Seed vigor is an important index to evaluate seed quality in plant species. How to evaluate seed vigor quickly and accurately has always been a serious problem in the seed research field. As a new physical testing method, multispectral technology has many advantages such as high sensitivity and accuracy, nondestructive and rapid application having advantageous prospects in seed quality evaluation. In this study, the morphological and spectral information of 19 wavelengths (365, 405, 430, 450, 470, 490, 515, 540, 570, 590, 630, 645, 660, 690, 780, 850, 880, 940, 970 nm) of alfalfa seeds with different level of maturity and different harvest periods (years), representing different vigor levels and age of seed, were collected by using multispectral imaging. Five multivariate analysis methods including principal component analysis (PCA), linear discriminant analysis (LDA), support vector machine (SVM), random forest (RF) and normalized canonical discriminant analysis (nCDA) were used to distinguish and predict their vigor. The results showed that LDA model had the best effect, with an average accuracy of 92.9% for seed samples of different maturity and 97.8% for seed samples of different harvest years, and the average sensitivity, specificity and precision of LDA model could reach more than 90%. The average accuracy of nCDA in identifying dead seeds with no vigor reached 93.3%. In identifying the seeds with high vigor and predicting the germination percentage of alfalfa seeds, it could reach 95.7%. In summary, the use of Multispectral Imaging and multivariate analysis in this experiment can accurately evaluate and predict the seed vigor, seed viability and seed germination percentages of alfalfa, providing important technical methods and ideas for rapid non-destructive testing of seed quality.

Deterioration during seed storage generally causes seed vigour declining. However, the mechanism of deterioration occurred still not clear. Seeds and embryos of oat (Avena sativa L.) were selected to analyze the relation of physiological and metabolic reactions with DEGs by using RNA-seq. Oat seed vigour declined during seeds aged 0 day (CK), 16 days (CD16) and 32 days (CD32). The changes of MDA and H2O2 contents, antioxidant enzymes activities of APX, DHAR, MDHAR and GR related with AsA-GSH cycle in embryos illustrated that seed vigour declined to the minimum at CD32. Transcriptomic analysis showed a total of 11335 and 8274 DEGs were identified at CD16 and CD32 compared with CK respectively, of which 4070 were overlapped. When seed vigour declined to the moderate level (CD16), the accumulation of H2O2 caused by the inhibition of complex I in ETC could be alleviated with AsA-GSH cycle. RNA-seq and qRT-PCR results both showed alternative oxidase in alternate respiratory pathway was upregulated which would maintain seed respiration. However, as seed vigour was at the lowest level (CD32), blocked ETC caused by down-regulation of complex III, including Ubiquinol-cytochrome C reductase complex 14kD subunit and Ubiquinol-cytochrome C reductase, UQCRX/QCR9 like, were more seriously and H2O2 scavenging was limited by the inactive AsA-GSH cycle. It could be suggested that the function of AsA-GSH would play a key role for regulating the physiological responses of ETC in embryos during seed ageing. These results would provide an insight into embryo for the transcriptomic information during oat seed ageing.

The high fat content in oat seeds makes them susceptible to aging during storage, leading to reduced seed vigor, delayed germination, and even seed death. Much evidence suggests that lipid remodeling is closely associated with successful seed germination. However, the dynamic behavior and response mechanisms of lipids during the germination of aged oat seeds remain unclear. In this study, ‘Monida’ (aging-tolerant) and ‘Haywire’ (aging-sensitive), were used to investigate the lipid profiles in the embryo and endosperm and the dynamic transcriptomic differences in the embryo during the germination. The results demonstrate that phospholipid alterations during the germination of aged seeds are more significant compared to unaged seeds, indicating that aging affects lipid remodeling during germination, particularly in the ‘Haywire’. Further analysis revealed that the most critical lipid response events occurred at the end of germination stage II (32 h) in embryo, primarily regulated through the PLC-DGK pathway to modulate phospholipid and glycerolipid molecules. Specifically, transcripts of PLC, DGK, and DGAT were upregulated, promoting the generation of diacylglycerol (DG) from various phospholipids, which further increased the monogalactosyldiacylglycerol/digalactosyldiacylglycerol (MGDG/DGDG) ratio, thereby influencing membrane repair. Additionally, at 6 h of germination in aged seeds, PC(3:0/0:0) levels significantly decreased. Compared to ‘Monida,’ the aging-sensitive ‘Haywire’ seeds exhibited substantial production of PE(19:0/0:0) and PC(15:0/0:0) at 32 h of germination, which may be key factors contributing to the seed's sensitivity to aging and the significant reduction in germination percentage after aging. Therefore, PC(3:0/0:0), PE(19:0/0:0), and PC(15:0/0:0) could serve as important lipid metabolic markers in future studies on the mechanisms of oat seed vigor. The findings of this study provide insights into the specificity of lipid remodeling and its response mechanisms during the germination of aged oat seeds, providing a theoretical foundation for the safe preservation of oat germplasm and the development of aging-tolerant varieties.

Zoysiagrass (Zoysia japonica) is a popular turfgrass species and is widely used for sport turf and urban landscape. Zoysiagrass is often infected by Puccinia zoysiae, which causes a loss in turf quality. The physiological and molecular mechanisms of rust resistance are poorly understood in this species. In this study, the rust-resistant and susceptible lines of zoysiagrass were inoculated with P. zoysiae, and alterations of leaf cell structure, physiological indicators and transcriptomic response were investigated at the various stages of inoculation. After inoculation, the cell membranes, nucleus, mitochondria, and chloroplast were all impaired, followed by abnormal physiological metabolism. The damage occurred earlier and more severely in the susceptible line. Changes in electrolyte leakage and chlorophyll content varied with the genotype and the inoculation stages. The transcriptome analysis showed that plant hormones, MAPK signal transduction pathway, photosynthesis and energy generation pathways were significantly enriched in the early response, in both the resistant and susceptible lines. The results provided insights into the physiological and molecular mechanisms of rust disease resistance and would benefit the breeding of rust-resistant varieties in zoysiagrass and related turfgrass species.

The color of bracts generally turns yellow or black from green during cereal grain development. However, the impact of these phenotypic changes on photosynthetic physiology during black bract formation remains unclear. Two oat cultivars (Avena sativa L.), ‘Triple Crown’ and ‘Qinghai 444’, with yellow and black bracts, respectively, were found to both have green bracts at the heading stage, but started to turn black at the flowering stage and become blackened at the milk stage for ‘Qinghai 444’. Their photosynthetic characteristics were analyzed and compared, and the key genes, proteins and regulatory pathways affecting photosynthetic physiology were determined in ‘Triple Crown’ and ‘Qinghai 444’ bracts. The results show that the actual PSII photochemical efficiency and PSII electron transfer rate of ‘Qinghai 444’ bracts had no significant changes at the heading and milk stages but decreased significantly (p < 0.05) at the flowering stage compared with ‘Triple Crown’. The chlorophyll content decreased, the LHCII involved in the assembly of supercomplexes in the thylakoid membrane was inhibited, and the expression of Lhcb1 and Lhcb5 was downregulated at the flowering stage. During this critical stage, the expression of Bh4 and C4H was upregulated, and the biosynthetic pathway of p-coumaric acid using tyrosine and phenylalanine as precursors was also enhanced. Moreover, the key upregulated genes (CHS, CHI and F3H) of anthocyanin biosynthesis might complement the impaired PSII activity until recovered at the milk stage. These findings provide a new insight into how photosynthesis alters during the process of oat bract color transition to black.