Phosphorus (P) is a major plant nutrient and developing crops with higher P‐use efficiency is an important breeding goal. In this context we have conducted a comparative study of irrigated and rainfed rice varieties to assess genotypic differences in colonization with arbuscular mycorrhizal (AM) fungi and expression of different P transporter genes. Plants were grown in three different soil samples from a rice farm in the Philippines. The data show that AM symbiosis in all varieties was established after 4 weeks of growth under aerobic conditions and that, in soil derived from a rice paddy, natural AM populations recovered within 6 weeks. The analysis of AM marker genes (AM1, AM3, AM14) and P transporter genes for the direct Pi uptake (PT2, PT6) and AM‐mediated pathway (PT11, PT13) were largely in agreement with the observed root AM colonization providing a useful tool for diversity studies. Interestingly, delayed AM colonization was observed in the aus‐type rice varieties which might be due to their different root structure and might confer an advantage for weed competition in the field. The data further showed that P‐starvation induced root growth and expression of the high‐affinity P transporter PT6 was highest in the irrigated variety IR66 which also maintained grain yield under P‐deficient field conditions.

SUMMARY: In cereals, the root system is mainly composed of post‐embryonic shoot‐borne roots, named crown roots. The CROWN ROOTLESS1 (CRL1) transcription factor, belonging to the ASYMMETRIC LEAVES2‐LIKE/LATERAL ORGAN BOUNDARIES DOMAIN (ASL/LBD) family, is a key regulator of crown root initiation in rice (Oryza sativa). Here, we show that CRL1 can bind, both in vitro and in vivo, not only the LBD‐box, a DNA sequence recognized by several ASL/LBD transcription factors, but also another not previously identified DNA motif that was named CRL1‐box. Using rice protoplast transient transactivation assays and a set of previously identified CRL1‐regulated genes, we confirm that CRL1 transactivates these genes if they possess at least a CRL1‐box or an LBD‐box in their promoters. In planta, ChIP‐qPCR experiments targeting two of these genes that include both a CRL1‐ and an LBD‐box in their promoter show that CRL1 binds preferentially to the LBD‐box in these promoter contexts. CRISPR/Cas9‐targeted mutation of these two CRL1‐regulated genes, which encode a plant Rho GTPase (OsROP) and a basic helix–loop–helix transcription factor (OsbHLH044), show that both promote crown root development. Finally, we show that OsbHLH044 represses a regulatory module, uncovering how CRL1 regulates specific processes during crown root formation.

This study quantified nutrient accumulation and partitioning among the kernel, shell, husk, rachis, and leaves during fruit development in three macadamia cultivars. Racemes and leaves were sampled at biweekly intervals until kernel maturity. The shell and rachis ceased to accumulate biomass earlier in the season than the husk or kernel. Nitrogen (N) and potassium (K) were the dominant nutrients accumulated in the fruit. Despite declining concentrations between 80 and 140 DAF, total kernel nutrient content continued to increase, indicating sustained nutrient import during this critical period. The kernel was the primary sink for N, phosphorus (P), sulfur (S), and magnesium (Mg), with peak accumulation occurring during rapid kernel growth at 80–175 days after flowering (DAF). In contrast, the accumulation of calcium (Ca) and manganese (Mn) into the kernel ceased earlier, suggesting limited late-stage mobility. The husk accumulated more K than the kernel and remained an active sink for K, S, Mg, Ca, and Mn until maturity, while N, P, and boron (B) accumulation slowed after ~107 DAF. The shell contributed minimally to nutrient demand, with N, zinc (Zn), and B accumulation ceasing after shell hardening (90–110 DAF). The cultivars exhibited consistent temporal patterns, differing mainly in magnitude. Nutrient partitioning efficiency among-the fruit components was highest for cv. A38. The rachis acted as a transient sink early in development before declining in mobile nutrients, while leaf nutrient dynamics did not reflect fruit demand.

Cluster roots enhance phosphorus (P) acquisition in macadamia (Macadamia integrifolia), yet their development under different P levels and effects of different grafted scion/rootstock combinations are not well understood. This study examined cluster root formation in seedlings under varying soil P levels and evaluated cluster root differences between two different rootstocks, each grafted with five different scions. Cluster roots first appeared at 42 days after planting (DAP), with low P promoting greater root number but without increasing biomass. High P application (800 mg P pot⁻¹) suppressed cluster root number by around 50%, corresponding to leaf P concentrations of ~1.05 mg g⁻¹. Scions and rootstocks influenced cluster root development, with the H2 rootstock supporting more cluster roots than Beaumont. These results show that cluster root formation in macadamia is modulated by both P availability and genetics.

SUMMARY: Winter bud dormancy is a critical adaptive process in temperate fruit trees, safeguarding meristems from freezing temperatures and aligning growth with seasonal cues. Dormancy encompasses two primary phases: endodormancy, where internal signals, particularly elevated abscisic acid (ABA), block growth and necessitate chilling for release; and ecodormancy, where buds regain growth competence but remain quiescent until external conditions are favourable. In apple ( Malus domestica ), we demonstrated that BRANCHED1 ( MdBRC1 ) serves as a central inhibitor of bud growth specifically during ecodormancy. In many plant species, BRC1-like transcription factors integrate environmental and hormonal signals, activating gene networks linked to growth repression, notably those involved in ABA biosynthesis and signalling. Gain-of-function studies in poplar confirmed that MdBRC1 robustly suppresses shoot growth in trees. Our comparative transcriptomic analyses revealed that MdBRC1 directly regulates a suite of dormancy-associated genes, reinforcing its role as a molecular brake on bud break. Importantly, we show that the apple gene FLOWERING LOCUS T2 ( MdFT2 ) is transcriptionally upregulated after dormancy and might act as a key inducer of bud break. Our data reveal that MdFT2 physically interacts with MdBRC1, reducing MdBRC1 activity during ecodormancy. This antagonistic interaction acts as a molecular switch, facilitating the transition from ecodormancy to active bud growth as spring approaches. Together, these findings uncover a regulatory module that finely tunes bud break timing in apple trees and provide a foundation for breeding strategies to enhance fruit tree resilience and adaptability in the context of climate change.

Daddow is a macadamia cultivar that yields poorly because flowers and fruitlets frequently abort early in development. The objective was to determine whether resource availability limits fruitlet retention in this cultivar. Racemes of Daddow and three other cultivars, 849, A38, and A203, were sampled weekly during flowering and fruit set, and trends in nutrients and non-structural carbohydrates were assessed. Starch concentrations in the flowers and rachis were lower in Daddow than in the other cultivars before fruit set. Rachis concentration of glucose, an important signalling molecule, was also lower in Daddow at flowering. Most flower and fruitlet nutrient concentrations in Daddow were comparable to those of the other cultivars. However, potassium concentrations were lower in both the rachis and leaves of Daddow, while boron concentration, important for pollen tube growth, was higher. These results suggest altered signalling mechanisms, inadequate carbohydrate supply and deficiencies in specific nutrients may have been contributing factors to the high flower and fruitlet abortion rates of Daddow.