QTL mapping of salinity tolerance in African bermudagrass
Developing salinity-tolerant bermudagrass (Cynodon spp.) is a strategy to address the challenge of water conservation by utilizing reclaimed water for irrigation and in areas that rely on well water with high salt concentrations. African bermudagrass (Cynodon transvaalensis Burtt-Davy) has been used to cross with common bermudagrass [C. dactylon (L.) Pers.] for creation of interspecific hybrid cultivars. Little information regarding the molecular basis of salinity tolerance is available in African bermudagrass. Thus, this project was conducted to estimate the heritability of salinity tolerance and to identify the quantitative trait loci (QTL) associated with the salinity tolerance in African bermudagrass.
A first generation selfed (S1) population of 104 individuals derived from African bermudagrass genotype OKC 1163 was evaluated in the greenhouse for salinity response. In the first week, all plants were subjected to saline water with 5 decisiemens per square meter daily increment until 25 decisiemens per square meter. Then, plants were irrigated with 25 decisiemens per square meter saline water for two weeks. The salinity concentration was increased to 30 decisiemens per square meter for another two weeks. Leaf firing and percent green cover were collected weekly for ANOVA and QTL mapping.
Significant difference was found among the genotypes for leaf firing and percentage green cover. Heritability for LF was 0.85 and for PGC was 0.92. Altogether, 13 QTL associated with salinity tolerance were found across six linkage groups (LGs) 1, 2, 3, 4, 6, 7 in African bermudagrass. Results from this research will provide a foundation to understand the genetic mechanism of salinity tolerance in African bermudagrass and can be used in the marker-assisted selection for turf-type bermudagrass salinity tolerance improvement.
— Prabha Adhikari (prabha.adhikari@okstate.edu); Mingying Xiang, Ph.D.; Yanqi Wu, Ph.D.; Charles Fontanier, Ph.D.; Dennis L. Martin, Ph.D.; and Shuhao Yu, Ph.D.; Oklahoma State University, Stillwater
Investigation of PGPR Bacillus subtilis UD1022 for disease management in creeping bentgrass: Systemic defense responses vs. antagonism
Disease management is a major challenge to the turfgrass industry. Current disease-management practices heavily rely on the use of synthetic pesticides, emphasizing the need for the development of ecofriendly alternatives. Certain strains of plant growth promoting rhizobacteria (PGPRs) activate systemic defense responses in the plants against phytopathogens. While Bacillus subtilis strain UD1022 (hereafter UD1022) has demonstrated antagonistic activity against the dollar spot pathogen Clarireedia jacksonii, its potential for disease control in creeping bentgrass (Agrostis stolonifera L.) remains unknown. Specifically, it is unclear whether UD1022 can suppress dollar spot in planta, and, if so, what mechanisms play a crucial role. Whether disease suppression occurs through induced plant defense responses or direct antagonism needs further investigation. Addressing these knowledge gaps is crucial for developing sustainable disease-management strategies in turfgrass.
Controlled environment experiments were conducted to investigate the potential of UD1022 to induce systemic defense responses in creeping bentgrass. Penn A4 creeping bentgrass plants were primed with UD1022 inoculation six and seven weeks post planting. The expression of defense-related genes (NPR1, PR3, ERF and MYC2) involved in salicylic acid, ethylene and jasmonic acid signaling pathways was quantified using real time quantitative polymerase chain reaction. Subsequently, plant leaves were inoculated with C. jacksonii three days after priming, and disease severity was evaluated using detached leaf assays.
The findings show UD1022 induces systemic resistance with defense genes upregulation; however, priming alone does not significantly suppress the pathogen. A significant reduction in dollar spot severity was observed when defense priming was combined with foliar application for direct antagonism. The mechanistic understanding of how benign microbes alter and modulate a host plant’s innate immune system could potentially contribute to the development of sustainable strategies for disease management in turfgrass.
— Charanpreet Kaur (ckdhiman@udel.edu); Harsh P. Bais, Ph.D.; Erik Ervin, Ph.D.; University of Delaware, Newark
Darrell J. Pehr (dpehr@gcsaa.org) is GCM’s science editor.