John Hamblin

Increased efficiency of wool growth and live weight gain in Merino sheep fed transgenic lupin seed containing sunflower albumin

The aim of this experiment was to assess, using sheep, the nutritive value of lupin seed transgenically modified to contain sunflower seed albumin. Eighty Merino wether sheep of mean live weight 32.3 kg were divided into two groups and fed 796 g dry matter (DM) day−1 of a cereal hay-based diet containing 350 g kg−1 of either the transgenic or parent (unmodified) lupin seed for 6 weeks. Measurements were made of wool growth and live weight gain. After 6 weeks, half the sheep in each group were selected for a urine and faeces balance study in which organic matter (OM), nitrogen (N) and urinary purine metabolites were measured. Blood samples were taken from all sheep at the beginning and end of treatment and analysed for amino acids and plasma metabolites. A comprehensive chemical analysis of the grains showed that there was little difference between them in terms of most nutritional components, but the transgenic lupin seed contained a 2.3-fold higher methionine concentration and 1.3-fold higher cysteine than did the parent. There were no significant differences between grains in OM digestibility, rumen microbial protein synthesis or in sacco degradability of dry matter. Sheep fed the transgenic lupin grain had an 8% higher rate of wool growth (P   0.1). Plasma urea N was lower in the sheep fed the transgenic grain than those fed the parent grain (6.5 vs 6.8 mmol l−1, P < 0.05). The results show that genetic modification of a feed grain can improve its nutritive value for ruminants. The size and nature of the responses were consistent with the transgenic lupins providing more methionine to the tissues, a first-limiting amino acid for sheep. © 2000 Society of Chemical Industry

The Interaction of phosphorus and potassium with seed alkaloid concentrations, yield and mineral content in narrow-leafed lupin (Lupinus angustifolius L.)

We tested the impact of P deficiency, K deficiency, and their interaction on seed alkaloid concentrations and profile, yield and mineral content in sweet (low-alkaloid) and bitter (high-alkaloid) varieties of narrow-leafed lupin (Lupinus angustifolius L.). P deficiency reduced seed alkaloid concentrations in sweet, but not in bitter, varieties. Under P deficiency, the alkaloid profile in harvested seed of sweet varieties mimicked that of the bitter variety Fest, with 13-hydroxylupanine dominating over lupanine. With adequate or abundant P, lupanine was the predominant alkaloid in sweet varieties. K deficiency was associated with an 8-fold increase of seed alkaloid concentrations in the sweet variety Danja (from 1000 to 8000 mg kg−1 DM), mostly due to the stimulation of lupanine production. There was a significant interaction between P and K that affected seed alkaloid concentrations in two ways: (i) the inhibitory effect of P deficiency was only apparent under K deficiency and (ii) the lowest seed alkaloid concentrations occurred with abundant K (240 mg K kg−1) and P (60 mg P kg−1). Seed yield of all varieties increased asymptotically with increasing P and reached a maximum at adequate P (30 mg P kg−1). There was no impact of K deficiency on seed yield. In sweet and bitter varieties P supply increased seed N, P and Zn concentrations, but not K. In contrast, seed K concentrations increased and P concentrations decreased with increasing K supply. These findings suggest that P fertiliser should be supplemented with K, to avoid high seed alkaloid concentrations stimulated by asymptomatic K deficiency at high P levels.

Potassium nutrition effects on seed alkaloid concentrations, yield and mineral content of lupins (Lupinus angustifolius)

To ensure that narrow-leafed lupin (Lupinus angustifolius L.) meets feed quality standards, the concentration of alkaloids must be kept under the maximum acceptable limit of 200 mg kg−1 DM. One of the factors that may affect seed alkaloid concentration is soil nutrient deficiency. In this paper, we report the results of glasshouse and field experiments that tested the effect of potassium (K) deficiency on seed alkaloid concentrations. In the glasshouse, seed alkaloid concentrations increased by 385, 400 and 205% under severe K deficiency in sweet varieties (Danja, Gungurru and Yorrel, respectively) of L. angustifolius. The concentration of alkaloids in Fest, the bitter variety, was always high regardless of soil K status. At all levels of applied K (0–240 mg kg−1 soil), lupanine was the predominant alkaloid in sweet varieties, whereas 13-hydroxylupanine prevailed in the bitter variety. Seed yield of all varieties increased exponentially with increasing amounts of applied K, reaching a maximum at 60 mg K kg−1 soil. In the field, application of K to deficient soils decreased seed alkaloid concentration at Badgingarra, Western Australia (WA) but not at Nyabing, WA, in 1996. In both field trials, seed yield and mineral content were not affected by the amounts of K fertiliser applied. These findings highlighted the need for adequate K fertilisation of deficient soils in WA to avoid the risk of producing low quality lupin seed with high alkaloid concentrations. K deficiency is involved in stimulating alkaloid production in sweet varieties of L. angustifolius.

Variation in Chlorophyll Content per Unit Leaf Area in Spring Wheat and Implications for Selection in Segregating Material

Reduced levels of leaf chlorophyll content per unit leaf area in crops may be of advantage in the search for higher yields. Possible reasons include better light distribution in the crop canopy and less photochemical damage to leaves absorbing more light energy than required for maximum photosynthesis. Reduced chlorophyll may also reduce the heat load at the top of canopy, reducing water requirements to cool leaves. Chloroplasts are nutrient rich and reducing their number may increase available nutrients for growth and development. To determine whether this hypothesis has any validity in spring wheat requires an understanding of genotypic differences in leaf chlorophyll content per unit area in diverse germplasm. This was measured with a SPAD 502 as SPAD units. The study was conducted in series of environments involving up to 28 genotypes, mainly spring wheat. In general, substantial and repeatable genotypic variation was observed. Consistent SPAD readings were recorded for different sampling positions on leaves, between different leaves on single plant, between different plants of the same genotype, and between different genotypes grown in the same or different environments. Plant nutrition affected SPAD units in nutrient poor environments. Wheat genotypes DBW 10 and Transfer were identified as having consistent and contrasting high and low average SPAD readings of 52 and 32 units, respectively, and a methodology to allow selection in segregating populations has been developed.

Accelerated Generation of Selfed Pure Line Plants for Gene Identification and Crop Breeding

Production of pure lines is an important step in biological studies and breeding of many crop plants. The major types of pure lines for biological studies and breeding include doubled haploid (DH) lines, recombinant inbred lines (RILs), and near isogenic lines (NILs). DH lines can be produced through microspore and megaspore culture followed by chromosome doubling while RILs and NILs can be produced through introgressions or repeated selfing of hybrids. DH approach was developed as a quicker method than conventional method to produce pure lines. However, its drawbacks of genotype-dependency and only a single chance of recombination limited its wider application. A recently developed fast generation cycling system (FGCS) achieved similar times to those of DH for the production of selfed pure lines but is more versatile as it is much less genotype-dependent than DH technology and does not restrict recombination to a single event. The advantages and disadvantages of the technologies and their produced pure line populations for different purposes of biological research and breeding are discussed. The development of a concept of complete in vitro meiosis and mitosis system is also proposed. This could integrate with the recently developed technologies of single cell genomic sequencing and genome wide selection, leading to a complete laboratory based pre-breeding scheme.

Factors affecting the potential for gene flow from transgenic crops of Lupinus angustifolius L. in Western Australia

Australian sweet lupins (Lupinus angustifolius L.) and their naturalised wild progenitor occur widely throughout the agricultural zone of Western Australia. Before unrestricted release of transgenic lupins is allowed, an assessment is needed of the likely level of gene flow between the wild and cultivated lupins. Three sets of data were collected to evaluate the likelihood of outcrossing and gene flow. These were the level of outcrossing between adjacent lupin crops, the spatial distribution of crops and wild lupins, and the relative flowering times of the crops and wild lupins. The level of outcrossing within the first 1.5 m of adjacent crops, assessed over 1.56 million plants, was 1 cross in 3600 plants. No crossing was detected at distances greater than 2.25 m (outcrossing rate less than 1 in 148 000). The distribution of 216 crops and 237 wild populations in Western Australia rarely overlapped. Only 5 wild populations were detected in the area where crops were found. No crops occurred in the areas where the remaining wild lupins (232 populations) were found. The crops were all early flowering, whereas the 3 selected wild populations, representing 3 different (medium, high, and very high rainfall) climatic zones, all flowered later. We conclude that the likelihood of gene flow from a transgenic lupin crop to wild lupin populations is extremely low. This is consistent with the fact that reverse gene flow from wild lupins carrying dominant genes for blue flowers and bitter seeds has never been found in farmers’ fields, despite 35 years of lupin cropping where areas of over 1 000 000 ha per year have been grown in Western Australia.

Host–Multi-Pathogen Warfare: Pathogen Interactions in Co-infected Plants

Studies of plant–pathogen interactions have historically focused on simple models of infection involving single host-single disease systems. However, plant infections often involve multiple species and/or genotypes and exhibit complexities not captured in single host-single disease systems. Here, we review recent insights into co-infection systems focusing on the dynamics of host-multi-pathogen interactions and the implications for host susceptibility/resistance. In co-infection systems, pathogen interactions include: (i) Competition, in which competing pathogens develop physical barriers or utilize toxins to exclude competitors from resource-dense niches; (ii) Cooperation, whereby pathogens beneficially interact, by providing mutual biochemical signals essential for pathogenesis, or through functional complementation via the exchange of resources necessary for survival; (iii) Coexistence, whereby pathogens can stably coexist through niche specialization. Furthermore, hosts are also able to, actively or passively, modulate niche competition through defense responses that target at least one pathogen. Typically, however, virulent pathogens subvert host defenses to facilitate infection, and responses elicited by one pathogen may be modified in the presence of another pathogen. Evidence also exists, albeit rare, of pathogens incorporating foreign genes that broaden niche adaptation and improve virulence. Throughout this review, we draw upon examples of co-infection systems from a range of pathogen types and identify outstanding questions for future innovation in disease control strategies.

Real-Time PCR for Diagnosing and Quantifying Co-infection by Two Globally Distributed Fungal Pathogens of Wheat

Co-infections – invasions of a host-plant by multiple pathogen species or strains – are common, and are thought to have consequences for pathogen ecology and evolution. Despite their apparent significance, co-infections have received limited attention; in part due to lack of suitable quantitative tools for monitoring of co-infecting pathogens. Here, we report on a duplex real-time PCR assay that simultaneously distinguishes and quantifies co-infections by two globally important fungal pathogens of wheat: Pyrenophora tritici-repentis and Parastagonospora nodorum. These fungi share common characteristics and host species, creating a challenge for conventional disease diagnosis and subsequent management strategies. The assay uses uniquely assigned fluorogenic probes to quantify fungal biomass as nucleic acid equivalents. The probes provide highly specific target quantification with accurate discrimination against non-target closely related fungal species and host genes. Quantification of the fungal targets is linear over a wide range (5000–0.5 pg DNA μl-1) with high reproducibility (RSD ≤ 10%). In the presence of host DNA in the assay matrix, fungal biomass can be quantified up to a fungal to wheat DNA ratio of 1 to 200. The utility of the method was demonstrated using field samples of a cultivar sensitive to both pathogens. While visual and culture diagnosis suggested the presence of only one of the pathogen species, the assay revealed not only presence of both co-infecting pathogens (hence enabling asymptomatic detection) but also allowed quantification of relative abundances of the pathogens as a function of disease severity. Thus, the assay provides for accurate diagnosis; it is suitable for high-throughput screening of co-infections in epidemiological studies, and for exploring pathogen–pathogen interactions and dynamics, none of which would be possible with conventional approaches.

Regional reviews: The Australian Scene

This paper examines the changing situation of pulse production in Australia over the last 30 years and projections to the year 2005. During the 30 years there has been a rapid change in the industry. In 1967 pulse production was 30,000 tonnes whilst in 1996 some 2,300,000 tonnes were produced. It is anticipated that between 3,500,000 and 4,000,000 tonnes will be produced in 2005. For most of the last 30 years Lupinus angustifolius has been the most important pulse. Australia is the major producer and the only country to export lupins into world markets. Over the last decade we have seen expansion in production of peas, chickpeas, faba beans and lentils as well as lupins. The production of these alternative pulses is now some 1,000,000 tonnes and should double by 2005. We predict Australia will be the largest pulse exporter in the world by year 2005.