华南早稻干旱灾害评估模型及其时空特征

建立华南早稻干旱灾害定量评估模型,分析干旱灾害时空特征,为主动防旱减灾、制定气候变化适应政策提供参考。根据分县早稻产量及生育期资料,采用逐日气象干旱指数DI计算各生育期干旱指数,并由统计回归方法率定各生育期干旱指数对产量影响系数。华南近30年(1981—2010)早稻干旱年频率平均为10.4%,平均减产率为0.82%,以轻旱为主。早稻干旱主要发生在移栽-分蘖期。干旱频率及减产率均呈西高东低分布,旱年频率在20%~50%、减产率在1%~3%的区域集中在广西西南部至广东雷州半岛一带。近30年华南早稻最旱的3年为1991、2002、1998,早稻干旱总体趋于增强但不显著,增强趋势显著的站点约占10%,分布于华南北部和北部湾至粤西沿海地区。基于不同生育期干旱指数建立的评估模型,揭示早稻不同生育期对干旱敏感性差异,精细刻画早稻干旱时空特征,克服基于全生育期降水的干旱评估模型的局限性。     

基于干旱灾害风险综合评估指数的西藏主要农区青稞干旱时空格局

为研究西藏主要农区青稞的干旱时空变化特征,笔者从干旱灾害的致灾因子危险性、承灾体易损性、灾损脆弱性、防灾减灾能力等4个风险因子考虑,采用专家打分法和熵权法确定各因素权重,构建干旱灾害风险综合评估模型,并进行干旱灾害时空格局分析。结果表明：干旱灾害综合风险整体呈现中间低、两边高的态势,高风险区分布比较分散,次高风险区多集中在研究区的边缘地带,中等风险区以左斜H型分布在拉萨、山南、林芝市部分区域,而次低和低风险区零星分布在加查、索县、比如、林芝等站;且干旱灾害风险较高年份出现在1999、2005、2006、2007、2009、2010、2012、2014、2015年。西藏主要农区青稞各个干旱风险因子的分布具有明显的区域差别和一定的连片性,研究区和分区的干旱趋势随年份递增而加重。     

福建省粮食产量气象灾害风险评估

利用福建省1978-2004年66个县（区）的粮食单产资料,通过统计处理得到相对气象产量,并以相对气象产量的变化来表征福建粮食产量气象灾害风险程度。采用歉年平均减产率,歉年减产率变异系数,相对气象产量小于－5％的保证率三个风险指标作为综合风险评估指标,来评估福建粮食单产气象灾害风险。结果表明全省各县综合风险指数介于0.08～0.73之间,高风险区主要分布在平潭县、泉州和漳州的大部县市、龙岩和三明的西部县市、宁德市东北部和南平的部分县市,这些区域的台风、暴雨、干旱和寒害等灾害对粮食单产的影响较大;低风险区主要分布在福建中部沿海县市及内陆县市,气象灾害对对粮食单产的影响相对小些。     

黑龙江省农业干旱灾害风险评价与区划研究

摘 要：本文运用降水距平公式对黑龙江省1971-2000年干旱程度进行划分,分析了不同时期干旱灾害的时间分布特征及规律,对黑龙江省74个站点,采用人类生存环境风险评价法,结合GIS软件对玉米干旱灾害风险指数DDRI进行研究与区划。结果表明：（1）黑龙江省一般干旱和强干旱的发生频率均表现为20世纪70年代最高,90年代次之,80年代最低;（2）黑龙江省玉米干旱灾害高风险区主要集中在西部齐齐哈尔和大庆地区,这一地区应该成为黑龙江省防御农业干旱的重点区域,低风险和轻微风险主要分布在中部地区及东部平原区。     

内蒙古西部地区自然灾害对玉米产量影响及气象因子分析

为明确内蒙古自治区玉米产量受灾害性天气影响情况,根据内蒙古自治区2005—2017年自然灾害情况、玉米播种面积、单产和总产情况,分析气象灾害影响和减产情况。结果表明：旱灾造成的内蒙古受灾面积占到70%以上,灾害发生频率最多、产生影响最大,且旱灾导致2009年玉米单产水平为近年最低。分析内蒙古自治区西部地区4个地市的23个气象站点气候条件,玉米生长季5—9月期间,气温、降水和风速等信息各站点差别不大,降水主要集中在7月和8月,呼和浩特市风速较低。比较各地市减产概率,巴彦淖尔市降水偏少,灾年平均减产率较高,受气候波动的影响较大,但是灌溉比例高,玉米单产变异系数最低,产量稳定性较好。呼和浩特市灾年平均减产率最高,玉米单产变异系数也最高,产量波动较大,稳定性较差。从玉米种质资源收集利用入手,提高育成玉米品种抗逆性能,是降低自然灾害和气象风险的有效手段。     

近60年河北省冬小麦干旱风险时空规律

干旱是造成作物减产的主要自然灾害,开展作物干旱成因机制和时空特征研究,对于稳定区域粮食生产有重要意义。本研究基于河北省内18个国家标准气象站点1958—2016年的长时间序列观测资料,采用水分亏缺指数(CWDI)作为干旱评价指标,分析了近60年来河北省冬小麦的干旱风险时空格局;通过CWDI对不同气象因子的敏感性分析,进一步探究了冬小麦干旱的成因机制。研究表明,冬小麦生育期需水量和干旱风险呈先增后减再增加的特征,在拔节–抽穗阶段的干旱风险最高,其次是抽穗-成熟阶段。冬小麦全生育期间干旱等级以重旱和特旱为主,特别在其产量形成的关键生长中后期,河北省东南部黑龙港地区面临较高的旱灾风险。冬小麦干旱受降水、气温、湿度等多种因素的影响,其中影响最大的是降水;气温是影响冬小麦生育后期干旱程度的关键因子,伴随近几十年气候变化冬小麦生长期内温度明显升高,将增加冬小麦生长期的耗水量和灌溉需求。本研究揭示了气候变化影响下河北省冬小麦干旱风险的时空演变规律,识别出了干旱灾害的高风险区和关键生育期阶段,可为优化冬小麦灌溉管理和农田防灾减灾提供参考依据。     

陕西猕猴桃高温干旱灾害风险区划研究

为了掌握猕猴桃果实膨大期高温干旱灾害发生的风险水平和空间分布情况,进行陕西猕猴桃高温干旱风险区划研究,为果业部门开展猕猴桃生产的防灾减灾,以及猕猴桃高温干旱灾害保险设计、理赔以及避灾抗灾政策措施提供参考。本研究基于自然灾害风险形成原理,利用气象数据、基础地理信息数据、社会经济统计数据和历史灾情等方面资料,从致灾因子危险性、孕灾环境敏感性、承灾体易损性以及防灾减灾能力4个方面,构建陕西猕猴桃高温干旱灾害风险评估模型,利用GIS技术,开展陕西猕猴桃高温干旱风险区划研究。结果表明,重度风险区主要分布在关中东部渭河下游低海拔地区,该区域重度高温干旱灾害约3年1遇,同时存在约2年1遇的中度、1年1遇的轻度高温干旱灾害;中度风险区主要分布在关中中东部和陕南汉江下游两岸部分地区,该区中度高温干旱灾害2~3年1遇,同时存在3~4年1遇的重度灾害和少于1年1遇的轻度灾害;轻度风险区主要分布在关中中度风险区南部、北部和西部,以及陕南汉江及其支流两岸、金钱河、丹江及其支流两岸、南洛河两岸海拔较高的地区。     

内蒙古河套灌区主要作物气象产量的风险分析

为弄清作物产量面临的风险水平,通过分析内蒙古河套灌区1953—2011年间12个旗县（市、区）的粮食、小麦、玉米和向日葵的产量资料,利用5年直线滑动平均模型分离实际产量,计算了气象产量的变异系数、年平均减产率、风险概率和综合风险指数等指标,对该区域作物产量灾害风险进行研究。结果表明：河套灌区粮食单产的4种风险指数总体小于小麦、玉米和向日葵的,以向日葵的最大,小麦和玉米的风险指数介于粮食和向日葵的风险指数;地区间以准格尔旗的几种单产的风险要高于其他地区;4种风险指数的最小值,在不同作物上没有明显区域特点。从减产风险概率看,河套灌区作物增产的地区多于减产地区的概率略高一些。     

安徽省淮北平原夏玉米主要生育时期旱涝指标与影响评估

为给淮北平原夏玉米高产稳产和防灾减灾以及保险理赔等工作提供参考依据。利用1961—2010年安徽省淮北平原夏玉米生育期间降水资料,采用积分回归分析方法确定了逐旬降水量对夏玉米的增产或减产效应及其影响的关键时段,同时采取降水概率≤20%与≥80%分位数法设计了夏玉米不同生育时段及其全生育期间旱与涝的气候指标,统计分析了夏玉米旱与涝灾的区域分布和灾损率及其风险分布特征。结果表明：淮北平原夏玉米生育期间逐旬降水量的负效应多于正效应,抽雄—乳熟期间降水对夏玉米产量影响显著,期间发生旱或涝灾的减产率分别为12.6%和16.3%。淮北平原夏玉米播种—出苗、苗期—拔节、拔节—抽雄、抽雄—成熟和全生育期旱灾与涝灾的气候指标分别是各自时段内的降水总量≤17.0、≤50.0、≤95.0、≤110.0、≤370.0 mm和≥95.0、≥235.0、≥265.0、≥280.0、≥740.0 mm。淮北平原夏玉米生育期间涝灾多于旱灾,且旱灾与涝灾风险分别呈经向和纬向分布,全生育期旱灾与涝灾的气象相对减产率分别为-22.4%和-28.9%,其他生育时段旱与涝灾的气象相对减产率在-8%~-16%之间。     

干旱对陇东及陇东南地区粮食产量的影响评估

干旱灾害是影响陇东南及陇东地区粮食生产的主要气候灾害。评估其对该地粮食生产的影响及粮食作物种植的风险程度,是干旱研究工作的目的之一。根据陇东南及陇东4市1981-2006年粮食产量及各地同期历年降水资料,借助数理统计方法分析了4市的干旱灾害变化的基本特征和该地冬小麦和玉米受干旱影响的减产程度,构造了评价冬小麦及玉米种植风险系数及评价方法。结果表明,陇东地区比陇东南地区更容易发生旱灾,春旱以陇东地区的庆阳最易发生且程度严重,初夏旱以陇东地区的平凉最易发生,伏旱以陇东南地区的天水最易发生。冬小麦的种植比玉米的种植风险大,陇东地区粮食作物的种植的风险比陇东南地区大。冬小麦种植风险最大的地方为平凉,其次为庆阳,最小的为陇南。玉米种植风险最大的地方是庆阳,其次为平凉,最小为陇南。     

A note on the origin of Kalanchoë x vadensis Boom & Zeilinga (Crassulaceae)

Summary K x vadensis is a hybrid of K. blossfeldiana and K. marmorata obtained after doubling the number of chromosomes.     

Mechanisms and diversity of resistance to sorghum shoot fly,Atherigona soccata

Sorghum shoot fly, Atherigona soccata, is one of the important pests of postrainy season sorghums. Of the 90 sorghum genotypes evaluated for resistance to this pest, RHRB 12, ICSV 713, 25026, 93046 and 25027, IS 33844‐5, Giddi Maldandi and RVRT 3 exhibited resistance in postrainy season, while ICSB 463, Phule Anuradha, RHRB 19, Parbhani Moti, ICSV 705, PS 35805, IS 5480, 5622, 17726, 18368 and 34722, RVRT 1, ICSR 93031 and Dagidi Solapur showed resistance in rainy season, suggesting season‐specific expression of resistance to A. soccata. ICSB 461, ICSB 463, Phule Yasodha, M 35‐1, ICSV 700, 711, 25010, 25019 and 93089, IS 18662, Phule Vasudha, IS 18551 and 33844‐5 and Barsizoot had fewer deadhearts than plants with eggs across seasons, suggesting antibiosis as one of the resistance mechanism. Five genotypes exhibited resistance with high grain yield across seasons. Correlation, path and stepwise regression analyses indicated that leaf glossiness, seedling vigour, trichome density, oviposition and leaf sheath pigmentation were associated with the expression of resistance/susceptibility to shoot fly, and these can be used as marker traits to select and develop shoot fly‐resistant sorghums.     

Reaction of tritordeum to Fusarium culmorum and Septoria nodorum

Summary Hordeum chilense is a wild barley extensively used in wide crosses in the Triticeae. It could be a valuable source of resistance to Fusarium culmorum and Septoria nodorum. Some H. chilense x Triticum spp. amphiploids, named tritordeums, were more resistant than the parental wheat line to these diseases, others were not. Average contents of ergosterol and deoxynivalenol (DON) suggested that resistance to colonization by Fusarium was the highest for Hordeum chilense, followed by tritordeum and wheat in decreasing order. In particular, the H. chilense genotypes H7 and H17 enhanced the wheat resistance to F. culmorum in its tritordeum offsprings. Resistance to S. nodorum in tritordeum was not associated with tall plant height. There is sufficient genetic variation for resistance to F. culmorum and S. nodorum among tritordeum to allow the breeding of lines combining short straw and resistance to both diseases.     

Avoidance of leaf rust fungi in wild relatives of cultivated cereals

Summary Avoidance of rust fungi that was based on poor appressorium induction was previously found in Hordeum chilense. In the present study 95 accessions of Triticeae were screened for avoidance of Puccinia hordei. The percentage of appressorium formation per germinated spore ranged from 6 to 90%. On none of the 41 accessions of Aegilops, Agropyron, Elymus, Secale, Thinopyrum or Triticum studied was the rate of appressorium formation lower than 25%. Lower rates of appressorium formation were, however, found on accessions of wild barley species Hordeum brachyantherum, H. marinum, H. parodii and H. secalinum. Its implications in cereal breeding are discussed.     

Disease resistance in protected crops and mushrooms

Summary Cultivars of tomatoes, cucumbers, lettuce and peppers have been bred for resistance to one or more pathogens. Some tomato and cucumber cultivars have resistance to a wide range of diseases. Resistance has been transient in many cases and a succession of cultivars with new genes or new combinations of resistance genes has been necessary to maintain control. There has been a number of notable exceptions and these have included durable resistance to such pathogens asFulvia fulva and tomato mosaic virus. With lettuce the resistance situation is complicated by the occurrence of fungicide resistant pathotypes. There are no strains ofAgaricus bisporus purposely bred for disease resistance.In protected flower crops only resistance to Fusarium wilt in carnations has been purposely bred but differences in disease resistance are apparent in cultivars of many ornamental crops. This is particularly so in chrysanthemums where there are cultivars with resistance to many of the major pathogens. Similar situations occur with other flower crops and pot plants. Cultivars of some species have not been systematically investigated for resistance.The need for genetic resistance will increase with the further reduction, in the limits on pesticide use and an increasing public awareness and importance of pesticide pollution.ADAS is an executive agency of the Ministry of Agiculture, Fisheries and Food and the Welsh Office.     

Genetic constitution and diversity in four narrow endemic redwoods from the family Cupressaceae

The genetic constitution and diversity of four relictual redwoods are discussed in this review. These include monotypic genera of the family Cupressaceae: coast redwood (Sequoia sempervirens), giant sequoia (Sequoiadendron giganteum), dawn redwood (Metasequoia glyptostroboides), and alerce (Fitzroya cupressoides). All four species are narrow endemics, share a number of common phenotypic traits, including red wood, and are threatened species. Fossil history suggests that the ancestors of redwoods probably originated during the Cretaceous and Tertiary periods and flourished thereafter for millions of years. Towards the end of the Tertiary period began their decline and struggle for existence that continued during the subsequent geologic upheavals and climate changes, until the survival of the present-day redwoods in the current restricted locations in the world (USA, China, and South America). Although two species, Sequoiadendron and Metasequoia, are diploids (2n = 22), and the other two are polyploids: Fitzroya a tetraploid (2n = 4x = 44), and Sequoia a hexaploid (2n = 6x = 66); they all share the same basic chromosome number x = 11. The genome size in the hexaploid Sequoia is one of the largest (31,500 MB) in the conifers, while the genome sizes of diploid Metasequoia and Sequoiadendron are about one-third (~10,000 MB) of Sequoia. Genetic diversity in the redwoods is lower than most other gymnosperms, except in Sequoia, which seems to rank near the upper quarter of the coniferous forest trees. Genomic research is sparse in the redwoods, and should be pursued for a better understanding of their genome structure, function, and adaptive genetic diversity.     

Distribution,ecology and reproductive biology of wild tomatoes and related nightshades from the Atacama Desert region of northern Chile

Over the past 20 years, several expeditions were made to northern Chile to collect populations of wild tomatoes (Solanum chilense, S. peruvianum) and allied nightshades (S. lycopersicoides, S. sitiens), and obtain information about their geographic distribution, ecology and reproductive biology. Restricted mainly to drainages of the Andean and the coastal cordillera, populations are geographically fragmented. The two nightshade species are rare and threatened by human activities. Adaptation to extreme aridity and soil salinity are evident in S. chilense and S. sitiens (the latter exhibits several xerophytic traits not seen in the tomatoes) and to low temperatures in S. lycopersicoides and S. chilense. All tested accessions are self-incompatible, with the exception of one S. peruvianum population collected at the southern limit of its distribution. Several distinguishing reproductive traits—anther color, attachment, and dehiscence, pollen size, and flower scent—suggest S. sitiens and S. lycopersicoides attract different pollinators than S. chilense and S. peruvianum. The four Solanum spp. native or endemic to Chile provide a variety of novel traits which, through hybridization and introgression with cultivated tomato, could facilitate development of improved varieties, as well as research on a variety of basic topics, including plant-pollinator interactions, abiotic stress responses, and evolution of reproductive barriers.     

The induction in vitro of adventitious shoots in Rosa

Summary Adventitious shoots were formed on excised leaves, roots and callus of Rosa persica x xanthina and on excised leaves of R. laevigata and R. wichuraiana on culture media that included BAP and NAA as growth regulators. Shoots formed freely on freshly cultured callus of R. persica x xanthina but their production declined in successive cultures and ceased after twelve weeks. Transplantation to soil was improved by rooting plantlets in cellulose plugs in vitro and transferring plantlets to soil while still in the plugs.     

The exploration of genetic resources of Portuguese cabbage and kale for resistance to several Brassica diseases

Summary Twenty three accessions of nine Portuguese cabbage and kale land races from different geographic origins were tested at the seedling stage for resistance to several important brassica diseases. Resistance to downy mildew (Peronospora parasitica), expressed as necrosis of the cotyledon mesophyll, was found in all the accessions. Type A resistance to cabbage yellows (Fusarium oxysporum f. sp. conglutinans race 1) was present in most of the landraces. Resistance to clubroot (Plasmodiophora brassicae race 6) was found in one accession of the Portuguese tree kale. High resistance to blackleg (Leptosphaeria maculans) and white rust (Albuco candida) was not detected, although several accessions showed 20 to 30% of plants with intermediate expression of resistance. All Portuguese cole accessions were susceptible to blackrot (Xanthomonas campestris pv. campestris).     

Production and characterization of intergeneric diploid cybrids derived from symmetric fusion between Microcitrus papuana Swingle and sour orange (Citrus aurantium)

Plants were regenerated from intergeneric somatic hybridization between embryogenic protoplasts of Microcitrus papuana Swingle and leaf-derived protoplasts of sour orange (Citrus aurantium L.) via electrofusion. The regenerated plants were morphologically similar to the leaf parent in growth vigor, leaf and branch structure. FCM analysis showed that they were diploids. Simple-sequence-repeat (SSR) and cleaved-amplified-polymorphic-sequence(CAPS) were employed for hybridity characterization. SSR banding patterns of the regenerated plants were identical to the leaf parent, sour orange, indicating that they possessed nuclear component derived from sour orange. DNA amplification with chloroplast and mitochondrial universal primers, followed by restriction endonuclease digestion, revealed polymorphism between the fusion parents. Therefore, this method was used to determine the cytoplasmic compositions of the regenerated plants. Banding patterns for all the polymorphic primer/enzyme combinations of the regenerated plants were similar to those of the embryogenic parent, M. papuana, suggesting that only the cytoplasmic components derived from the embryogenic parent were present in the regenerated plants. FCM, SSR and CAPS demonstrated that intergeneric diploid cybrids have been successfully obtained by symmetric fusion. Related results concerning nuclear and cytoplasmic composition of previous diploid somatic hybrids and potential mechanism for regeneration of such kind of plants are discussed herein. This revised version was published online in July 2006 with corrections to the Cover Date.