Further studies on resistance to Leptosphaeria coniothyrium in the red raspberry and related species

Rubus pileatus and its F₁ hybrids with raspberry (R. idaeus) were resistant to cane blight (Leptosphaeriu conioth-yriurn), but little resistance was obtained in subsequent backcross generations apart from a hybrid identified in the second backcross. Two hybrids from backcrossing R. coreanus to raspberry also showed resistance. R. pileatus and its F, hybrids produced hard growth, unlike that of raspberries, which may have been associated with a form of resistance that could not easily be transferred to commercial raspberry cultivars. Some of the genotypes used as parents showed intermediate levels of resistance and it is possible that the highly resistant genotype identified in the second backcross arose from a recombination of genes for resistance. Plants with pubescent canes (gene H) were up to 20% more resistant to mycelial inoculation than those with non-pubescent canes (gene h), and the percentage of machine-harvester inflicted wounds with disease symptoms that resulted from natural infection was also less in genotypes with pubescent canes. Many genotypes with intermediate levels of resistance suffered only limited damage from mycelial inoculation and so there are good prospects for breeding cultivars with an effective resistance, despite the limited value of R. pileatus as a donor species.     

Resistance to Didymella applanata in red raspberry and some related species

When raspberry canes were inoculated in summer with a mycelial inoculum of Didymella applanata resistant genotypes developed relatively small lesions which produced few fruiting bodies in the following spring. Scores of the frequency of these fruiting bodies provided the best discrimination between genotypes. Very strong resistance was found in R. pileatus, R. occidentalis and R. coreanus and in hybrids of these species with red raspberry. Hybrids with R. crataegifolius were less resistant. Resistance was also found in Malling 1473/35, a derivative of red raspberry cv. Chief, and in red raspberry segregates with gene H which determines cane pubescence. Both the expression of resistance and the ranking of resistance sources for their resistance was similar for D. applanata to that reported for Botrytis cinerea.     

Effect of machine-harvester wounds and Leptosphaeria coniothyrium on yield of red raspberry

When wounds on raspberry canes caused by machine harvesting in the previous year were infected by Leptosphaeria coniothyrium the potential yield per cane was reduced by 45% compared with that of uninfected hand harvested canes. However, the corresponding reduction per plot was less (c. 25%) because the yield of wounded but uninfected canes was not reduced and some canes were not wounded. The advantages and disadvantages of recording potential yield per cane are discussed.     

Effects of straddle-harvester design on cane blight (Leptosphaeria coniothyrium) of red raspberry

A new fruit catching device developed for raspberry straddle harvesters to reduce wounding of young canes and their consequent infection by Leptosphaeria coniothyrium was tested. During picking the young canes were contacted only by the foam rubber on a pair of belts which moved backwards along the harvester at the same speed that the machine advanced. The incidence of canes with cane blight lesions in 1981 was 18% following the use of the new device in 1980, and 79% following the use of a conventional commercial harvester equipped with overlapping metal fruit-catching plates. In comparison with the latter plates, the new device avoided wounding the cane surface directly: when the belt marks on these canes were inoculated with mycelium, however, the disease incidence was 77%. The new device caused wounds in 1980 by ripping leaves from nodes. In comparison with the commercial harvester the new device led to smaller lesions in 1981 and a lower percentage of canes dead above the fruit-catching zone. A modified new catching device tested in 1982 made barely detectable pressure marks on the young canes without bruising them. Only 6·6% of these canes developed vascular lesions after inoculation, an incidence similar to that for unwounded control canes (2·5%). The modified new device is advised for regions prone to cane blight where the cropping system has young and fruiting canes growing together.     

Cane blight (Leptosphaeria coniothyrium) in mechanically harvested red raspberry (Rubus idaeus)

Leptosphaeria coniothyrium, the cane blight pathogen, was the fungus most commonly isolated from vascular lesions developing from mechanical harvester wounds on first-year red raspberry canes. When inoculated to scalpel wounds, it induced similar lesions which were later associated with bud failure and cane death as were infected wounds on machine damaged canes. Cane resistance increased from May until August, inoculations later than July inducing only small lesions and rarely causing bud failure.     

The effect of sprays of thiophanate–methyl on cane diseases and yield in red raspberry, with particular reference to cane blight (Leptosphaeria coniothyrium)

Spur blight (Didymella applanata), cane botrytis (Botrytis cinerea) and cane blight (Leptosphaeria coniothyrium) were studied in two consecutive seasons in unsprayed raspberries and in plots sprayed with thiophanate-methyl in the first season alone, (a) twice pre-harvest, (b) twice post-harvest, or (c) twice pre- plus twice post-harvest. Pre-harvest, but not post-harvest sprays, gave moderate control of both spur blight and cane botrytis; both diseases occurred mainly on the lower halves of canes, the latter being the less common. Cane blight occurred at the base of canes where they were wounded by old cane stubs. In the first year it was severe; 37% of canes died before harvest in the unsprayed plots. The three spray programmes all decreased cane death due to cane blight and they all increased yield by c. 45% even in those plots sprayed post-harvest where spur blight was severe and not controlled. Clearly this last disease, despite its high incidence, had no effect on potential yield in this experiment. In the second year cane blight was common but less severe and the incidence of its lesions was reduced similarly by all programmes, but only 4% of canes died in control plots. Analysis of the potential yield and the sizes of lesions caused by L. coniothyrium in canes inoculated at fortnightly intervals in the previous year showed that potential yield loss occurred only when lesions girdled canes. A bimodal distribution in the lesion sizes, measured by length or girdling, indicated some endogenous control of lesion development which might explain the marked differences in the effect of cane blight on potential yield in two seasons.     

Factors affecting the development of cane blight (Leptosphaeria coniothyrium) on red raspberries in Washington, Scotland and Germany

The effects of cultivar, virulence of isolates of Leptosphaeria coniothyrium, cane maturation and wound healing were examined in a series of inoculation experiments carried out over a 3–yr period in three countries in an attempt to explain why cane blight has caused serious yield losses in machine-harvested red raspberries in Europe, but not in the Pacific Northwest of America. Three isolates of L. coniothyrium from Puyallup (USA), Dundee (UK) and Dossenheim (FRG) were pathogenic on the three test cultivars Willamette, Malling Jewel and Glen Isla in all the experiments. Isolates and cultivars differed for aggressiveness and susceptibility respectively but their ranking was dependent on the test conditions and the differences were small and unlikely to explain the differences in incidence and severity of cane blight in raspberry fields in Scotland and the Pacific Northwest. Conditions at Dossenheim were most favorable for lesion development. At all sites, canes inoculated in late summer produced shorter lesions than those inoculated earlier. A delay between wounding and inoculation produced shorter lesions than simultaneous wounding and inoculation.     

Penetration of the Periderm of Red Raspberry Canes by Leptosphaeria coniothyrium

Umwounded raspberry canes were inoculated with Leptosphaeria coniothyrium. After penetration of the epidermis the fungus invaded the cortex readily. The accumulation of mycelium in this tissue lead to a partial digestion of the middle lamellae of the outermost cork layer within the polyderm. The fungus penetrated this single cell barrier through the openings between the separated cells and colonized the phelloid tissue between the first and second cork layer. After vigorous growth in this non-suberized tissue the fungus penetrated the second cork barrier in the same way as the first layer. This mode of penetration was repeated until the fungus had spread beyond the periderm and into the vascular tissues. The invasion process occurred rather slowly and was enhanced by weakening of the canes by defoliation at the time of inoculation.     

Resistance to Botrytis cinerea in canes of Rubus idaeus and some related species

Mycelial inoculation of canes with Botrytis cinerea proved a useful method for assessing Rubus material for resistance. When canes were inoculated in summer resistant genotypes developed relatively small lesions which produced few small sclerotia in the following spring. The size of lesions in autumn generally provided the best discrimination between genotypes. Very strong resistance was found in several species, of which Rubus pileatus and R. occidentalis are the most useful for breeding; hybrids of raspberry with these species or with R. crataegifolius also had strong resistance. The resistance shown by a derivative of red raspberry cv. Chief was less strong, as was the resistance conferred by gene H, which determines cane pubescence.     

Resistance to raspberry cane midge (Resseliella theobaldi) and its association with wound periderm in Rubus crataegifolius and its red raspberry derivatives

Rubus parviflorus, R. odoratus and F₂ plants from the cross R. crataegifolius x R. idaeus were resistant to the raspberry cane midge (Resseliella theobaldi) when exposed to the pest in an insectary or in the field. Histological studies of R. crataegifolius and one of its hybrids with R. idaeus showed that resistance was associated with a wound periderm of suberised and lignified cells. These cells were formed from the primary cortex and phelloid cells of the polyderm as a rapid response to the occurrence of natural splits and wounds which are the oviposition sites of R. theobaldi. In the hybrid, new tissues from this wound periderm prevented the peeling of the mature primary cortex, thereby precluding serious midge attack, and resulted in a reticulate appearance on the cane surface, a distinctive cane feature useful for identifying resistant segregates.     

An immunochemical approach to species relationship in Triticum and some related species

Summary An immunological reaction, precipitation in gel, was produced using a rabbit antiserum directed to a specific protein constantly present in bread wheats (T. aestivum, genome AABBDD), but absent in durum wheat (T. durum Desf., genome AABB). This protein was isolated in the soluble-protein fraction of bread wheat caryopses by combined biochemical and immunological techniques.The availability of such a specific anti-bread wheat serum made possible the analysis of a series of varieties and species of wheat and of some closely related (Secale, Aegilops) and less closely related (Hordeum, Haynaldia) taxa to determine whether the protein was present or absent. Hordeum vulgare, Haynaldia villosa, Triticum monoccocum and Triticum turgidum gave a negative result, while positive results were obtained in T. aestivum, T. timopheevi, T. zhukovskyi, Secale cereale, Aegilops speltoides, Ae. mutica, Ae. comosa, Ae. caudata, Ae. umbellulata, Ae. squarrosa, and also in the artificial amphiploids (Ae. speltoides x T. monococcum) and (Ae. caudata x T. monococcum).It is concluded that these results agree closely with the classification of Triticum proposed by MacKey in 1966. The investigated protein not only permits the differentiation of T. aestivum from T. turgidum, but also T. turgidum from T. timopheevi at tetraploid level and T. monococcum from all the diploid species of Aegilops.     

Evidence that elevated CO2 reduces resistance to the European large raspberry aphid in some raspberry cultivars

Global climate change, such as elevated atmospheric carbon dioxide (eCO₂), may accelerate the breakdown of crop resistance to insect pests by compromising expression of resistance genes. This study investigated how eCO₂ (700 μmol/mol) affected the susceptibility of red raspberry (Rubus idaeus) to the European large raspberry aphid (Amphorophora idaei) Börner (Homoptera: Aphididae), using a susceptible cultivar (Malling Jewel) and cultivars containing either the A₁ (Glen Lyon) or A₁₀ (Glen Rosa) resistance genes. Compared to plants grown at ambient CO₂ (aCO₂) (375 μmol/mol), growth rates were significantly increased (ranging from 42–300%) in all cultivars at eCO₂. There was some evidence that plants containing the A₁ gene were more susceptible to aphids at eCO₂, with aphid populations doubling in size compared to the same plants grown at aCO₂. Moreover, aphids grew 38% larger (1.36 mg compared with 0.98 mg) on plants with the A₁ resistance gene at eCO₂ compared with those at aCO₂. Aphid performance on plants containing the A₁ gene grown at eCO₂ was therefore similar to that of aphids reared on entirely susceptible plants under either CO₂ treatment. In contrast, aphids did not respond to eCO₂ when reared on plants with the A₁₀ resistance gene, suggesting that plants with this resistance gene remained resistant to aphids at eCO₂.     

Resistance to Leptosphaeria maculans in Hybrids of Brassica oleracea and Brassica insularis

The inheritance of hypersensitive resistance to Leptosphaeria maculans in a cross between B. oleracea var. alboglabra and B. insularis was studied. Analyses of F₁ and F₂ progeny suggested that resistance is determined by two dominant, independently-segregating genes. F₁ hybrids were semifertile but normal levels of fertility were restored in a proportion of the F₂ progeny.     

Further studies on the occurrence and inheritance of resistance in red raspberry to a resistance-breaking strain of raspberry bushy dwarf virus

A strain of raspberry bushy dwarf virus (RBDV-RB), discovered in England in 1981, readily infects by grafting many raspberry cvs that have gene Bu, which confers strong resistance or immunity to isolates of the common strain. Haida is one of two cultivars that are highly resistant or immune from RBDV-RB, but both its parents, cvs Creston and Malling Promise, are infectible. Studies of the segregation of resistance to both RBDV-RB and a common strain of RBDV (D200) in four progenies related to cv. Haida or its two parents, showed that resistance to RBDV-RB was heritable and occurred when gene Bu was present with a second resistance component whose inheritance is probably multigenic. There was some indication that the second component might be a form of partial resistance to graft inoculation of varying expression, and that cv. Haida possesses this resistance at a high level that has not been distinguished from immunity in the graft inoculations used. Cultivars Creston and Malling Promise possibly have this resistance to a lesser degree, while resistance in cv. Heritage has been distinguished from immunity only by extensive graft tests. Some possible implications for breeding RBDV-RB resistant cultivars are discussed.     

红火蚁对我国一些生物潜在影响的初步分析

通过分析国际上对红火蚁影响生境中其他生物的研究成果,认为红火蚁主要通过以下3种方式危害其他生物:(1)攻击、捕食刚孵化的地栖性卵生动物个体,或者以群体力量捕食昆虫幼虫、成虫等;(2)竞争有限的食物资源,导致其他物种因为缺乏足够食物供给而种群数量减少甚至灭绝;(3)通过叮咬而使得某些动物存活率降低,改变生境,甚至弃巢外逃,或者因为受攻击活动量加大而增加被捕食的几率。同时初步分析在《国家重点保护野生动物名录》中列举的379种野生动物名录中,有22种鸟类(占9.6%)、1种两栖类(占14%)、所有的18种爬行类(占100%)可能因为红火蚁的入侵导致种群数量下降甚至灭绝。     

Callus induction and thallus regeneration in some species of red algae

Callus induction was obtained from axenic explants of 14 species of red algae. ASP12NTA solid medium (1.5% agar) supplemented with indole-3-acetic acid (IAA) and 6-benzylaminopurine (BAP) was used for callus induction. In most of the species, addition of IAA or BAP at 0.1 mg/L or 1.0 mg/L enhanced callus induction rate or callus size. The combination of IAA (0.1 mg/L) and BAP (0.1 mg/L) was more effective among eight species, while high concentrations of IAA (10 mg/L) showed an inhibitory effect. Great variation in callus form, source tissue, and color of the induced callus were observed. The callus mainly originated from medullary and cortical tissue of the explant. Callus with filamentous, oval and spherical cell chains or disorganized cell mass was observed. The excised calluses from the explants of six species showed sustained growth on subculture. On transfer of the subdivided callus mass of seven species to PES liquid medium, shoot formation and thallus regeneration were observed.     

Electrophoretic karyotypes of some related Mucor species

Contour clamped homogeneous electric field (CHEF) gel electrophoresis was used to obtain electrophoretic karyotypes from nine Mucorstrains representing five different species (M. bainieri, M. circinelloides, M. mucedo, M. plumbeus and M. racemosus). The chromosomal banding patterns revealed high variability among the isolates. The sizes of the DNA in the Mucor chromosomes were estimated to be between 2.5 and 8.7 Mb. The total genome sizes were calculated to be between 30.0 and 44.7 Mb. The applicability of these electrophoretic karyotypes for the investigation of genome structure, for strain identification and for species delimitation is considered.     

Genetic diversity in the red yeast Cryptococcus hungaricus and its phylogenetic relationship to some related basidiomycetous yeasts

Cryptococcus hungaricus is a basidiomycetous yeast with the abilities to synthesize carotenoid pigments and to grow under psychrophile conditions. Six C. hungaricus strains have been isolated so far from different habitats. In this study we wished to clarify the relationships amongst them. Morphological and physiological characters, mitochondrial DNA restriction profiles, and the presence of mycoviruses were examined. Internal transcribed spacers together with the 5.8S rDNA, the D1/D2 region of 26S rDNA, and partial sequences of the 18S rRNA gene were also analysed. On the basis of the phylogenetic analyses the type strain CBS 4214(T) together with four other C. hungaricus isolates were closely related to Bullera armeniaca and Bullera crocea, while strain CBS 6569 was much more similar to Cystofilobasidium than to the other C. hungaricus isolates.     

红火蚁及其重要近似种的鉴别

介绍了红火蚁及其重要近似种的分类特征和分布,以及火蚁属中国已知种类,还提供了上述种类的鉴别检索表。     

Further studies on breeding for resistance to Botrytis cinerea in red raspberry canes

A high level of resistance to cane botrytis caused by Botrytis cinerea was transferred from Rubus pileatus to the red raspberry through three generations of backcrossing. The strength of the resistance showed little diminution through these generations and it was therefore thought that a major gene for resistance had been transferred. But discontinuity in the resistance levels observed was detected in plants of only one group of the progenies and so evidence for a major gene is lacking. The results showed the considerable influence of gene H, which confers pubescence, and emphasised that resistance must be separately assessed for pubescent and non-pubescent segregates.