Genetic Variability, Character Association, and Path Coefficient Analysis in Transplant Aman Rice Genotypes.

A field experiment was carried out with 20 genotypes of Transplant Aman (T. Aman) rice at the Department of Genetics and Plant Breeding, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Salna, Gazipur-1706, Bangladesh. The study was performed to evaluate the genetic deviation, trait association, and path coefficient (PC) based on grain yield (GY) and different yield-contributing agronomic characters. Variance analysis displayed extensive traits-wise variations across accessions, indicating variability and the opportunity for genetic selection for desirable traits. The high mean, range, and genotypic variances observed for most of the characters indicated a wide range of variation for these traits. All the characters indicated the minimum influence of environment on the expression of the trait and genetic factors had a significant role in the expressivity of these characters. High heritability in broad sense (h2b) and high to moderate genetic advance in percent of the mean (GAPM) were recorded for all the characters except for panicle length (PL). Based on mean, range, and all genetic parameters, the selection of all the traits except for PL would contribute to the development of T. Aman rice genotypes. A correlation study revealed that selection based on plant height (PH), number of effective tillers per hill (NET), PL, number of filled spikelets per panicle (NFS), flag leaf length (FLL), spikelet sterility (SS) percentage, and harvest index (HI) would be effective for increasing the GY of rice. Genotypic correction with grain yield (GCGY), PC and principal component analysis (PCA) revealed that direct selection of NFS, HI, SS%, and FLL would be effective for improving the GY of rice in future breeding programs.

A Coordinated Suite of Wild-Introgression Lines in Indica and Japonica Elite Backgrounds.

Rice, Oryza sativa L., is a cultivated, inbreeding species that serves as the staple food for the largest number of people on earth. It has two strongly diverged varietal groups, Indica and Japonica, which result from a combination of natural and human selection. The genetic divergence of these groups reflects the underlying population structure of their wild ancestors, and suggests that a pre-breeding strategy designed to take advantage of existing genetic, geographic and ecological substructure may provide a rational approach to the utilization of crop wild ancestors in plant improvement. Here we describe the coordinated development of six introgression libraries (n = 63 to 81 lines per library) in both Indica (cv. IR64) and Japonica (cv. Cybonnet) backgrounds using three bio-geographically diverse wild donors representing the Oryza rufipogon Species Complex from China, Laos and Indonesia. The final libraries were genotyped using an Infinium 7K rice SNP array (C7AIR) and analyzed under greenhouse conditions for several simply inherited (Mendelian) traits. These six interspecific populations can be used as individual Chromosome Segment Substitution Line libraries and, when considered together, serve as a powerful genetic resource for systematic genetic dissection of agronomic, physiological and developmental traits in rice.

Corrigendum: A Coordinated Suite of Wild-Introgression Lines in Indica and Japonica Elite Backgrounds.

[This corrects the article DOI: 10.3389/fpls.2020.564824.].

A major natural genetic variation associated with root system architecture and plasticity improves waterlogging tolerance and yield in soybean.

Natural genetic variations in waterlogging tolerance are controlled by multiple genes mapped as quantitative trait loci (QTLs) in major crops, including soybean (Glycine max L.). In this research, 2 novel QTLs associated with waterlogging tolerance were mapped from an elite/exotic soybean cross. The subsequent research was focused on a major QTL (qWT_Gm03) with the tolerant allele from the exotic parent. This QTL was isolated into near-isogenic backgrounds, and its effects on waterlogging tolerance were validated in multiple environments. Fine mapping narrowed qWT_Gm03 into a genomic region of <380 Kbp excluding Rps1 gene for Phytophthora sojae resistance. The tolerant allele of qWT_Gm03 promotes root growth under nonstress conditions and favourable root plasticity under waterlogging, resulting in improved waterlogging tolerance, yield, and drought tolerance-related traits, possibly through more efficient water/nutrient uptakes. Meanwhile, involvement of auxin pathways was also identified in the regulation of waterlogging tolerance, as the genotypic differences of qWT_Gm03 in waterlogging tolerance and formation of adventitious/aerial roots can be complemented by an exogenous auxin-biosynthesis inhibitor. These findings provided genetic resources to address the urgent demand of improving waterlogging tolerance in soybean and revealed the determinant roles of root architecture and plasticity in the plant adaptation to waterlogging.

Different responses of two genes associated with disease resistance loci in maize (Zea mays L.) to 3-allyloxy-1,2-benzothiazole 1,1-dioxide.

Probenazole (3-allyloxy-1,2-benzothiazole 1,1-dioxide, PBZ) is a bactericide and fungicide that acts by inducing plant defense systems. It has been shown to induce the expression of NBS-LRR genes like RPR1 (rice probenazole-response gene) in rice (Oryza sativa L.) and systemic acquired resistance (SAR)-like disease resistance. Two maize (Zea mays L.) genes Zmnbslrr1 (a NBS-LRR gene, cloned from a disease resistance analog PIC11 based) and Zmgc1, (a putative guanylyl cyclase-like gene) have both been associated with quantitative resistance loci (QTL) for resistance to Fusarium graminearum. PIC11 was associated with Fusarium stalk rot and ZmGC1 showed resistance to Gibberella ear rot caused by F. graminearum. The objectives of the current study here were to characterize the Zmnbslrr1 gene and to determine whether it and Zmgc1 respond to the inducer PBZ. The transcript abundance of Zmnbslrr1 expression was significantly reduced in corn seedlings of the Gibberella ear rot resistant genotype CO387 48 h after PBZ treatment. In contrast, the transcript abundance of the maize Zmgc1 gene increased more than 10-fold 8h after the treatment. Therefore, the two genes do not appear to be coordinately regulated by PBZ.