Showing papers on "Plant disease resistance published in 1982"

Expressed resistance to black shank among tobacco callus cultures.

Abstract: Quantitatively inherited resistance to the black shank pathogen (Phytophthora parasitica var. ‘nicotianae’) was expressed among callus tissue cultures of tobacco (Nicotiana). Tissue cultures of genotypes known to posses polygenic mechanisms for black shank resistance expressed that resistance in vitro when challenged by the viable pathogen. Callus of a susceptible cultivar was readily parasitized in culture. Furthermore, single gene resistance to the common pathogen race was also shown to operate in vitro. Nongenetic factors examined did not contribute significantly to the observed differences. Disease expression in vitro appeared to be highly correlated with its expression at the whole plant level. Screening for quantitative disease resistance can be complicated at the whole plant level by variable hostpathogen reactions and by significant genotype × environment interactions. Since quantitatively inherited mechanisms of black shank resistance are expressed in tobacco callus cultures, an in vitro host-pathogen system may be useful in screening tobacco lines for black shank resistance.

Further evidence on the effects of gene H, which confers cane hairyness, on resistance to raspberry diseases

Abstract: Gene H determines cane hairyness in raspberries and was reported to facilitate escape from infection by Botrytis cinerea and Didymella applanata. However, experiments with mycelial inoculations of wounded canes showed that it conferred a form of resistance which was evident for a long period after the establishment of infections by these pathogens. The gene also contributed to the resistance of fruit to B. cinerea and of canes to Leptosphaeria coniothyrium. Alternative hypotheses to explain these observations are discussed: two based upon its possible genetic linkage with a gene or genes for resistance and one based upon its possible pleiotropic effects.

Breeding for resistance to yellow disease of hyacinths. II. Influence of flowering time, leaf characters, stomata and chromosome number on the degree of resistance

Abstract: Analysis of an incomplete diallel design with 14 hyacinth cultivars and 4 wild accessions of Hyacinthus orientalis showed a significant GCA component for resistance to yellow disease. The late flowering hyacinth cultivars ‘King of the Blues’ and ‘Marconi’ and the early flowering Hyacinthus orientalis 70129 were found to be the best combiners for yellow disease resistance. Within a cultivar, the degree of earliness itself was not associated with the degree of resistance. Correlation coefficients of leaf characters and degree of resistance showed that hyacinths with short and/or narrow leaves are generally more resistant than those with long and/or broad leaves. Tetraploid cultivars with few, large stomata tend to be susceptible, diploid ones with many small stomata tend to be the more resistant.

Genetic relationships of brown planthopper resistance to dwarf disease and stripe disease resistance in rice

Abstract: In order to clarify the linkage relationships among resistance genes to the brown planthopper, Nilaparvata lugens Stal., the dwarf disease and the stripe disease, intercrosses among Kanto PL 2, Kanto PL 3, Mineyutaka and Nipponbare were made. Kanto PL 2 is a parental line of japonica type rice resistant to the brown planthopper, and has Bph 1 gene derived from Mudgo. On the other hand, Kanto PL 3 is a japonica parental line resistant to the dwarf disease, and has one dominant gene derived from Pe-bi-hun. These two lines are also resistant to the stripe disease. Mineyutaka is the first resistant cultivar to the stripe disease in Japan, and has St2i gene derived from Modan. Firstly, based on the segregation of F3 lines of the reciprocal crosses between Kanto PL 2 and Kanto PL 3, it was estimated that Bph 1 is independent of the gene for resistance to the dwarf disease in Kanto PL 3.

Progress in the integration of characters in gall mite (cecidophyopsis ribis)-resistant black currants

Abstract: SummaryProgress in breeding black currants combining gall mite resistance conferred by the gene Ce from gooseberry with improved agronomic characters and disease resistance is described. The main donors include Scandinavian cultivars, and the wild species R. bracteosum, R. glutinosum and R. dikuscha. Crosses are being made in 1981 between parents carrying a total of seven of the nine characters: late flowering, frost resistance, large fruit size, high fruit number, good setting, fruit quality, erect habit, mildew resistance and leafspot resistance. BC3, BC4 and BC5 derivatives of gooseberry are now under selection. Several of these progenies include all three other donor species in their ancestry. Further backcrossing may be needed in some lines to restore the Baldwin-type flavour required by juice manufacturers.

Inheritance of field resistance to sorghum charcoal rot and selection for multiple disease resistance

Abstract: Six segregating and nonsegregating generations of three R x S and two S x S crosses were studied for charcoal rot resistance under epiphytotic conditions. CSV-5 (148/168) was comparatively the most resistant parent. The F1 showed partial dominance of resistance.

Effect of different levels of calcium nitrate and potassium dihydrogen phosphate on powdery mildew (Erysiphe graminis DC) infection in resistant and susceptible barley and wheat

Abstract: Y Cultivars of barley and wheat, resistant and susceptible to powdery mildew (Erysiphe graminis), were grown in perlite with added nutrient solutions in which the Ca(N03)2 : KH2P04 ratio was from one-third to three times the normal (1:1) amount in a balanced nutrient solution, i.e., 3:3, 3:1/3, 1/3:1/3, and 1/3:3. The degree of mildew infection was measured by planimetry, or by determining the number of conidia rer 10 g of leaf tissue or estimated visually. The Ethiopian barley cultivar CI 3926/3 was more resistant to mildew than ‘Kenia’, but the level of resistance varied depending on the Ca(N03)h : KH2P04 ratio; both CI 3926/3 and ‘Kenia’ were more resistant when grown in 1/3:3 than in the other treatments. Small darkbrown streaking lesions were produced on CI 3926/3 and to a lesser extent on ‘Kenia’ grown in the high levels of Ca(N0}3h. ‘Aotea’ wheat plants were also resistant to mildew when grown in 1/3:3 and to some extent in 3:3, but susceptible in 1: 1, 3:1/3 and 1/3:1/3. Chlorotic flecking lesions...

Effects of leaf blight and rust on maize in lowland and highland Cameroon environments.

Abstract: COCA (highland), TZPB (lowland) and COCA x TZPB maize varieties were tested at Bambui Plain (1330 m) and Ekona (550 m). Leaf blight and rust were controlled chemically with Dithane-M45 and Benlate, and their use significantly increased the yields of COCA when grown in lowland environments, where it does not possess resistance to lowland leaf blight ( H. maydis ) and rust ( P. polysora ); yields of TZPB were similarly increased in highland areas, where it is susceptible to highland leaf blight ( H. turcicum ) and rust ( P. sorghi ). COCA x TZPB was intermediate in resistance to both diseases at the two locations.