Showing papers on "Leaf spot published in 1970"

Inheritance of resistance to Cercospora leaf spot in sugarbeet.

Abstract: Despite the importance of resistance to leaf spot of sugarbeet, caused by Ccrcospora beticola Sace., and the attention it has received in breeding progTams, there have been few reports of actual experiments designed to provide information concerning the inheritance of resistance. Although experimental evidence is lackjng, resistance is belived to be a quantitative character, ap­ parently governed by several pairs of genes and subject to a con­ siderable amount of environmental influence (1,3,5,7)3. Knowledge of the heritability of a character is important to the breeder, since it indicates the extent and rate of improve­ m ent attainable through selection. The extent of genetic segregation in advanced generations of a cross is a reflection of the heritabilIty of the character in question. Lush (4) defined heritability in two ways. Tn the broad sense, heritability refers to the ratio of genetic variance to total variance. In the narrow sense, heritabili ty is defined as the ratio of additive genetic vari­ ance to total variance. Using Beta maritima as a source of leaf spot resistance, Bilgen et al. evaluated the backcross method of plant breeding as a tool for transferring the higher resistance of B . maritima to sugarbeet. They concluded that estimates of genetic variation and heritabili ty ratios for leaf spot resistance vvere relatively 101·'1 in open-pollinated backcross populations, prob­ ably because of over estimation of environmental variances. The presen t investigation is intended to provide information on the heritabllity of resistance to Cercospora and to provide an :estimate of the minimum number of genes governing resistance.

Records of fungi parasitic on plants in New Zealand 1966-68.

Abstract: Sixteen fungi are described from New Zealand material; the occurrence of 10 of these species has already been noted (Dingley 1969), but 6 species are new recordings from this country. These are Peronospora manshurica (Naoum.) Syd. ex Gaum. on soybean (Glycine max (L.) Merr.), Taphrina betulina Rostr. on silver birch (Betula pendula Roth.), Diplocarpon earlianum (Ell. & Ever.) Wolf on strawberry leaves (Fragaria sp. cult.), Phoma apiicola Kleb. on celery (Apium graveolens L. var. dulce (Mill.) Pers.), Cercoseptoria neriella (Sacc.) comb. nov. on leaves of oleander (Nerium oleander L.), and Alternaria alternata (Fr.) Keissler f.sp. fragaria n.f.sp., which is described as causing a leaf spot on some varieties of strawberry.

Short communication: Algal leaf spot associated with Cephaleuros virescens 1 Ulvophyceae)

Abstract: Sunpapao A, Pitaloka MK, Arikit S. 2015. Algal leaf spot associated with Cephaleuros virescens (Trentepohliales, Ulvophyceae) on Nephelium lappaceum in Thailand. Biodiversitas 17: 31-35. Algal leaf spot disease of Nephelium lappaceum (rambutan) was observed in southern Thailand. The algae were isolated on Bold’s basal medium (BBM) a nd identified based on appearance of the lesions, algal morphology and molecular properties. Characteristics of the filamentous thallus cells, sporangiophores, sporangia, gametes and zoospores were clarified. A portion of the 18S small subunit rRNA was amplified to validate the morphological identification by sequence similarity. To summarize the main results, the plant parasite causing algal leaf spot was identified as Cephaleuros virescens, and in sequencing-based phylogenetic analysis the Cephaleuros PSU-R5.1 isolate from rambutan grouped with the algae in genus Cephaleuros. This confirms C. virescens as a causal organism of algal leaf spot disease on rambutan in southern Thailand.

Seimatosporium leaf spot of Ledum and Rhododendron

Abstract: Seimatosporium ledi sp. nov. causing leaf spot of Ledum groenlandicum Oeder. in Canada is described and its relationship with allied fungi including S. lichenicola (Corda) Shoemaker & Muller (= Coryneum vaccinii Fuckel; = C. rhododendri Schw. var. fusoideum Dearness nom. nud.) and S. rhododendri (Schw.) comb. nov. (≡ C. rhododendri Schw.; = C. triseptatum Peck) is discussed.

The measurement of brown leaf spot on Rice.

Abstract: To obtain the potential range in disease development, a progressive increase in spore concentration of the imperfect state of Cochliobolus miyabeanus was used on twelve rice varieties differing in their resistance to brown leaf spot An analysis of the relative contributory effect of increase in lesion size and numbers on the percentage leaf area diseased was used as a basis to develop a quantitative scoring method in chart form for brown spot disease The chart was aided by the provision of diagrams of the different categories in disease intensity The usefulness of this disease scoring chart and its limitations are discussed Other methods of assessment are proposed to overcome the limitations especially in respect of varietal resistance and seedling blights

A canker and foliage disease of yellow birch. II. Artificial infection studies with Diaporthe alleghaniensis

Abstract: Disease symptoms found in nature on yellow birch (Betula alleghaniensis Britt.) infected by Diaporthe alleghaniensis R. H. Arnold, were induced by inoculation of seedlings and saplings with mycelium or conidia. On vigorously growing yellow birch plants, cankers, dead shoots, blackened necrotic petioles and mid-veins of leaves, and leaf spot developed during the inoculation year, and dieback occurred the next spring. Spore tendrils of the Phomopsis state of the pathogen were found on the most recently killed parts of the plants from May until early July. Initial symptoms were most severe on young tissues, and inoculation of shoots caused more damage to seedlings than inoculation of older tissues. The pathogen persisted in the host for several years without symptom expression, or in healed-over cankers. Initial symptoms were more severe on unshaded than on shaded seedlings, but shading increased the ultimate severity of the disease. Soil temperature and soil moisture did not influence artificial infection a...

Some aspects of transmission and electron microscopy of necrotic leaf spot of Aspen.

Abstract: Continued studies on the necrotic leaf spot disease of Populus tremuloides Michx. and related hybrids have verified transmission of the causal agent by grafting and demonstrated its passage through seed. Attempted transmissions by mechanical means to a wide variety of herbaceous hosts were negative except for extracts from two hybrids which induced necrotic spots on Vigna sinensis cv. Black Eye.Some aspects of disease development were revealed by electron microscopy. Attempts to visualize a causal agent were not successful but occasional virus-like aggregates were observed.

Forest microfungi. IV. A leaf spot of Populus caused by Cladosporium subsessile

Abstract: The binomial Phaeoramularia maculicola (Rom. & Sacc.) n. comb. (≡ Torula maculicola Rom. & Sacc, syn. Cladosporium subsessile Ell. & Barth.) is proposed for a fungus causing leaf lesions on various Populus species in Canada, the United States, and Sweden. The generic relationships of the organism are discussed, a detailed description provided, and an account of the symptoms, host range, and distribution of the disease given. Differences in morphology of the fungus and symptoms of the disease are emphasized in distinguishing this syndrome from the shoot and leaf blight caused by Pollaccia radiosa (Lib.) Bald. & Cif.