Pollen competitive ability in maize: within population variability and response to selection

Summary Male gametophytic selection can play a special role in the evolution of higher plant populations. The main assumption — gametophytic-sporophytic gene expression of a large portion of a plant's genes — has been proven by a number of studies. Population analyses have revealed a large amount of variability for male gametophytic fitness. However, the data available do not prove that at least a portion of this variability is due to postmeiotic gene expression. This paper reports the analysis of a synthetic population of maize based on a gametophytic selection experiment, carried out according to a recurrent scheme. After two cycles of selection, the response was evaluated for gametophytic and sporophytic traits. A parameter representing pollen viability and time to germination, although showing a large amount of genetic variability, was not affected by gametophytic selection, indicating that this variability is largely sporophytically controlled. Pollen tube growth rate was significantly affected by gametophytic selection: 21.6% of the genetical variability was released by selection. Correlated response for sporophytic traits was observed for mean kernel weight: 15.67% of the variability was released. The results are a direct demonstration that pollen competitive ability due to pollen tube growth rate and kernel development are controlled, to a considerable extent, by genes expressed in both tissues. They also indicate that gametophytic selection in higher plants can produce a higher evolution rate than sporophytic selection; it can thus serve to regulate the amount of genetic variability in the populations by removing a large amount of the genetic load produced by recombination.     

基于竞争和扩散能力的非捕食-被捕食集合种群系统的竞争机制

对于非捕食 被捕食(食饵)生态系统,强弱物种之间存在一定的竞争影响.在不考虑栖息地毁坏的情况下,引进双向竞争机制,将Tilman的单向竞争模式推广为n集合种群双向竞争模型,并对6-集合种群的竞争动态进行了计算机模拟研究.结果表明,在平衡态,种群竞争共存的条件是其竞争能力与扩散能力呈现指数型负相关关系,竞争的结果使物种的强弱序列发生变化;物种竞争排除与共存受迁移扩散能力和竞争能力影响很大,在局域斑块上竞争排斥的集合种群在广域尺度上可以竞争共存,即逃亡共存.     

Occurrence and activity of phosphate-solubilizing fungi from coconut plantation soils

Summary The occurrence of phosphate-solubilizing fungi in coconut plantation soil types was investigated. The laterite, alluvial and clayey soils harboured more of the P-solubilizing fungi than the sandy soils. The isolated P-solubilizing fungi solubilized 26 to 74 per cent of the tricalcium phosphate in 5 to 15 days. The competitive saprophytic ability of the active P-solubilizing fungi in soil varied between the isolates. Eight fungi with high P-solubilizing capacity and high competitive saprophytic ability were recognised. They have better capacity to survive in soil and express their role in P-solubilization.Contribution No. 291 of the Central Plantation Crops Research Institute, Kasaragod, India     

Competitive ability and the potential for lotteries among territorial reef fishes

Stegastes diencaeus and S. dorsopunicans are mutually territorial Caribbean damselfishes. S. diencaeus is larger, grows faster and lives longer than S. dorsopunicans. S. diencaeus is a habitat specialist that shares its primary habitat mainly with S. dorsopunicans. Field manipulations show that both S. diencaeus and S. dorsopunicans readily take over living space from smaller, but not larger, heterospecific neighbors. Natural changes in the use of living space by both species occur frequently and adult S. diencaeus often aggressively usurp the living areas of smaller S. dorsopunicans. Lunar and seasonal patterns of juvenile recruitment by S. diencaeus and S. dorsopunicans are similar. Large size bestows competitive superiority on S. diencaeus by giving its adults a superior ability to aggressively acquire living space, and by enabling its juveniles to quickly escape the period when they lack a size advantage. Hence they spend much of their lives as competitive dominants. There is no evidence that competitive advantages arising from large size are offset either by other adult attributes or by differences in temporal patterns of recruitment that affect priority of access to space. The lottery hypothesis for species coexistence relies on patterns of abundance being determined by patterns of recruitment to vacant space because different species have equal space-holding abilities. These data show that the existence of such a mechanism is doubtful.     

Immature maize spikelets develop and produce pollen in culture

Immature maize spikelets have been successfully grown in vitro. Culture conditions were refined to maximize development of normal pollen grains. Kinetin was not required for normal development, in contrast to the absolute requirement for this plant growth regulator for in vitro tassel development. Development occured in all stages sampled, from premeiosis to postvacuolation, and there was no lag in progression through the various stages of development as compared to greenhouse-grown material. Cultured spikelets produced pollen that appeared morphologically normal, accumulated starch and had the normal two sperm nuclei and single vegetative nucleus.     

gaMS-1: A gametophytic male sterile mutant in maize

Several pollen-specific genes from different species have been isolated and characterized at the molecular level, but the precise role of most of them is unknown. Mutant analysis represents a direct approach to uncovering gene function, but the paucity of available mutants affecting pollen development and/or function and the poor characterization of the known mutants have so far limited the exploitation of this approach. Here we present the cytological characterization ofgametophytic male sterile-1 (gaMS-1), a maize mutant that we identified in a program of transposon insertion mutagenesis for the production of mutations in gametophytically acting genes involved in microsporogenesis.gaMS-1 is expressed during or immediately after the first microspore division and leads to the production of immature, nonfunctional pollen grains. The mutation appears to affect the events leading to the developmental switch that follows the first microspore mitosis.     

半干旱区春小麦品种竞争能力与产量关系的研究

 采用de Wit替代系列法研究了黄土高原半干旱雨养农业区传统地方品种(和尚头)与现代品种(陇春8275)之间在混播条件下的竞争结局。在单播条件下现代品种较之地方品种具有更高的产量;但在混播条件下,和尚头具有明显的竞争优势。本项研究结果说明竞争优胜者并非是单播条件下产量性能更佳的品种,即作物品种的竞争能力与生产性能之间存在着负相关关系。形成这种关系的主要原因在于作物群体内个体竞争选择的方向与人类农业生产追求的目标不一致。     

植物28kD蛋白的纯化及部分性质研究

经丙酮粉、硫酸铵分级沉淀和阴离子交换层析等方法,首次从玉米花粉细胞质粗提物中纯化了一种具有ＡＴＰａｓｅ活性的可溶性蛋白。ＳＤＳ－ＰＡＧＥ测得分子量为２８ｋＤ,ＩＥＦ－ＰＡＧＥ测得等电点为８．３。免疫印迹鉴定结果表明该酶蛋白与抗牛脑动蛋白或动力蛋白的抗体无免疫交叉反应。最大紫外吸收波长为２７８ｎｍ,并作了ＣＤ谱分析。底物特异性研究表明：ＡＴＰａｓｅ水解活性最高。药理学研究表明：该酶蛋白可被矾酸钠强烈抑制,但对ＮＥＭ基本不敏感,氟化钠可使酶活力丧失５０％左右,寡霉素、硝酸钾及乌本苷对酶活力没有抑制作用．     

玉米花粉单倍体植株染色体上异染色质的变异

我们用Giemsa BSG C-带技术检查了玉米花药培养获得的花粉单倍体植株根尖细胞染色体上异染色质的变异,观察结果表明,有的植株所显示的C-带数目是与供体植株的相一致,有的植株所显示的C-带数目则发生了显著变化,其中有的增加,有的减少。并讨论了异染色质发生变异的可能原因。还相应地观察到间期核中染色中心的变化是与中期染色体上C-带数目的变化相一致。     

三个玉米合成群体选系的配合力及杂种优势分析

采用NCⅡ遗传交配设计,通过在黑龙江省哈尔滨和泰来的两点试验,以玉米自交系Mo17、B73、444和丹340为测验种,对从群体品综1号、中综3号和陕综5号选育的18份自交系进行配合力及杂种优势分析,以探讨群体选系在我国东北早熟玉米区的利用途径。结果表明,供试自交系间一般配合力存在较大差异;陕综5号群体选系HR14、HR17和HR15、中综3号选系HR9和HR8、品综1号选系HR4的一般配合力较高。在供试的72个组合中HR15×丹340、HR17×丹340、HR9×Mo17、HR14×丹340、HR7×B73、HR8×B73、HR6×444、HR5×丹340产量的特殊配合力及对照优势较高,表现出较高的利用潜力。依据特殊配合力及对照优势分析,中综3号选系与旅大红骨群、陕综5号选系与兰卡斯特群、品综1号选系与瑞德群遗传关系较近。结合育种实践,在我国北方早熟春玉米区陕综5号×旅大红骨、中综3号×瑞德或兰卡斯特、品综1号×旅大红骨或唐四平头可能组成较大利用潜力的杂种优势模式。     

Comparison of competitive ability between native and introduced salmonids: evidence from pairwise contests

Brown trout, Salmo trutta, and rainbow trout, Oncorhynchus mykiss, have been introduced to freshwaters in Hokkaido, Japan. Today, it is recognized that these introduced salmonids have negative impacts on native salmonids such as white-spotted charr, Salvelinus leucomaenis, and masu salmon, O. masou. In particular, interspecific competition may be an important mechanism that could contribute to the exclusion for native salmonids. In this study, experimental pairwise contests were conducted to compare interference competitive ability between native and introduced salmonids. We demonstrated that brown trout were competitively superior to white-spotted charr and masu salmon whereas rainbow trout were superior to white-spotted charr. We suggest that introduced brown trout negatively impact both white-spotted charr and masu salmon, and introduced rainbow trout negatively impact white-spotted charr.