The rice root-knot nematode, Meloidogyne graminicola, is the major bottleneck in aerobic and direct-seeded rice cultivation. Host plant resistance is an environmentally-friendly and cost-effective approach to mitigate damage caused by M. graminicola. Considering the limited availability of genetic resources in Asian rice (Oryza sativa) cultivars, exploration of novel sources of resistance to M. graminicola is necessary. In the present study, we screened 192 diverse wild rice accessions from nine species (Oryza longistaminata, O. barthii, O. glaberrima, O. meridionalis, O. nivara, O. punctata, O. officinalis, O. glumaepatula and O. rufipogon) to identify sources of resistance to M. graminicola. Based on gall number and multiplication factor, two immune and 25 resistant accessions were identified. 'Pusa Basmati 1121' and 'W-27-1' displayed the highest number of galls per root system and multiplication factor, whereas 'NW-1' and 'NW-17' had the lowest. Further examination of nematode development suggested that M. graminicola penetrated less often into highly resistant varieties, and, if they penetrated, the juveniles failed to develop into females. Multi-variate analysis was used to investigate the diversity among the wild rice accession for M. graminicola resistance. Analyses showed that the 192 wild accessions of rice could be divided into six clusters based upon their resistance levels. Thirty-four wild accessions exhibited high resistance to M. graminicola, while most accessions showed susceptibility. Analysis of 49 resistant accessions in soil assay correlated very strongly with the identical accessions in 'PF-127' assay using the same parameters, indicating the high reproducibility of 'PF-127'based assay. The resistant accessions identified in the current study would be a useful resource for studying genetics and the mechanism of resistance to M. graminicola.

The degree of soil salinization is still on the rise. In saline environments, NaCl is the main substance that causes plant salt damage, with the toxicity of ions under salt stress primarily involving sodium (Na+) or chloride (Cl-). However, fewer studies have focused on Cl- stress. This study investigated the differences in the growth and physiology of five blueberry varieties under Cl- stress, aiming to understand the mechanisms of Cl- tolerance and the physiological responses to Cl- stress in these varieties. Five blueberry varieties ('Northland', 'PL19', 'Duke', 'Reka', and 'Bonnie') were used as test materials. This study examined the changes in growth and physiological indices of blueberry plants under different concentrations of Cl- (A1-A6: 50, 100, 150, 200, 250, and 300 mmol/L) treatments. A control treatment (CK) was included to serve as a baseline for comparison. We comprehensively evaluated the Cl- tolerance of these five varieties to screen for chlorine-tolerant varieties. This study examined the concentration-dependent changes in growth and physiological indices of blueberry plants, including plant height, leaf area, chlorophyll content, electrical conductivity, levels of soluble sugar (SS), malondialdehyde (MDA), proline (Pro), and soluble protein (SP), as well as the activities of superoxide dismutase (SOD) and catalase (CAT). The results revealed that as the Cl- concentration increased, the growth of all blueberry varieties was inhibited; plant height, leaf area, and chlorophyll content consistently declined, whereas electrical conductivity showed a steady increase. SS and MDA content exhibited a biphasic response, with an increase at lower Cl- concentrations followed by a decrease at higher concentrations. The activities of SOD and CAT in 'Duke' consistently increased with rising Cl- levels. In 'PL19' and 'Reka', chlorophyll content decreased with increasing Cl-, while their proline content rose initially and then declined. In contrast, the other varieties generally showed an increasing trend in proline content. Similarly, the soluble protein content of 'Northland' and 'PL19' increased at lower Cl- levels and decreased at higher concentrations, whereas 'Bonnie', 'Duke', and 'Reka' displayed an overall declining trend. Principal component analysis indicated that the Cl- tolerance of the blueberry varieties ranked as follows: 'Duke' > 'Bonnie' > 'Reka' > 'PL19' > 'Northland'. These findings lay a foundation for blueberry cultivation in saline-alkaline soils and support the selection and development of new, chlorine-tolerant varieties.