Unlocking the genetic variability of Paspalum species: genomics & cytogenetics for improved perennial forage feedstocks

• Grant number: 19/23434-2
• Support Opportunities: Regular Research Grants
• Start date: May 01, 2020
• End date: July 31, 2022
• Field of knowledge: Biological Sciences - Genetics - Plant Genetics
• Agreement: Texas A&M University
• Mobility Program: SPRINT - Projetos de pesquisa - Mobilidade
• Principal Investigator: Alessandra Pereira Fávero
• Grantee: Alessandra Pereira Fávero
• Principal researcher abroad: Russell William Jessup
• Institution abroad: Texas A&M University, United States
• Host Institution: Embrapa Pecuária Sudeste. Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA). Ministério da Agricultura, Pecuária e Abastecimento (Brasil). São Carlos , SP, Brazil
• Associated researchers: Anete Pereira de Souza ; Bianca Baccili Zanotto Vigna ; Byron L. Burson ; Heather Dawn Baldi
• Associated research grant: 18/07624-3 - Polyploidization and characterization of P. lenticulare and P. compressifolium accessions, AP.R

Abstract

The ongoing Fapesp Regular Project (grant number 2018/07624-3) was approved in August 2018 and focuses on: 1) inducing polyploidization of two diploid Paspalum species, 2) determining the cytogenetic and reproductive behaviors of all polyploids recovered and 3) identifying molecular markers linked to apomixis in Paspalum. Significant progress has been made to date, including: 1) confirmation that two superior genotypes have 20 chromosomes, are sexual and allogamous, 2) colchicine treatment of 4222 seeds collected from both genotypes, and 3) identification of three chimeric, mixoploid plants out of 250 recpovered progeny by flow cytometry. Equivalent activities have been done for related grass spp. at Texas A&M University (TAMU) by Dr. Jessup. The PI of FAPESP Regular project (Dr. Fávero) was a Visiting Scientist at TAMU for 13 months to collaboratively develop improved protocols for these techniques from Dr. Jessup and Dr. Byron L. Burson (USDA-ARS). This SPRINT proposal aims to continue information exchange and capacity building regarding novel techniques for chromosome doubling, germplasm development, and characterizing apomixis in Paspalum spp. One of the main complications of induced chromosome doubling is the recovery of chimeric plants. Two novel methods targeting Paspalum polyploidization with both reduced occurrence of chimeras and increased rate of induced chromosome doubling will be performed at TAMU. Additional new techniques of chromosome doubling involving caryopsis treatment with significantly higher colchicine concentrations and shorter exposure times position will also be performed at Embrapa Pecuária Sudeste.The ongoing Fapesp Regular Project includes the search for molecular markers (MM) linked to apomixis in Paspalum species using different approaches, of which some have been applied to related species at TAMU by Dr. Jessup. The ongoing project has found differentially expressed sequences associated to apomixis in the P. notatum transcriptome that are syntenic to chromosomes 2 and 12 from rice. These sequences are candidates for markers associated to apomixis in other apomictic Paspalum species. Additional candidate genes will be investigated via comparative genomic approaches using apomixis linked regions in other grass taxa to mine sequence data from syntenic regions in publicly available annotated genomes and map in developed Paspalum populations. Both groups are also interested in searching for epigenetic markers associated to apomixis based on previous findings obtained by the current Fapesp project. Discussions will be ongoing regarding this topic between the two research groups throughout the proposed SPRINT project in order to pursue additional approaches. The proposed project has significant potential relevance not only within forages but also across plant sciences. Outputs related to apomixis would help facilitate development of additional crops with the high-value trait, as indicated for example by the Bill & Melinda Gate's Foundation's 'Capturing Heterosis' project investment in developing apomictic sorghum and cowpea. Chromosome doubling improvements would similarly improve breeding programs, benefiting in particular sterile triploid crops (seedless watermelon, banana, grapes, etc.). With the existing, major tissue culture and in-vitro regeneration barriers to new gene editing technologies (CRISPR, etc.), any in planta microneedle SAM injection methods developed in the project would have obvious value.Moreover, future proposals will be discussed to address the need for more genomics resources for Paspalum species as genetic maps and genome sequencing in diploid species to provide genomic tools for the tetraploid species. (AU)