Dehiscence of Fruit in Oilseed Rape (Brassica napus L.): I. ANATOMY OF POD DEHISCENCE

The development sequence of anatomical changes taking placewithin the pericarp tissues of Brassica napus siliquae havebeen studied at a fine- and ultra-structural level. Tissue differentiationoccurred during the initial 20 d after anthesis (DAA) and allowedthe identification of dehiscence zone cells. This descrete tissuewas subsequently further delineated by extensive lignificationof adjacent valve edge and replar vascular cells. Concomitantwith the onset of pericarp lignification, cytoplasmic contentsof the thin-walled dehiscence zone cells exhibited progressivesenescence and degradation. Wall breakdown, initially evidentin pods by 60 DAA, exclusively affected cells within the dehiscencezone, and eventually extended throughout this tissue from theepidermal suture to the locule, thus precipitating valve detachment.Ultrastructural examination confirmed that this loss of cellularcohesion was primarily attributable to middle lamella degradationand, furthermore, the dissolution of wall material was apparentlydependent on rupture of the dehiscence zone protoplast. Thesignificance of dehiscence zone cell modifications in relationto autolytic cell wall breakdown, together with possible implicationsfor the regulation of pod shatter, are discussed. Key words: Oilseed rape, Brassica napus, pod shatter, dehiscence zone, cell wall breakdown     

Dehiscence of Fruit in Oilseed Rape (Brassica nap us L.): II. THE ROLE OF CELL WALL DEGRADING ENZYMES AND ETHYLENE

Pod shatter in oilseed rape is accompanied by the degradationof the cell wall at the site of fruit dehiscence. Cell separationis preceded by an increase in the activity of the hydrolyticenzyme cellulase (ß 1,4-glucanase, E.C. 3.1.2.4 [EC] ),and this rise in enzyme activity is restricted to the dehiscencezone cells. In contrast, the activity of the cell wall degradingenzyme polygalacturonase (E.C. 3.2.1.15 [EC] ) exhibits no correlationeither temporally or spatially with pod dehiscence. An analysisof the ethylene production profile by intact pods during maturationhas revealed the existence of an ethylene climacteric and thisis temporally correlated with the tissue-specific increase incellulase activity. The major site of ethylene production bythe fruit has been identified to be the developing seed. Sincemaintenance of intact pods in ethylene accelerates both thesenescence and dehiscence of the tissue, it is possible thatthis gaseous regulator plays an important role in the processof pod shatter in vivo. Key words: Oilseed rape, Brassica napus, pod shatter, cellulase, polygalacturonase, ethylene     

Genome-Wide Delineation of Natural Variation for Pod Shatter Resistance in Brassica napus

Resistance to pod shattering (shatter resistance) is a target trait for global rapeseed (canola, Brassica napus L.), improvement programs to minimise grain loss in the mature standing crop, and during windrowing and mechanical harvest. We describe the genetic basis of natural variation for shatter resistance in B. napus and show that several quantitative trait loci (QTL) control this trait. To identify loci underlying shatter resistance, we used a novel genotyping-by-sequencing approach DArT-Seq. QTL analysis detected a total of 12 significant QTL on chromosomes A03, A07, A09, C03, C04, C06, and C08; which jointly account for approximately 57% of the genotypic variation in shatter resistance. Through Genome-Wide Association Studies, we show that a large number of loci, including those that are involved in shattering in Arabidopsis, account for variation in shatter resistance in diverse B. napus germplasm. Our results indicate that genetic diversity for shatter resistance genes in B. napus is limited; many of the genes that might control this trait were not included during the natural creation of this species, or were not retained during the domestication and selection process. We speculate that valuable diversity for this trait was lost during the natural creation of B. napus. To improve shatter resistance, breeders will need to target the introduction of useful alleles especially from genotypes of other related species of Brassica, such as those that we have identified.     

Identification of genome regions controlling cotyledon,pod wall/seed coat and pod wall resistance to pea weevil through QTL mapping

Pea weevil, Bruchus pisorum, is one of the limiting factors for field pea (Pisum sativum) cultivation in the world with pesticide application the only available method for its control. Resistance to pea weevil has been found in an accession of Pisum fulvum but transfer of this resistance to cultivated pea (P. sativum) is limited due to a lack of easy-to-use techniques for screening interspecific breeding populations. To address this problem, an interspecific population was created from a cross between cultivated field pea and P. fulvum (resistance source). Quantitative trait locus (QTL) mapping was performed to discover the regions associated with resistance to cotyledon, pod wall/seed coat and pod wall resistance. Three major QTLs, located on linkage groups LG2, LG4 and LG5 were found for cotyledon resistance explaining approximately 80 % of the phenotypic variation. Two major QTLs were found for pod wall/seed coat resistance on LG2 and LG5 explaining approximately 70 % of the phenotypic variation. Co-linearity of QTLs for cotyledon and pod wall/seed coat resistance suggested that the mechanism of resistance for these two traits might act through the same pathways. Only one QTL was found for pod wall resistance on LG7 explaining approximately 9 % of the phenotypic variation. This is the first report on the development of QTL markers to probe Pisum germplasm for pea weevil resistance genes. These flanking markers will be useful in accelerating the process of screening when breeding for pea weevil resistance.     

我国格木的地理分布与种实表型变异

在调查格木(Erythrophleum fordii)主要天然分布区及资源现状的基础上, 研究了荚果和种子的11个表型性状在8个格木天然群体内和群体间的变异规律, 探讨了种实表型变异与地理、环境因子的相关性。结果显示: 格木天然林主要分布在广西、广东和福建3省区北回归线附近低海拔地区, 大部分呈散生状态或小群体; 格木荚果和种子的长度、宽度、形态指数以及每个荚果内种子数、种子厚度和千粒重在群体间和群体内单株间均存在显著差异; 荚果性状在群体间和群体内的变异均大于种子性状; 每个荚果内种子数与荚果的长度、形态指数以及种子的长度、大小呈显著正相关, 种子长度和宽度与荚果大小、种子千粒重与荚果宽度均呈显著正相关; 荚果形态指数与经度呈显著负相关, 种子千粒重与纬度、种子宽度与海拔和年降雨量、种子形态指数与年均气温、种子大小与年降雨量均呈显著正相关。通过聚类分析可将8个格木群体分为3类: GX03单独为1类, GX01与GX02聚为1类, 其余5个群体聚为1类。研究结果为进一步开展格木保护生物学和遗传育种研究奠定了基础。     

我国格木的地理分布与种实表型变异

在调查格木（Erythrophleum fordii）主要天然分布区及资源现状的基础上,研究了荚果和种子的11个表型性状在8个格木天然群体内和群体间的变异规律,探讨了种实表型变异与地理、环境因子的相关性。结果显示：格木天然林主要分布在广西、广东和福建3省区北回归线附近低海拔地区,大部分呈散生状态或小群体：格木荚果和种子的长度、宽度、形态指数以及每个荚果内种子数、种子厚度和千粒重在群体间和群体内单株间均存在显著差异：荚果性状在群体间和群体内的变异均大于种子性状：每个荚果内种子数与荚果的长度、形态指数以及种子的长度、大小呈显著正相关,种子长度和宽度与荚果大小、种子千粒重与荚果宽度均呈显著正相关：荚果形态指数与经度呈显著负相关,种子千粒重与纬度、种子宽度与海拔和年降雨量、种子形态指数与年均气温、种子大小与年降雨量均呈显著正相关。通过聚类分析可将8个格木群体分为3类：GX03单独为1类,GX01与GX02聚为1类,其余5个群体聚为1类。研究结果为进一步开展格木保护生物学和遗传育种研究奠定了基础。     

扁蓿豆不同分布区野生居群形态多样性研究

结合数量统计分析对扁蓿豆14个居群的14项形态特征进行了研究,结果表明:除叶长、荚果长、荚果宽、荚果形状、种子长和千粒重以外,其余形态性状在居群间或居群内都表现显著差异;以14个形态性状为基础的聚类分析将所研究的14个居群分为4类;主成分分析结果显示株高、叶面积、花序结荚数、花序种子数和种子宽等5个性状是造成扁蓿豆表型差异的主要因素.     

Morphology of the slashed pod trait in lentil

Reducing losses from pod shatter is a major goal of most lentil (Lens culinaris) improvement programs, however, genetic variability is limited. Recently, a slashed pod trait was suggested to have potential value for reducing losses from shattering, but little was known about the trait. In this study we determined the anatomical features which were associated with the slashed pod trait. Histological specimens from ‘Brewer’ lentil (normal pods) and from germplasm lines expressing the slashed pod trait were compared to each other and to specimens from normal and reduced pod parchment pea (Pisum sativum) lines. Reduced parchment pea pods had less sclerenchyma tissue and fewer fibers than pea pods with normal parchment, but all lentil pods examined had comparable sclerenchyma tissue with similar quantities of fiber. The slashed pod trait was not the result of reduced sclerenchyma tissue (parchment) as had been previously suggested. Apparently, the slashed pod trait resulted from the stresses which develop between fiber cells within the sclerenchyma layer of the pod wall during pod maturation and drying. The trait had little effect on quality of seeds for human utilization in the environments tested but may have an undesirable effect in other environments. Although seed loss due to shatter appeared to be decreased in pods exhibiting the trait, the uncertainty of expression due to environmental influences makes the trait an unlikely candidate for use in lentil improvement programs.     

Rate of Increase in Size and Dry Weight of Individual Pods of Field Grown Soya Bean Plants

The dry weight of the whole fruit, the pod wall and an enclosedseed of randomly harvested soya beans is estimated from theexternal dimensions of the attached pod. The relations betweendimensions and dry weight are independent of cultivar and growthcondition and can be used on pods from 1 cm in length untilthe seeds reach their maximum fresh weight. Dimensions of tagged pods of three cultivars of field grownsoya beans differing in time to reach maturity were measuredevery 2–3 days from initial pod elongation until maturation.Dry weights for each pod were estimated from the dimensions,and the dry weight accumulation with time was fitted to thelogistic function to find the growth rate that best characterizedthe data for each pod. The final weight, the specific growthrate and the maximum growth rate of the whole fruit, the podwall and a single seed were subjected to analysis of variance. The most significant difference between pods of these cultivarswas the specific growth rate of individual seeds, which decreasedwith increasing maturity group. There were no differences ingrowth of the pod wall. However, most of the variation was betweenindividual pods within a cultivar, where the rate of dry weightaccumulation of the whole fruit, governed largely by the seedgrowth rate times the number of seeds, was highly correlatedwith the earlier growth of the pod wall. This suggests thatthe growth of individual whole fruit was determined early inpod development and was slightly influenced by factors appliedduring the period of rapid seed growth. Glycine max (L.) Merrill, Soya bean, seed growth analysis, specific growth rate     

内蒙古东部地区小叶锦鸡儿表型变异研究

根据小叶锦鸡儿(Caragana microphylla Lam.)资源分布状况,对内蒙古东部地区的13个小叶锦鸡儿天然居群进行表型变异研究。结果表明：小叶锦鸡儿表型性状在居群间均表现为极显著差异（p<0.001）;主成分分析显示种子宽、种子长、荚果长是小叶锦鸡儿表型变异的最主要影响因子;回归分析和偏相关分析显示地理生态因子对小叶锦鸡儿的表型变异有较强的影响;通过聚类分析将13个小叶锦鸡儿居群分为3类。     

Musculotendon variability influences tissue strains experienced by the biceps femoris long head muscle during high-speed running

The hamstring muscles frequently suffer injury during high-speed running, though the factors that make an individual more susceptible to injury remain poorly understood. The goals of this study were to measure the musculotendon dimensions of the biceps femoris long head (BFlh) muscle, the hamstring muscle injured most often, and to use computational models to assess the influence of variability in the BFlh’s dimensions on internal tissue strains during high-speed running. High-resolution magnetic resonance (MR) images were acquired over the thigh in 12 collegiate athletes, and musculotendon dimensions were measured in the proximal free tendon/aponeurosis, muscle and distal free tendon/aponeurosis. Finite element meshes were generated based on the average, standard deviation and range of BFlh dimensions. Simulation boundary conditions were defined to match muscle activation and musculotendon length change in the BFlh during high-speed running. Muscle and connective tissue dimensions were found to vary between subjects, with a coefficient of variation (CV) of 17±6% across all dimensions. For all simulations peak local strain was highest along the proximal myotendinous junction, which is where injury typically occurs. Model variations showed that peak local tissue strain increased as the proximal aponeurosis width narrowed and the muscle width widened. The aponeurosis width and muscle width variation models showed that the relative dimensions of these structures influence internal muscle tissue strains. The results of this study indicate that a musculotendon unit’s architecture influences its strain injury susceptibility during high-speed running.     

Anatomical and Biochemical Changes Associated with the Induction of Oilseed Rape (Brassica napus) Pod Dehiscence by Dasineura brassicae (Winn.)

Dehiscence of pods at an early stage of development is a characteristicof oilseed rape pods damaged by Dasineura brassicae (pod midge).Anatomical examination of pods exhibiting symptoms of infestationrevealed a loss of cohesion between intact cells of the dehiscencezone, a narrow tissue of thin-walled cells present between thevalve margins. Determination of hydrolytic enzyme activity inpericarp tissues of damaged siliquae showed localized enhancementof both polygalacturonase (EC 3.2.1.15 [EC] ) and cellulase (ß1,4 glucanase, EC 3.1.2.4 [EC] ) activity, positionally consistent withthese factors being responsible for the observed cell wall degradation.Mechanistic similarities of midge-induced and maturation-associatedpod dehiscence are discussed. Oilseed rape, Brassica napus L. cv., Bienvenu, pod shatter, pod midge, Dasineura brassicae (Winn.), cellulase, polygalacturonase     

内蒙古扁蓿豆野生资源形态学特性研究

对产自内蒙古不同分布区12份扁蓿豆种质资源的12个形态性状进行主成分和聚类分析。结果表明,除荚果形状和种子宽外,其余形态性状在材料间都表现显著差异,扁蓿豆种质资源遗传变异丰富;通过多变量的主成分分析,第一主成分和第二主成分代表了扁蓿豆形态多样性的62.30%,枝条长、叶面积、荚果宽、种子长和千粒重等5个性状是造成扁蓿豆表型差异的主要因素;基于形态性状的聚类分析把12份材料聚为4类,其中第 1类MR-12扁蓿豆资源的株高、枝条长和株丛直径明显高于其他类,叶片大且叶量丰富,营养性状表现良好;结实性状中荚果长和千粒重较大,综合性状表现较好,可以作为合适的材料作为引种驯化和育种的试验材料。     

皂荚南方天然群体种实表型多样性

以系统揭示表型变异程度和变异规律为目的, 对皂荚(Gleditsia sinensis)南方分布区的10个天然群体的11个种实性状进行了比较分析。采用方差分析、多重比较、相关分析等多种分析方法, 对群体间和群体内的表型多样性以及与地理、环境因子的相关性进行了讨论。方差分析结果表明; 皂荚果实、种子等性状在群体间和群体内存在丰富的变异, 11个性状在群体间、群体内均达显著差异; 荚果性状在群体间和群体内的变异均大于种子性状, 11个性状的平均表型分化系数为20.42%, 群体内的变异(32.28%)大于群体间的变异(7.19%), 群体内的变异是皂荚的主要变异来源; 皂荚各性状平均变异系数为11.20%, 变异幅度为4.55%-18.38%。群体间荚果的变异(14.75%)高于群体间种子变异(6.95%), 表明种子变异稳定性高。荚果和种子各性状之间多呈极显著或显著正相关, 表现为荚果越大, 则种子越大, 种子的千粒重也越大; 荚果表现为同地理经度的南北变异, 种子则表现为同地理纬度的东西变异。研究结果为进一步开展皂荚遗传育种、保护生物学研究和皂荚种质资源利用奠定了基础。     

四川省不同天然种群珙桐叶片解剖结构与其耐热性的关系

以四川省15个珙桐种群为试材,采用石蜡切片法、NaClO法观察叶片16项解剖结构,应用变异系数、聚类分析、相关性分析对叶片解剖结构进行筛选,利用隶属函数法对不同种群的耐热性进行综合评价,以期了解珙桐应对热胁迫的生理变化机制,为野生珙桐资源的保护及园林应用提供参考。结果表明：珙桐叶片为异面叶,气孔主要分布于下表皮。16项解剖结构指标在不同种群间达到极显著差异水平;栅海比、栅栏组织厚度、气孔密度、下表皮角质厚度、主脉凸起度、上表皮角质层厚度、下表皮细胞厚度是影响珙桐耐热性的主要解剖结构指标,叶厚度、海绵组织厚度、主脉厚度、上表皮细胞厚度、主脉维管束厚度、气孔长度、气孔宽度、叶片结构紧密度、叶片结构疏松度与耐热性关系不大;15个珙桐种群耐热性存在一定差异,其强弱顺序为：汉源 > 筠连 > 雷波 > 沐川 > 屏山 > 荥经 > 天全 > 美姑 > 平武 > 碧峰峡 > 北川 > 洪雅 > 宝兴 > 大邑 > 邛崃;15个种群耐热性大致分为4类：汉源种群为耐热型,筠连、雷波、沐川等3个种群为中度耐热型,屏山、荥经、天全、美姑、平武、碧峰峡、北川为低耐热型,洪雅、宝兴、雷波、邛崃等4个种群为不耐热型。     

贵州省野生皂荚种实表型性状多样性分析

为深入了解贵州省野生皂荚(Gleditsia sinensis)荚果表型性状的遗传多样性及其变异类型,为皂荚的遗传改良、种质鉴定、亲本选择以及品种培育奠定理论基础。该研究以贵州省7个野生皂荚群体70个个体为研究对象,采用方差分析、主成分分析、相关性分析及多性状综合评价等方法对皂荚群体的10个种实表型性状进行系统分析和综合评价。结果显示：(1)所测皂荚的表型性状差异在群体内均达到极显著水平(P＜0.01);在群体间,除每荚粒数、种子宽、种子长宽积以及种子长宽比之外,其余表型性状的差异均达极显著水平(P＜0.01)。(2)7个居群野生皂荚各性状平均变异系数为21.16%,其中凯里市(P4)居群的变异系数最高(24.44%);居群间荚果的变异(29.22%)高于种子的变异(11.04%),且变异主要来自于群体内。(3)相关分析显示,皂荚种实各性状之间存在不同程度的关联性;主成分分析显示,前4个主成分(皂荚种子大小、单个荚果出籽数量、种子形态指数因子、与荚果长和种子厚相关的因子)的累积贡献率达69.783%,可基本反映皂荚表型性状的大部分信息;以10个种实性状对皂荚野生群体进行综合评价发现,来自于惠水县(P7)群体的皂荚种实性状综合评价最高。研究表明,贵州省野生皂荚在群体间及群体内具有丰富的表型变异,且群体内的变异大于群体间的变异,变异主要来自于群体内。     

Odontometric variations of permanent crown in Punjabi and U.S. twins

The study reports odontometric variations within and between Punjabi and U.S. twins. The data are based on 23 MZ and 35 DZ Punjabi twin pairs and 32 MZ and 43 DZ U.S. pairs. None of the t' tests indicates differences between MZ and DZ mean dental dimensions in either sample. Mean tooth dimensions of Punjabi twins are in general greater than those of U.S. twins with significant differences for about 25% of the traits. Coefficient of variation is highest in lateral incisors and canines and lowest in first molars in both samples. The two samples differ more in their variances than in their means. The results indicate that buccolingual dimensions of mandibular traits are under relatively greater selection pressure.