Introgression Progress for Phenotypic Traits and Parent-progeny Diversity at Advanced Segregation Population From Oryza Barthii and Oryza Glaberrima/oryza Sativa Crosses

Rice is a cereal staple of global fame and importance. Oryza barthii, a wild species holds significant traits and its utilization in rice breeding is rare. This study traced introgression trend of heritable traits in the offspring of O. barthii with an Africa-Asian progenitor to F8 and assessed diversity between the parents and the F8 population. Significant (P<0.05) genotypic variation existed for all the traits except tiller number, panicle/meter squared, grains/panicle and 1000 grain weight. Grains/panicle and days to 50% flowering had respective least (3.34%) and highest (96.32%) broad sense heritabilities. All traits had lower GCV compared to PCV. The least (5.28% and 8.05%) and the highest (90.8% and 98.1%) GCV and PCV were respectively from grains/panicle and tiller number. Clear variations on the panicles and grains include: variations in sizes, shapes, colours, presence or absence of awns. The total variance explained by five principal component axes was 80.1%. Plant height at maturity was the only trait with significant (p ≤ 0.01) correlation and regression between F6 and F7. Progenies resemblance to Parent 1(IRGC 104084) retrogressively declined but parent-offspring to parent 2 (TGS 25) progressively increased from F6 to F8. Three visible groups of rice type in this study were: the O. barthii (11%), O. sativa (67%) and the intermediate group (22%). This research has added to rice genetic resources; an investigation of the nutritional status of the progenies would be an interesting research.

Oryza sativa cv. Nipponbare and Oryza barthii as Unexpected Tolerance and Susceptibility Sources Against Schizotetranychus oryzae (Acari: Tetranychidae) Mite Infestation

Cultivated rice (Oryza sativa L.) is frequently exposed to multiple stresses, including Schizotetranychus oryzae mite infestation. Rice domestication has narrowed the genetic diversity of the species, leading to a wide susceptibility. This work aimed to analyze the response of two African rice species (Oryza barthii and Oryza glaberrima), weedy rice (O. sativa f. spontanea), and O. sativa cv. Nipponbare to S. oryzae infestation. Surprisingly, leaf damage, histochemistry, and chlorophyll concentration/fluorescence indicated that the African species present a higher level of leaf damage, increased accumulation of H2O2, and lower photosynthetic capacity when compared to O. sativa plants under infested conditions. Infestation decreased tiller number, except in Nipponbare, and caused the death of O. barthii and O. glaberrima plants during the reproductive stage. While infestation did not affect the weight of 1,000 grains in both O. sativa, the number of panicles per plant was affected only in O. sativa f. spontanea, and the percentage of full seeds per panicle and seed length were increased only in Nipponbare. Using proteomic analysis, we identified 195 differentially abundant proteins when comparing susceptible (O. barthii) and tolerant (Nipponbare) plants under control and infested conditions. O. barthii presents a less abundant antioxidant arsenal and is unable to modulate proteins involved in general metabolism and energy production under infested condition. Nipponbare presents high abundance of detoxification-related proteins, general metabolic processes, and energy production, suggesting that the primary metabolism is maintained more active compared to O. barthii under infested condition. Also, under infested conditions, Nipponbare presents higher levels of proline and a greater abundance of defense-related proteins, such as osmotin, ricin B-like lectin, and protease inhibitors (PIs). These differentially abundant proteins can be used as biotechnological tools in breeding programs aiming at increased tolerance to mite infestation.