Photoperiod shapes aluminium tolerance in plants

Aluminium is a limiting factor for crop productivity in acidic soils (pH ≤ 5.5). Since acid soil distribution on Earth cannot adequately explain the differential Al tolerance across the plant kingdom, we investigated photoperiod effects on plant Al tolerance. We observed that with increasing distance from the equator, Al tolerance disappears, suggesting a relationship with the photoperiod. Long-day (LD) species are generally more Al-sensitive than short-day (SD) species, whereas genetic conversion of tomato for SD growth boosts Al tolerance. Reduced Al tolerance correlates with DNA-checkpoint activation under LD. DNA-checkpoint-related genes are under positive selection in Arabidopsis accessions from regions with shorter days, suggesting photoperiod acts as a selective barrier for Al tolerance. Our findings revealed that diel regulation and genetic diversity affect Al tolerance, suggesting that day-length orchestrates Al tolerance.One-Sentence SummaryAluminum is a major constraint for crop yield worldwide. We reveal that photoperiod acts as a barrier for Al tolerance in plants.

Recent molecular breeding advances for improving aluminium tolerance in maize and sorghum.

Citrate transporters belonging to the multidrug and toxic compound extrusion (MATE) family of membrane transporters in sorghum and maize, SbMATE and ZmMATE1, respectively, play a major role in aluminium (Al) tolerance. However, these MATE members show regulatory differences, as well as peculiarities in their genetic effect and mode of action. These aspects, which are discussed in this chapter, have to be considered to design successful breeding programmes in order to achieve maximum Al tolerance and, consequently, to improve grain and biomass production in regions of the world with Al toxicity. As shown in this chapter, target genes with major effects and molecular tools are available for marker-assisted breeding for improving Al tolerance both in sorghum and maize. However, wide adaptation to acid soils should be sought by pyramiding genes controlling different traits such as drought tolerance, P acquisition, resistance to diseases and other stresses commonly found in each agroecological environment.

History of mutation breeding and molecular research using induced mutations in Japan.

Following the construction of the Gamma Field at the Institute of Radiation Breeding in 1960, mutation breeding was accelerated in Japan. The facility is used, with a radiation dose up to 2 Gy/day (ca. 300,000 times that of natural background), to induce mutations at a higher frequency than occurs in nature. There have been 318 direct- use mutant cultivars representing 79 species generated through irradiation of gamma-rays, X-rays, ion beams and chemicals and somaclonal variation. Approximately 79% of these direct-use cultivars were induced by radiation. There have been 375 indirect-use mutant cultivars, including 332 rice, of which 162 cultivars (48.8%) were derived from the semi-dwarf mutant cv. 'Reimei'. The economic impact of these mutant cultivars, primarily of rice and soybean, is very large. Some useful mutations are discussed for rice, such as low digestible protein content, low amylose content, giant embryo and non-shattering. Useful mutations in soybean such as radiosensitivity, fatty acid composition and super-nodulation have been identified. Japanese pear and apple resistant to Alternaria disease have also been identified. The achievements of biological research such as characterization and determination of deletion size generated by gamma-rays, the effect of deletion size and the location, and a mechanism of dominant mutation induction are identified. Similarly, genetic studies on mutations generated through the use of gamma-ray induced mutations, such as phytochrome response, aluminium tolerance, stay-green (Mendel's gene) and epicuticular wax have also been conducted. Mutation breeding is a very useful technology for isolating genes and for elucidating gene functions and metabolic pathways in various crops.

Multidimensional analysis of actin depolymerising factor family in pigeon pea under different environmental stress revealed specific response genes in each subgroup

Actin depolymerising factor (ADF) is an actin binding protein that is ubiquitous in animal and plant cells. It plays an important role in plant growth and development, as well as resistance to biotic and abiotic stress. The research of plant ADF family has been restricted to Arabidopsis thaliana (L.) Heynh. and some herb crops, but no woody cash crops have been reported to date. All members of the Cajanus cajan (L.) Millsp. ADF (CcADF) family were identified from the pigeon pea genome, and distributed among the four subfamilies by phylogenetic analysis. CcADFs were relatively conservative in gene structure evolution, protein structure and functional expression, and different CcADFs showed specific expression patterns under different treatments. The expression characteristics of several key CcADFs were revealed by analysing the stress response pattern of CcADFs and the time series RNA-seq of aluminium stress. Among them, CcADF9 in the first subgroup specifically responded to aluminium stress in the roots; CcADF3 in the second subgroup intensively responded to fungal infection in the leaves; and CcADF2 in the fourth subgroup positively responded to various stress treatments in different tissues. This study extended the relationship between plant ADF family and aluminium tolerance, as well as adding to the understanding of CcADF family in woody crops.

Deep expression scrutiny provides genetic basis of aluminium tolerance in wild (Lens nigrican) and cultivated lentil (Lens culinaris Medik.)

The authors have requested that this preprint be withdrawn due to erroneous posting.

A new genome allows the identification of genes associated with natural variation in aluminium tolerance in Brachiaria grasses

Toxic concentrations of aluminium cations and low phosphorus availability are the main yield-limiting factors in acidic soils, which represent half of the potentially available arable land. Brachiaria grasses, which are commonly sown as forage in the tropics because of their resilience and low demand for nutrients, show greater tolerance to high concentrations of aluminium cations (Al3+) than most other grass crops. In this work, we explored the natural variation in tolerance to Al3+ between high and low tolerant Brachiaria species and characterized their transcriptional differences during stress. We identified three QTLs (quantitative trait loci) associated with root vigour during Al3+ stress in their hybrid progeny. By integrating these results with a new Brachiaria reference genome, we identified 30 genes putatively responsible for Al3+ tolerance in Brachiaria. We observed differential expression during stress of genes involved in RNA translation, response signalling, cell wall composition, and vesicle location homologous to aluminium-induced proteins involved in limiting uptake or localizing the toxin. However, there was limited regulation of malate transporters in Brachiaria, which suggests that exudation of organic acids and other external tolerance mechanisms, common in other grasses, might not be relevant in Brachiaria. The contrasting regulation of RNA translation and response signalling suggests that response timing is critical in high Al3+-tolerant Brachiaria.

Farm yard manure enhances phosphate fertilizer use efficiency in different upland rice genotypes through mitigating aluminium toxicity

Upland rice production on weathered soils is often constrained by phosphorus (P) deficiency and soil acidity. Farmyard manure application (FYM) can sharply enhance yields and agronomic P fertilizer (TSP) efficiency. We tested the hypothesis that rice genotypes differ in the extent of using organic P and offering distinct benefits under TSP-FYM combinations. Multiple field trials were conducted in the uplands of Madagascar, with factorial combinations of six genotypes, FYM, and TSP applications, with blanket N&K additions. Rice grain yields reached 6 t ha-1 after three years of TSP+FYM application, were lower when FYM or TSP were used separately, while crops failed under zero P input. Genotypic differences were inferior to the large treatment effects. Application of FYM increased soil pH and CaCl2-extractable P while decreasing CaCl2-extractable aluminium. An additional liming trial indicated that beneficial effects of FYM over TSP relate to liming effects. Genotypic ranking of yields and agronomic efficiency was inconsistent, without superior genotypes under FYM versus TSP. However, Chomrong Dhan and FOFIFA 172 showed superior yields under TSP+FYM. The FYM application lowers aluminium toxicity which overrules potential effects of organic P supply. Aluminium tolerance should be included when developing rice genotypes for low P tolerance in weathered soils.