Genotype × environment interactions for shoot fly resistance in sorghum (Sorghum bicolor (L.) Moench): Response of recombinant inbred lines

Sorghum shoot fly (Atherigona soccata) is a serious pest that destabilizes the performance of sorghum cultivars and ultimately reduces sorghum production in many parts of the world. Identifying sorghum genotypes with stable resistance to shoot fly is important as it helps to reduce the cost of cultivation and stabilizes yields. In the present study, our objective was to identify stable shoot fly resistant genotypes among 385 recombinant inbred lines (RILs) of a cross between a susceptible parent and a resistant parent. We evaluated this set of RILs in eight environments over three years (2006-2008) for shoot fly resistance and component traits. Non-significant genotype-environment (G × E) linear component and significant pooled deviation for deadheart percentage indicated that the performance of genotypes was unpredictable over the environments. However, five lines had deadheart percentages much less than the population mean with regression coefficient (bi) values close to unity, and non-significant deviation from regression, indicating that they have stable shoot fly resistance and are well adapted to all the environments. Additive main effect and multiplicative interaction (AMMI) analysis partitioned main effects into genotype, environment and G × E interacts with all the components showing highly significant effects (p < 0.001). Environment had the greatest effect (69.2%) followed by G × E interactions (24.6%) and genotype (6.2%). Low heritability and high environmental influence for deadheart percentage suggested that shoot fly resistance is a highly complex character, emphasizing the need for marker assisted selection. We observed transgressive variation in the RIL population for all the traits indicating the contribution of alleles for resistance from both resistant and susceptible parents. Since the alleles for shoot fly resistance are contributed by both resistant and susceptible parents, efforts should be made to capture favourable alleles from resistant and susceptible genotypes.     

柞蚕全茧量的主基因-多基因混合遗传分析

全茧量性状是柞蚕育种的重要指标之一。选择全茧量有显著差异的2个柞蚕品系582(P1)、宽青(P2)为亲本,通过对P1、P2及F1和F2作4家系世代联合分析,研究柞蚕全茧量遗传规律。结果表明:柞蚕全茧量由2对主基因控制,同时存在多基因的修饰作用和性别上的差异,雌性个体符合2对等加性主基因+加显多基因模型,雄性个体符合2对等显性主基因+加显多基因模型;雌、雄个体主基因遗传力分别为49.01%和24.35%,多基因遗传力分别为0.53%和26.47%。柞蚕育种对全茧量的选择应依据性别采用不同的选择方案:雌个体应强化早期选择;雄个体需多代连续选择,并强化后续世代选择。     

Heritability estimates for winter hardiness in lentil under natural and controlled conditions

Heritability analysis for cold tolerance in lentil was conducted using parental, F₂ and F₃ populations at two locations in Balochistan, Pakistan and one controlled environment in Fort Collins, Colorado, USA. Populations of parental and F₂ families were grown over 2 years (1991‐92 and 1992‐93) at Quetta, Balochistan, Pakistan. In 1992‐93, parental and F₃ families were studied at Quetta, and Kalat, Balochistan, Pakistan. Evaluation for normality using non‐transformed and log‐transformed data failed. Attempts to use analysis of variance were then abandoned in favour of parent‐offspring regression for narrow‐sense heritability. Estimates of narrow‐sense heritability ranged from 0.31±0.06 to 0.71 ± 0.06 under field conditions. Under controlled conditions, the estimated heritability was maximized at 1.00 ± 0.17 using 6‐ to 8‐week‐old lentils. Significant transgressive segregants were found in five of the six populations in the F₃ generation. Transgressive segregants appeared in the controlled F₃ generation but were not observed in field environments. This indicates that cold tolerance is under additive gene control and is environmentally sensitive in gene expression.     

Genetic analysis of grain mould resistance in coloured sorghum genotypes

Grain moulds are a major constraint to sorghum production and to adoption of improved cultivars in many tropical areas. Information on the inheritance of grain mould reaction is required to facilitate breeding of resistant cultivars. The genetic control of grain mould reaction was studied in 7 crosses of 2 resistant sorghum genotypes. P₁, P₂, F₁, F₂, BC₁ and BC₂ families of each cross were evaluated under sprinkler irrigation for field grade and threshed grade scores and subjected to generation mean analysis. Frequency distributions for grain mould reaction were derived and F₂ and BC₁ segregation ratios were calculated. Grain mould reaction in crosses of coloured grain sorghum was generally controlled by two or three major genes. Resistance to grain moulds was dominant. Significant additive gene effects were also found in all cross/season combinations. Significant dominance effects of similar magnitude to additive effects were also observed in five out of ten cross/season combinations. Gene interactions varied according to the parents with both resistant and susceptible parents contributing major genes. Choice of parents with complementary resistance genes and mechanisms of resistance will be critical to the success of resistance breeding. This revised version was published online in July 2006 with corrections to the Cover Date.     

香菇单核菌丝生长速度与交配型分布的关系

研究分析鉴定了香菇担孢子的交配型,并对各类交配型的比例进行了统计分析.通过4种交配型担孢子的比例变化关系,探讨造成香菇担孢子4种交配型单核体比例偏离1:1:1:1分离的遗传背景.结果表明,交配型因子偏分离与菌落形态、培养条件及单核体间交配反应的特征无关,不同菌株4种交配型的担孢子在菌落形态上有较大的差异,但这些菌落形态与交配型比例之间没有相关性;4种单核体之间发生亲和性反应的形态特征有多种形式,这些形态特征与交配型比例之间亦没有直接的联系;但同一双核菌株的F1代担孢子的萌发能力、生长速度是有差异的,从而导致有些菌株的担孢子中4种交配型分布不均衡,甚至导致有些菌株中只能检测到2种或3种交配型的担孢子.     

交配型因子和细胞质对香菇双核体中两组成型核比例的影响

    对造成香菇原生质体单核化后两种交配型单核体比例偏离1,1分离的遗传背景进行探讨.结果表明,B因子或是与B因子连锁的因子对这种偏离有明显的影响,而A因子对此影响不明显.B因子特异性不同,与之相对应的交配型单核体出现的比例亦不同,特异性越高,其对应交配型单核体在经原生质体单核化后将以较大的比例出现.参试的2个香菇菌株中4个B因子特异性顺序为B1B>3B>4B>2.双-单杂交所形成的由受体细胞质和受体、供体细胞核组成的同质异核体经原生质体单核化裂解后均与受体交配型相同的核居多,表明受体细胞质环境对双一单杂交所得异核体裂解后的核的存活和数量起着重要作用.作为供体的2个核中只有亲和力强的那个核优先迁移到受体中,形成新的异核体,即存在先导核.先导核与B因子的亲和特异性有关,特异性越高,先导核迁移速度越快.     

利用SSR标记分析川育12×人工合成小麦Syn780重组自交系群体中的偏分离现象

利用栽培小麦“川育12”和“硬粒小麦—节节麦人工合成小麦”Syn780杂交得到的F8代重组自交系,对103个SSR分子标记的偏分离现象进行了分析,结果表明,22.3%的位点出现偏分离,发生偏分离的标记主要集中分布在A染色体组。为进一步利用该重组自交系标记双亲重要性状提供了参考信息。     

Determining the consistency of thermal habitat segregation within and among Arctic charr morphotypes in Gander Lake,Newfoundland

Abstract – Otolith carbon and oxygen isotope data obtained from distinct genetic and ecological groups of lacustrine Arctic charr, Salvelinus alpinus L., from Gander Lake, Newfoundland, were used to examine hypotheses regarding the consistency of differential habitat use among the groups. Results indicated thermal habitat separation by group, with small ‘pale’ individuals consistently remaining in cooler profundal habitats and larger ‘dark’ individuals more frequently occupying warmer upper water column habitats. Theoretical measures of resource separation and competition indicated lower thermal habitat overlap among the forms and greater within‐form competition. Depth at capture data indicated more varied short‐term use of available lake habitats by ‘dark’ form Arctic charr, possibly as a result of cannibalistic foraging on profundal ‘pale’ form fish. Nominal capture depth data only partially explained observed variation in the mean temperature of occupied thermal habitat, suggesting that capture depth can only be used as a rough index of thermal habitat use. Provided that sufficient thermal gradients exist in the environments being studied, otolith oxygen isotopes provide a useful means of establishing the significance of niche differentiation among individuals.     

Observations on the oesophageal glands in some Tanzanian anurans

The occurrence and function of oesophageal glands In some anurans from Tanzania was investigated. The compound glands were present in the oesophageal submucosa of Ptychadena oxyrhynchus Smith, Ptychadena porosissima Steindachner, Phrynobatrachus acridoides Cope, Chiromantis xerampelina Peters, Leptopelis argenteus Pfeffer, Kassina maculata Dumeril, Afrixalus brachycnemis brachycnemis Boulenger, Hyperolius argus Peters, Hyperolius puncticulatus Pfeffer and Hyperolius tuberilinguis Smith, but were absent in Xenopus muelleri Peters, Bufo gutturalis Power and Phrynomerus bifasciatus bifasciatus Smith. It is suggested that in anurans, the oesophageal and gastric glands have similar functions.     

水稻杂种偏分离位点SegD8的精细定位

【目的】通过研究水稻渐渗系群体构建时产生的偏分离现象,可以发现更多与偏分离相关的基因,有助于解析偏分离在水稻中的主要作用及其产生机制。【方法】应用籼粳组合华占/Koliya构建的一套渐渗系群体,以其后代基因型的分离比作为表型对偏分离位点进行定位。【结果】在第8染色体上发现一个染色体区段在其后代中的基因型分离比偏离孟德尔分离定律。进一步分析表明该偏分离现象受第8染色体上两个位点控制,分别命名为SegD8A和SegD8B,其中SegD8A为偏分离位点,但其偏分离属性受SegD8B调控。当SegD8A和SegD8B位点都为杂合型时,子代中SegD8A^HH和SegD8A^KK的比例接近1∶4;当SegD8B为纯合华占基因型时,子代中SegD8A^HH和SegD8A^KK的比例接近1∶1;当SegD8B为纯合Koliya基因型时,子代中SegD8A^HH几乎不出现。我们将SegD8A基因定位在一个大小为46.5 kb的区间内,SegD8B基因定位在一个大小为1160.2 kb的区间内。【结论】本...