Pleiochaeta Setosa Research Articles

The potential of Brassicaceae biofumigant crops to manage Pleiochaeta setosa in sustainable lupin cultivation

Lupin is prone to infection by Pleiochaeta setosa (Kirchn.) Hughes causing brown spot and root rot in Lupinus species. The control of these diseases is crucial to limit yield losses, but an increased public awareness and European legislative restrictions have resulted in a drastic reduction of allowed pesticides and many research groups invest in alternative biocontrol strategies. In the current study, the inhibitory effect of volatiles, released by two members of the Brassicaceae family (white mustard (Sinapis alba) and fodder radish (Raphanus sativus)), on brown spot and root rot in Lupinus species was evaluated in vitro and in vivo. The in vitro trial showed that root tissue of Brassicaceae was more effective in reducing the vegetative growth of Pleiochaeta setosa than leaf and stem tissues. Furthermore, R. sativus was more effective than S. alba. The GC–MS analysis revealed that dimethyl disulfide and dimethyl trisulfide were predominantly emitted by the tissues of both Brassicaceae. Additionally, the ground root tissue of R. sativus emitted 4-isothiocyanato-1-(methylthio)-1-butene, whereas the stem + leaf tissue emitted benzyl isothiocyanate. Benzyl isothiocyanate was also released by the ground S. alba root tissue, whereas the leaf + stem tissue emitted 3-butenyl isothiocyanate. In vitro trials with pure dimethyl disulfide and dimethyl trisulfide confirmed the antifungal effect of the volatiles released by these sulfides. For dimethyl disulfide 7.95 mg per Petri dish was necessary to (almost) completely inhibit mycelium growth, whereas for dimethyl trisulfide 1.20 mg per Petri dish was sufficient to prevent fungal growth. In addition, a trial with allyl isothiocyanate showed that for this compound even lower doses (0.50 mg per Petri dish) stopped the growth of the fungus. The results obtained with the pot trial illustrated that the amendment of Brassicaceae species significantly reduced the P. setosa infection level. Also in the field, incorporation of Brassicaceae species suppressed P. setosa. From this study, it can be concluded that Brassicaceae species are a powerful tool to manage P. setosa in lupin cultivation. However, it should be combined with other control practices since the amendment of these biofumigant crops could not completely inhibit symptom development.

Exploration of essential oils as alternatives to conventional fungicides in lupin cultivation

Lupin (Lupinus L.) has the potential to become a true alternative for soybean as protein source, especially in the more temperate regions in the world. However, diseases such as anthracnose (Colletotrichum lupini), gray mold (Botrytis cinerea), and root rot or brown spot (Pleiochaeta setosa) are important threats for lupin production, leading to yield and quality losses. Although conventional fungicides offer a solution to these problems, there is a growing interest in the use of alternative (biological) treatments. In this research, the applicability of four pure plant essential oils (clove oil, juniper oil, tea tree oil, and thyme essential oil) and timbor® (a Thymus vulgaris-derived plant extract) as alternatives for synthetic fungicides towards the lupin pathogens—C. lupini, B. cinerea, and P. setosa—was investigated. The anti-fungal effect of juniper oil was limited, whereas the other oils and timbor® clearly suppressed the growth and spore germination of all fungi. The in vitro experiments revealed that thyme essential oil and timbor® were most effective to inhibit conidial germination and mycelium growth. Furthermore, the results of the pot experiments demonstrated that these Thymus-derived compounds were able to suppress P. setosa brown spot and root rot symptoms. Additional trials are necessary to evaluate the effect of these compounds under field conditions. However, based on these in vitro and pot experiments, it can be concluded that pure essential oils and Thymus-derived plant extracts are promising anti-fungal agents, having the potential to become true alternatives for conventional fungicides in lupin cultivation. To the best of our knowledge, this is the first study demonstrating the potential of plant-derived compounds to treat the main diseases affecting lupin production.

First Report of Leaf Spot on Blue Lupin (Lupinus pilosus) Caused by Pleiochaeta setosa in Israel

HomePlant DiseaseVol. 100, No. 2First Report of Leaf Spot on Blue Lupin (Lupinus pilosus) Caused by Pleiochaeta setosa in Israel PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Leaf Spot on Blue Lupin (Lupinus pilosus) Caused by Pleiochaeta setosa in IsraelL. Gur and O. FrenkelL. GurSearch for more papers by this author and O. FrenkelSearch for more papers by this authorAffiliationsAuthors and Affiliations L. Gur O. Frenkel , Department of Plant Pathology and Weed Research, Institute of Plant Protection, Agricultural Research Organization (ARO), The Volcani Center, Bet Dagan, 50250, Israel. Published Online:4 Dec 2015https://doi.org/10.1094/PDIS-05-15-0558-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Pleiochaeta setosa Kirchn. causes brown spot and root rot, serious diseases of lupin (Lupinus spp.) worldwide (Yang and Sweetingham 2002). Lupinus pilosus Murr., blue lupin, is a wild native species in the Mediterranean region but lately grown in private and public gardens as an ornamental plant. L. pilosus also has the potential to serve as a genetic source for breeding commercial lupin species due to its adaptation to calcareous soils, and high range of intraspecific variation (Brand et al. 2002). During February 2015, brown necrotic spots were observed on leaves and petiols of blue lupin in a 0.1-ha public garden in Ramat-Gan (central Israel). The disease affected about 90% from hundreds of plants. Symptoms included circular or irregular-shaped, dark brown, necrotic lesions not limited by leaf veins. Small pieces (1 to 2 mm) from infected leaves and petioles, were placed in 0.3% hypochlorite solution for 30 s, washed twice with sterilized water, and placed onto potato dextrose agar (PDA). Isolation yielded dark, olive-green colonies. Cultures were grown at 25°C with a 12-h photoperiod/day. Morphological examination of the mycelia and conidia in comparison with the literature (Garibaldi et al. 2012) indicated the fungus was P. setosa Kirchn. Mycelium had hyaline, septate hyphae that became dark olive on maturation and produced dark chlamydospores. The conidia were cylindrical with a truncated base, three to seven transverse septa and three to five hyaline appendages. Apical and basal cells were subhyaline, whereas the intermediate cells were olive-brown. The conidia measured 65 to 90 × 15 to 23 (average 76 × 19) μm. Appendage length was 40 to 130 (average 76) μm. DNA was extracted and the rDNA internal transcribed spacer region of three isolates was amplified using primers ITS1 and ITS4, and sequenced. BLAST analysis of our 517-bp fragments (represented by GenBank Accession No. KR536610) showed 100% identity to ITS rDNA sequences of P. setosa (EU167563 and JQ358708). Pathogenicity of two isolates (PSLP1 and PSLP2) was verified by two assays: (i) 5-mm-diameter PDA disks colonized by mycelium from 14-day-old cultures were placed onto five attached leaves of three healthy blue lupin plants (15 leaves in total). The plants were covered with plastic bags for 4 days in a growth chamber set at 23°C with a 12-h photoperiod/day. (ii) Five µl of an aqueous suspension of mycelium scraped from 14-day-old PDA cultures were placed on detached leaves, which were in turn placed on water agar in three petri dishes (three leaves per dish) and incubated at 25°C (12-h photoperiod/day) for 10 days. Three plants inoculated with noncolonized PDA disks and three detached leaves inoculated with sterilized water (treated as described above) served as negative controls. Lesions developed on the attached and detached leaves 4 and 10 days after inoculation, respectively, whereas control plants and detached leaves remained asymptomatic. P. setosa was isolated (as described above) consistently from these lesions. Similar pathogenicity tests with isolate PSLP1 were also carried out successfully on L. albus and L. palaestinus plants and leaves. P. setosa was reported on several lupin species (Yang and Sweetingham 2002). This is, to our knowledge, the first report of P. setosa on L. pilosus in Israel or anywhere in the world.

Patogenic fungi associated with blue lupine seeds

Over 10% ofseeds harvested in 1991 and 1992 (50 samples, 400 seeds in each sample) proved to be infested with various fungi. <em>Fusarium</em> spp. and <em>Botrytis cinerea</em> were the most common pathogens isolated. <em>Fusarium avenaceum</em> was the most common and highIy pathogenic species. <em>Fusarium semitectum</em> and <em>F. tricinctum</em> were highly pathogenic to lupin seedlings but they were the least common <em>Fusarium</em> isolated from seeds. Similarily, <em>Sclerotinia sclerotiorum</em> was isolated only from 0,2% seeds tested but this fungus was highly pathogenic to lupin seedlings. Some other fungi know as lupin pathogens (<em>F. oxysporum, Stemphylium botryosum, Pleiochaeta setosa</em> and <em>Phomopsis leptostromiformis</em>) were also noted in tested seeds.

First Report of Leaf Spot of Garden Lupin (Lupinus polyphyllus) Caused by Pleiochaeta setosa in Italy.

Lupinus polyphyllus Lindl., common name garden lupin, is used in commercial, private, and public landscapes and sold as a cut flower. During summer 2011, extensive brown necrotic areas were observed on young and old leaves of plants grown in a private garden near Biella (northern Italy). The disease affected about 50 of 80 2-year-old plants. Early symptoms included circular to irregular-shaped brown lesions of alternating pale and dark brown concentric bands. Lesions coalesced and often were surrounded by chlorotic halos at an advanced development stage. Lesion expansion was not limited by leaf veins. When lesions covered much of the leaf area, the leaf curled and remained attached. However, expansion of stem lesions often resulted in plant death. A fungus was consistently isolated from 15 infected leaves on potato dextrose agar (PDA). Cultures were grown at 21 to 25°C under 16 h of light and 8 h of darkness. Mature colonies were dark olive-green and produced orangeochre pigments in the medium. Ten isolates were obtained and three strains were used in the morphological study. The mycelium had olivaceous, septate hyphae that produced abundant dark, intercalary chlamydospores. The conidia were cylindrical to elliptical, slightly curved, with a truncated base, five to seven transverse septa and three hyaline appendages. Apical and basal cells were subhyaline, whereas the intermediate cells were olivebrown. The conidia measured 76 to 94 × 14 to 19 (average 85 × 16) μm. Appendages were up to 84 μm long. On the basis of its morphological characteristics the pathogen was identified as Pleiochaeta setosa Kirchn. DNA was extracted using Terra PCR Direct Polymerase Mix (Clontech). The internal transcribed spacer region of rDNA was amplified using primers ITS 1 and 4 (4) and sequenced. BLAST analysis (1) of the 570 bp fragment showed a 100% homology with a P. setosa isolate submitted to GenBank (accession no. EU167563). The nucleotide sequence was submitted to GenBank (JQ358708). Pathogenicity was verified on healthy 5-month-old garden lupin plants by placing 8-mm mycelial disks from 15-day-old cultures on 10 unwounded leaves per plant with five plants per treatment. Ten leaves of five plants were inoculated with PDA disks to serve as a negative control. Plants were covered with plastic bags for 4 days after inoculation and maintained in a growth chamber at 20 ± 1°C. Lesions developed on 80% of leaves 3 days after inoculation, whereas control plants remained healthy. P. setosa was consistently isolated from these lesions. The pathogenicity test was carried out twice. The presence of P. setosa on L. polyphyllus was reported in Australia, United States (2), and Poland (3). This is, to our knowledge, the first report of P. setosa in Italy. The impact of this disease is currently limited.

Pecosa-Baer: A New Cultivar of New Cultivar Cultivar of White Lupin with Determined Bushy Growth Habit, Sweet Grain and High Protein Content

The expansion of white lupin (Lupinus albus L.) cultivation in Chile is subject to the availability of cultivars presenting high yield potential, tolerance to the main fungal diseases and homogeneous ripening. In response to these requirements, a new cultivar has been developed and registered as ‘Liapec-1’, commercially registered as ‘Pecosa-Baer’. This new cultivar has determined bushy growth habit. Its flowering period is concentrated in approximately 40 days, less than the 77 days of cv. Rumbo-Baer. This trait allows it to reach harvest without heterogeneity problems. The seed is speckled, flat and medium-sized (370 g/1000 grains aprox.). The kernels are sweet and have a high protein content of around 41% (dry matter basis). In field assays, ‘Pecosa-Baer’ presents a good tolerance to diseases caused by Colletotrichum lupini and Pleiochaeta setosa. The new cultivar has outstanding stability and yield levels, even under low fertilization conditions. An average yield of 5.43 t ha -1 was obtained over four seasons in two locations. In order to maximize its yield, ‘Pecosa-Baer’ must be sown between April and June at a rate of 140-160 kg ha -1 . Given the high protein content and low alkaloid levels of the seeds, they can be included in the diet of all types of animals.

Breeding Lupinus albus for resistance to the root pathogen Pleiochaeta setosa

Pleiochaeta root rot (PRR) caused by Pleiochaeta setosa is a serious, widespread fungal disease in lupin crops, especially in Lupinus albus (broad-leaf lupin, or white lupin). PRR resistance is common in the gene pool of L. albus with various landraces from the Mediterranean region being the most resistant, and suitable for use in breeding new cultivars. Heritability of resistance is sufficient to make good gains from selection but only when controlled-environment (CE) screening is used. Field disease nurseries on loamy soil gave much lower heritability of resistance. Field disease nurseries had spatially variable spore counts despite continuous lupin cropping, and this was partly responsible (along with climatic conditions) for their reduced precision compared to tests conducted in a CE. Giving infected L. albus roots a single, most-severe-lesion score on a 0–9 scale was adequate for CE screening but not as precise or discriminating as the more time-consuming method of six scores per root. Replication in CE experiments was reduced to two pots of 16 seedlings each without sacrificing genotype discrimination.

Genetic variation ofPleiochaeta setosafromLupinus albus

A hierarchical collection of isolates of the fungal pathogen Pleiochaeta setosa was made from field-grown Lupinus albus plants across southern NSW, Australia in 2004. This collection, along with some historical reference isolates, was analysed for genetic variation using random amplified polymorphic DNA and enterobacterial repetitive intergenic consensus primer PCR. Anchored inter-simple sequence repeat primers were tested but produced little or no amplification or no detectable polymorphism. The observed overall variation was not explained by the hierarchical structure of the population (individual seedling, host species, host cultivar, regional location, or year). There was significant genetic variation between isolates even at the finest sampling scale (within a single seedling). Some very distinct individual isolates were identified. The high level of scale-independent genetic diversity seen in P. setosa suggests that field-based screening for Pleiochaeta root rotresistant genotypes in a L. albus breeding program at a single location is likely to result in resistance which is effective at multiple and widely separated locations. This resistance would have an increased chance of being polygenically controlled and durable under commercial cultivation conditions.

Penetration and symptom development of Pleiochaeta root rot in susceptible and resistantLupinus albuscultivars

Pleiochaeta root rot caused by Pleiochaeta setosa is a major threat to the Australian lupin industry. Although Pleiochaeta root rot-resistant Lupinus albus varieties have been bred, there is no information on the likely mechanism of this resistance. Susceptible (Kiev mutant) and resistant (P25758) albus lupin cultivars were inoculated with spores of P. setosa strain PS6-1 and the infection process studied microscopically. No specialised penetration structures were observed on the roots, and infecting hyphae entered roots of both cultivars by growing directly between root surface cells. Lengths of conidial germ tubes on resistant hosts was significantly longer than on susceptible hosts, suggesting that a component of the resistance is via reduced host recognition by the pathogen.

Effects of ozone exposure or fungal pathogen on white lupin leaves as determined by imaging of chlorophyll a fluorescence

Chlorophyll fluorescence has been used routinely to investigate photosynthetic activity in plants subjected to both biotic and abiotic stresses. The aim of this work was to compare the perturbations in photosynthesis induced by ozone and by a pathogen. By using a conventional fluorometer a similar response pattern was observed in inoculated and O 3-fumigated leaves. The application of chlorophyll fluorescence imaging provided further detailed information on the spatial–temporal heterogeneity of the response of white lupin leaves to fungal pathogen or to ozone fumigation. In particular, 48 h after artificial inoculation with the necrotrophic fungal pathogen Pleiochaeta setosa, the leaves showed a remarkable alteration in PSII operating efficiency (Φ PSII), which affected the whole surface. Afterwards, the infection site was surrounded by a ring of increased photosynthetic activity. The response of ozonated leaves was quite different. The reduction in Φ PSII was already evident 24 h after fumigation; moreover, a distinct heterogeneity of the fluorescence yield was observed and the major veins displayed a lowered Φ PSII.

Seed alkaloid concentrations are not affected by agronomic and phosphorus-nutrition treatments that reduce Pleiochaeta setosa Hughes disease on narrow-leafed lupin (Lupinus angustifolius)

The severity of brown spot caused by the fungus Pleiochaeta setosa (Kirchn.) Hughes in narrow-leafed lupin (Lupinus angustifolius L.) is reduced by improving phosphorus (P) nutrition and using agronomic treatments that extend crop rotation or increase cereal stubble retention. The aim of this work was to investigate the impact of these treatments on the alkaloid concentrations of the harvested seed of 3 sweet cultivars of L. angustifolius that differed in their susceptibility to this fungal disease: Merrit (susceptible), Tallerack and Myallie (both moderately resistant). Because abiotic and biotic stresses appear to stimulate plant alkaloid biosynthesis, we hypothesised that higher levels of disease pressure may increase alkaloid concentrations in the harvested seed, particularly in the disease-susceptible Merrit. The main effects of P nutrition, cereal stubble retention, genotype and crop rotation were significant for the severity of brown spot and plant biomass of narrow-leafed lupin in a field trial in Wongan Hills, Western Australia, but were not significant for total alkaloid concentrations or the relative proportions of individual alkaloids of the harvested seed. Seed total alkaloid concentrations were in most cases below the maximum permitted concentration established for lupin seed (200 mg/kg dry matter) and were independent of the severity of brown spot on leaves. The great fluctuations of seed total alkaloid concentrations observed in grower deliveries to bulk handling facilities and in lupin cultivar yield testing trials are unlikely to result from the nutritional and agronomic treatments such as those investigated in this experiment, or the various disease levels that resulted from these treatments.

Evaluation of Lupinus albus L. Germplasm for the Southeastern USA

While white lupin (Lupinus albus L.) has potential as a new minor winter crop, adapted germplasm have to be discovered and considerations for cold tolerance, pest resistance, and other traits determined. We evaluated 100 accessions in 1990–1991 and 616 in 1991–1992 at two locations in central Alabama, USA. Twenty‐four seeds per accession were hand sown in an upland area on a Marvyn sandy loam (fine‐loamy, kaolinitic, thermic, Typic Kahapludults) and in a river bottom area on a Wickham fine sandy loam (clayey, kaolinitic, thermic, Typic Rhododults). Backward stepwise and canonical discriminate analysis (CDA) was used to determine which agronomic traits and groups of accessions were most important for adaptation. Accessions were selected for further evaluation and breeding on the basis of survival through physiological maturity in 1990–1991 and on grain yields ≥27.6 g plot−1 (2128 kg ha−1 equivalent) in 1991–1992. The first two canonical discriminate variates (CAN) had Eigenvalues ≥1 and accounted for ≥51% of the total variance for both years. Vernalization type ratings (winter, semiwinter, spring) were most highly correlated (≥0.87) with CAN 1 for both years, so CAN 1 was labeled vernalization type. The continuum for vernalization requirements was represented by CAN 1 in the 1990–1991 data. On the basis of correlations with CAN 2 for both years, earlier flowering of spring types was detrimental to survival. Selection of accessions with cold tolerance proved to be more important than extremely high vernalization requirements in severe winter types. Brown spot leafspot and root rot [caused by Pleiochaeta setosa (Kirchn.) Hughes] were the most prevalent diseases. East and West Mediterranean germplasm comprised >55% of the selections for further testing; these lines were better adapted to the Southeast, while Southwest Asian and North African severe spring types with little or no vernalization requirement were better suited for use in short season areas of the northern USA.

Impact of tillage on lupin growth and the incidence of pathogenic fungi in southern New South Wales

Narrow-leafed lupins (Lupinus angustifolius) were grown in cultivated and direct-drilled plots at 4 field sites in southern New South Wales in 1998 to determine the effect of tillage on seedling vigour, disease and yield. The early growth of lupins in direct-drilled plots was reduced compared with seedlings in cultivated plots at 3 of the sites. However, the biomass of lupin plants in the direct-drilled treatments was 20% greater than in adjacent cultivated plots at harvest. The lower biomass in cultivated plots appeared to be primarily related to an increased incidence and severity of stem rot caused by Sclerotinia sclerotiorum. The increased stem rot in cultivated plots was also associated with a decline in yield of between 16 and 35% across the sites compared with direct-drilled plots. The direct-drilled treatment reduced the severity of brown spot, caused by Pleiochaeta setosa, at the 2 sites where stubble was retained from the previous wheat crop. These results suggest that direct drilling into cereal residue provides benefits over cultivation for the growth of lupins in southern New South Wales where crop infection by Sclerotinia and/or brown spot may be significant.

Fungicide seed treatments reduce seed transmission and severity of lupin anthracnose caused by Colletotrichum gloeosporioides

Lupin production is a vital part of the farming system on coarse-textured soils throughout Western Australia. The continued viability of the lupin industry was threatened in 1996 by the outbreak of anthracnose caused by Colletotrichum gloeosporioides. The use of fungicides as seed dressings was investigated as a potential control for this disease. Twenty one fungicides were examined in vitro for their effect on growth of C. gloeosporioides: nine fungicides, including thiram and fluquinconazole, were identified with ED50 of less than 1.0 μg/mL. In a series of glasshouse experiments using artificial spray inoculation, and field experiments using rain-splashed infection from infected spreader plots, seed treatment with carbendazim or fluquinconazole provided lupin seedlings with systemic protection from anthracnose infection. Iprodione, procymidone and thiram showed no systemic activity against anthracnose. In field experiments, thiram, fluquinconazole and carbendazim were able to reduce anthracnose transmission from infected seed. Iprodione and procymidone, widely used on lupin seed in Western Australia for control of brown spot caused by Pleiochaeta setosa, did not provide systemic protection from anthracnose and were not as effective as other fungicides at reducing seed transmission. The efficacy of thiram, fluquinconazole or carbendazim was not reduced by mixing with iprodione or procymidone and these mixtures were generally more effective than iprodione or procymidone alone. As a result of these investigations, thiram has been registered as a seed treatment in Western Australia for control of anthracnose seed transmission in lupins.

Profiling of flavonoid conjugates in Lupinus albus and Lupinus angustifolius responding to biotic and abiotic stimuli.

Qualitative and quantitative composition of flavonoid and isoflavonoid glycosides as well as free aglycones in lupin seedlings (roots and aerial parts) grown under different light conditions or responding to infection with Pleiochaeta setosa, a fungus causing brown leaf spot, were monitored by liquid chromatography with UV and/or mass spectrometric detection. Both physical and biotic factors affected flavonoid and isoflavonoid levels in lupin tissues. Fungal infection evoked significant increase in the amounts of genistein, 2'-hydroxygenistein, and their prenylated derivatives that are thought to function as lupin phytoalexins. Effect on quantitative changes of glycosylated flavonoids and isoflavonoids in the roots and aerial parts was less significant. Moreover, different light conditions applied during seedling growth caused relative changes of flavonoid and isoflavonoid conjugates composition, especially in the leaves of white lupin plants. The chemical structures of flavonoid and isoflavonoid conjugates present in Lupinus angustifolius were elucidated. In addition to genistein and 2'-hydroxygenistein glycosides, flavonol conjugates were identified in leaves, while the composition of root isoflavonoids was similar to that of L. albus reported earlier.

Inheritance of partial resistance to the brown spot disease in Lupinus angustifolius L

Brown spot (BS) is a damaging disease of narrow-leafed lupins (Lupinus angustifolius L.), particularly in Western Australia. Breeding for resistance to the causal agent [Pleiochaeta setosa (Kirchn.) Hughes] has had some success. Here, earlier data on the extent and inheritance of resistance to BS are presented as a possible guide for future breeding programs. In 1980, 236 Mediterranean wild accessions from the Australian germplasm collection, and 17 cultivars and 20 breeding lines of L. angustifolius and L. albus L., were tested by natural infection in replicated short rows at 2 sites in southern New South Wales. The area of lower leaves covered by lesions was up to 70% lower on partially resistant lines than on commercial cultivars. Twelve wild accessions were consistently more resistant than 5 cultivars at Wagga Wagga in 1980 and in 2 subsequent years, in which 66 wild lines and 6 cultivars were tested. However, the rankings at Wagga Wagga differed from those in coastal Western Australia, suggesting that spatial differences occur in the pathotype composition of the fungus. The absence of sexual reproduction in the fungus suggests that its pathotype spectrum would change only slowly at each location. Unimodal distributions of BS scores for individual plants were found in the F2 of Illyarrie (susceptible) � CPI 67877 (resistant) and in the backcross to Illyarrie. The F2 mean was intermediate between the 2 parental means, and only a few plants had a score as low as the resistant parent. The regression of the mean scores for 15 F2 families from crosses among 7 wild lines, and between these and 2 susceptible cultivars, on the respective mid-parent values gave a narrow-sense heritability estimate of 0.94 ± 0.17 on a family mean basis. Thus, resistance was controlled by many loci with co-dominant alleles and should be robust. There was no linkage of resistance genes to the low alkaloid or white flower/green plant loci. Assuming the absence of dominance, the upper limit of narrow-sense heritability on a single plant basis was 0.50 ± 0.13. Several rounds of selection of partially resistant individuals in F2 families and intercrossing among F3 plants from many different wild � domesticated crosses are likely to produce cultivars with much more resistance than those now available. The applicability of the results at Wagga Wagga to the eastern wheatbelt of Western Australia, where BS is acute, and optimum field selection procedures are discussed.

Variation in morphology and pathogenicity of Pleiochaeta setosa isolates from Lupinus spp. and other legumes

Two morphological types of Pleiochaeta setosa are described from Australia, the lupin-type (isolates collected from Lupinus spp.), and the serradella-type (isolates collected from Ornithopus spp.). The lupin-type produces smaller conidia (64–70 × 17–19 μm) with 3–5 septa and 2–4 appendages. The terminal appendages are predominantly unbranched (91–100%). The serradella-type produces larger conidia (80–85 × 20–23 μm) with 4–6 septa and 3–5 appendages. A much higher proportion of the conidia of the serradella-type have branched terminal appendages (47–79%). The difference in conidial morphology between the two types is stable after cross-infection to opposite host plants and re-isolation. The delineation of the two Australian types is supported by random amplified polymorphic DNA (RAPD) analysis. The lupin-type is highly virulent to lupin, causing severe leaf infection and root rot, but is only weakly virulent to leaves and roots of serradella and biserrula (Biserrula pelecinus). The serradella-type is more virulent than the lupin-type to serradella and biserrula, causing severe disease on leaf, root and hypocotyl tissues. However, the serradella-type can also cause significant leaf, but not root, infection on lupin. Conidial morphology and RAPD analysis of isolates from other parts of the world reveal that additional types exist within the species P. setosa. The pathogenicity of imported cultures could not be determined due to quarantine restrictions.

Effect of Pleiochaeta setosa on field responses of Lupinus angustifolius and L. luteus to applications of phosphorus

The effect of the fungus Pleiochaeta setosa on grain yield responses of lupins to applications of phosphorus (P) fertiliser (0–40 kg P/ha as triple superphosphate banded 80 mm below seed while sowing at 40 mm) was measured for 4 lupin cultivars that differed in reaction to the pathogen: Lupinus angustifolius cv. Merrit (susceptible), cv. Tallerack (moderately resistant), cv. Myallie (resistant) and L. luteus cv. Teo (very resistant). Variable levels of P. setosa inoculum (as resting spores in the soil) were generated by different rotations. Disease levels of lupin foliage were manipulated by either burning or retention of the previous wheat (Triticum aestivum) stubble. The severity of brown spot (caused by P. setosa infecting the foliage) was influenced by the previous rotation, by the stubble treatment, and by the susceptibility of each lupin cultivar to the disease. Pleiochaeta setosa was least in and had little or no effect on yield of the very resitant Teo, but P. setosawas greatest and decreased yields most in the susceptible Merrit. Where grain yields were affected by P. setosa, there were increases in grain yield with increasing amounts of P applied. For Merrit, Tallerack and Myallie, grain yield responses to P addition tended to increase with increasing disease. Grain yield increases to P application were greatest for Merrit with the highest P. setosa level, and were least for L. luteus cv. Teo with the lowest P. setosa level.

Fungicidal control of foliar diseases of white lupin ( Lupinus albus)

A range of fungicides was tested against rust ( Uromyces lupinicolus) and brown spot ( Pleiochaeta setosa) on autumn-sown white lupin ( Lupinus albus) in three experiments in harvest years 1995, 1997 and 1998. Rust was severe in all three years but did not develop in an additional experiment in 1996. Brown spot occurred only in 1997 and 1998 when natural inoculum was augmented by an artificial source and weather conditions were favourable for inoculum dispersal and disease development. Tebuconazole was the only fungicide tested that controlled rust consistently, whereas iprodione+thiophanate-methyl, tebuconazole and prochloraz each decreased the severity of brown spot. Yield increases in 1997 and 1998 were thought to be attributable mainly to control of rust. Fungicides were most effective when applied as soon as symptoms were observed. Two applications of an effective fungicide generally controlled disease more than a single application; a third application gave no additional benefit.

Effects of cold shock on the susceptibility of white lupins to fungal diseases

Summary.Experiments in controlled environments tested interactions between freezing soil (a compost‐vermiculite mixture) and below‐ground infection of white lupins with each of three pathogenic fungi (Botrytis cinerea, Fusarium avenaceum or Pleiochaeta setosa) on plant disease and death. Whilst soil freezing (up to 4 days at – 1oC) caused slight necrosis and increased the severity of disease symptoms, incidence of plant death was increased only after inoculation, before freezing, of the lower hypocotyl of the youngest plants (soil frozen at less than 17 days old) with P. setosa. It is concluded that the contribution of below‐ground infection by pathogenic fungi to overwinter losses in autumn‐sown white lupin crops is exacerbated to a negligible extent by soil freezing, the main primary cause of such losses.