Components of adult plant resistance to powdery mildew (Erysiphe graminis f. sp. avenae) in oats

The adult plant reaction to mildew (Erysiphe graminis f. sp. avenae) of four oat genotypes was studied. A negative relationship existed in these genotypes between length of latent period and the percentage leaf area with mildew. The very susceptible CI 4877 had the shortest latent period and the largest area of leaf infected, while the highly resistant Cc 4761 had the longest latent period and the least leaf area covered with mildew. The same association also occurred between leaves within a genotype, particularly those genotypes with adult plant resistance, i.e., Maldwyn and Cc 4761. The more recently developed upper leaves showed the longest incubation period and least percentage area affected compared with lower leaves. A visual score of pustule sporulation indicated that CI 4877, Milford and Maldwyn had similar well-sporulating foci, but in Cc 4761 the pustules showed significantly less sporulation. Estimates of the relative number of spores produced per day over a 15 day period reflected the level of resistance. Thus the most susceptible genotype CI 4877 released over 50 times more spores than Cc 4761, while Milford and Maldwyn respectively produced 9 and 4.5 times more spores than the highly resistant Cc 4761. The longer latent period of Cc 4761 was reflected in the delay this genotype showed in reaching its relatively low peak production of spores. The possible use of the latent period as a factor when selecting for adult plant resistance in early growth stages is discussed.     

The effect on grain yield of adult plant resistance to mildew in oats

Lines were selected from progeny of the crosses Maldwyn × Milford and Maldwyn × Sun II which consistently exhibited small and large amounts of mildew in similar situations. These are referred to as ‘low’ and ‘high’ mildew lines respectively. In small plot field trials conducted in 1971, 1972 and 1973 the low mildew lines produced substantially more grain each year compared with the high mildew lines in plots where mildew was allowed to develop normally. In plots which were kept comparatively free from infection by spraying with tridemorph, both low and high mildew lines gave similar yield. When the unsprayed plots were compared with the sprayed plots the low mildew lines invariably showed very small losses in grain yield and the high mildew lines usually very large losses. This same trend was evident also in the parent cultivars in 1972. Maldwyn, with only 7·9% mildew cover in the unsprayed plots due to its resistance, suffered a decrease of only 9·2% in grain yield compared with losses of 17·1 and 20·3% in the more susceptible cultivars Milford and Sun II. Certain lines and cultivars sustained heavy levels of mildew without corresponding loss of grain yield, i.e. showed low sensitivity to the disease. The importance of combining low sensitivity (or tolerance) with adult plant resistance to mildew is discussed.     

The preconditioning effect of day-length and light intensity on adult plant resistance to powdery mildew in oats

Oat genotypes with partial resistance to mildew exhibited a higher level of adult plant resistance (a.p.r.) when grown in 16 h compared with 8 h day-length. This increased resistance was expressed in the upper leaves, and to some extent in the lower, earlier-developed leaves. The expression of increased resistance coincided with floral initiation in Maldwyn, but preceded it in CC4761. The development of a.p.r. and floral initiation were thus not inherently linked, but conditions which accelerated the plants' ontogeny also caused earlier expression of resistance. For the most efficient testing of breeding material, plants should be grown at long day-length and high light intensity. When plants are grown at 16 h day-length and constant temperature of 15 ^oC, the leaf segments should be inoculated at the 6 to 8 leaf stage because normally susceptible genotypes showed marked resistance when inoculated later.     

Probenazole-induced accumulation of salicylic acid confers resistance to Magnaporthe grisea in adult rice plants

Probenazole (PBZ) is the active ingredient of Oryzemate, an agrochemical which is used for the protection of rice plants from Magnaporthe grisea (blast fungus). While PBZ was reported to function upstream of salicylic acid (SA) in Arabidopsis, little is known about the mechanism of PBZ-induced resistance in rice. The role of SA in blast fungus resistance is also unclear. The recommended application period for Oryzemate is just before the Japanese rainy season, at which time rice plants in the field have reached the 8-leaf stage with adult traits. Thus, the involvement of SA in PBZ-induced resistance was studied in compatible and incompatible blast fungus-rice interactions at two developmentally different leaf morphology stages. Pre-treatment of inoculated fourth leaves of young wild-type rice plants at the 4-leaf stage with PBZ did not influence the development of whitish expanding lesions (ELs) in the susceptible interaction without the accumulation of SA and pathogenesis-related (PR) proteins. However, PBZ pre-treatment increased accumulation of SA and PR proteins in the eighth leaves of adult plants at the 8-leaf stage, resulting in the formation of hypersensitive reaction (HR) lesions (HRLs). Exogenous SA induced resistance in adult but not young plants. SA concentrations in blast fungus-inoculated young leaves were essentially the same in compatible and incompatible interactions, suggesting that PBZ-induced resistance in rice is age-dependently regulated via SA accumulation.     

Soil-plant-water aspects of ozone phytotoxicity in tomato plants

Summary Tomato (Lycopersicon esculentum Mill.) plants were grown in controlled environments and subjected to different soil water regimes. At 3-, 5-, and 7-leaf growth stages, plants were fumigated with ozone at 50 or 100 pphm for 1 h. Plants at 5- or 7-leaf stage were not as sensitive to ozone as were the young plants fumigated at 3-leaf stage. At the 7-leaf stage, leaf injury at nearoptimum water condition was very minimal, even at ozone concentration of 100 pphm. Ozone treatment decreased total dry matter of optimally watered plants fumigated at the 3-leaf stage. Plants subjected to water stress resulting in low leaf relative turgidity prior to ozone fumigation, were considerably protected from ozone phytotoxicity. Open stomata were an important factor in ozone phytotoxicity. Post-fumigation water regimes had no effect on eventual leaf injury. re]19720627     

Inheritance of adult plant resistance to mildew in oats

Adult plant resistance of a durable nature in oat cv. Maldwyn was studied in a cross with the very susceptible cv. Selma, using a replicated F₃ population grown under field conditions. Segregation was found to be continuous, with no discrete classes, and a preponderance of segregants showing intermediate values between the two parents indicating additive genetic control. The number of effective genetic factors segregating in this cross was estimated to be four when material was at the ‘boot stage’ (G.S. 45) and eight or nine at the stage when flowering was complete (G.S. 69). At this latter stage Maldwyn was estimated to be contributing about seven factors for resistance, and the susceptible Selma one or possibly two. Further improvement, through accumulation of factors from both parents, could be expected and this has subsequently been achieved. The possible effects, on the durability of resistance in highly resistant transgressive segregants, from increased selection pressure on the pathogen are discussed.     

水稻对受体植物化感作用的遗传生态学研究

选用化感作用潜力差异较大的 5个水稻品种 (系 ) ,按不完全双列杂交设计 (4× 5 )配制成一套包括亲本、F1两个世代的遗传材料 ,在不同环境条件下 ,测定其不同叶龄时期对受体植物莴苣幼苗茎长的抑制作用 .采用包括基因型与环境互作的数量性状加性 显性发育遗传模型 ,分析了水稻化感作用的动态遗传及与环境互作效应 .结果表明 ,水稻叶龄在 7叶期对莴苣茎长的化感作用受加性效应的影响 ,在 3叶期和 6叶期由显性效应控制 ,在 5叶期和 8叶期加性和显性效应均有作用 ,以显性效应为主 ,呈现间断表达的遗传特点 .普通狭义遗传率在 5叶期、7叶期和 8叶期达显著水平 ,随叶龄增大趋于下降 .水稻化感作用受基因型与环境互作效应的影响较大 ,应注意控制水稻生长发育的环境 ,以达到最佳利用水稻化感作用潜力的目的 .     

THE EFFECT OF MCPA AND 2:4-D HERBICIDES ON THE QUALITY OF SPRING OATS FOR MILLING AND PROVENDER FEEDING

MCPA applied to oats at the 1- to 2-leaf stage had slight effects on grain quality, whereas 2:4-D at this stage generally increased kernel weight, husk ash content, and content of abnormal grains, and decreased the grain yield. Applied at the 4- to 5-leaf stage, 2:4-D also increased kernel nitrogen content and decreased kernel oil content. Effects were enhanced as the dosage increased. Yielder and Craigs Afterlea were most susceptible to 2:4-D at the 4- to 5-leaf stage; Sun II, a relatively resistant variety, at the 6- to 7-leaf stage.     

Changes in apoplastic antioxidants induced by powdery mildew attack in oat genotypes with race non-specific resistance

Three oat (Avena sativa L.) lines which show differential responses to attack by the biotrophic fungal pathogen Blumeria graminis DC f. sp. avenae Marchal, which causes powdery mildew, were studied: Maldwyn shows the strongest resistance in adult plants; Selma shows greater susceptibility; while a Selma × Maldwyn hybrid, OM1387, has a similar degree of resistance to Maldwyn. Host responses to pathogen attack were complete 48 h after inoculation but largely accomplished within the first 24 h, the point when material was taken for enzyme and metabolic assays. In Maldwyn and OM1387 about 80% of attacked cells showed localized autofluorescent host-cell responses but this fell to less than 20% in Selma. A cytoplasmic marker enzyme, glucose 6-phosphate dehydrogenase, was used to determine contamination of the apoplastic extracts by cellular components. After correction for cytoplasmic contamination, up to 4% of the total foliar activities of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase and monodehydroascorbate reductase activities were detected in the apoplast. The apoplast contained about 2% of the total foliar glutathione pool and dehydroascorbate, but not ascorbate, at values amounting to 10% of the total foliar ascorbate plus dehydroascorbate pool. Twenty-four hours after inoculation the foliar or apoplastic ascorbate pools were similar in inoculated and control leaves. Foliar catalase activity increased in both susceptible and resistant responses. Resistance correlated with increased total foliar glutathione, an increase in the ratio of reduced to oxidized glutathione and with decreased total activities of foliar ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase and monodehydroascorbate reductase. Received: 17 April 1998 / Accepted: 28 August 1998     

Effects of Four Temperature Regimens on the Gibberellin Content of Winter Wheat cv. Kharkov

Kharkov 22 M.C. winter wheat was grown continuously from seed under four temperature regimens; 2°C; 2°C then transferred to 20°C; 6°C, and 20°C. Plants were harvested at the 4-leaf stage (except the 2°C plants which were harvested at the 3-leaf stage) and the levels of endogenous gibberellins (GAs) were measured and their cold hardiness determined. The GA content of 20°C and the 6°C seedlings were about equal and greater (by 4- to 30-fold) than the GA content of 2°C seedlings that had been transferred to 20°C (i.e. vernalized). The GA content of the 2°C seedlings was least of all, being 28- to 320-fold less than the 20°C seedlings. At harvest the leaves of the 20°C seedlings were somewhat larger than those of the seedlings grown at 2°C and transferred to 20°C. The leaves of the 6°C seedlings were very much smaller and the leaves of the 2°C seedlings were smallest of all. It is concluded that while GAs may play a role in controlling leaf size and level of cold hardiness of wheat, they are not the most important factor.     

Effect of three resistant soybean genotypes on the fecundity, mortality, and maturation of soybean aphid (Homoptera: Aphididae)

The fecundity, longevity, mortality, and maturation of the soybean aphid, Aphis glycines Matsumura (Homoptera: Aphididae), were characterized using three resistant soybean, Glycine max (L.) Merrill, genotypes ('Dowling', 'Jackson', and PI200538 'Sugao Zarai') and two susceptible genotypes ('Pana' and 'Loda'). Antibiosis in the resistant genotypes was demonstrated by a significant decrease in fecundity and longevity and increased mortality of A. glycines. Aphid fecundity, measured as number of offspring produced in the first 10 d by each viviparous aptera, was higher on Pana than on the resistant genotypes. Aphid longevity, the mean number of days a 1-d-old adult lived, was 7 d longer on Pana than on Dowling and Jackson. The mortality of both viviparous apterae and nymphs on resistant genotypes was significantly higher than on susceptible genotypes. A greater number of first instars survived to maturation stage (date of first reproduction) on susceptible plants than on resistant plants. None of the first instars placed on Dowling and PI200538 leaves survived to maturation. Observations of aphid behavior on leaves indicated that aphids departed from the leaves of resistant plants 8-24 h after being placed on them, whereas they remained indefinitely on leaves of susceptible cultivars and developed colonies. Reduced feeding due to ingestion of potentially toxic compounds in soybean may explain the possible mechanism of resistance to the soybean aphid.     

Evaluation of Rice Cultivars under Greenhouse Conditions for Adult-Plant Resistance to Pyricularia oryzae

Six rice cultivars showing various types of resistance or susceptibility to Pyricularia oryzae in the field were compared under controlled environmental conditions. The resistance of the cultivars with adult-plant resistance was race-specificat early growth stage. On all cultivars tested, blast infection became increasingly reduced on either leaves of adult plants or older leaves, as observed in rice plants of different leaf stages infected with different individual races. Their increase inhost resistance was marked by an apparent transition in infection type and reduced blast severity depending on leaf age and developmental stage of plants. The ranking of disease severity of the adult-plantresistant cultivars to different races was constant during plant development, whereas that of the susceptible cultivars was differential. It is suggested that different degrees of resistance in rice cultivars may exist in seedlings and be consistently maintained during plant development, probably becoming more distinct as rice plants mature.     

Contribution of ethylene biosynthesis for resistance to blast fungus infection in young rice plants

The role of ethylene (ET) in resistance to infection with blast fungus (Magnaporthe grisea) in rice (Oryza sativa) is poorly understood. To study it, we quantified ET levels after inoculation, using young rice plants at the four-leaf stage of rice cv Nipponbare (wild type) and its isogenic plant (IL7), which contains the Pi-i resistance gene to blast fungus race 003. Small necrotic lesions by hypersensitive reaction (HR) were formed at 42 to 72 h postinoculation (hpi) in resistant IL7 leaves, and whitish expanding lesions at 96 hpi in susceptible wild-type leaves. Notable was the enhanced ET emission at 48 hpi accompanied by increased 1-aminocyclopropane-1-carboxylic acid (ACC) levels and highly elevated ACC oxidase (ACO) activity in IL7 leaves, whereas only an enhanced ACC increase at 96 hpi in wild-type leaves. Among six ACC synthase (ACS) and seven ACO genes found in the rice genome, OsACS2 was transiently expressed at 48 hpi in IL7 and at 96 hpi in wild type, and OsACO7 was expressed at 48 hpi in IL7. Treatment with an inhibitor for ACS, aminooxyacetic acid, suppressed enhanced ET emission at 48 hpi in IL7, resulting in expanding lesions instead of HR lesions. Exogenously supplied ACC compromised the aminooxyacetic acid-induced breakdown of resistance in IL7, and treatment with 1-methylcyclopropene and silver thiosulfate, inhibitors of ET action, did not suppress resistance. These findings suggest the importance of ET biosynthesis and, consequently, the coproduct, cyanide, for HR-accompanied resistance to blast fungus in young rice plants and the contribution of induced OsACS2 and OsACO7 gene expression to it.     

35S驱动Pib基因启动区和编码区的转基因初步分析

将包含Pib基因启动区及下游完整编码区的9.9 kb DNA片段克隆到双元载体pPZP2Ha3(+)中, 构建了35S驱动的正义表达载体pNAR701(20.3 kb); 同时将Pib基因编码区6 986~9 392 bp之间的DNA片段, 克隆到双元载体pPZP2Ha3(-)中, 构建了35S驱动的反义表达载体pNAR703(12.8 kb); 用农杆菌介导法转入中感稻瘟病水稻品种R109中。PCR、Southern blot鉴定以及转基因T0代种子的潮霉素抗性鉴定证明, 目的基因已经整合到R109基因组中, 并能在后代稳定遗传。Northern blot分析表明含有启动区及下游完整编码的Pib基因片段在35S驱动下能够在转基因后代中表达。对T1代苗期转基因植株和分蘖期离体叶片进行抗稻瘟病初步分析, 结果显示pNAR701转基因植株对稻瘟病生理小种ZD1和ZG1的抗性较对照增强, 而转反义片段的pNAR703转基因植株对稻瘟病的抗性较对照减弱。     

Quantitative resistance of some Elite wheat lines to Puccinia striiformis f. sp. tritici

Host resistance is the most economical way to manage wheat stripe rust caused by Puccinia striiformis f. sp. tritici. Slow rusting, a type of quantitative resistance, has been reported to last for a long time. Quantitative resistance, in terms of slow rusting parameters including final rust severity (FRS), apparent infection rate (r), relative area under disease progress curve (rAUDPC) and coefficient of infection (CI), was evaluated in a set of 29 wheat genotypes along with susceptible control during 2008–2009 and 2009–2010 cropping seasons. This study was conducted in field plots at Ardabil Agricultural Research Station (Iran) under natural infection conditions with two times artificial inoculation. Artificial inoculation was carried out by yellow rust inoculum having virulent genes against Yr2, Yr6, Yr7, Yr9, Yr22, Yr23, Yr24, Yr25, Yr26, Yr27, YrA and YrSU. Results of mean comparison for resistance parameters showed that lines C-86-1, C-86-2, C-87-1 and C-87-3 along with susceptible had the highest values of FRS, CI, r and rAUDPC, therefore were selected as susceptible lines. The lines C-86-3, C-86-9, C-87-2, C-87-6, C-87-8, C-87-11 and C-87-18 were susceptible at the seedling stage and had low level infection at adult plant stage. Consequently, these lines with low different parameters most probably have slow rusting resistance. The remaining lines had no infection or were at low level of infection. Thus, they were selected as resistant or moderately resistant lines. In this study, correlation coefficient between different parameters of slow rusting was significantly high (r = 0.92–0.99).     

Metabolic regulation in diseased leaves. I. The respiratory rise in barley leaves infected with powdery mildew

Photosynthetic and respiratory activities have been measured in leaves of Hordeum vulgare L. var. Manchuria (barley) after infection with Erysiphe graminis var. hordei (powdery mildew). Two isogenic lines, one resistant to infection and the other highly susceptible, were examined.

These isogenic lines showed very different physiological responses following infection. Photosynthesis and the chlorophyll content of resistant leaves was unaffected by infection. Respiration increased slightly and this was accompanied by small increases in activities of enzymes of glycolysis, the pentose-P pathway and the tricarboxylic acid cycle.

The infection of susceptible leaves resulted in a slight increase in photosynthesis 48 hours after inoculation, but subsequently there was a progressive decrease in the photosynthesis of these leaves compared with that of noninfected leaves. The capacity of infected leaves for partial reactions of photosynthesis such as the Hill reaction and the photoreduction of nicotinamide adenine dinucleotide phosphate (NADP¹) decreased during the later stages of infection. The levels of chlorophyll, NADPH-diaphorase and aldolase also declined. There was no detectable difference in the respiration of infected and noninfected leaves until 48 hours after inoculation. After this time, the infected leaves showed a higher respiration, the maximum difference occurring about 144 hours after inoculation. The respiratory increase was not accompanied by significant changes in the levels of enzymes of glycolysis and the tricarboxylic acid cycle with the exception of malate dehydrogenase which was lower in infected leaves. In contrast, the activities of glucose-6-P dehydrogenase and 6-P-gluconate dehydrogenase showed changes similar to that observed for respiration.

The respiration and the activities of glucose-6-P dehydrogenase and 6-P-gluconate dehydrogenase did not increase in infected leaves of etiolated plants, even when excellent growth of the fungus was established by growing the plants in White's basal medium supplemented with sucrose. The respiration of a susceptible mutant barley (the yellow-green virescent mutant of the variety Himalaya) when grown in the light at 11° was not changed by infection although the characteristic respiratory rise occurred in plants grown at 15°. At the lower temperature chloroplasts fail to develop in this mutant, although development is normal at 15°.

It is suggested that the pathogen is not directly responsible for the increase in respiration in green leaves, rather that this is a response in the host cells to a loss of photosynthetic capacity.

     

拟南芥与大豆疫霉菌的非寄主互作及一个感病突变体的遗传分析

非寄主抗病性是一种普遍的自然现象,该文通过建立拟南芥．大豆疫霉菌（Arabidopsis thaliana—Phytophthora sojae）非寄主互作系统,筛选对大豆疫霉菌感病的拟南芥突变体,为研究植物对卵菌的非寄主抗病性遗传机制奠定基础。以大豆疫霉菌游动孢子接种拟南芥T—DNA插入突变体离体叶片,从代表12000个独立转化株系的40000株T3代T。DNA插入拟南芥突变体中获得一系列对大豆疫霉菌感病的突变体。其中突变体581-51感病性状表现稳定,离体叶片接菌后3天内出现明显的水渍状病斑,4—5天后产生大量卵孢子和／或孢子囊。细胞学观察发现有典型的吸器形成。Southern杂交和遗传分析结果表明,581—51突变体含有4个T-DNA插入事件,其感病性状可能由隐性单基因控制。     

拟南芥与大豆疫霉菌的非寄主互作及一个感病突变体的遗传分析

非寄主抗病性是一种普遍的自然现象, 该文通过建立拟南芥-大豆疫霉菌(Arabidopsis thaliana-Phytophthora sojae)非寄主互作系统, 筛选对大豆疫霉菌感病的拟南芥突变体, 为研究植物对卵菌的非寄主抗病性遗传机制奠定基础。以大豆疫霉菌游动孢子接种拟南芥T-DNA插入突变体离体叶片, 从代表12 000个独立转化株系的40 000株T₃代T-DNA插入拟南芥突变体中获得一系列对大豆疫霉菌感病的突变体。其中突变体581-51感病性状表现稳定, 离体叶片接菌后3天内出现明显的水渍状病斑, 4–5天后产生大量卵孢子和/或孢子囊。细胞学观察发现有典型的吸器形成。Southern杂交和遗传分析结果表明, 581-51突变体含有4个T-DNA插入事件, 其感病性状可能由隐性单基因控制。     

Characterization of Geminivirus resistance in an accession of Capsicum chinense Jacq

Pepper golden mosaic virus (PepGMV) and Pepper huasteco yellow vein virus (PHYVV), members of the Geminiviridae family, are important pathogens of pepper (Capsicum annuum L.) and other solanaceous crops. Accession BG-3821 of C. chinense Jacq. was reported earlier as resistant to mixed infection with PepGMV and PHYVV. In this work, we characterized the Geminivirus resistance trait present in BG-3821. Segregation analysis suggested that resistance depends on two genes. Our data showed that PepGMV replication in protoplast of resistant plants is approximately 70% lower when compared with the levels observed in protoplasts from susceptible plants. Additionally, viral movement is less efficient in resistant plants. We also evaluated several characteristics commonly associated with systemic acquired resistance (SAR), which is a conserved defensive mechanism. The concentration of salicylic acid was higher in resistant plants inoculated with PepGMV than in susceptible plants. Marker genes for SAR were induced after inoculation with PepGMV in resistant leaves. Similarly, we found a higher accumulation of reactive oxygen species on resistant leaves compared with susceptible ones. A model for the mechanism acting in the Geminivirus resistance detected in BG-3821 is proposed. Finally, the importance of BG-3821 in Geminivirus resistance breeding programs is discussed.