Showing papers on "Leaf spot published in 1977"

Disease and insect resistance in rice.

Abstract: Publisher Summary This chapter reviews the progress made in developing rice that is resistant to diseases and insects. Among cereal crops, rice is the host of the largest number of diseases and insect pests. These cause serious yield loss annually. The magnitude of loss caused by diseases and insects, increases as the level of rice production per unit area increases. The chapter discusses the nature of the disease or insect, its distribution, genetic variability of the pathogen, host resistance, genetics of resistance, and breeding for resistance. Fungal diseases attack the plant foliage, stems, roots, leaf sheath, or inflorescence, and grains. Four fungal diseases: blast, sheath blight, brown spot, and narrow brown leaf spot; two bacterial diseases: bacterial blight and bacterial streak; and five virus diseases: tungro, grassy stunt, stripe, dwarf, and hoja blanca have been discussed in the chapter. To minimize yield loss from disease and insect attacks, varieties with multiple resistances to most major diseases and insects are required. Also, a systematic international survey of races or biotypes of major diseases and insects should be carried out with the use of differential varieties.

Genetical relationships between reactions to bacterial leaf spot, yellow mosaic and Cercospora leaf spot diseases in mungbean (Vigna radiata)

Abstract: Studies on the inheritance pattern of bacterial leaf spot (BLS), yellow mosaic (YM) and Cercospora leaf spot (CLS) reactions in crosses of BLS and YM resistant/tolerant but CLS susceptible × CLS resistant but BLS and YM susceptible parents indicated that resistances to BLS and CLS were governed by single dominant genes, whereas YM tolerance was a monogenic recessive character. The studies also indicated that these three genes were inherited independently. The simple inheritance pattern and independent assortment of the genes governing resistance/tolerance to these diseases suggest that the usual breeding methods will be adequate to develop multi-disease resistant mungbean cultivars.

Accumulation of the flavonoids betagarin and betavulgarin in Beta vulgaris infected by the fungus Cercospora beticola

Abstract: The flavanone betagarin and the isoflavone betavulgarin occur in necrotic lesions resulting from infection of sugarbeet (Beta vulgaris) leaves by Cercospora beticola. In whole infected leaves from cultivars of varied leaf spot susceptibility, there were significant differences among cultivars in content of both flavonoids, but only betavulgarin content was significantly correlated with a visual rating of disease severity. In lesions, the content of both compounds differed significantly among cultivars, but only betavulgarin content differed with time after disease initiation. At 3 weeks after plants were inoculated with a suspension of fungal spores, lesion betagarin concentrations were 300 to 1050 μg/ml, depending on cultivar, and betavulgarin contents were from 50 to 200 μg/tnl. When compared with data from in vitro bioassays, these amounts appear potentially capable of limiting fungal growth. However, the correlation coefficient between visual rating of disease severity and compound contents per lesion was non-significant for each flavonoid.

Groundnut Rust in the United States and the Caribbean

Abstract: Groundnut rust, caused by Puccinia arachidis Speg., is endemic in the West Indies and has occurred with increasing frequency in the United States in recent years. Since 1970 this highly destructive fungus has become established throughout Asia and Oceania, in Australia, and in much of Africa. Rust, together with the leaf spots, greatly restricts production of groundnuts in the Caribbean and in Central America. However, it has not been a major cause of crop losses in the USA except in South Texas during 1971. The fungus does not overwinter in the USA but airborne uredospores are blown in from subtropical areas. Several fungicides currently recommended for leaf spot control are also effective against rust. Three distinct groundnut genotypes are known sources of marked resistance: Tarapoto (P.l.s 259747, 341879, 350680, 381622, 405132); Israel Line 136 (P.l.s 298115 and 315608); and DHT 200 (P.l. 314817). The resistance is physiological and apparently bigenic and recessive. Variation in reaction to ...

Effects of Pseudopeziza leaf spot disease on growth and yield in lucerne

Abstract: Growth analysis of lucerne plants infected with Pseudopeziza medicaginis compared with growth analysis of healthy plants showed that, while infection caused a general decrease in relative growth rate and leaf area ratio and affected the relative proportions of leaf, stem and root, there was no overall change in the growth pattern during the experimental period (7 weeks). In addition to retarding the net assimilation rate in leaves and roots, infection did slow down the rate of increase of net assimilation rate in leaves as well as its rate of decrease in roots. Infection delayed and possibly reduced flowering. Glasshouse, phytotron and field trials showed that infection with P. medicaginis can reduce dry matter production in lucerne by over 40%. It was shown that, in the absence of fresh infections, the influence of a single period of infection can have a considerable long-term effect.

A Comparison of the Esterase and Catalase Zymograms of Fusarium Species with Special Reference to the Classification of a Causal Fungus of Fusarium Leaf Spot of Rice

Abstract: The causal agent of Fusarium leaf spot of rice (Kasshokuhagare-byo) was identified as Fusarium nivale (pink snow mold) in 1970, however, there are still some objections. To clarify this problem zymograms of non-specific esterase and catalase excreted by the causal fungi were compared. A preliminary comparison of various formae speciales of F. oxysporum and F. solani showed that the zymograms are species specific and useful for identification and taxonomy of Fusarium species. The zymograms of the leaf spot of rice were strikingly different from those of F. nivale causing typical pink snow mold. Differences were also observed between F. nivale from pink snow mold and that from various graminaceous plants in summer. The significance of zymogram diversity in the taxonomy of Fusarium species and the classification of the leaf spot fungus of rice were discussed.

Genetical relationships between reactions to bacterial leaf spot . yellow mosaic and cercospora leaf spot diseases in mungbean

Abstract: Studies on the inheritance pattern of bacterial leaf spot (BLS), yellow mosaic (YM) and Cercospora leaf spot (CLS) reactions in crosses of BLS and YM resistant/tolerant but CLS susceptible x CLS resistant but BLS and YM susceptible parents indicated that resistances to BLS and CLS were governed by single dominant genes, whereas YM tolerance was a monogenic recessive character The studies also indicated that these three genes were inherited independently The simple inheritance pattern and independent assortment of the genes governing resistance/tolerance to these diseases suggest that the usual breeding methods will be adequate to develop multi-disease resistant mungbean cultivars

Necrotic Leaf Spot of Egg Plant Caused by Pseudomonas cichorii

Abstract: A new bacterial disease was found on leaves of egg plant grown under vinyl-house condition in winter of 1969 in Tokushima prefecture, Japan. The disease usually occurred on leaves, peduncles, and buds, and rarely occurred on stems, petioles, and fruit. The small necrotic spots appeared at first and they fused into large lesions with irregular margin. From this symptom, •gnecrotic leaf spot of egg plant•h was proposed as the disease name. The pathogen attacked egg plant, pot marigold, lettuce, and tomato by artificial spraying inoculation. The bacteriological and serological characteristics of the pathogen were determined. The bacterium was aerobic, Gram negative, and motile by 1 to 7 polar flagella. It produced acid on Hugh-Leifson medium only under aerobic condition. It grew Uschinsky's and Cohn's solution, and did not change Litmus milk. It showed positive reaction in the test of production of green fluorescent pigment, Kovacs' oxidase, and ƒÀ-glucosidase, while negative in arginine dihydrolase, hydrolysis of margarine, and potato rot. It did not produce hydrogen sulfide, levan, and 2-keto gluconate. It produced acid from glucose, fructose, galactose, glycerol, and mannitol, but no acid from sucrose, maltose, lactose, and salicin. It produced alkali from tartrate, malonate, and citrate. It could not grow at 35C. Optimum temperature for growth was 25C and thermal death point was 48C. Antiserum made from living whole cells of the isolate Ep-1, reacted to all of the 5 isolates of the pathogen tested in agar gel diffusion method, but did not react to other pseudomonads. On the basis of bacteriological and serological characteristics and pathogenicity, the present bacterium was identified as Pseudomonas cichorii (Swingle) Stapp 1928. This is the first report of this bacterium to occur on egg plant in the field. Pseudomonas calendulae (Takimoto) Dowson 1943 is thought to be synonym of P. cichorii. (Received September 24, 1977)

Peanut leaf spot and rust control on the Atherton Tableland

Abstract: An account of the rates and vols. of bravo flowable and du-ter extra used to control leaf spot (Cercosporidium personatum) [Mycosphaerella berkeleyii] and rust (Puccinia arachidis) on groundnut in this part of Qd

Perpetuation of Pyricularia penniseti causing brown leaf spot of bajra

Abstract: Conidia of the pathogen of Pennisetum typhoides are relatively short lived. Stromata remained viable at high summer temps. The fungus could survive in the soil throughout the year, producing hyphae and chlamydospores. It was externally seed borne

Fungicidal composition for agriculture and horticulture use

Abstract: PURPOSE:Fungicidal composition comprising a benzanilide fungicide and a specific org phosphorus compound, which shows synergistic effects in combatting sheath blight, blast, and Helminthosporium leaf spot on rice with a small amount of application

HOW TO Identify and Control Leaf Spot Diseases of Black Walnut

Abstract: Growing black walnut in pure stands is becoming more and more common. Although this practice has definite economic advantages, it can aggravate disease problems. This is especially true of leaf spot diseases, which multiply rapidly where large numbers of susceptible leaves are concentrated in a small area. Three such diseases are especially common on lack alnut: walnut anthracnose, bull's-eye leaf spot, and white mold. All are becoming more prevalent as more walnut plantations are established. The symptoms produced by each of the three diseases are distinct and the grower can easily learn to tell them apart.

Incidence of a New Disease, Zonate Leaf Spot of Tea in Japan and the Morphology and Cultural Characters of the Pathogenic Fungus

Abstract: 昭和48年,鹿 児島県 内山間地帯の数地域の茶園で,成 葉が集団的 に葉枯症状を呈 し,落 葉する新 病 害が発生 し た。 この うち一部 地域では既 に10年 位の発 生歴が あ り, 発生面積は 漸次 拡大 してき た とい うことで,著 者 らが発 生 を確 認 した当時か ら被害の拡大が憂 慮 され ていた。 こ の予想にたがわず,本 病は51年 には県 内十数 の市町の茶 園でみ られ るようにな り,静 岡県,島 根県で の発生報告 もあ り,今 後 さらに発生お よび被 害 の増大の可能性 が推測 され てい る。 り病 葉か らの菌 の分離お よびそれ らを用い た接種試験の結果,病 原は糸状菌で,こ の菌 は茶樹以外の多数 の植物に対 して も病原性を 示 し,数 種のツバ キ科植物や ツツ ジ等では 自 然発病 も確認 された。本病 は茶樹および関連 作物に病徴,病 原菌 に関 して類 似の病害の報 告が見当 らないた め新病害 と考え られ る。 そ こでその発生 の概要 とこれまでに行 った 試験結果を報告す る。なお,病 原菌は未同定 であるが,本 病 をその病徴か ら茶輪紋葉枯病 と呼ぶ ことを提案す る。