Dl McNeil

Next generation of elevated [CO2] experiments with crops: A critical investment for feeding the future world

A rising global population and demand for protein-rich diets are increasing pressure to maximize agricultural productivity. Rising atmospheric [CO(2)] is altering global temperature and precipitation patterns, which challenges agricultural productivity. While rising [CO(2)] provides a unique opportunity to increase the productivity of C(3) crops, average yield stimulation observed to date is well below potential gains. Thus, there is room for improving productivity. However, only a fraction of available germplasm of crops has been tested for CO(2) responsiveness. Yield is a complex phenotypic trait determined by the interactions of a genotype with the environment. Selection of promising genotypes and characterization of response mechanisms will only be effective if crop improvement and systems biology approaches are closely linked to production environments, that is, on the farm within major growing regions. Free air CO(2) enrichment (FACE) experiments can provide the platform upon which to conduct genetic screening and elucidate the inheritance and mechanisms that underlie genotypic differences in productivity under elevated [CO(2)]. We propose a new generation of large-scale, low-cost per unit area FACE experiments to identify the most CO(2)-responsive genotypes and provide starting lines for future breeding programmes. This is necessary if we are to realize the potential for yield gains in the future.

Comparison of low and high molecular weight wheat glutenin allele effects on flour quality

Abstract Five crosses were made, using a set of New Zealand wheat cultivars, to measure the effect of glutenin allele differences on baking quality parameters. The alleles involved were: Glu-A1 (2*, 1 and n), Glu-D1 (5+10, 2+12), Glu-A3 (c, d and e), Glu-B3 (Sec-12, Sec-13, b and g), Glu-D3 (a and b). The allelic variation of F3 individual plants was identified by SDS-PAGE, and plants with the same HMW-GS and LMW-GS patterns were grouped. Quality parameters were then measured on the grouped F4 bulks. Quality parameters measured for this study were wholemeal flour protein content (WFP), grain hardness (HAR), SDS sedimentation volume (SED), Pelshenke time (PEL), mid-line peak value (MPV) and the mid-line peak time (MPT) of a mixograph. The results showed there were significant quality differences within most populations associated with the possession of a particular allele, reaching magnitudes of up to 42% for the range between populations. Most glutenin allelic comparisons showed significant differences for at least one of the resultant measured quality parameters. Allelic differences of Glu-A1 significantly influenced all characters except MPT, with the null allele apparently inferior; possession of 5+10 at Glu-D1 significantly increased Pelshenke time and SED volumes relative to allele 2+12; WFP, SED and MPV were significantly affected by the Glu-A3 alleles tested. Glu-B3 alleles significantly affected all characters except hardness and the Glu-D3 alleles tested significantly affected all characters other than hardness and SDS sedimentation volume.

Factors that influence Agrobacterium rhizogenes-mediated transformation of broccoli (Brassica oleracea L. var. italica)

Abstract An improved broccoli transformation system was developed by optimising several factors that affect the rate of effective Agrobacterium-mediated transformation. Leaf explants of cultivar Shogun were co-cultivated with Agrobacterium rhizogenes strain A4T harbouring the binary vector pART278. The T-DNA of this binary vector contains a neomycin phosphotransferase II (NOS-NPTII-NOS) gene for kanamycin resistance and a β-glucuronidase (35S-GUS-OCS) gene. Several media and factors were evaluated including combinations of arginine, mannopine, acetosyringone and the use of feeder cell layers. The new protocol includes the use of 200 μm acetosyringone in LB medium for bacterial growth, the use of a Brassica campestris feeder cell layer, 10 mm mannopine and 50 μm acetosyringone in the co-cultivation medium and 1 mm arginine in the selection medium. The use of this optimised protocol produced transformation rates of 33% in preliminary experiments transforming broccoli with the antisense 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase gene from pTOM13.

Yield components, harvest index and plant type in relation to yield differences in field pea genotypes

SummaryThe effectiveness of yield components, harvest index and morphological characteristics as selection criteria among four field pea (Pisum sativum L.) genotypes was examined. Genotypes were grown at a wide range of plant populations (9 to 400 plants m-2) to maximise environmental diversity.Both biological and seed yields approximately doubled from 9 to 100 plants m-2. This response flattened from 100 to 400 plants m-2. Differences among the genotypes were found only at 225 and 400 plants m-2. Analysis of the yield components highlighted the plasticity and large genotype by environment interactions of field peas. The numbers of pods per plant and peas per pod were maximised when each genotype was grown as spaced plants, but the low plant numbers meant seed yields per unit area were at their lowest.Genotypic differences for plant harvest index (PHI) were also only found at 225 and 400 plants m-2. Broad sense heritability estimates indicated that direct selection for PHI was not feasible. The inference from the yield component and PHI results was that alternative selection criteria such as physiological or morphological characteristics may be necessary for improved yield potential. Classification of each genotype indicated that low seedling vigour may be a positive attribute for crop plants of semi-leafless and conventionally leafed field peas. Selection based on any single plant attribute is unlikely to lead to dramatic improvements in the yield potential of field peas. Selection should be based on plant characteristics rather than on differences in yield components.

Agrobacterium rhizogenes-mediated transformation of broccoli (Brassica oleracea L. var. italica) with an antisense 1-aminocyclopropane-1-carboxylic acid oxidase gene

Abstract An improved protocol was developed for Agrobacterium rhizogenes-mediated transformation of broccoli. This procedure uses compounds that enhance the virulence of A. rhizogenes and a Brassica campestris feeder cell layer. Leaf explants or intact cotyledons of three broccoli cultivars: Green Beauty, Shogun and Green Belt, were co-cultivated with A. rhizogenes strain A4T harbouring the binary vector pLN35. The T-DNA of this binary vector contains genes encoding antisense 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (35S-ACC-5′7′) and neomycin phosphotransferase II (NOS-NPTII-NOS). Two cultivars were successfully transformed, Shogun and Green Beauty, with a transformation efficiency of 35% and 17%, respectively. Fertile plants were regenerated from kanamycin-resistant hairy roots by transfer to hormone-containing media. Integration of the T-DNA was confirmed by the polymerase chain reaction (PCR) and Southern analyses. Analysis of ethylene production by fully open flowers of three transgenic lines of Shogun demonstrated the feasibility of down-regulating ethylene biosynthesis using an antisense ACC oxidase gene. One transgenic line, Sh/2, showed a 91% reduction in ethylene production after 96 h in comparison to the non-transgenic control.

Genetic relationships in Lens species and parentage determination of their interspecific hybrids using RAPD markers

Broadening of the genetic base and systematic exploitation of heterosis in cultivated lentils requires reliable information on genetic diversity in the germplasm. The ability of random amplified polymorphic DNA (RAPD) to distinguish among different taxa of Lens was evaluated for several geographically dispersed accessions/cultivars of four diploid Lens species. This study was carried out to assess whether RAPD data can provide additional evidence about the origin of the cultivated lentil and to measure genetic variability in lentil germplasm. Three cultivars of Lens culinaris ssp. culinaris, including one microsperma, and two macrosperma types, and four wild species (L. culinaris ssp. orientalis, L. odemensis and L. nigricans) were evaluated for genetic variability using a set of 1 11-mer and 14 random 10-mer primers. One hundred and fifty-eight reproducible and scorable DNA bands were observed from these primers. Genetic distances between each of the accessions were calculated from simple matching coefficients. Split decomposition analysis of the RAPD data allowed construction of an unrooted tree. This study revealed that (1) the level of intraspecific genetic variation in cultivated lentils is narrower than that in some wild species. (2) L. culinaris ssp. orientalis is the most likely candidate as a progenitor of the cultivated species, (3) L. nigricans accession W6 3222 (unknown) and L. c. ssp. orientalis W6 3244 (Turkey) can be reclassified as species of L. odemensis and (4) transmission of genetic material in Lens interspecific hybrids is genotypically specific, as identified by the RAPD markers in our study.

Comparison of crossability, RAPD, SDS-PAGE and morphological markers for revealing genetic relationships within and among Lens species.

The phylogenetic relationships among (sub)-species in the genus Lens have been reviewed based on recent published reports. There was both a substantial level of agreement and disagreement between reports based on different analytical procedures and different plant germ plasms. Lens culinaris ssp. orientalis appeared as the wild progenitor of the cultivated lentils. A gene flow from L. odemensis and L. ervoides during lentil crop evolution was suggested. Morphological characters (quantitative and qualitative) showed a different taxonomic pattern in the genus Lens. The use of nuclear and biochemical markers (RFLPs, RAPDs, seed-protein electrophoresis) appeared to be the most consistent and reliable methods for determining genetic relationships. It is suggested that these techniques be used in combination for taxonomic analysis of the genus Lens.

Identification and molecular mapping of a dwarfing gene in barley (Hordeum vulgare L.) and its correlation with other agronomic traits

Ninety-two doubled haploid (DH) lines, generated from a cross between Franklin and TX9425 (a Chinese Landrace), were grown in three environments to identify quantitative trait loci (QTLs) controlling agronomic traits including heading date, plant height and spike characteristics. The DH lines showed a wide range of variations for all the agronomic traits tested. Most of the traits were controlled by one or two major QTLs which explained 9.5–80.9% of the phenotypic variation. Two dwarfing genes were identified from the cross. One of the dwarfing genes was from Franklin, which is the same as the previously reported denso gene. The other dwarfing gene was from the Chinese landrace variety. Both dwarfing genes were temperature and/or day length sensitive. The dwarfing gene from Franklin was more effective in early sowing trials (shorter day length and lower temperature) while the gene from TX9425 was more effective in later sown trials. The dwarfing gene from TX9425 was located at a similar position to the uzu gene. However, it differed from this gene being temperature sensitive with very close links to short spikes, awns and high grain density which is more like a brh gene. To effectively use this gene in a breeding program, it is necessary to break the linkage between the dwarfing gene and the unfavourable spike traits.

Variability in yield of four grain legume species in a subhumid temperate environment. I. Yields and harvest index

SUMMARY In 1998/99 and 1999/2000, field trials were conducted to try to explain why grain legume yields and harvest index are more variable than many other crops. Treatments involved varying plant populations and sowing depths and were selected to maximize plant variability. Both yields and harvest index were variable. Total dry matter (TDM) production generally increased as plant population increased up to twice the optimum population. Increases ranged from 80 to 130 % with lupins producing the highest yields of 878 and 972 g/m 2 of TDM in 1998/99 and 1999/2000 respectively. While plants sown at 10 cm depth produced more TDM than did plants sown at 2 cm, the difference was only 3 %. Seed yields followed similar trends to TDM, with maximum yields (mean of 403 g seed/m 2 ) produced at twice the optimum population. Crop harvest index (CHI) was quite variable and ranged from 0 . 31 to 0 . 66. Crop HI was lowest (0 . 43) at the lowest population and increased to 0 . 55 at twice the optimum plant population. In both seasons, lentil had the highest CHI and lupin the lowest. While CHI was variable there were very close relationships between seed yield and TDM which suggested that maximum seed yield depends on maximizing TDM production. The results also suggest that growers should increase population by a factor of two to obtain maximum seed yields.

Identification and genetic characterization of different resistance sources to ascochyta blight within the genus Lens

Genetic regulation of host resistance in lentil to ascochyta blight was found to be controlled by two complementary dominant gene pairs in wild species of Lens ervoides and Lens odemensis. Both genes must be present in the dominant form, whether homozygous or heterozygous, for complete resistance. When one pair of genes is present in homozygous recessive state, they mask the effect of the other dominant gene pair and ultimately makes the lentil plant susceptible to the pathogen, a case of duplicate recessive gene interaction. The results also suggested that in Lens culinaris ssp. orientalis, ascochyta blight resistance was controlled by a single dominant gene pair. The possible utilization of wild Lens species to improve the genetic resistance of cultivated lentil to ascochyta blight is reported and it is suggested that interspecific hybrids should be included in lentil breeding programmes aiming at ascochyta blight resistance.