zoospores, secondary plasmodia), symptom development, and for clubroot severity at 24 DAI. Temperature affected every stage of clubroot development; RHI was highest and visual symptoms initiated earliest at 25°C, intermediate at 20 and 30°C, and lowest and latest at 15 and 10°C. Root hair infection was observed at every temperature, but clubroot symptoms developed only above 15°C. A substantial delay in the development of the pathogen was observed at 10 and 15°C. No symptoms were observed at 28 DAI in plants grown at 10°C. Swelling of the tap root was visible at 28 DAI in plants at 15°C, 14 DAI at 20 and 30°C, and 10 DAI at 25°C. These results support and explain the observation in companion studies that cool temperatures result in slower development of clubroot symptoms in brassica crops.     

白菜雄性不育相关基因BcMF3功能的反义RNA验证

为了研究白菜等十字花科植物花粉发育及雄性不育发生的机理,根据编码果胶甲酯酶的白菜雄性不育相关基因BcMF3的cDNA序列设计特异引物,从普通白菜(Brassica campestris ssp.chinensis var.communis,syn.B.rapa ssp.chinensis var.communis)花蕾cDNA中扩增出458 bp的片断,构建BcMF3的反义RNA植物表达栽体,然后转化菜心(B. campestris ssp.chinensis var.parachinensis).研究发现,31.3%菜心转基因植株花粉表现出畸形,而且只有部分花粉具有活力,花粉离体萌发率降低为31.6%,其花药果胶甲酯酶活性降低了12.8%.上述结果表明BcMF3基因与普通白菜和菜心等白菜植物的花粉发育密切相关.     

白菜雄性不育相关基因BcMF4的反义RNA验证

根据普通白菜(Brassica campestris ssp.chinensis var.communis)雄性不育相关基因BcMF4的cDNA序列设计特异引物,从普通白菜花蕾cDNA中扩增出607 bp的片断,然后将该片段连接至双元载体pBI12l中,得到反义RNA植物表达载体并导入农杆菌LBA4404菌株中;通过组织培养途径转化菜心(B.campestris ssp.chinensis var.parachinensis),得到了12株转基因植株,其中5株的43.7%的花粉为缩小空瘪畸形,29.6%的花粉缺乏生活力,而且其花粉离体萌发率降低至24.7%.结果表明,反义RNA技术沉默BcMF4基因导致了菜心转基因植株的部分花粉发育不良,BcMF4基因在普通白菜和菜心等花粉发育中起着重要作用.     

8个白菜型冬油菜品种抗寒性的初步评价

以8个抗寒性不同的白菜型冬油菜为试验材料,研究了冬油菜品种的抗寒性与越冬率、植物学特征、生长发育特性、干物质积累特性等指标的关系.结果表明:参试品种可划分为4种类型,即超强抗寒性品种、强抗寒品种、抗寒性品种和一般抗寒品种.抗寒性强的品种MXW-1,DQW-1冬前生长发育较缓慢,匍匐生长,叶色浓绿,叶脉微紫,越冬期叶片数偏少,平均为8～9片,较早进入枯叶期.根系发达,根冠比大.返青晚,成熟期晚,生育期较长.