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The GRAS transcription factors play an indispensable role in plant growth and responses to environmental stresses. The GRAS gene family has extensively been explored in various plant species; however, the comprehensive investigation of GRAS genes in white lupin remains insufficient. In this study, bioinformatics analysis of white lupin genome revealed 51 LaGRAS genes distributed into 10 distinct phylogenetic clades. Gene structure analyses revealed that LaGRAS proteins were considerably conserved among the same subfamilies. Notably, 25 segmental duplications and a single tandem duplication showed that segmental duplication was the major driving force for the expansion of GRAS genes in white lupin. Moreover, LaGRAS genes exhibited preferential expression in young cluster root and mature cluster roots and may play key roles in nutrient acquisition, particularly phosphorus (P). To validate this, RT‐qPCR analysis of white lupin plants grown under +P (normal P) and −P (P deficiency) conditions elucidated significant differences in the transcript level of GRAS genes. Among them, LaGRAS38 and LaGRAS39 were identified as potential candidates with induced expression in MCR under −P. Additionally, white lupin transgenic hairy root overexpressing OE‐LaGRAS38 and OE‐LaGRAS39 showed increased root growth, and P concentration in root and leaf compared to those with empty vector control, suggesting their role in P acquisition. We believe this comprehensive analysis of GRAS members in white lupin is a first step in exploring their role in the regulation of root growth, tissue development, and ultimately improving P use efficiency in legume crops under natural environments. [ABSTRACT FROM AUTHOR]

• The co-occurrence of heat and water-deficit stress during flowering negatively impacts crop productivity. • Heat, water-deficit, and their combination alter developmental processes associated with plant reproduction. • Stress-induced changes in sugar metabolism, reactive oxygen species and hormone levels are thought to play a role in yield reduction during stress combination. • Understanding the molecular processes associated with yield reduction during stress combination would allow the development of climate-resilient crops. Historically, extended droughts combined with heat waves caused severe reductions in crop yields estimated at billions of dollars annually. Because global warming and climate change are driving an increase in the frequency and intensity of combined water-deficit and heat stress episodes, understanding how these episodes impact yield is critical for our efforts to develop climate change-resilient crops. Recent studies demonstrated that a combination of water-deficit and heat stress exacerbates the impacts of water-deficit or heat stress on reproductive processes of different cereals and legumes, directly impacting grain production. These studies identified several different mechanisms potentially underlying the effects of stress combination on anthers, pollen, and stigma development and function, as well as fertilization. Here we review some of these findings focusing on unbalanced reactive oxygen accumulation, altered sugar concentrations, and conflicting functions of different hormones, as contributing to the reduction in yield during a combination of water-deficit and heat stress. Future studies focused on the effects of water-deficit and heat stress combination on reproduction of different crops are likely to unravel additional mechanisms, as well as reveal novel ways to develop stress combination-resilient crops. These could mitigate some of the potentially devastating impacts of this stress combination on agriculture. [ABSTRACT FROM AUTHOR]

The article discusses a study which investigated the effects of different light intensities on biomass production and nitrogen concentration and nodule number and nodule biomass of Desmodium canescens, Desmodium canadense, and Desmodium illinoense. The species were grown in N-free media while supplying N-free nutrient solution as required by the study. Among the findings were the variations in legume species in dry weight and number of nodules produced.

The article investigates the effects of three different light intensities, namely 100%, 45% and 20% on biomass production and nitrogen concentration, and nodule number and nodule biomass of three native legume species, including Desmodium canescens, Desmodium canadense and Desmodium illinoense. It relates the features of the greenhouse experiment. It has revealed that these native legumes grow as well at 45% light as they do at 100% light.

Nitrogen supplied by N2 fixation to soybean [Glycine max (L.) Merr.] may not be sufficient to maximize yield. Field studies were conducted in 2002, 2003, and 2004 on Sharkey clay soil (very-fine, smectitic, thermic Chromic Epiaquert) at Stoneville, MS (33°26′ N lat). The objective was to determine the effect of high rates of N applied as a replacement for N2 fixation in nonirrigated and irrigated environments. Eight cultivars ranging from Maturity Group II to IV were planted on 17 Apr. 2002, 2 Apr. 2003, and 25 Mar. 2004. Not all cultivars were evaluated in all 3 yr. Glyphosate herbicide was used in all 3 yr and a non-glyphosate herbicide treatment was applied in 2002. Cultivars grown in 2003 were also evaluated under an application of 21.3 kg ha-1 of Mn. All cultivar, herbicide, and Mn treatments were evaluated in irrigated and nonirrigated environments with fertilizer N (PlusN treatment) or without fertilizer N (ZeroN treatment). In the PlusN treatment, granular NH4NO3 was surface applied at soybean emergence at rates of 290 kg ha-1 in 2002, 310 kg ha-1 in 2003, and 360 kg ha-1 in 2004. When analyzed over all management practices (years, cultivars, herbicide, and Mn treatments), the PlusN treatment resulted in significantly decreased ureide concentration (57.2 and 53.5% reduction) and significantly increased biomass accumulation (14.1 and 16.7%), N accumulation (12.8 and 28.1%), and seed yield (7.7 and 15.5%) for the irrigated and nonirrigated environments, respectively. The majority of the yield increase in each environment resulted from increased number of seed (9.5% irrigated and 16.2% nonirrigated). These results confirm the sensitivity of N2 fixation to drought and indicate that N2 fixation may limit yield of soybean grown in both irrigated and nonirrigated environments of the midsouthern USA, and that N2 fixation deficiencies occur before the beginning of processes that determine number of seed. [ABSTRACT FROM AUTHOR]

Episodes of prolonged drought coupled with heat waves (i.e. drought and heat combination) can have a devastating impact on agricultural production and crop yield. It is therefore not surprising that improving tolerance to drought and heat combination has been a major goal for breeders and biotech companies. Although much is known about the physiological and molecular responses of vegetative tissues to a combination of drought and heat stress, less is known about the impact of this stress combination on yield and different yield components. Here, we used a meta‐analysis approach to synthesize results from over 120 published case studies of crop responses to combined drought and heat stress. Our findings reveal that drought and heat stress combination significantly impacts yield by decreasing harvest index, shortening the life cycle of crops, and altering seed number, size and composition. Furthermore, these impacts are more severe when the stress combination is applied during the reproductive stage of plants. We further identify differences in how legumes and cereals respond to the stress combination and reveal that utilizing C3 or C4 metabolism may not provide an advantage to plants during stress combinations. Taken together our study highlights a need to focus future studies, as well as breeding efforts, on crop responses to drought and heat combination at the reproductive stage of different crop species. [ABSTRACT FROM AUTHOR]

Soybean (Glycine max (L.) Merr.) meets a large portion of its nitrogen (N) need via biological N2 fixation, which is highly sensitive to drought stress. Nitrogen isotope ratios between 15N and 14N (δ15N) can be used as a metric for relative differences among soybean genotypes for N2 fixation, as δ15N is negatively associated with N2 fixation. This study aimed to dissect the genetic basis of δ15N using a mapping population of 196 F6-derived recombinant inbred lines developed from a cross between PI 416997 and PI 567201D that was evaluated in multiple environments. There was a wide range of δ15N in all environments and narrow-sense heritability for δ15N was 35% when estimated across environments. Analysis of variance of δ15N showed significant effects of genotype and environment, whereas the genotype × environment interaction was not significant (P < 0.05). Inclusive composite interval mapping for individual environments identified 10 additive QTLs on seven chromosomes with additive effects ranging from 0.02 to 0.13‰ and that individually explained phenotypic variations from 1.72 to 9.34%. In total, eight QTL × environment interactions were found, and several genomic regions were involved in QTL × QTL interactions that were not identified as additive QTLs. These identified QTLs were co-localized with genomic regions associated with N2 fixation and other physiological traits identified in previous studies. A search for candidate genes resulted in detection of genes for nodulation and N-metabolism underlying many additive and epistatic QTLs. These identified regions may serve as potential targets for enhancing N2 fixation in soybean. [ABSTRACT FROM AUTHOR]

• Long-term soybean breeding for yield has increased plant N demands. • Total shoot N and N from BNF increased with cultivar year of release. • Sensitivity of BNF to soil mineral N has not changed over years of soybean breeding. Long-term soybean [ Glycine max (L) Merr.] breeding for yield has increased plant nitrogen (N) demands. On one hand, because N fertilizer application in soybean production systems continues to be insignificant, increased plant N demands over time may have been satisfied from greater biological N fixation (BNF). On the other hand, increased soil residual N over time may have affected the sensitivity of nodulation and BNF. To understand the impact of breeding for greater yield and the effect of soil residual N on nodulation and BNF, two field and a greenhouse study were conducted. Field studies were conducted with maturity group IV soybean cultivars released from 1930 to 2005 and included experiments in four environments. Total shoot N and N from BNF increased with cultivar year of release in two of the four environments. Simulation of different levels of residual soil mineral N by application of 0, 34, 67, and 101 kg N ha−1 shortly after planting resulted in linear increases in shoot N content and δ15N, and linear decreases in nodule number and nodule dry matter in the field. Consistent with these results, fertigation of greenhouse-grown soybean cultivars with different levels of NH 4 NO 3 led to a reduction in nodule number, dry matter, and size. Overall, results from these studies indicate that increases in seed yields with cultivar year of release were associated with greater amounts of N derived from BNF as well as greater total shoot N accumulation, but the relative contribution of BNF to total shoot N did not change over time. Analysis also suggest that the sensitivity of nodulation and BNF to soil mineral N has not been altered over the course of soybean breeding. [ABSTRACT FROM AUTHOR]