Root exudates serve a vital function in recruiting beneficial phosphate-solubilizing bacteria (PSB), thereby enhancing plant adaptation to phosphorus (P) deficiency.  The C2H2-type zinc finger transcription factor STOP1 (sensitive to proton rhizotoxicity 1) regulates root organic acid (OA) exudation in plants.  However, the impact of STOP1-regulated root OA exudation on rhizosphere microbial composition remains unexplored.  This study revealed enhanced vegetation properties of soybean with higher P content in P-rich soils, while rhizosphere organic acid concentrations were elevated in P-poor soils.  The soybean genotype YC03-3 in P-deficient soils specifically recruited three PSB in acid soils: Gammaproteobacteria_Incertae_Sedis, KF_JG30_C25, and Solirubrobacterales.  These PSB abundances correlated positively with rhizosphere oxalate and citrate concentrations.  Under P-sufficient conditions, GmSTOP1-3 overexpression in soybean plants increased oxalate and citrate exudation compared to YCO3-3 wild type (WT), leading to preferential colonization by the same three PSB species naturally present in P-deficient WT rhizosphere.  The population dynamics of these PSB demonstrated strong positive correlations with the abundance of key genes involved in P cycling, particularly those governing acid/alkaline phosphatase activities and organic-P mineralization.  Given the phosphate starvation-enhanced expression pattern of GmSTOP1-3, the findings indicate that specific PSB recruitment for organic-P remobilization in soybean rhizosphere depends on GmSTOP1-3-mediated oxalate and citrate exudation in P-deficient acid soils.  This research establishes GmSTOP1-3 as a crucial regulator of rhizosphere microbiome assembly and P-acquisition efficiency in acid soils.

Megalurothrips usitatus causes significant economic losses in the regional cowpea industry in Hainan Province, China.  However, reports on M. usitatus-resistant varieties remain limited globally.  To address this gap, this study assessed the resistance of 210 cowpea germplasm resources through field experiments over two consecutive years, and comprehensively investigated the resistance mechanism of a selected resistant variety against M. usitatus.  Physiological measurements revealed that the resistant variety IZJU0044 had higher levels of total flavonoids and tannins, as well as lipoxygenase and β-1,3-glucanase activities, both before and after thrips feeding.  Thrips feeding stimulated flavonoid biosynthesis in cowpea flowers, and the contents of both constitutive and inducible luteolin in the resistant variety IZJU0044 were higher than those in the susceptible variety IZJU0120.  Laboratory toxicity tests confirmed the lethal effect of luteolin on thrips.  Moreover, thrips feeding strongly induced luteolin synthesis-related genes (chalcone isomerases, CHIs) in IZJU0044, indicating that luteolin likely conferred higher resistance to M. usitatus.  This study provides a theoretical basis for using thrips-resistant varieties in cowpea molecular breeding programs.

Stripe rust caused by Puccinia striiformis f. sp. tritici (Pst) is a serious disease affecting wheat production in China.  Wheat cultivar Aikang 58 (AK58) has exhibited effective resistance to stripe rust since its release in 2005.  But the genetic basis of its stripe rust resistance remains unknown. Two genetic populations from the crosses of Avocet S/AK58 (128 recombinant inbred lines) and Kenong 9204/AK58 (1,042 F_2:3 families) were used to dissect the genetic basis of stripe rust resistance in AK58, respectively. In addition, Panel 1 consisting of 688 wheat accessions were used for genome-wide association study (GWAS) and sweep selection analysis to validate the presence of the resistance haplotype of the target region and Panel 2 consisting of 388 Chinese cultivars and breeding lines was genotyped using molecular markers to evaluate the prevalence and distribution of the resistant loci in AK58. The genetic populations were evaluated for stripe rust responses at Yangling and Guiyang over five cropping seasons (2017-2022) and genotyped using GBW16 K SNP array and KASP markers. Using quantitative trait loci (QTLs) analysis, seven QTL were detected on chromosome arms 1BL, 2BS, 2BL, 5BL and 7BL (three QTLs).  Among them, QYrak.nwafu-2BL identified as Yr5b conferred all-stage resistance to Pst race V32L; three QTL within the 7BL chromosome arm region 715.77-733.25 Mb based on Chinese Spring RefSeq v.2.1, were designated YrAK58.1, YrAK58.2 and YrAK58.3, respectively.  YrAK58.1 confirmed as Yr6, and YrAK58.2 conferred all-stage resistance to multiple Pst races and were also effective in field environments. YrAK58.3 contributed stable resistance in all field environments. The remaining QTL were environment-dependent with minor effect. GWAS and sweep selection analyses revealed specific genomic regions with artificial selection signals for the three QTL on chromosome arm 7BL in different breeding groups.  A haplotype combination of high-throughput molecular markers tightly flanking Yr6, YrAK58.2 and YrAK58.3 detected all three genes in 3.6% of entries in Panel 2. The same marker set can be used to further exploit the resistance gene combination in breeding programs.