The use of coal fly ash in sodic soil reclamation

An experiment was conducted for two years in northwest India to explore the feasibility of using coal fly ash for reclamation of waterlogged sodic soils and its resultant effects on plant growth in padi–wheat rotation. The initial pH, electrical conductivity, exchangeable sodium percentage and sodium adsorption ratio of the experimental soil were 9.07, 3.87 dS m⁻¹, 26.0 and 4.77 (me l)^−1/2, respectively. The fly ash obtained from electrostatic precipitators of thermal power plant had a pH of 5.89 and electrical conductivity of 0.88 dS m⁻¹. The treatments comprised of fly ash levels of 0.0, 1.5, 3.0, 4.5, 6.0 and 7.5 per cent, used alone as well as in combination with 100, 80, 60, 40, 20 and 10 per cent gypsum requirement of the soil, respectively. There was a slight reduction in soil pH while electrical conductivity of the soil decreased significantly with fly ash as measured after padi and wheat crops. The sodium adsorption ratio of the soil decreased with increasing fly ash levels, while gypsum treatments considerably added to its favourable effects. Fly ash application increased the available elemental status of N, K, Ca, Mg, S, Fe, Mn, B, Mo, Al, Pb, Ni, Co, but decreased Na, P and Zn in the soil. An application of fly ash to the soil also increased the concentrations of above elements except Na, P and Zn in the seeds and straw of padi and wheat crops. The available as well as elemental concentrations in the plants was maximum in the 0 per cent fly ash + 100 per cent gypsum requirement treatment except Na and heavy elements like Ni, Co, Cr. The treatment effects were greater in the fly ash + gypsum requirement combinations as compared to fly ash alone. Saturated hydraulic conductivity and soil water retention generally improved with the addition of fly ash while bulk density decreased. Application of fly ash up to 4.5 per cent level increased the straw and grain yield of padi and wheat crops significantly in both years. The results indicated that for reclaiming sodic soils of the southwest Punjab, gypsum could possibly be substituted up to 40 per cent of the gypsum requirement with 3.0 per cent acidic fly ash. Copyright © 2003 John Wiley & Sons, Ltd.     

小麦灌浆期抗禾谷缢管蚜的生化机制

对禾谷缢管蚜不同小麦抗性品种灌浆期麦穗的几种化学物质和含水量测定表明,抗蚜性与氮素－氨基酸、锌和植物总酚的含量有关。主成分分析表明,高含量氮素－氨基酸、锌和植物总酚对降低该蚜虫的繁殖率最有利,高含量锌可以提高若蚜的死亡率,提高这些物质含量对小麦品种的抗蚜性具有重要的作用。进一步分析氮素中的17种氨基酸表明,高含量异亮氨酸和酪氨酸有助于小麦的抗蚜性。     

A novel method for molecular targeting of insecticide resistance in Rhopalosiphum padi L. (Homoptera: Aphididae)

The bird cherry-oat aphid (Rhopalosiphum padi L.) is a devastating cereal pest that develops high resistance to organophosphate and carbamate insecticides. Because acetylcholinesterase (ACE) is the target of carbamate and organophosphate insecticides, the resistance mechanism usually involves mutations occurring in ACE-encoding genes, Ace1 and Ace2. Here, we describe a novel polymerase chain reaction (PCR)-based method for the diagnosis of resistance cases associated with the point mutation F368L in the Ace2 gene. We amplified a 127 bp DNA fragment from Ace2 gene using a modified reverse primer, and digested the amplification product using SmaI endonuclease. This procedure enabled a simple and rapid distinction between resistant and susceptible genotypes for F368L mutation. Subsequently, we screened 152 R. padi samples, and found that F368L mutation occurred at low frequency, in both the homozygous (R/R) and heterozygous (R/S) states. Based upon the results of this study, we believe that molecular diagnosis of insecticide resistance should be generalized to genes and mutations involved in this process, toward an optimal accuracy of insecticide applications.     

麦蚜迁飞的研究进展

麦蚜分布广、食性杂、繁殖力强,是世界性的农业害虫。在此,从麦蚜的田间网捕、传毒能力、飞行磨测试以及分子遗传学研究等七方面介绍了麦蚜迁飞行为的主要研究进展,讨论了麦蚜迁飞的生态意义,可能的蚜源基地及需要进一步研究的问题。     

小麦生长中后期2种麦蚜垂直分布及生态位的研究

研究了小麦生长中后期麦长管蚜和禾谷缢管蚜的垂直分布及生态位,结果表明,2种麦蚜在麦田混合发生,种群动态相似,主要分布于小麦穗部和中上部叶片,时间生态位和空间生态位宽度值接近,生态位相似性比例分别高达0.8513和0.8418,禾谷缢管蚜的空间生态位重叠值大于麦长管蚜,麦长管蚜的时间生态位重叠值大于禾谷缢管蚜。     

Wheat cultivars and natural-based substances: Impacts on epidemiological parameters of yellow dwarf disease

For many years, control methods against aphid-transmitted barley/cereal yellow dwarf viruses (B/CYDV) in cereal fields were mainly based on the use of neonicotinoid (NNI)-coated seeds. The ban of NNI by the EU in 2018 has reinforced the interest of the scientific community in the characterization of genetic resources and biological protections to find alternatives to chemicals for the management of B/CYDV. Eleven BYDV-susceptible wheat varieties were tested using a set of experimental procedures to evaluate their potential to alter parameters linked to the biology of aphids (Rhopalosiphum padi) and spread of virus (BYDV-PAV). Moreover, two natural-based substances (azadirachtin and mineral oil) were tested for their impact on the ability of aphids to survive, colonize and transmit the virus. Results showed that the 11 genotypes tested have a level of susceptibility to virus infection similar to the susceptible reference cv. Rubisko. However, when characterization focused on virus load, latency period and aphid fecundity, partial resistance phenotypes were observed for some cultivars. Furthermore, azadirachtin increased aphid mortality and decreased aphid fecundity. Thus, in addition to genes described for their ability to limit B/CYDV infections, the genetic backgrounds of B/CYDV-susceptible wheat cultivars and azadirachtin-based treatment should be considered for future management strategies against yellow dwarf disease.     

禾谷缢管蚜、麦长管蚜乙酰胆碱酯酶基因片段的克隆与序列分析

采用RT—PCR技术，设计简并上、下游引物，从禾谷缢管蚜（Rhopalosiphum padi（Linnaeus））和麦长管蚜（Sitobion avenae （Fabricius））中均克隆出2种不同乙酰胆碱酯酶的cDNA片段，分别命名为Rp.acel、Rp.ace2和Sa.acel、Sa.ace2。同源性分析结果表明，Rp.acel、Sa.acel与棉蚜（Aphis gossypii）和桃蚜（Myzus persicae）的Ⅰ型乙酰胆碱酯酶（Acel）基因序列具有96％以上的相似性，Rp.ace2和Sa.ace2与棉蚜和桃蚜的Ⅱ型乙酰胆碱酯酶（Ace2）以及从麦二叉蚜（Schizaphis graminum）中克隆出的乙酰胆碱酯酶基因序列具有95％以上的相似性。说明禾谷缢管蚜和麦长管蚜体内都存在2种乙酰胆碱酯酶基因，而且预示蚜虫体内可能普遍存在2种不同的乙酰胆碱酯酶基因，这2种基因都具有相应的功能。     

龟纹瓢虫对禾谷缢管蚜捕食功能反应的研究

为了了解龟纹瓢虫对禾谷缢管蚜的控制能力,在室内条件下,采用单因素试验设计,分别将禾谷缢管蚜密度(20、40、60、80、100和120头/皿)和龟纹瓢虫密度(1、2、3、4、5和6头/皿)各设6个处理,研究了龟纹瓢虫雌、雄成虫对禾谷缢管蚜的捕食功能反应。结果表明:龟纹瓢虫雌、雄成虫的捕食功能反应均符合HollingⅡ型方程,其捕食量随着猎物密度的增大而增加,但寻找效应随之降低。龟纹瓢虫雌、雄成虫对禾谷缢管蚜的最大日捕食量分别为106.16头和84.56头。龟纹瓢虫的寻找效应还受其种内干扰影响,随着龟纹瓢虫密度的增大,其单头寻找效应呈下降趋势。龟纹瓢虫成虫对禾谷缢管蚜有较强的控制能力,其捕食功能反应符合HollingⅡ模型。     

吡蚜酮对禾谷缢管蚜的亚致死效应

本文研究了吡蚜酮对禾谷缢管蚜的亚致死效应。试验利用刺探电位图谱(EPG)技术测定了亚致死剂量的吡蚜酮对禾谷缢管蚜成虫取食行为的影响,结果表明:经吡蚜酮处理的蚜虫口针从开始刺探到持续吸食韧皮部和木质部汁液的时间明显延长,分别延长至(199.9±34.0)min和(236.4±29.5)min,对照分别为(155.5±18.1)min和(145.5±27.1)min。并且,经药剂处理的蚜虫口针在韧皮部和木质部中持续取食的时间明显缩短,分别为(44.7±9.4)min和(11.8±2.5)min,对照分别为(93.0±24.9)min和(19.0±3.6)min。通过生长和繁殖试验可知:亚致死剂量的吡蚜酮使禾谷缢管蚜的重量显著减轻,繁殖率明显降低。经药剂处理的蚜虫最大重量和最高繁殖率分别为(1.28±0.025)mg/10头和(2.9±0.2)头/成蚜,而对照分别为(1.56±0.099)mg/10头,(5.2±0.2)头/成蚜。