Biology subjects

Haarith, D.

Publications and source records attributed to Haarith, D..

3 recordsLinked to original sources

bioRxiv2025

Soybean Rhg1 resistance to Heterodera glycines impedes theparasitism of Pratylenchus penetrans

Rhg1 has been the most effective QTL deployed in soybeans (Glycine max) to control soybean cyst nematode (Heterodera glycines; SCN). However, the resistance mechanisms and specificity of Rhg1 towards SCN as opposed to other plant parasitic nematodes are not well known. In this study we report that Rhg1 can hinder the parasitism of the root lesion nematode Pratylenchus penetrans (Pp), which is commonly found along with SCN in northern U.S. soybean fields. Two elite public soybean varieties, carrying either rhg1-a + Rhg4 or rhg1-b, negatively impacted Pp populations measured at 30 dpi. This contribution of Rhg1 was more rigorously demonstrated using near isogenic lines for rhg1-b. Additionally, in three of the four soybean genetic backgrounds tested we observed significantly more Pp at 30 dpi when Pp were co-inoculated with SCN, consistent with a previous study. No significant changes in SCN cyst numbers upon co-inoculation with Pp were observed for any of the SCN-resistant rhg1 lines. No nematode-induced changes in Rhg1 transcript abundances were observed when sampling infected root sections in any of the plant genotypes, and no changes in a jasmonate response indicator were observed. However, the 3 dpi salicylate-mediated response to SCN or Pp became more robust during SCN + Pp co-infection. Multiple hypotheses for further dissection and manipulation of soybean resistance to Pratylenchus root lesion nematodes are suggested based on the present findings.

plant biology↗

bioRxiv2024

Overexpression of α-SNAPRhg1 can improve rhg1-a mediated soybean resistance to soybean cyst nematode

(i)The rhg1-a and rhg1-b haplotypes of the soybean Rhg1 locus are economically effective tools for the control of soybean cyst nematode (SCN; Heterodera glycines), but ongoing SCN evolution requires improved sources of resistance. Both Rhg1 haplotypes carry multiple tandem repeat copies of a four-gene block encoding four disparate proteins; resistance efficacy scales with copy number. The haplotypes encode different variants of an unusual -SNAP protein whose abundance increases in the nematode-reprogrammed plant cells that form the syncytium (nematode feeding site), which subsequently collapses. Simultaneous presence of the two -SNAPRhg1 protein types, or substantially elevated expression of either type, was hypothesized to improve SCN resistance but has not been achievable by conventional plant breeding methods. We accomplished both, by transgenic additions to an rhg1-a Rhg4 soybean line. Existing resistance to HG type 0 and HG type 2.5.7 SCN was strengthened, but resistance was not improved against an HG type 1.3.6.7 SCN population that was already highly virulent on the parent line. No significant yield penalties from constitutive overexpression of transgenic -SNAP genes were observed in greenhouse or initial field studies. Cisgenic combination or elevated expression of the different -SNAP genes may extend the efficacy and/or durability of Rhg1-mediated resistance. We also observed differential protein abundances for some -SNAPRhg1 isoforms after inoculation with different HG type populations of SCN. These approaches provide opportunities to understand the different mechanisms of the two Rhg1 haplotypes and to possibly fine-tune them for better management of SCN.

plant biology↗

bioRxiv2019

Fungal Communities in Soybean Cyst Nematode-Infested Soil under Long Term Corn and Soybean Monoculture and Crop Rotation

Corn (Zea mays) and soybean (Glycine max) production forms an integral part of economies worldwide, but yields are limited by biotic and abiotic factors associated with short rotations and long-term monocultures. In this study, a long-term rotation study site with corn and soybean planted in annual rotation, five-year rotation, and long-term monoculture was utilized to examine the relationships between crop sequences, soil fungal communities, soybean cyst nematode (SCN, Heterodera glycines) densities, soil properties, and crop yields. High throughput sequencing of the ITS1 region of fungal rDNA revealed that soil fungal community structure varied significantly by crop sequence, with fungal communities under five consecutive years of monoculture becoming progressively similar to communities in long-term monoculture plots associated with their respective crop hosts. Total alpha diversity was greater under corn, but patterns of diversity and relative abundance of specific functional groups differed by crop host, with more pathotrophs proliferating under soybean and more saprotrophs and symbiotrophs proliferating under corn. Soil phosphorus (P) varied significantly by crop sequence, with lower levels of P corresponding with relative abundance of Glomerales, Paraglomerales, and Sebacinales and higher levels of P corresponding with relative abundance of Mortierellales. Soil density of the SCN was positively correlated with relative abundance and diversity of nematode-trapping fungi and with relative abundance of many potential nematode egg parasites. These results suggest several possible explanations for the improved yields associated with crop rotation, including decreased pathogen pressure, modification of soil properties, and increased diversity of soil fungal communities. Future research should investigate the potential of nematode-trapping fungi to regulate SCN densities and examine the relationships between soil P and specific arbuscular mycorrhizal and mortierellalean fungi associated with corn and soybean hosts.

bioinformatics↗