Eyre, J. | bioRxiv Science

bioRxiv2025

The potential to breed for genetic legacy effects in sustainable farming systems

Legume crops provide protein-rich food, critical disease breaks in cereal rotations, and contribute to soil fertility through symbiotic nitrogen fixation. However, crop improvement programs typically focus on within-crop performance rather than system-level benefits. We hypothesise that legacy effects (the influence of one crops genotype on subsequent crop performance) are under genetic control and could be leveraged in breeding programs. To test this, we evaluated how 309 genetically diverse mungbean genotypes influence subsequent wheat performance. The mungbean panel was grown, followed by a single wheat cultivar sown in the same plot locations. Remarkably, wheat yield varied by nearly 1 t ha{square}{superscript 1} (2.52-3.49 t ha{square}{superscript 1}) depending solely on the preceding mungbean genotype, with legacy traits displaying moderate heritability (H{superscript 2}: 0.43-0.65), demonstrating untapped genetic potential for breeding. Analyses of mungbean traits, soil properties, and volatile organic compounds implicated root architecture, symbiotic nitrogen fixation and soil microbiome as potential biological drivers of legacy effects. Haplotype mapping identified genomic regions in mungbean associated with wheat yield and protein, revealing trade-offs between within-crop and legacy performance. Genetic simulations using empirically derived marker effects compared genomic selection strategies targeting mungbean yield, wheat yield, or both simultaneously. Balanced selection (50:50 weighting) achieved simultaneous gains in both crops (19.5% and 7.6%), highlighting the opportunity to breed for system-level productivity with reduced input requirements.

plant biology↗

bioRxiv2023

Adapting to heat stress by sowing summer grain crops early in late winter: Sorghum root growth, water use, and yield

CONTEXTDrought and extreme heat at flowering are common stresses limiting the yield of summer crops, which are likely to intensify and become more frequent as projected under climate change. OBJECTIVEThis study explores the idea that adaptation to these stresses could be increased by sowing summer crops early in late winter or spring, to avoid the overlap with critical crop stages around flowering. Here we report on the impacts of early sowing i.e., in late winter and spring on sorghum crop and root growth and function (i.e., water use), and final grain yield. METHODSTwo seasons of on-farm genotype (G) by environment (E) by management (M) sorghum experimentation were conducted in the Darling Downs region of Queensland, Australia. Each trial consisted of a factorial combination of three times of sowing (TOS, referred to as late winter, spring, and summer), two levels of irrigation, four plant populations, and six commercial genotypes. Treatments were replicated three times. Crop roots and shoot were sampled at the flag leaf stage for each TOS. Crop water use across the growing season was monitored using time-lapse electromagnetic induction (EMI) surveys. EMI was also used to calculate a root activity factor. Final grain yield and yield components were determined at maturity. RESULTSResults showed that TOS, irrigation levels, and their interactions significantly influenced crop root and shoot traits, water use, and yield, though results were not always consistent across seasons. In the first season which was dry and had large temperature contrasts between TOS, crop growth in the early sown crops was primarily limited by temperature. In contrast, the second season was much warmer and crop growth was instead primarily limited by water availability. Cold air and soil temperatures in the early sowing dates i.e., late winter and spring during the first season, lead to smaller crops with smaller rooting systems and root-to-shoot ratios, and roots having a larger average root diameter. In general terms, root length and root length density responded positively to increasing pre-flowering mean air temperatures ranging between 16 and 20{degrees}C, while root average diameters were larger below 19 {degrees}C or above 21{degrees}C. Early sowing advanced flowering and therefore decreased the risk of extreme heat during the critical stages around flowering and affected water use before and after flowering. The root activity factor was directly related to the crop root length density. The early sown crops increased yield by transferring water use from vegetative to reproductive stages. The larger yield of the early sown crop was associated with larger grain numbers, particularly for the tillers, and a larger water use efficiency. As expected, irrigated and summer-sown crops exhibited lowest water use efficiency. The early-sown crops left more water in the soil profile at maturity, particularly under irrigated conditions and with small plant populations. CONCLUSIONSWe conclude that early sown sorghum is a potential option to increase crop adaptation to hotter and drier environments. Here we propose that in the race to increase crop adaptation to heat stresses, plant breeding efforts should consider cold tolerance traits during crop germination, emergence, and early vegetative stages so that sorghum sowing windows could be significantly advanced.

plant biology↗

bioRxiv2021

New fossils of Australopithecus sediba reveal a nearly complete lower back

Adaptations of the lower back to bipedalism are frequently discussed but infrequently demonstrated in early fossil hominins. Newly discovered lumbar vertebrae contribute to a near-complete lower back of Malapa Hominin 2 (MH2), offering additional insights into posture and locomotion in Australopithecus sediba. We show that MH2 demonstrates a lower back consistent with human-like lumbar lordosis and other adaptations to bipedalism, including an increase in the width of intervertebral articular facets from the upper to lower lumbar column ("pyramidal configuration"). This contrasts with recent work on lordosis in fossil hominins, where MH2 was argued to demonstrate no appreciable lordosis ("hypolordosis") similar to Neandertals. Our three-dimensional geometric morphometric (3D GM) analyses show that MH2s nearly complete middle lumbar vertebra is human-like in shape but bears large, cranially-directed transverse processes, implying powerful trunk musculature. We interpret this combination of features to indicate that A. sediba used its lower back in both human-like bipedalism and ape-like arboreal positional behaviors, as previously suggested based on multiple lines of evidence from other parts of the skeleton and reconstructed paleobiology of A. sediba.

paleontology↗