Characterization of some biological control agents from rice seeds in China and in the Philippines

It is well known that rice seed contains large amount of seedborne bacterial pathogens. However, little is known about antagonistic bacteria of the rice seed.     

Characterization of Pseudomonas spp.and related bacteria from rice seeds in the subtropics and the tropics

To explore the bacterial diversity for sustain-able management of the major rice diseases,asurvey of bacterial diversity of rice seed wasconducted in Luzon Island of the Philippines(the tropics)and in Zhejiang Province of China(the subtropics),during 1993-1998.One hun-dred sixteen(0.5kg/sample)and 129(1kg/sample)seed samples were collected from the subtropics and the tropics,respectively.Morethan 3000 bacterial isolates were picked and examined under the UV light for their fluores-cence.After colony morphological,pathogeni-cal,and some bacteriological tests,816 non-pathogenic bacteria isolates were selected forfurther identification using a numeric taxono-     

Morphological and Molecular Characterization of Novel Salt-Tolerant Rice Germplasms from the Philippines and Bangladesh

To screen for new sources of salinity tolerance, 688 traditional rice varieties from the Philippines and Bangladesh were obtained, and their tolerance to hypersaline conditions at the seedling stage was examined. A total of 29 Philippine lines and 15 Bangladeshi lines were scored as salt-tolerant.Morphological assessment(plant height, biomass and Na-K ratio) revealed that among the 44 salt-tolerant accessions, Casibon, Kalagnon and Ikogan had significantly higher relative shoot length difference, relative shoot growth reduction and shoot Na-K ratio than the tolerant check FL478.Additionally, AC and Akundo exhibited significantly higher Na-K ratios than the other genotypes. The genetic diversity of the 44 genotypes was assessed using 34 simple sequence repeat markers. A total of 133 alleles were detected across all loci. Cluster analysis showed that AC, Akundo and Kuplod were clustered along with FL478, indicating a strong genetic relatedness between these genotypes. IR29(susceptible check) was singly separated. The haplotype analysis revealed that none of the 44 genotypes had a similar allele combination as FL478. These accessions are of interest since each genotype might be different from the classical salinity-tolerant Pokkali.     

南方优质中稻新品种引进试验初报

引进南方各省科研单位选育的11个优质中稻新品种(组合)进行试验筛选，试验结果表明K优818、宜香优1577、红莲2号、谷优527等组合，不但高产稳产，而且米质优，抗性强，福建省可加大试验力度．     

Proteins and amino acids of some local varieties of rice seeds (Oryza Sativa L.)

Proteins and amino acids in four local rice (Oryza Sativa L.) varieties were identified. Albumin and globulin were extracted from rice seeds, and the major promoters of these proteins were investigated by polyacrylamide gel electrophoresis to show their patterns.Amino acid composition of the rice seed were determined quantitatively and qualitatively, and classified according to their acidic, basic and uncharged polar groups.Essential amino acids for each variety were determined, and the hydrophobicity index value of Amber 33 was (0.6078), Mishkhab 1 (0.63372), Hybrid 2 (0.6523) and Hwazawi (0.7411).     

关于噬菌体在防治水稻白叶枯病上的研究

培育抗白叶枯病菌的水稻品种,是公认的防治水稻白叶病的一条有效途径。但由于水稻抗性基因单一,容易导致对该病抗性的脆弱;化学防治方法的效果不理想。且易造成环境污染。因此。急需探索一条有效、安全、廉价的新途径。本研究从生物防治的角度出发,建立了一套新的技术体系。利用噬菌体来防治水稻白叶枯病。结果显示。特殊的病原噬菌体能够显著地降低水稻白叶枯病的发病率。     

Genetics for improving biological control agents: the case of entomopathogenic nematodes

Genetics is a powerful means of enhancing the beneficial traits of biological control agents. This is exemplified by the enhancement of tolerance of the entomopathogenic nematode (EPN) Heterorhabditis bacteriophora towards environmental extremes. The genetic approaches taken include selection (for heat tolerance and resistance to nematicides); screening for natural isolates displaying heat tolerance; hybridization (aided by genetic markers) and mutagenesis for generating mutants displaying either desired beneficial traits or marker mutations. Genetic engineering is a most promising tool for enhancing beneficial traits in biological control agents. The success in genetic transformation of EPN opens the way for generating transgenic nematodes carrying genes conferring resistance to various environmental extremes.     

Evaluation of bacterial biological control agents for control of root-knot nematode disease on tomato

Among 19 bacterial strains isolated in Yunnan from rhizosphere soils and plant tissues, Bacillus methylotrophicus strain R2-2 and Lysobacter antibioticus strain 13-6 exhibited the highest antagonistic activity against the tomato root-knot nematode Meloidogyne incognita in plate and greenhouse pot experiments. The two strains, when applied as soil drenches or seed treatments in greenhouse experiments, reduced root-knot severity and incidence on tomato compared to no-bacteria controls. In tomato field trials conducted in separate years, soil drench treatment with either strain reduced root-knot disease levels and increased yields compared to the control. Levels of disease control and yield enhancement provided by the strains were higher than those using the chemicals abamectin and carbofuran. This is the first report of B. methylotrophicus being used as a biocontrol agent against a plant parasitic nematode and the first demonstration that B. methylotrophicus and L. antibioticus can suppress disease caused by root-knot nematodes in the field.     

Economic losses by rats on experimental rice farms in the Philippines

Fifty-one scientists at the International Rice Research Institute took part in a survey to determine the extent of rat damage on experimental rice fields in 1980 and the resultant data loss. Their responses suggested that rat damage occurred in 86·0% of 171 field experiments, causing complete loss of data in 6·4% and partial loss in 59·1%. Survey results indicated that rat damage was unaffected by season or among plots protected by a non-electrified fence, electrified fence, or no fence. The incidence of complete loss of research data was highest in experimental plots protected by an electrified fence. Data losses were estimated as equivalent to monetary losses of about US$ 370 000 for 1 year.     

闭花受精水稻的生物学特性观察

为探索闭花受精水稻的生物学特性,对基因型、基因环境互作型和环境型的３类闭花受精材料共９个品种,进行了花器构造和开花撒粉特性的研究,结果表明,水稻颖花中除了２片较大的浆片外,大多数颖花还有数量不等、发育不一的水浆片存在。水稻在闭颖条件下裂药撒粉能否受精,取决于撒粉量的多少和撒粉时期。     

我国水稻病虫害综合防治技术研究新进展

我国水稻病虫害综合防治技术研究和应用,一直受到国家的高度重视,并从“六五”以来列入国家重大科技攻关计划。经过近ZO年在全国范围内组织的协作攻关,从根本上改变了过去水稻病虫害防治几乎完全依靠化学农药的局面,取得了显著的经济效益、生态效益和社会效益。但随着耕作制度、种植结构和栽培技术的发展与变化,病虫害防治出现了新问题。为此,“九五’潮间国家继续立项支持,组织全国IO个科研和教学单位协作攻关,取得以下主要研究进展。一、组建了水稻重大病虫害GIS预测预报系统在“八五”基础上,搜集了江淮、江汉、四J;D、太…     

Impact of preharvest application of biological control agents on postharvest diseases of fresh fruits and vegetables

During the storage of harvested commodities, environmental parameters are quite stable. For this and other reasons, it is generally believed that biological control by means of microbial antagonists may have a greater potential for success when applied postharvest. However, one of the major obstacles to the development of postharvest biocontrol agents is that they are unable to control previously established infections, such as latent and quiescent infections and incipient infections occurring through wounds resulting from harvesting operations. Field application of biocontrol agents may enable early colonisation of fruit surfaces, thus protecting from these infections. Moreover, preharvest applications can be an appropriate strategy for fruits and vegetables subject to damage in postharvest handling. To be successful in preharvest applications, putative biocontrol agents must be able to tolerate low-nutrient availability, UV radiation, high temperature and dry conditions. Some reports of postharvest biological control accomplished by preharvest applications, include apples, avocados, sweet cherries, grapes, and strawberries. This paper provides a brief overview on particular aspects of preharvest application of biocontrol agents to reduce postharvest decay. Research areas relevant for the development of this strategy are also indicated.     

Characterization of oils and chemical analyses of the seeds of wild plants

The Chemical compositions of the seeds of some wild plants have been investigated. The seeds ofHematostaphis berteri, Balanites aegytiaca andXimenia americana contain high levels of oils with values in the range, 38.2–54.5% (w/w). The iodine values of the oils were determined and, forXimenia americana, the value was high, i.e., 149.8 mg/100 g. The storage properties of the oil ofHematostaphis berteri were examined over a period of fifty six days by exposure to light at ambient temperature. The peroxide value of the oil over the period increased by 12-fold of its initial value of 27.5 mEq/kg, suggesting light susceptibility to photo-oxidative degradation. The proximate protein contents were low but the concentrations of mineral elements in the seeds examined were generally high, exceeding the values for the corresponding mesocarps by several orders of magnitude.Abbreviations IV iodine values - PV peroxide values - SV saponification values     

Persistence of seeds of some grass species in cultivated soil

Freshly collected ripe caryopses of twenty-five indigenous grasses were mixed with the top 7–5 cm of sterilized soil confined in cylinders sunk in the ground and cultivated three times yearly. There was a flush of seedlings of most species shortly after sowing, but species differed in the persistence of viable seeds. About one third, including Bromus sterilis, B. hordeaceus, Lolium perenne ssp. perenne, Arrhenatherum elatius and Alopecurus pratensis , produced few seedlings after the initial flush. Others such as Deschampsia cespitosa, Holcus lanatus and Poa trivialis , recognized as forming persistent seed banks in grassland soils, produced appreciable numbers of seedlings in the second year after sowing. Most persistent were species that occur as arable weeds ( Avena fatua, Poa annua ) or in wetlands ( Glyceria plicata, G. maxima, Alopecurus geniculatus ). Emergence from the seed bank generally followed soil disturbance but some species ( Aira praecox, Avena fatua, A. sterilis ssp. ludoviciana, Danthonia decumbens ) exhibited consistent seasonal patterns which may be associated with cyclic changes in germination requirements of the buried seeds.     

Irrigation management transfer (IMT) and system of rice intensification (SRI) practice in the Philippines

SRI practices can usually increase the yield of paddy without using special varieties of rice or chemicals. High yield of paddy can be simply achieved through the combination of transplanting single seedlings about 8–10 days old with just two leaves on 40 cm × 40 cm spacing, providing organic fertilizer, and intermittent irrigation. No pesticides are applied. Historically, integrated management of water and crop (particularly rice) in the Philippines, had its beginning with the Spaniards, but more formal events were recorded in the 1950s by Margate (1954) in “Rice: 100 Cavans (50 kg/cavan) per Hectare.” This was followed by the Water Management Manual released in the 1970s by the Asian Development Bank (ADB) and National Irrigation Administration (NIA). Recently, the Southern Philippines Irrigation Sector Project (SPISP), a joint ADB–NIA effort, has commenced trials with the system of rice intensification (SRI) practice. One of the most specific features of SRI is the intermittent irrigation system which requires assured water supply at necessary timing. It is easier to attain assured water supply on timely manner through irrigation management transfer (IMT) which encourages the empowerment of fair water distribution. This article analyzes the merit of IMT for SRI.