Microbial consortium inoculant increases pasture grasses yield in low-phosphorus soil by influencing root morphology, rhizosphere carboxylate exudation and mycorrhizal colonisation.

BACKGROUND: Pasture farming in south-western Australia is challenged by nutrient-poor soils. We assessed the impact of microbial consortium inoculant (MI) and rock mineral fertiliser (MF) on growth, nutrient uptake, root morphology, rhizosphere carboxylate exudation and mycorrhizal colonisation in three pasture grasses - tall fescue (Festuca arundinacea L.), veldt grass (Ehrharta calycina Sm.) and tall wheatgrass (Thinopyrum ponticum L.) grown in low-phosphorus (P) sandy soil in a glasshouse for 30 and 60 days after sowing (DAS). RESULTS: Veldt grass produced the highest specific root length and smallest average root diameter in both growth periods, and had similar shoot weight, root surface area and fine root length (except at 30 DAS) to tall fescue. Compared with the control, MI alone or combined with MF significantly increased shoot and root biomass (except root biomass at 30 DAS), likely due to the significant increases in root surface area and fine root length. Plants supplied with MI + MF had higher shoot N and P contents than those in the MI and the control treatments at 60 DAS. Malate, citrate and trans-aconitate were the major rhizosphere carboxylates exuded at both 30 and 60 DAS. Malate exudation varied among species and treatments in both growth periods, but citrate exudation was consistently higher in the low-P treatments (control and MI) than the MF and MI + MF treatments. CONCLUSION: Microbial consortium inoculant can positively influence pasture production in low-P soil by increasing root surface area and fine root length, whereas exudation of nutrient-mobilising carboxylates (citrate) is dependent more on soil P supply than microbial consortium inoculant. © 2021 Society of Chemical Industry.

Genetic Divergence and Diversity in Himalayan Puccinia striiformis Populations from Bhutan, Nepal, and Pakistan.

The western Himalayan region in Pakistan has been shown to be the center of diversity of Puccinia striiformis; however, little is known about its genetic relations with the eastern part of the Himalayas. We studied the genetic structure of P. striiformis from Nepal (35 isolates) and Bhutan (31 isolates) in comparison with 81 Pakistani samples collected during 2015 and 2016, through microsatellite genotyping. Genetic analyses revealed a recombinant and highly diverse population structure in Pakistan, Bhutan, and Nepal. A high level of genotypic diversity (>0.90) was observed for the three countries of Pakistan (0.96), Bhutan (0.96), and Nepal (0.91) with the detection of 108 distinct multilocus genotypes (MLGs) in the overall population; 59 for Pakistan, 27 for Bhutan, and 26 for Nepal. Mean number of alleles per locus and gene diversity were higher in Nepal (3.19 and 0.458, respectively) than Bhutan (3.12 and 0.458, respectively). A nonsignificant difference between the observed and the expected heterozygosity in all populations further confirmed the recombinant structure. A clear population subdivision between the Himalayan region of Nepal, Bhutan, and Pakistan was evident, as revealed by FST values (ranging between 0.111 to 0.198), discriminant analysis of principal components, and resampling of MLGs. Limited gene flow could be present between Nepal and Bhutan, while the population from Pakistan was clearly distinct, and no divergence was present between two populations from Pakistan (Bajaur and Malakand). The overall high diversity and recombination signature suggested the potential role of recombination in the eastern Himalayan region (Nepal and Bhutan), which needs to be considered during host resistance deployment and in the context of aerial dispersal of the pathogen. Further surveillance should be made in the Himalayan region for disease management in the region and in the context of worldwide invasions.