The yellow–green leaf mutant can be exploited in photosynthesis and plant development research. A Triticum aestivum mutant with the chlorina phenotype, here called B23, was produced by treatment with the chemical mutagen sodium azide. This B23 mutant showed significantly lower chlorophyll content than wild-type Saannong33, and its chloroplast structure was abnormal. All its yield-related traits, except for the number of spikes per plant, were also significantly decreased. Genetic analysis confirmed that the mutant phenotype was controlled by a recessive gene, here designated cn-A1. Using bulked segregant analysis and the wheat 660K single nucleotide polymorphism array, the cn-A1 gene was mapped to chromosome 7AL, and 11 polymorphic markers were developed. Further analysis showed that cn-A1 was located in a 1.1-cM genetic region flanked by Kompetitive allele specific PCR (KASP) markers 660K-7A12 and 660K-7A20, which corresponded to a physical interval of 3.48 Mb in T. aestivum cv. Chinese Spring chromosome 7AL containing 47 predicted genes with high confidence. These results are expected to accelerate the process of cloning the cn-A1 gene and facilitate understanding of the mechanisms underlying chlorophyll metabolism and chloroplast development in wheat.

Bread wheat (Triticum aestivum L.) is a popular cereal crop worldwide, but its future use is threatened by its limited genetic diversity because of the evolutionary bottleneck limiting its ability to combat abiotic and biotic stresses. However, synthetic hexaploid wheat (SHW) is known for its genetic diversity resulting from of the artificial crossing used to transfer elite genes from donors. SHW is therefore a potential source for genetic variations to combat stress. We studied two SHW lines from CYMMIT (cSHW339464 and cSHW339465) and a Korean bread wheat (cv. KeumKang) to determine their ability to tolerate heat stress and leaf rust infection. Our results showed that cSHW339464 could tolerate heat stress because of its maintained-green phenotype, high accumulation of anthocyanin, antioxidant activity (DPPH), proline content, and the response of heat-shock proteins after being challenged by heat stress. On the other hand, cSHW339465 is resistant to leaf rust and can inhibit the growth of pathogens on the leaf surface, owing to the induction of genes encoding β-1,3-glucanase and peroxidase and subsequent enzyme activities. In conclusion, these two SHW lines could prove good candidates contributing to the improvement of current wheat resources.

Ascorbic acid (Asc) is one of the major antioxidants in plants. l-Galactono-1,4-lactone dehydrogenase (GLDH) is an enzyme that catalyses the last step of Asc biosynthesis in higher plants. In this study the effects of endogenous Asc on the distribution of photosynthetic electron flow were investigated in wild-type (ZH-11) rice (Oryza sativa L.) and in GLDH-overexpressing (GO-2) and GLDH-suppressed (GI-2) transgenic rice. The ratio of photosynthetic electron flow distributed to Rubisco-dependent carboxylation was highest in GO-2, whereas other electron flows in addition to carbon fixation were highest in GI-2 after flowering. Further examination showed that the photosynthetic electron flow, GLDH content and reactive oxygen species-scavenging ability were highest in GO-2 and lowest in GI-2. Therefore, the senescence of leaves was faster in GI-2 but slower in GO-2 compared with ZH-11. In addition, leaves with higher Asc content had more Rubisco content and a superior photosynthetic rate, which increased rice yield. These results suggest that increasing the endogenous Asc content of rice delays senescence, maintains a higher photosynthetic rate and results in more photosynthetic electron flow distributed to Rubisco-dependent carboxylation, ultimately leading to increased rice yield.

The projected adverse impact of climate change on food grain production of tropical and subtropical latitudes necessitates the development of suitable agro-adaptations. We used open top chamber (OTC) experimental facility and simulation analysis to study the effect of elevated [CO₂] with varying nutrients management on rice grain yield and to evaluate planting time adjustment as adaptation to climate change. The OTC experiments with ambient [CO₂] level ([CO₂] ∼390 ppm) and elevated [CO₂] (25% higher than the ambient) using cultivar ‘Swarna sub1 (140–145 days)’ were conducted during wet season of the years 2011 and 2012 at West Medinipur, India. Using CERES model, we simulated rice grain yield for future climate scenario (A1B) during the years 2020 (2010–2039) and 2080 (2071–2099) at four selected locations of the subtropical India. The elevated [CO₂] in OTC increased panicle number, but decreased filled grain number per panicle, 1000-grain weight and grain yield. The increasing [CO₂] had smaller adverse impact for integrated nutrients management as compared with chemical fertiliser. The model simulated grain yield reduction of 6.1−13.0% during 2020 and 14.4 −25.0% during 2080 with rising temperature 1.6 and 4.6°C, respectively, compared with the base period (1961–1990). Early planting during 25 June to 25 July received closure favourable temperature and rainfall during the crop growing period, hence had better adaptation to the climate change. Increasing dose of integrated nutrients and early planting is expected to minimise the adverse impact of climate change on rice production of the subtropical India.

The sweet corn variety of maize (Zea mays L.) has become popular worldwide. The recessive allele of sugary1 (su1) encoding starch de-branching enzyme has been much used for sweet corn cultivar development. Here, we aimed to develop su1-based functional marker(s) by using six diverse inbred lines of sugary type and five inbred lines of wild type, and using 27 overlapping primers. In total, 12 indels (insertion and deletion) and 96 SNPs (single nucleotide polymorphisms) were identified that clearly differentiated the dominant and recessive allele of su1. Among these, a 36-bp indel (at position 1247) in the promoter region included a TATA-box, and a 6-bp indel (at position 6456) in intron-10 was predicted to have SRp40 exon-splicing enhancer. Nucleotide substitution in exon-2 at position 2703 (SNP-2703) was involved in C to G mutation leading to conversion of phenylalanine to leucine. The 6-bp and 36-bp indels and SNP-2703 were used to develop breeder-friendly codominant markers: SuDel6-FR, SuDel36-FR and SNP2703-CG-85/89. All three markers were validated in five F₂ populations, and SuDel36-FR and SNP2703-CG-85/89 were validated in a set of 230 diverse inbreds having both mutant and wild-type alleles of Su1. This is the first report of development and validation of universal functional markers for su1. These markers (SuDel36-FR and SNP2703-CG-85/89) assume great significance in marker-assisted breeding program.

The naturally drought-prone climate of the Tibetan Plateau has produced highly drought-resistant Brassica juncea. The objective of the present study was to examine improvement in drought resistance in B. napus by distant hybridisation between B. juncea and B. napus. Distant hybridisation was performed to generate F₁ hybrids, which were open-pollinated by a set of breeding lines of B. napus. Continuous self-crossing was then performed to produce the F₂–F₆ generations, and 74 lines of new-type Brassica napus with stable fertility and morphological phenotypes were selected. The drought resistance of the 74 lines was evaluated during the germination stage by simulating drought stress at 15% PEG-6000, and a wide range of genetic variation in drought resistance was scored. Cytological identification of four lines chosen from strongly, intermediate and weakly drought-resistant clusters demonstrated that their chromosomes had gradually stabilised to B. napus (2n = 38) after advanced self-crossing. A drought-resistant line (line 290) and a drought-susceptible line (line 299) were selected to determine the physiological response to drought stress at the seedling stage. The results showed that proline, soluble protein and malondialdehyde contents of the drought-resistant line were always lower than those of the drought-susceptible line and other common rapeseed variety under drought stress and rewatering conditions. This indicates that the drought-resistant line may have a better reactive oxygen species scavenging system with a less extreme reaction to drought stress. Additionally, the results revealed that the genetic diversity of B. napus under drought resistance was broadened by distant hybridisation, which could encourage breeders to utilise the germplasm resources of B. juncea in the Tibetan Plateau to achieve the goal of drought resistance.

Conservation agriculture has changed the farming landscape. Reduced tillage, stubble retention and changes in crop agronomy have provided considerable benefits to farmers and the environment, but such practices have also influenced arthropod communities residing in these landscapes. Within Australia, there has been an increase in the pest status of several introduced arthropods including Armadillidium vulgare (common pillbug), Forficula auricularia (European earwig) and Ommatoiulus moreleti (black Portuguese millipede). In the present study, the role of insecticide seed treatments in managing these species was examined. Species differed in their responses when exposed to seedlings coated with four commercially-available seed treatments. F. auricularia numbers were reduced by treatments of fipronil (Cosmos) and a mixture of clothianidin and imidacloprid (Poncho Plus). These treatments also reduced A. vulgare numbers, as did a third product, a mixture of thiamethoxam and lambda-cyhalothrin (Cruiser Opti). Mortality of O. moreleti was affected by all four seed treatments. Importantly, arthropod mortality did not always correlate with the levels of protection conferred by each treatment. This points to a complexity of interactions between plant, chemical and pest feeding behaviour. These results are discussed in the context of developing pest management options for these widespread arthropods.

The study of plant growth-promoting bacteria (PGPB) can identify outstanding bacteria for crops. For forage grasses adapted to drylands, the selection of PGPB can increase the field performance of pastures. The aim of this study was to isolate, and characterise at molecular, biochemical and symbiotic levels, diazotrophic bacteria obtained from buffel grass (Cenchrus ciliaris), sorghum (Sorghum bicolor) and Tifton 85 (Cynodon spp.) from Brazilian semi-arid region fields. Field-grown plants were collected, and the roots were surface-disinfected, crushed and inoculated in a semi-solid medium. After the formation and confirmation of microaerophilic pellicles, the bacteria were isolated and purified. All bacterial isolates were subjected to nifH gene amplification and identified by their partial 16S rRNA gene sequences. The bacteria were evaluated for the production of auxins and siderophores, calcium phosphate solubilisation, and diazotrophic ability as ‘in vitro’ plant growth-promotion traits. A plant inoculation assay was conducted to assess the plant growth-promotion abilities of the bacterial isolates. Twenty-one bacterial isolates harboured the nifH gene (nifH⁺), among which nine were obtained from sorghum, eight from buffel grass, and four from Tifton 85. The bacterial isolates were classified as Bacillus (8), Stenotrophomonas (7), Agrobacterium (4), Cellulomonas (1) and Paenibacillus (1). All were shown to be auxin producers, with 14 isolates showing diazotrophic capacity ‘in vitro’. Fourteen isolates increased plant N content, but the bacterial strains ESA 392 and ESA 398 (Bacillus), ESA 397 and ESA 407 (Stenotrophomonas), and ESA 401 (Agrobacterium) were shown to promote both plant growth and N nutrition. These strains are candidates for further assays to evaluate their agronomic performance under field conditions, aiming inoculant production for forage grasses in drylands.

Mapping of the apparent soil electrical conductivity (ECa) can be used to estimate the variability of forage yield within a plot. However, forage production can vary according to the growing season and to soil properties that do not affect the ECa (e.g. nitrogen (N) content). The aim of this study was to assess the relationship between ECa and forage yield of tall fescue (Lolium arundinaceum (Schreb.) Darbysh.) during different regrowth periods and contrasting levels of N availability and then use this information to determine potential management zones. The ECa was measured and geo-referenced in a 5.75-ha paddock that sustained a permanent pasture dominated by tall fescue. In addition, a 30 m by 30 m grid cell size was chosen and 43 sampling areas, each 4 m² in size, were geo-referenced and divided into two experimental units of 1 m by 2 m, one of which was fertilised with 250 kg N ha^–1 (N250) at the beginning of four regrowth periods (spring 2015, spring 2016, autumn 2016 and autumn 2017) and the other was not fertilised with N (N0). At the end of each regrowth period, we estimated the accumulated biomass. During the spring growing season, accumulated biomass was positively associated with ECa in both N0 and N250 treatments (R² = 47% and 54%, respectively). By contrast, in autumn, accumulated biomass and ECa were poorly associated (R² = 10% and 27% for N0 and N250). This may be due to seasonal interactions that alter soil–yield relationships. To assess whether ECa can be used to determine management zones, the differences in accumulated biomass were compared through analysis of variance. Results showed that ECa is associated with the spatial distribution of tall fescue forage yield variability in spring at different N availabilities. Thus, ECa can be reliably used for defining management zones in marginal soils under permanent pastures.