Quality protein maize (QPM; Zea mays L.) has effectively enhanced levels of the amino acids, lysine, and tryptophan, over normal maize and provided balanced dietary protein for the health and development of monogastric animals and humans. However, as in normal maize, QPM varieties are low in provitamin A (ProVA), a precursor of vitamin A, which can lead to vitamin A deficiency in humans when maize is a significant part of their diet. In this study, maize inbred Hp321-1 carrying the favorable alleles crtRB1-5′TE-2 and crtRB1-3′TE-1 that can enhance levels of ProVA, was used as donor for improving ProVA in QPM inbred lines CML161 and CML171. Functional markers for identifying the favorable alleles crtRB1-5′TE-2 and crtRB1-3′TE-1 were used in foreground selection, and simple sequence repeat markers were used in background selection for the BC₁F₁, BC₂F₁, and BC₂F₂ generations. The background recovery rates were 77.4 and 84.5 % for CML161 and CML171 populations, respectively, in the BC₁F₁ generation, and 89.9 and 92.1 % in the BC₂F₂ generation. With foreground and background selection, the mean ProVA concentration has been improved from 1.60 µg g⁻¹ in the parent of CML161 to 5.25 µg g⁻¹ in its BC₂F₃ offspring, from 1.80 µg g⁻¹ in the parent of CML171 to 8.14 µg g⁻¹ in its BC₂F₃ offspring while maintaining similar QPM characteristics of the recurrent parents. The success from this study offers maize breeders a procedure for increasing ProVA in QPM lines, which will greatly mitigate vitamin A deficiency and protein-energy malnutrition in developing countries.

Ear diameter (ED) is a critical component of grain yield (GY) in maize (Zea mays L.). Studying the genetic basis of ED in maize is of great significance in enhancing maize GY. Against this backdrop, this study was framed to (1) map the ED-related quantitative trait locus (QTL) and SNPs associated with ED; and (2) identify putative functional genes that may affect ED in maize. To accomplish this, an elite maize inbred line, Ye107, which belongs to the Reid heterotic group, was used as a common parent and crossed with seven elite inbred lines from three different heterotic groups (Suwan1, Reid, and nonReid) that exhibited abundant genetic variation in ED. This led to the construction of a multi-parent population consisting of 1215 F₇ recombinant inbred lines (F₇RILs). A genome-wide association study (GWAS) and linkage analysis were then conducted for the multi-parent population using 264,694 high-quality SNPs generated via the genotyping-by-sequencing method. Our study identified a total of 11 SNPs that were significantly associated with ED through the GWAS, and three QTLs were revealed by the linkage analysis for ED. The major QTL on chromosome 1 was co-identified in the region by the GWAS at SNP_143985532. SNP_143985532, located upstream of the Zm00001d030559 gene, encodes a callose synthase that is expressed in various tissues, with the highest expression level in the maize ear primordium. Haplotype analysis indicated that the haplotype B (allele AA) of Zm00001d030559 was positively correlated with ED. The candidate genes and SNPs identified in this study provide crucial insights for future studies on the genetic mechanism of maize ED formation, cloning of ED-related genes, and genetic improvement of ED. These results may help develop important genetic resources for enhancing maize yield through marker-assisted breeding.

Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is among the oldest known bacterial diseases found for rice in Asia. It is the most serious bacterial disease in many rice growing regions of the world. A total of 47 resistance (R) genes (Xa1 to Xa47) have been identified. Nonetheless, these R genes could possibly be defeated to lose their qualitative nature and express intermediate phenotypes. The identification of sources of novel genetic loci regulating host plant resistance is crucial to develop an efficient control strategy. Wild ancestors of cultivated rice are a natural genetic resource contain a large number of excellent genes. Medicinal wild rice (Oryza officinalis) belongs to the CC genome and is a well-known wild rice in south China. In this study, O. officinalis was crossed with cultivated rice HY-8 and their hybrids were screened for BB resistance genes deployed through natural selection in wild rice germplasm. The molecular markers linked to R genes for BB were used to screen the genomic regions in wild parents and their recombinants. The gene coding and promoter regions of major R genes were inconsistently found in O. officinalis and its progenies. Oryza officinalis showed resistance to all thirty inoculated Xoo strains with non-availability of various known R genes. The results indicated the presence of novel genomic regions for BB resistance in O. officinalis. The present study not only provides a reference to investigate medicinal rice for R gene(s) identification against BB but also identified it as a new breeding material for BB resistance.

The rice blight poses a significant threat to the rice industry, and the discovery of disease-resistant genes is a crucial strategy for its control. By exploring the rich genetic resources of Yuanjiang common wild rice (Oryza rufipogon) and analyzing their expression patterns, genetic resources can be provided for molecular rice breeding. The target genes’ expression patterns, subcellular localization, and interaction networks were analyzed based on the annotated disease-resistant genes on the 9th and 10th chromosomes in the rice genome database using fluorescent quantitative PCR technology and bioinformatics tools. Thirty-three disease-resistant genes were identified from the database, including 20 on the 9th and 13 on the 10th. These genes were categorized into seven subfamilies of the NLR family, such as CNL and the G subfamily of the ABC family. Four genes were not expressed under the induction of the pathogen Y8, two genes were significantly down-regulated, and the majority were up-regulated. Notably, the expression levels of nine genes belonging to the ABCG, CN, and CNL classes were significantly up-regulated, yet the expression levels varied among roots, stems, and leaves; one was significantly expressed in the roots, one in the stems, and the remaining seven were primarily highly expressed in the leaves. Two interaction network diagrams were predicted based on the seven highly expressed genes in the leaves: complex networks regulated by CNL proteins and specific networks controlled by ABCG proteins. The disease-resistant genes on the 9th chromosome are actively expressed in response to the induction of rice blight, forming a critical gene pool for the resistance of Yuanjiang common wild rice (O. rufipogon) to rice blight. Meanwhile, the disease-resistant genes on the 10th chromosome not only participate in resisting the rice blight pathogen but may also be involved in the defense against other stem diseases.

Endophytic bacteria play crucial roles in plant pathogen protection and growth. Oryza eichingeri is a unique wild rice species rich with genetic resources. Studies have explored beneficial endophytic bacteria and investigated the synergistic interaction between microbes and wild rice. However, the endophytic bacterial community of Oryza eichingeri and their plant growth-promoting (PGP) abilities characteristics remain largely unknown. Here, endophytic bacteria in the root, stem, and leaf tissues of Oryza eichingeri were characterized using metagenomic Illumina 16S rRNA gene sequencing. Additionally, culturable endophytic bacteria were isolated. The metagenomic analysis showed that, compared to those in other tissue compartments, the endophytic bacterial community in the roots had a more complex structure and enhanced functions, and each compartment had its own specific endophytic bacterial biomarkers. A total of 94 endophytic bacteria were isolated from Oryza eichingeri, among which 80 strains possessed PGP traits including increasing phosphate solubilization, siderophore production, IAA production, and nitrogen fixation. These strains displayed good PGP effects on cultivated rice seedlings, promoting the formation of strong root systems, stimulating biomass accumulation, and increasing root length and plant height. These findings provide insights into the composition of the bacterial endosphere of Oryza eichingeri and potential applications of the dominant PGP bacteria in rice cultivation.

Leaf morphology traits determine photosynthetic efficiency, high-density planting tolerance, and grain yield in maize (Zea mays L.). Understanding the gene