Climate change research that aims to accelerate the adaptation process of agricultural production systems first requires understanding their climatic vulnerability, which is in part characterised by their exposure. This paper’s approach moves beyond traditional metrics of climate variables and proposes specific indicators for grassland-based livestock systems. The indicators focus on the variation in seasonal boundaries and seasonal and yearly herbage productivity in response to weather conditions. The paper shows how statistical interpretations of these indicators over several sites and climatic years (past and future) enable the characterisation of classes of climatic years and seasons as well as their frequencies of occurrence and their variation from the past to the expected future. The frequency of occurrence and succession of seasonal extremes is also examined by analysing the difference between observed or predicted seasonal productivity and past mean productivity. The data analysis and corresponding statistical graphics used in our approach can help farmers, advisers, and scientists envision site-specific impacts of climate change on herbage production patterns. An illustrative analysis is performed on three sites in south-western France using a series of climatic years covering two 30-year periods in the past and the future. We found that the herbage production of several clusters of climatic years can be identified as ‘normal’ (i.e. frequent) and that the most frequent clusters in the past become less common in the future, although some clusters remain common. In addition, the year-to-year variability and the contrast between spring and summer–fall (autumn) herbage production are expected to increase.

Interspecific F₁ hybrids were obtained from a cross between a male sterile Brassica napus (2n = 4x = 38, AA (20) and CC (18) genomes) and an inbreeding line B. rapa (Purple Cai-Tai inbred line 9418, 2n = 2x = 20, AA (20) genome) to introgress male sterility from a tetraploid into a diploid through backcrossing. The morphological characteristics of F₁ plants were more like the female parent B. napus and segregated considerably in BC₁ when backcrossed to the recurrent parent Purple Cai-Tai. The progeny became stable and more similar to Purple Cai-Tai by BC₄. Most C genome chromosomes were found to be eliminated, based on cytogenetic analysis. The majority of chromosomes were eliminated at very early backcross stages, with only 20–26 chromosomes in BC₁ plants, and some chromosomes were eliminated gradually with increased backcross generations. The BC₄ plants were generally stable with exactly 20 chromosomes. Analysis by AFLP indicated that 49.5–68.7% of the total bands eliminated from F₁ to BC₄ were female parent specific, and ∼12% of B. napus bands were retained with increased backcrossing. The genetic materials controlling sterility from the female parent B. napus were introgressed successfully into the BC₄ plants even though most B. napus chromosomes/genetic materials were eliminated during the backcross process.

A glasshouse study was conducted under ideal conditions to determine leaf appearance, elongation, and senescence rates along with life span and leaf length characteristics of four grass species: wheat (Triticum aestivum L.), brown back wallaby grass (Rytidosperma duttonianum (Cashmore) Connor and Edgar), phalaris (Phalaris aquatica L.), and annual ryegrass (Lolium rigidum Gaud.). This study provided a comprehensive characterisation of leaf turnover rates for the entire life cycle of these grasses, some of which are poorly characterised. Importantly, leaf senescence rate has been captured in the same conditions as the other leaf rates of the life cycle. Leaf position proved to be a significant explanatory variable in each of the leaf turnover rates. The relationships between leaf position and the components of leaf turnover were most commonly represented by non-linear models.

Further studies may be necessary to validate these statistical models to field situations. However, this information will be useful to calibrate the senescence algorithms of plant growth models in agricultural decision support tools, which may then be applied to simulation studies including the assessment of grass curing for planning activities such as resource allocation, wildfire suppression, and execution of prescribed burning programs by fire management agencies.

Improved dryland pastures for sheep and beef cattle production in south-western Victoria are typically based on summer-dormant cultivars of perennial ryegrass (Lolium perenne L.) or phalaris (Phalaris aquatica L.). These are highly productive in spring but exhibit low accumulation rates over summer–autumn. Summer-active perennial pasture species could potentially alleviate this summer–autumn feed gap.

Three pasture systems that used different pastures on each of the three landscape classes (crest, slope, and valley floor) were compared over 4 years. The perennial ryegrass system (henceforth Ryegrass) had a different ryegrass cultivar on each landscape class. The Triple system used lucerne (Medicago sativa L.) (crest), perennial ryegrass (slope), and summer-active tall fescue (Lolium arundinaceum (Schreb) Darbysh.) (valley floor). The Novel system used chicory (Cichorium intybus L.) (crest), Italian ryegrass (Lolium multiflorum Lam.) or hybrid ryegrass (L. × boucheanum Kunth.) (slope), and kikuyu (Pennisetum clandestinum Hochst. ex Chiov.) (valley floor). The pastures were grazed by either one (in the case of the Novel system) or three (in the case of the Ryegrass and Triple systems) animal systems that varied over the life of the experiment.

Total annual herbage accumulation of the Ryegrass and Triple systems did not differ. The Novel system consistently had lower total annual dry matter accumulation than the other two systems. Lucerne pastures generally had the highest accumulation rates over summer, followed by the chicory pastures. The kikuyu pastures responded well to summer rainfall but otherwise had similar accumulation rates to the perennial ryegrass and tall fescue pastures over summer. Tall fescue pastures grew well in autumn following wet summers. In spring the perennial ryegrass pastures based on Fitzroy or Avalon were highly productive but seldom grew faster than other pastures.

The results support the hypothesis that incorporating deep-rooted, summer-active perennial species will increase pasture production over summer–autumn compared with conventional pasture systems but not at the expense of winter–spring production.

Perennial ryegrass populations previously subjected to two or four cycles of selection for short or long leaf length were studied to determine the response of morphological traits to selection and interaction to determine yield. Measured morphological traits were leaf length, leaf appearance interval, ligule appearance interval, leaf elongation duration, leaf elongation rate, tiller number, tiller dry weight, and herbage dry matter. Additionally, Rubisco concentration during leaf development was measured to determine the association of Rubisco turnover with morphological characteristics and yield. Rubisco was measured and modelled as a three-parameter (D, peak Rubisco concentration; G, time of D; and F, curve width measure), log-normal curve. Leaf length, leaf elongation rate, tiller weight, and plant dry matter diverged after two cycles of selection and further divergence occurred, with these traits being, respectively, 35, 28, 53, and 61% greater in the long- than the short-leaved plants after four cycles of selection. Opposite trends were displayed by Rubisco turnover, with selection for long leaves co-selecting for increased Rubisco turnover time and selection for short leaves resulting in increased leaf Rubisco concentration. There was indication of coupling of leaf appearance with Rubisco turnover. Across populations, multivariate analysis indicated that plant yield was associated with Rubisco concentration rather than Rubisco turnover. The association between higher yield and lower Rubisco concentration could be targeted in the breeding of high-yielding, nitrogen-efficient forage grasses. Plant yield was mainly associated with increased leaf area, indicating that yield could be improved by selecting for longer leaves and faster rates of leaf expansion.

Manganese (Mn) toxicity can induce oxidative stress and impair photosynthesis in plants. The activity of antioxidant enzymes such as superoxide dismutase (SOD) is increased in Lolium perenne (perennial ryegrass) in response to Mn toxicity (mainly in tolerant cultivars), but it remains unclear whether non-enzymatic antioxidant compounds may have a role in Mn tolerance. Seedlings of perennial ryegrass cv. Nui (Mn-sensitive) and cv. Kingston (Mn-tolerant) were grown in a greenhouse in nutrient solution at increasing Mn doses over 21 days. Even though both cultivars showed similar Mn uptake, dry weight decreases and lipid peroxidation caused by excess Mn were higher in cv. Nui than in Mn-tolerant Kingston. Maximum quantum yield of photosystem II (PSII) (Fv/Fm) declined only in cv. Nui at the highest Mn dose. Effective quantum yield (Ф PSII), electron transport rate, CO₂ assimilation, and total chlorophyll concentration in leaves decreased under excess Mn, particularly in the sensitive cultivar. Interestingly, chlorophyll a/b ratio increased (indicating relatively lower concentration of light-harvesting chlorophyll proteins as an adaptive defence mechanism) with an increase in Mn supply only in cv. Kingston, which partially explained its greater Mn tolerance compared with Nui. Concentration of carotenoids was not directly associated with non-photochemical quenching values, suggesting that ryegrass did not dissipate an excess of absorbed energy under Mn toxicity by this mechanism. At increasing excess Mn, both enzymatic (SOD activity) and non-enzymatic antioxidant responses (radical scavenging ability and phenolic concentration) were enhanced, mainly in Kingston. The enhanced antioxidant response in this cultivar suggests the hypothesis of increased capacity to control Mn-triggered oxidative stress as reflected in the reduced lipid peroxidation.

Conservation cropping systems with no-till and stubble retention improve soil condition and water conservation. However, tillage is replaced by herbicides for weed control in these systems, increasing the threat of herbicide resistance. In the medium to high rainfall zones of the southern wheatbelt of Australia and under irrigation, wider row spacing is used to enable seeding into heavy stubble loads and to avoid stubble burning. Some evidence suggests that wider rows lead to reduced crop competitive ability and crop yields, greater herbicide dependence, and increased spread of resistance. Our aim was to test the hypothesis that increasing seeding rate compensated for reduced competitive ability at wider row spacings, especially when herbicide performance was suboptimal. We examined the impact of two wheat row spacings (18 and 36 cm) and five seeding rates (resulting in a range of densities of ∼80–700 plants/m²) on control of Lolium rigidum with five rates of post-emergence application of diclofop-methyl (Hoegrass^®), ranging from label rate to lower rates, over two growing seasons. In the presence of L. rigidum, wheat grain yield was unaffected by row spacing but was significantly reduced at low seeding rates, especially at lower herbicide rates. Lolium rigidum was suppressed at higher crop densities but was also unaffected by row spacing. Grain yield was maximised when post-emergence herbicide was applied at 60–100% of the recommended dose at wheat densities >∼300 plants/m². Significant levels of the weed remained in the crop at anthesis in all treatments. Weed dry matter ranged from 525 g/m² at low crop densities and with no herbicide to 150 g/m² with the recommended rate of herbicide and high wheat densities. The implications of manipulating crop competitive ability to improve weed control are discussed, especially in conditions where herbicide performance is unreliable due to weeds developing herbicide resistance or adverse environmental conditions.

The temperate pasture grass Lolium perenne L. is commonly found in symbiotic association with the asexual fungal endophyte Neotyphodium lolii. Levels of endophyte colonisation and alkaloid content were evaluated in associations formed by plant genotypes from cv. Bronsyn with the standard endophyte (SE) and five distinct commercial endophyte strains. Bronsyn–SE produced all of the measured alkaloids (lolitrem B, peramine, and ergovaline). Bronsyn–AR1 produced only peramine, while Bronsyn–AR37 produced none of the tested alkaloids. Bronsyn–NEA2, Bronsyn–NEA3, and Bronsyn–NEA6 produced both ergovaline and peramine. Both endophyte strain and host genotype exerted significant effects on alkaloid production. Analysis of endophyte colonisation using qPCR revealed differences between each association. With the exception of Bronsyn–AR1 and Bronsyn–NEA3, host genotype also significantly affected colonisation levels. Phenotypic performance of each association was also assessed, based on measurement of morphological traits under glasshouse conditions in hydroponic culture. Significant variation due to different endophyte and host genotypes was observed. Collectively, these studies confirm that differences in both endophyte and host genotypes contribute to host–endophyte performance in a complex interactive manner.

The effects of waterlogging, alone and combined with ray blight disease (caused by Stagonosporopsis tanaceti), on pyrethrum (Tanacetum cinerariifolium) plant growth were quantified in glasshouse trials. Six pyrethrum cultivars were initially studied for their response to 6 days of waterlogging and their recovery from waterlogging during 26 days post-waterlogging. Waterlogging caused substantial root death and leaf wilting and accelerated senescence in all cultivars. Root growth was 80% more reduced than shoot growth. Cultivar ‘F’ showed significantly higher root porosity and growth following waterlogging than other cultivars. In contrast, cv. ‘C’ had the greatest growth reduction from waterlogging and poor root-system recovery after waterlogging. Plants of cvv. C and F inoculated with S. tanaceti and then waterlogged were more significantly affected than were those exposed to waterlogging only. For both cultivars, shoot growth under the combined treatment, relative to initial growth, recovered up to 25%, but root growth suffered irreversible damage. The combined treatment decreased the number of stems by 39% compared with waterlogging alone after the post-waterlogging period. In conclusion, pyrethrum cultivars showed differential reactions to waterlogging; but growth in all cultivars was seriously affected by a combination of waterlogging and infection by ray blight.