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Many of the soils in the Australian cereal belt have subsoils with chemical and physical properties that restrict root growth, which limits water use and yield. On alkaline sodic soils salinity, high pH, high available boron (B), deficiencies of zinc (Zn) and manganese (Mn) and high soil strength occur commonly and aluminium (Al) toxicity restricts root growth on acid soils. While the effects of individual subsoil constraints have been studied there is some debate about the relative importance to yield of the different soil stresses across the region. To address this issue yield variation among a set of 52 varieties of bread wheat was analysed using yield data from 233 trials conducted over 12 years. The trials were conducted in all mainland States but the majority were in South Australia and Western Australia. Each variety was characterised for its response to high B, high pH, Al toxicity, salinity, deficiencies in Zn and Mn and resistance to root lesion nematode (Pratylenchus neglectus), root growth through strong soil, seminal root angle, carbon isotope discrimination (CID) and maturity. This data was then used to examine the contribution of each trait to the genetic variation in yield at each of the 233 trials. The contribution of a specific trait to the genetic variation in yield at each site was used to infer the importance of a particular constraint to yield at that site. Of the traits linked to soil constraints, salinity tolerance, (measured by Na exclusion) was most often associated with genetic variation in grain yield (34% of all experiments), followed by tolerance to high Al (26%) and B tolerance (21%). Tolerance to low Zn and Mn were not consistently associated with yield variation. However, maturity was the trait that was most frequently associated with yield variation (51% of experiments), although the relative importance of early and late flowering varied among the States. Yield variation was largely associated with early flowering in Western Australia and the relative importance of late flowering increased as trials moved eastward into South Australia, Victoria and New South Wales. Narrow, rather than wide, seminal root angle was more commonly associated with high yield (25% of sites) and there was little evidence of any regional pattern in the importance of root angle. CID was important in 18% of trials with a low CID being most commonly associated with high yields. The yield advantage at sites where a trait contributed significantly to yield variation ranged from ∼15% for Na exclusion and B tolerance to 4% for tolerance to high pH. The analysis has provided an assessment of the relative importance of a range of traits associated with adaptation to environments where subsoil constraints are likely to affect yield and has indicated patterns in the importance and effects of these traits that may be linked to regional variation in rainfall and soils.
This study investigated the genetic and environmental influences and their interactions on seed protein profiles of five narrow-leafed lupin cultivars grown under three different environmental conditions. High throughput MALDI-TOF mass spectrometry revealed 133 reproducible seed protein mass peaks. Thirty-one seed protein mass peaks were detected in all 15 combinations of cultivar × environment. Twenty mass peaks were influenced by cultivars irrespective of environment. Only six protein mass peaks were influenced by environments. Seventy-six mass peaks were highly variable. Number of mass peaks of lupin seed protein is mostly genetically controlled (P = 0.008) with no significant influence of the environment (P = 0.131). Environment and cultivar interactions were not significant (P = 0.889). Multivariate analyses of mass peak profiles supported the above analysis showing that protein mass peak profile was significantly (P = 0.001) influenced by cultivar but not by environment (P = 0.053). This result indicates the possibility of breeding new lupin cultivars targeting specific proteins for human food and animal feed without being too concerned about environmental influences.
The use of cover plants is an important agricultural practice in no-tillage systems. Soil cover and nutrient recycling depend on the dynamics of plant residue decomposition. The objective of this study was to evaluate the effect of the chemical composition and decomposition rates of cover plants on maize yield in no-tillage systems in the savannah, central Brazil. Levels of hemicellulose, cellulose, and lignin, along with decomposition rates of the following plant species were determined at flowering and maturation: Urochloa ruziziensis, Cajanus cajan, Canavalia brasiliensis, Crotalaria juncea, Mucuna aterrima, Pennisetum glaucum, Raphanus sativus, Sorghum bicolor, and Triticum aestivum. Spontaneous vegetation growth in the fallow was used as a control. The highest dry matter yields were obtained from Sorghum bicolor, followed by P. glaucum, when harvested at maturation. Canavalia brasiliensis and U. ruziziensis, the species with lowest lignin levels, presented faster decomposition and lower half-life values compared with the residues of C. cajan and S. bicolor. Cover plants with the lowest lignin concentrations, and thus the fastest residue decomposition rates, such as C. brasiliensis, U. ruziziensis, and P. glaucum, resulted in higher maize yields. Urochloa ruziziensis and C. brasiliensis contributed to nutrient recycling due to their faster decomposition, while C. cajan aids in the formation of soil cover due to slower decomposition of its residues.
Seed loss caused by pod-shatter during harvesting is one of the main problems in rapeseed production worldwide. Quantitative trait loci (QTLs) for pod-shatter based on genetic mapping would help breeders develop cultivars resistant to pod-shatter. In this study, we constructed a genetic map of Brassica napus containing 107 simple sequence repeat (SSR) markers and 68 sequence-related amplified polymorphism (SRAP) markers using a doubled-haploid (DH) population of 276 lines derived from the cross H155 × Qva. This map covered 1382.8 cM with an average marker interval of 7.9 cM. In total, 13 QTLs for pod-shatter resistance were identified in this DH population at two experimental sites (in Wuhan and Zhengzhou); three of the QTLs were present at both locations. At Zhengzhou, nine QTLs, identified in linkage groups A1, A7, A8, C5, and C8, together explained 49.0% of the phenotypic variation. At Wuhan, four QTLs were mapped on the A1, A4, A7, and C8 linkage groups. These QTLs explained 38.6% of the phenotypic variation. These results may serve as a valuable basis for further molecular dissection of pod-shatter resistance in B. napus, and for development of the markers related to QTLs that may be useful for marker-assisted selection of pod-shatter resistant cultivars.
An efficient regeneration and transformation system was established and optimised for adzuki bean (Vigna angularis (Willd.) Ohwi & Ohashi). 6-Benzylaminopurine at 5 mg L–1 was used to increase adventitious bud induction frequency. The highest frequency of shoot elongation was 92.8% when using a medium composition of MS salts combined with 0.1 mg L–1 of IAA, 0.5 mg L–1 of GA3, 1.0 mg L–1 of zeatin-riboside, 50 mg L–1 of aspartic acid, and 50 mg L–1 of glutamic acid. In vitro rooting was 100% when shoots were cultured on the solid MS medium supplemented with 1.0 mg L–1 of NAA. Reproducible transformation of epicotyl explants was developed using the A. tumefaciens EHA105 strain. Using a concentration of 40 mg L–1 of acetosyringone, 20 mm MES, and 5 mg L–1 of 6-benzylaminopurine in the co-cultivation medium, a transformation efficiency of 12.6% was attained. Using this transformation protocol, we obtained transgenic adzuki bean plants resistant to soybean mosaic virus by introducing the V. angularis VaPR3 gene.
This study quantified the relationship between vegetative development and temperature of ‘Old New Zealand’ faba bean, ‘Milton’ oats, and ‘Feast II’ Italian ryegrass using thermal time (Tt, degree-days) calculations. Each species was sown on five dates in autumn and winter 2008 and three dates in autumn 2009. The linear model for rate of development calculated the Tt requirement of faba bean for 75% emergence as 217 degree-days (base temperature (Tb) = 1.2°C), compared with 132 (Tb = 1.6°C) for oats and 132 (Tb = 1.8°C) for Italian ryegrass. Leaf appearance had a Tb of 2.4°C for faba bean, 3.0°C for oats, and 0.7°C for Italian ryegrass. The mean phyllochron (degree-days leaf–1) was 66 ± 1 for faba bean, 123 ± 3.90 for oats, and 120 ± 4.21 for Italian ryegrass. Soil temperature at 20 mm depth was the most accurate predictor of Tb and the Tt requirements to reach 75% emergence. Conversely, air temperature on-site was required to predict the phyllochron for faba bean because of its elevated growing point. Either air or soil temperature at the experimental site or at a nearby meteorological station could be used to define the phyllochron for oats and Italian ryegrass. These results highlight the importance of both soil and air temperatures to accurately define vegetative development before the processes are included in simulation models for these winter annual forage crops.
Intercropping of maize (Zea mays L.) with perennial forage, such as palisade grass [Brachiaria brizantha (Hochst. ex A. Rich) Stapf], provides large amounts of biomass that can be used as straw for no-tillage systems or as pasture for animal grazing. In addition, the use of narrow row spacing may increase maize grain yield. However, it is important to evaluate intercrops at different row spacing to avoid reductions in both maize and forage biomass production. The objectives of this field experiment during two growing seasons in Brazil were as follows: (1) to evaluate the influence of intercropping and row spacing on maize yield, leaf nutrient concentration, and plant population and development; and (2) to assess the influence of row spacing on palisade grass herbage mass and leaf nutrient concentration. The experimental design was a randomised complete block design in a 2 × 2 factorial scheme, with eight replications. The treatments comprised two row spacing distances (0.45 and 0.90 m) and two crop management types (maize monoculture and intercropped with palisade grass). The nutrient concentrations in the leaves of the maize plants were in the ideal range for this crop under all conditions studied. Plant height, height of first ear, and number of grains per ear were higher with the narrow row spacing. Maize grain yield was similar in both crop management types (10 301 and 9745 kg ha–1 for monoculture maize and intercropped, respectively). However, maize grain yield at the narrow row spacing was higher than that obtained with the wide row spacing (9948 v. 8905 kg ha–1). In contrast, row spacing did not affect the nutrient level or quality (crude protein concentration) of palisade grass. The amount of dry matter (DM) from palisade grass was lower at maize harvesting (4.7 Mg ha–1) and 90 days after harvesting (6.9 Mg ha–1) under narrow spacing. However, the amount of DM was similar at both row spacings at 120 days after maize harvesting (9.2 Mg ha–1). When there is no problem with water and nutrient availability, the use of maize and palisade grass intercropping under both row spacing conditions (0.45 and 0.90 m) provides an option for the production of forage DM without reducing the maize grain yield.
Cytoplasmic male sterility (CMS) has proved to be an effective and efficient genetic tool in sorghum (Sorghum bicolor (L.) Moench) hybrid breeding programs. The A1 (milo cytoplasm) CMS type has been widely exploited to produce both commercial grain and forage sorghum hybrids. To explore the possibility of using alternative CMS (non-milo cytoplasm) sources, we studied the effect of cytoplasm on forage yield and quality in sorghum. Nine female (CMS) lines (representing three each in A1, A2, and A3 cytoplasms) and five male lines were used to generate 45 hybrids, which were evaluated in three environments. Cytoplasm and its first-order interaction with location and male and female lines showed the presence of a cytoplasmic effect on the majority of fodder yield and quality traits examined. The CMS lines possessing A3 cytoplasm (A3N213 and A3N193) were good combiners for important fodder yield and quality traits. For hydrocyanic acid, the CMS lines possessing A1 cytoplasm were good combiners. Mean performance of hybrids and combining ability analysis of parents revealed that A3 cytoplasm can be used along with the widely used A1 cytoplasm, which helps in the diversification of the male sterile base of forage sorghum hybrids.
Several morphological and agronomic traits and the genetic diversity of nine Dactylis glomerata L. populations collected throughout Sicily (semi-arid Mediterranean environment) were evaluated for two successive years. Significant differences were recorded for morphological traits (plant height, leaf length, leaf width). In relation to the measurement of summer dormancy, the results suggest the expression of different levels of dormancy (completely dormant, semi-dormant, and non-dormant). For biomass yield, some Sicilian populations (SD63 and SD56) characterised by low levels of summer dormancy show production levels similar to the summer-active control varieties (Medly and Porto). However, SD46, with a much higher level of dormancy, gave biomass yield higher than the summer-dormant control variety (Kasbah). The genetic diversity evaluated by fAFLP analysis confirms the observed morphological and agronomic variability.
Bituminaria bituminosa (L.) C.H. Stirton, commonly known as tedera, is a perennial legume of interest in Australia due to its adaptation to Mediterranean environments. Field experiments were conducted at two sites in Victoria, Australia, a high rainfall site at Hamilton and a low rainfall site at Bealiba, to evaluate tedera var. albomarginata lines against other forage species. At Hamilton, tedera achieved similar seedling densities to lucerne (Medicago sativa L.) following sowings in late spring 2009 and early winter 2010 (30–60 seedlings/m2). Forage production from the spring-sown tedera was between 1.0 and 2.3 t DM/ha at harvests in March and May 2010, but from May onwards the species failed to remain productive and its content in the swards decreased to become <10%. Forage production from all early winter-sown tedera swards was low (<0.5 t DM/ha). At Bealiba, some of the tedera lines outyielded lucerne. The tedera at Bealiba had a vigour rating of 8.3, on a scale of 1–10, in the summer of 2008–09, after surviving three summers. The tedera lines evaluated are unlikely to persist in cold wet winter environments but in drier zones tedera may persist and offer good DM yields of high nutritive value.
Submergence is a major factor affecting seedling recruitment in lowland grassland ecosystems. Our aim was to evaluate the tolerance to increasing flooding intensity of the seedlings of tropical grasses Chloris gayana K. and Panicum coloratum L., whose use as a forage species is increasing in humid grasslands. For this purpose, 2-week-old seedlings of C. gayana and P. coloratum were subjected to control, partial submergence (PS) and complete submergence (CS) in clear water for 14 days and allowed to grow for a subsequent 12-day period to assess their recovery. The following responses were assessed: generation of root aerenchyma, morphological changes and emergence from water, biomass allocation in relation to plant size, and biomass accumulation. Results showed that constitutive root aerenchyma was high in both species. Under PS and CS, root aerenchyma increased by up to 50–55% in C. gayana and up to 40–48% in P. coloratum. Under PS, the increase in seedling height for both species was the same as for controls. Under CS, C. gayana further increased its height and emerged more quickly from water; P. coloratum was not able to increase its height, and therefore the seedlings always remained underwater. The escape-from-water response of C. gayana was associated with preferential biomass allocation towards shoots and with a marked lengthening of leaf blades. By contrast, there was no change in allocation in P. coloratum, and its leaves were shorter under CS. The final biomass of C. gayana under CS was similar to that under PS, and equivalent to 54% of its controls. In P. coloratum, biomass under PS and CS were 64 and 21% of its controls (respectively), which indicates that injury caused by CS persisted during the post-submergence period. In conclusion, both species are tolerant to PS at the seedling stage. However, when flood depth increases by submerging the seedlings, C. gayana is able to escape from water while P. coloratum is not, thus strongly affecting its recovery. Therefore, C. gayana appears to be a more promising species for cultivation in lowland grasslands prone to flooding of unpredictable intensity.
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