Showing papers on "Plant disease resistance published in 1980"

Potato protoplasts in crop improvement.

Abstract: Clonal populations regenerated from single-leaf cell protoplasts of the potato cultivar `Russet Burbank9 display a high frequency of variation for several horticultural and disease resistance characters. Observations over a period of three tuber generations suggest stable changes in tuber shape, yield, and maturity date, in photo-period requirements for flowering, and in plant morphology. Enhanced resistance to early blight (Alternaria solani) and late blight (Phytophthora infestans) diseases also regularly occurs within regenerated populations. These findings are discussed in the context of possible application to varietal improvement, particularly as they pertain to asexually propagated plants.

Breeding for resistance to coffee berry disease in Coffea arabica L. II. Inheritance of the resistance.

Abstract: The inheritance of resistance to coffee berry disease (CBD) has been studied by applying a preselection test to F2 progenies of a half diallel cross between 11 coffee varieties with different degrees of resistance and to sets of parental, F1, F2, B11 and B12 generations of crosses between resistant and susceptible varieties. True resistance to CBD appears to be controlled by major genes on three different loci. The highly resistant variety Rume Sudan carries the dominant R- and the recessive K-genes. The non-allelic interaction between these two genes is of a duplicate nature. The R-locus has multiple alleles with R1R1alleles present in Rume Sudan and the somewhat less effective R2R2alleles in a variety like Pretoria, which also has the K-gene. The moderately resistant variety K7 carries only the recessive K-gene. The arabica-like variety Hibrido de Timor (a natural interspecific arabica x robusta hybrid) carries one gene for CBD resistance on the T-locus with intermediate gene action. It probably inherited this gene from its robusta parent. There is circumstantial evidence that the resistance to CBD is of a stable nature, but it is advisable to accumulate in one genotype as many resistance genes as possible by combining in the breeding programme the resistance of Rume Sudan with that of Hibrido de Timor.

Screening methods and further sources of resistance to peanut rust

Abstract: creened for resistance to rust at ICRISAT, India. Preliminary field screening was done during the 1977 rainy season when a natural epidemic of rust was in progress. The cultivars or lines which were rated between 2 and 5 on a Spoint scale during this screening were further tested during the 1977/78 dry season employing an infector row system of susceptible cultivars and spreader plants systematically interplanted with the test material. High relative humidity was maintained in the field by operating an overhead sprinkler irrigation system. Percentage leaf area damaged on the test material was estimated at 10 day intervals from approximately 90 days after their emergence until harvest. Each entry was also assessed on a scale proposed by Mazzani and Hinojosa. Two land races, NC.Ac. 17090 and EC. 76446 (292) were more resistant than either PI. 259747 or PI. 298115 which were reported resistant by other workers. In addition, NC.Ac. 17030, NC.Ac. 17132, NC.Ac. 17129, NC. Ac. 17135 and NC.Ac. 17124 were moderately resistant. Four cultivars or lines with different levels of resistance in the field were tested in the greenhouse at three different stages in development. The results indicated that resistance increased as the plants aged.

Effects of soil water level on the development of adult plant resistance to powdery mildew in barley

Abstract: SUMMARY Barley grown in dry soil developed greater adult plant resistance (APR) to powdery mildew (Erysiphe graminis DC. f. sp. hordei Merat) than barley grown in wet soil. Conidial germination and appressorium formation were less, and fungal development between formation of appressoria and elongating secondary hyphae on upper leaves was inhibited, when adult plants were grown in dry soil. Mildew colonies expanded more slowly on leaves of adult plants than on leaves of seedlings, especially if adult plants had grown in dry soil. APR was reduced if plants, previously grown in dry soil, were well watered more than 32 h before inoculation. Conidia originating from plants grown in dry soil had a lower solute potential and greater ability to infect plants grown in dry but not wet soil than conidia originating from plants grown in wet soil. APR could not be attributed simply to increased cell wall or cuticle thickness, nor to lowered leaf solute potentials, as has sometimes been suggested for powdery mildew diseases. Increasing plant age and water stress induced increases in cell wall and cuticle thickness, but these changes did not always coincide with changes in disease resistance. Increasing plant age and water stress also lowered leaf solute potentials but fungal solute potentials were lower than leaf solute potentials and, more importantly, were lower than leaf water potentials. Thus, fungal growth was not limited by the availability of water from the host during penetration and hyphal establishment. It is suggested that resistance levels may be determined not by the thickness of epidermal structures, nor by lowering of solute potential per se, but by specific substances harmful to the fungus which accumulate in either cell wall, cuticle or sap, and whose concentration is dependent on the age and water stress of leaves.

Cotyledon test for major gene resistance to white pine blister rust in sugar pine.

Abstract: Major gene resistance (hypersensitivity) to white pine blister rust can be detected on cotyledons of inoculated sugar pine seedlings shortly after germination. The cotyledon test reduces the time required for evaluating resistant genotypes from a few years to a few weeks.

Genetics of non-nodulation in groundnut (Arachis hypogaea L.

Abstract: In crosses between PI259747 (resistant to Puccinia arachidis) used as male parent on the one hand and NC17 and NC Ac2731 on the other, plants which had no nodules and which had yellow foliage were observed in the F2 from both crosses; the F3 from NC17 X PI259747 was also studied. The data from the F2 and F3 suggested that nodulation was controlled by independent duplicate genes and that it was plants with n1n1n2n2 which did not nodulate.

Induced Mutation for Resistance to Barley Yellow Mosaic Virus

Abstract: A barley mutant resistant to barley yellow mosaic virus (BYMV) was selected from a total of 150 early mutants induced from a variety Chikurin lbaraki I with physical and chemical mutagens. The original variety is a six-rowed covered form with winter habit. The mutant, coded as Ea 52, was originally screened as an early mutant from M3 after acute irradiation of growing plants at vegetative stage with 250R of gamma-rays. When grown in a field severely infested with BYMV, all early mutants except Ea 52 showed mpre or less leaf yellowing characteristic to BYMV disease and proved to be highly susceptible, while Ea 52 exhibited no such external symptoms. The mutant Ea 52 was crossed as male parent to a susceptible mutant Ea 17 that has a similar degree of earliness. Segregation of resistance and susceptibility to disease in F2 was clear-cut from the absence or presence of leaf yellowing and stunting. The number of resistant and susceptible plants was 44 and 126 respectively, giving a good fit to the Mendelian ratio of I : 3 that is expected from a single gene inheritance. The resistant character was completely recessive to the susceptible. No sign of association of the disease resistance with heading time was observed. Although diseased plants more or less reco-vered their growth as temperature rose ih April, almost all of them produced lower number of tillers, smaller plant weight and lower culm length at maturity.

Gene action and phenotypic stability for incidence of downy mildew disease in pearl millet.

Abstract: When line X tester (6 X 16) material of Pennisetum typhoides was infected with Sclerospora graminicola the genotype X environment interaction for disease incidence was predictable; av. performance and line responsiveness seemed correlated. There was a positive correlation between mean performance and general combining ability effects for disease resistance in the parents. A simple major gene mechanism was apparently absent from many crosses but the parent 5054A appeared to transmit resistance to most of its hybrids. Good combining parents included 2 male steriles and 6 male parents. Narrow sense heritability estimates were quite high in individual environments and on a pooled basis. Line selection for resistance appears promising

Effects of Fiji Disease-Resistant Sugarcane (Saccharum sp.) on the Biology of the Sugarcane Delphacid

Abstract: A study was made to correlate the known resistance to Fiji disease and resistance to Perkinsiella saccharicida Kirkaldy in 5 clones of Hawaiian sugarcane. Clone H51-8194, which is resistant to Fiji disease, showed strong resistance to this leafhopper since none of the leafhoppers (N = 90) developed to adulthood on this variety. However, on clone H60-5657, which is also resistant to Fiji disease, no resistance to the leafhopper was observed, suggesting that Fiji disease resistance ratings are not correlated with leafhopper resistance. Also, 2 methods of evaluating leafhopper resistance were evaluated and results showed that potted plants were superior to an excised leaf method.

Resistance in Cucumis sativus L. to tetranychus urticae Koch

Abstract: Chapter 1The role of plant breeding and particularly of host plant resistance in integrated control is discussed Host plant resistance to insects and mites, especially to Tetranychus urticae is reviewed A standard terminology for disease and pest resistance is recommendedChapter 2The relationship between the twospotted spider mite and cucumber has been studied on plants and on leaf disks of a number of varieties with different levels of resistance Existing laboratory tests are critically discussed and it appears that they are only reliable if many factors are taken into account A new, more efficient laboratory test for resistance, measuring acceptance and reproduction is describedChapter 3After a first screening of 800 cucumber varieties, a laboratory test and a practical test, the following nine varieties have been selected for their distinguishable level of resistance to the twospotted spider mite: PI 220860, 'Hybrid Long Green Pickle', PI 178885, 'Ohio MR 200', 'Taipei no 1', 'Robin 50', 'Aodai', PI 163222 and PI 218036 Besides resistance tolerance for the twospotted spider mite also appears to occur Related Cucumis species do not seem to possess higher levels of resistance than the most resistant C sativus varieties The resistance-parameters acceptance and reproduction appear to be positively correlated On resistant varieties the metabolism of the spider mites is clearly disturbed, but this seems not to be caused mainly by bitter principlesChapter 4For several generations subpopulations of the twospotted spider mite were reared on cucumber varieties previously selected as partially resistant Subsequently resistance tests were carried out in the laboratory and the glasshouse with mites from these subpopulations and concurrently with mites from a basic population reared on a susceptible cucumber line In these tests neither acceptance nor net reproduction or damage index on the partially resistant varieties depended on the kind of mite populations used as inoculum Therefore it is concluded that the resistance is genuine The stability of the resistance is discussedChapter 5After crossing partially resistant varieties some lines with a markedly higher resistance level were selected This transgression for resistance indicates a polygenic inheritance of the resistance On the most resistant F 5 lines selected, oviposition was reduced by 50 to 60 and the economic damage threshold was reached 5 to 8 weeks later than in the susceptible control The level of acceptance was not influenced by the selectionThe selection of individual F 2 plants was hampered by low heritabilities, whereas the heritabilities of F 3 - and subsequent line means were generally high enough Selection for higher resistance levels was attended by an unintended increase in cucurbitacin content This is explained by linkage of genes for resistance and bitterness rather than by identity of these genesChapter 6The bitter cucumber variety Improved Long Green did not differ in resistance to the twospotted spider mite from its near isogenic non-bitter mutant, the source of all non-bitter varieties Four pairs of near isogenic bitter and non-bitter varieties gave similar results Therefore any causal relation between bitterness and resistance is deniedChapter 7The inheritance of resistance to the twospotted spider mite and of bitterness in cucumber has been studied in three sets of P 1 , P 2 , F 1 , F 2 , B 11 and B 12 of crosses between three bitter, resistant lines and one non-bitter, susceptible line Resistance to the twospotted spider mite as measured by acceptance and oviposition appeared to be determined by several to many genes, which are inherited mainly in an additive fashion Bitterness is basically governed by the gene Bi, which, contrary to earlier reports, is inherited in an intermediary way, while the expression of Bi is influenced by additively inherited intensifier genes Whereas Bi and the bitterness intensifier genes are not related to the resistance factors acceptance and oviposition, they are related to resistance or tolerance as measured by the damage index This relation is explained by linkage rather than by identity of the genes concerned Changes in the test methods and breeding consequences are discussed

Breeding for resistance to yellow disease of hyacinths. I. Investigations on F1's from diallel crosses.

Abstract: Analysis of an incomplete diallel design with 14 hyacinth cultivars for resistance to yellow disease showed a significant GCA and a heritability of 0.75. A correlation appeared to exist between flowering date and degree of resistance to yellow disease, early flowering seedlings being generally less resistant. Of 1440 seedlings 69 were selected as resistant on the basis of absence of leaf symptoms. The results of the selection appeared to be in agreement with the breeding value (GCA) of the parent cultivars. The possible influence of chromosome numbers on the degree of resistance to yellow disease is discussed.

Resistance of Japanese and IRRI differential rice varieties to pathotypes of Xanthomonas oryzae in the Philippines and in Japan.

Abstract: The correlation coefficient between scoring systems developed in Japan and IRRI, based on infection by Xanthononas oryaae caused by two methods of inocula- tion, was highly significant...