Relative growth and photosynthetic response of water-seeded rice and Echinochloa oryzoides (Ard.) Fritsch to shade

Echinochloa oryzoides is a serious weed of rice worldwide and one of the most important weeds of water-seeded rice in California, USA, where resistance to most available herbicides has been detected. Developing new integrated weed management strategies that include rice suppression of E. oryzoides growth requires understanding their relative responses to resource limitation. The effects of shade on the growth, morphology and CO 2 exchange rates (CER) of E. oryzoides and rice (cv. M-202) were assessed in glasshouse and growth chamber experiments. Plants were grown at 100, 50 or 18% of full sunlight (glasshouse) or at 500 and 250 µmol PPFD m-2s-1 (growth chamber) within a completely randomized design with two factors and four replicates. Shade was imposed at 21 days after seeding (d.a.s.) (glasshouse) and at 14 d.a.s. (growth chamber). Height, leaf area, tillers, and leaf, stem, root and seed dry weights were determined for both species. CER were determined for plants in the growth chamber. Both species increased dry-matter allocation to leaves and maintained CER when subjected to low light. However, in contrast to rice, E. oryzoides maintained or increased leaf area, specific leaf area and leaf area ratio (LAR) in response to shade. E. oryzoides tiller number and seed output were reduced only at 18% sunlight. Rice lacked such adaptive ability and tiller number and seed were reduced at 50% sunlight. Shade alone may not prevent the seed production of E. oryzoides. However, E. oryzoides increased LAR at the expense of allocation to roots. Thus, for substantial E. oryzoides control, early nutrient deprivation by rice roots may be as relevant as improving rice ability to intercept light.     

Developing Groundnut Lines with Resistance to Seed Colonisation by Toxin-producing Strains of Aspergillus Species

Abstract

Evidence for the possible development of groundnut (Arachis hypogaea L.) cultivars with favourable agronomic characteristics and resistance to aflatoxinproducing strains of Aspergillus species is presented. In studies of F₂ and F₃ progenies from crosses of resistant and susceptible genotypes data on the frequency distribution and least square estimates of genetic effects showed the possibility of selecting for resistance to seed colonisation by the fungus. Yield, value and seed quality data for seven advanced lines developed by using pedigree selection from crosses showed that potential favourable groundnut cultivars may be developed.     

Propanil tolerance in Echinochloa crus‐galli (L.) Beauv

Abstract

Two morphological variants of Echinochloa crus‐galli were collected from rice fields of an area in Greece where rice has been grown for over a decade and growers have recently been complaining about reduced effectiveness of propanil. Seedling response of the two variants to propanil was compared with that of E. crus‐galli collected from vegetable fields in another area where rice has never been grown. Initial contact toxicity of propanil was similar in all collections. Growth inhibition thereafter was clearly different, resulting in death of the E. crus‐galli from vegetables but not of the E. crus‐galli from rice. The latter could overcome initial toxicity and resume growth at 8 kg/ha of propanil, whereas the former was killed at 2–4 kg/ha. Prevalence of E. crus‐galli forms of higher tolerance resulting from selection through rice husbandry and/or repeated use of propanil may account for the reduced effectiveness of propanil in the area of intensive rice growing.     

稗属植物DNA条形码研究

为评估DNA条形码在稗属植物鉴定中的有效性,选取核DNA条形码序列ITS和ETS及叶绿体DNA条形码序列psbA、trnL-F和matK作为候选序列进行了分析。本研究对无芒稗、稗、长芒稗和细叶旱稗4种稗属植物的不同DNA条形码序列进行了扩增、测序,并分析了不同候选条形码序列的特征。结果显示,matK序列变异位点占比最高(3.6%),ETS序列最低(1.7%);psbA序列种间变异最大,matK序列种内变异最大;邻接树分析显示,条形码序列ITS、ETS、psbA、trnL-F和matK均可以区分出长芒稗,支持率均大于80%;此外,ITS序列将无芒稗和稗聚于同一支,可以区分出细叶旱稗。因此,建议ITS作为鉴别稗属植物潜在的DNA条形码序列。     

湖南稷子栽培与再生技术研究进展

湖南稷子（Echinochloa frumentacea）是禾本科稗属植物,具有分蘖力强、耐旱、耐涝、耐盐碱等多种特性,其茎秆柔软、叶量丰富、适口性好、利用率高,是营养价值较高的牧草,目前已在我国多地引种栽培。湖南稷子的再生体系已初步建立。通过使用2,4-二氯苯氧乙酸（2,4-D）诱导愈伤组织,6-苄氨基嘌呤（6-BA）和α-萘乙酸（NAA）诱导芽分化,活性炭和NAA促进根形成。本文综述了湖南稷子栽培与再生技术的研究进展,为深入研究利用湖南稷子提供资料。     

稻田稗草对噁唑酰草胺的抗药性水平和ACCase活性

为明确稻田稗草Echinochloa phyllopogon(Stapf.)Koss.对噁唑酰草胺的抗药性水平,在对采自辽宁省、黑龙江省、湖南省和江西省共20个水稻产区的稗草种群按田间推荐剂量筛选后,测定了疑似抗药性稗草种群BN-1、BN-16、BN-17和疑似敏感性稗草种群BN-20的整株抗药水平,并离体测定了不同种群体内乙酰辅酶A羧化酶(acetyl co-enzyme A carboxylase,ACCase)对噁唑酰草胺的敏感性。结果显示,在田间推荐剂量下,种群BN-1、BN-16、BN-17和BN-20相对鲜重分别为92.6%、86.6%、64.9%和1.1%。相比种群BN-20,种群BN-1、BN-16和BN-17对噁唑酰草胺敏感性较低,抗性指数分别为33.83、30.07和14.87;ACCase活性测定结果显示,种群BN-1、BN-16和BN-17的抗性指数分别为33.71、27.16和15.23。结果表明稗草种群BN-1、BN-16和BN-17均对噁唑酰草胺产生了抗药性,抗性程度依次为BN-1BN-16BN-17,而其体内ACCase敏感性降低可能是其产生抗药性的原因之一。     

两种光敏化合物光诱导稗草细胞产氧自由基电子自旋共振的检测与分析

采用电子自旋共振光谱仪,检测两种光敏化合物α-三连噻吩(α-T)和1-苯基-4-(3,4-亚甲基二氧)苯基-丁二炔(简称化合物5)处理的稗草愈伤组织后,经近紫外光光照与非光照处理,诱导细胞内产氧自由基的总量.试验结果表明:两种光敏化合物在1mg/L的浓度下,光照组与非光照组愈伤组织产氧自由基的总量存在显著差异,α-T处理的光照与非光照电子自旋共振图谱氧自由基积分面积与愈伤组织量的比值分别是54.58和46.78mm2/mg;化合物5的氧自由基积分面积与愈伤组织量的比值分别是68.62和53.98mm2/mg.而两种光敏化合物处理的非光照组与空白对照处理的光照组与非光照组所诱导的氧自由基总量不存在显著差异.表明两种光敏化合物对稗草生长的光活化抑制作用与光活化Ⅰ型机制有一定的关系.     

农用有机硅对五氟磺草胺防治稗草的增效作用

为明确有机硅对五氟磺草胺防治稗草的增效作用和增效机理,本研究采用室内与田间试验测定有机硅助剂对五氟磺草胺的增效作用,并采用滴重法和HPLC方法分别探索有机硅对五氟磺草胺药液表面张力和吸收的影响.室内生测表明,有机硅对五氟磺草胺防治稗草具有显著的增效作用.当五氟磺草胺用量为7.5 g/hm2,有机硅添加浓度为0.04％时...