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A study to determine the physiological and biochemical responses of eight tea [Camellia sinensis (L.) O. Kuntze] cultivars to water-deficit stress was conducted in a 'rain-out shelter' using potted plants. Three levels of soil moisture content [34, 26, or 18% (v/v) water] were applied to three plants of each cultivar in a complete randomised design, and the whole experiment was replicated three-times. The treatments were applied for 12 weeks, during which time plant water status, shoot extension rates, changes in gas exchange parameters, and leaf proline and glycinebetaine concentrations were determined. The imposition of severe water-deficit conditions [18% (v/v) soil water content] caused a significant (P ≤ 0.05) decline in the relative water content of leaves, shoot water potentials, and shoot extension rates from mean values of 84.8% to 50.6%, -0.80 to -1.15MPa, and 1.87 to 0.29 mm d-1, respectively, compared to plants grown in a well-watered soil [34% (v/v) soil water content]. The three gas exchange parameters measured (stomatal conductance, evapotranspiration rate, and rate of net photosynthesis) also declined significantly (P ≤ 0.05) with decreasing soil moisture content. In contrast, water-deficit stress increased the accumulation of leaf proline and glycinebetaine from mean values of 0.104 to 0.244 µmol g-1 FW, and from 1.567 to 2.025 µmol g-1 DW, respectively. The eight tea cultivars differed significantly (P ≤ 0.05) in their responses to water-deficit stress. Proline accumulation was significantly (P ≤ 0.05) higher in the drought-tolerant cultivars, 'TRFK 306', 'TRFCA SFS150', and 'EPK TN14/3', suggesting that proline concentration could be used as a marker for drought-tolerance in tea. [ABSTRACT FROM AUTHOR]

Dairying in Australia is practiced in highly diverse climatic conditions and production systems, which means that re-ranking of genotypes could occur across environments that vary in temperature and humidity-that is, genotype-by-environment interactions (G × E) may exist. The objective of this study was to investigate G × E for heat tolerance with respect to milk production traits in Australian Holsteins. A total of 6.7 million test-day milk yield records for first, second, and third lactations from 491,562 cows and 6,410 sires that had progeny in different climatic environments were included in the analysis. The environmental gradient used was the temperature-humidity index (THI) calculated from climate data from 163 Australian public weather stations between 2003 and 2017. Data were analyzed using univariate reaction norm (RM) sire model, and the results were compared with multi-trait model (MT). The MT analysis treated test-day yields at 5th percentile (THI = 61; i.e., thermoneutral conditions), 50th percentile (THI = 67; i.e., moderate heat stress conditions), and 95th percentile (THI = 73; i.e., high heat stress conditions) of the trajectory of THI as correlated traits. A THI series of 61, 67, and 73, for example, is equivalent to average temperature and relative humidity of approximately 20°C and 45%, 25°C and 45%, and 31°C and 50%, respectively. We observed some degree of heterogeneity of additive (AG) and permanent environmental (PE) variance over the trajectory THI from RM analysis, with estimates decreasing at higher THI values more steeply for PE than for AG variance. The genetic correlations of the tests between the 5th and 95th percentiles of THI for milk, protein, and fat yield from RM were 0.88 ± 0.01 (standard error), 0.79 ± 0.01, and 0.86 ± 0.01, respectively, whereas the corresponding estimates from MT were 0.86 ± 0.02, 0.84 ± 0.03, and 0.87 ± 0.03. We observed lower genetic correlations between the 5th and 95th percentiles of THI for milk tests from recent years (i.e., 2009 and 2017) compared with earlier years (i.e., 2003 and 2008), which suggests that the level of G × E is increasing in the studied population and should be monitored especially in anticipation of future expected increase in daily average temperature and frequency of heat events. Overall, our results indicate presence of G × E at the upper extreme of the trajectory of THI, but the current extent of sire re-ranking may not justify providing separate genetic evaluations for different levels of heat stress. However, variations observed in the sire sensitivity to heat stress suggest that dairy herds in high heat load conditions could benefit more from using heat-tolerant or resilient sires., (The Authors. Published by FASS Inc. and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).)

In most smallholder dairy programmes, farmers are not fully benefitting from the genetic potential of their dairy cows. This is in part due to the mismatch between the available genotypes and the environment, including management, in which the animals perform. With sparse performance and pedigree records in smallholder dairy farms, the true degree of baseline genetic variability and breed composition is not known and hence rendering any genetic improvement initiative difficult to implement. Using the Girinka programme of Rwanda as an exemplar, the current study was aimed at better understanding the genetic diversity and population structure of dairy cattle in the smallholder dairy farm set up. Further, the association between farmer self-reported cow genotypes and genetically determined genotypes was investigated. The average heterozygosity estimates were highest (0.38 ± 0.13) for Rwandan dairy cattle and lowest for Gir and N'Dama (0.18 ± 0.19 and 0.25 ± 0.20, respectively). Systematic characterization of the genetic variation and diversity available may inform the formulation of sustainable improvement strategies such as targeting and matching the genotype of cows to productivity goals and farmer profile and hence reducing the negative impact of genotype by environment interaction.

Harvesting stage of sweet sorghum ( Sorghum bicolor L. Moench) cane is an important aspect in the content of sugar for production of industrial alcohol. Four sweet sorghum genotypes were evaluated for harvesting stage in a randomized complete block design. In order to determine sorghum harvest growth stage for bioethanol production, sorghum canes were harvested at intervals of seven days after anthesis. The genotypes were evaluated at different stages of development for maximum production of bioethanol from flowering to physiological maturity. The canes were crushed and juice fermented to produce ethanol. Measurements of chlorophyll were taken at various stages as well as panicles from the harvested canes. Dried kernels at 14% moisture content were also weighed at various stages. Chlorophyll, grain weight, absolute ethanol volume, juice volume, cane yield, and brix showed significant ( p = 0.05) differences for genotypes as well as the stages of harvesting. Results from this study showed that harvesting sweet sorghum at stages IV and V (104 to 117 days after planting) would be appropriate for production of kernels and ethanol. EUSS10 has the highest ethanol potential (1062.78 l ha -1 ) due to excellent juice volume (22976.9 l ha -1 ) and EUSS11 (985.26 l ha -1 ) due to its high brix (16.21)., Competing Interests: The authors declare that there is no conflict of interests.