Carotenoid evolution during postharvest storage of durum wheat (Triticum turgidum conv. durum) and tritordeum (×Tritordeum Ascherson et Graebner) grains

The process of in vivo esterification of xanthophylls has proven to be an important part of the post-carotenogenesis metabolism which mediates their accumulation in plants. The biochemical characterization of this process is therefore necessary for obtaining new and improved crop varieties with higher carotenoid contents. This study investigates the impact of postharvest storage conditions on carotenoid composition, with special attention to the esterified pigments (monoesters, diesters and their regioisomers), in durum wheat and tritordeum, a novel cereal with remarkable carotenoid content. For tritordeum grains, the total carotenoid content decreased during the storage period in a clear temperature-dependent manner. On the contrary, carotenoid metabolism in durum wheat was very much dependent on the physiological adaptation of the grains to the imposed conditions. Interestingly, when thermal conditions were more intense (37 °C), a higher carotenoid retention was observed for tritordeum, and was directly related to the de novo esterification of the lutein induced by temperature. The profile of lutein monoester regioisomers was constant during storage, indicating that the regioisomeric selectivity of the XAT enzymes was not altered by temperature. These data can be useful for optimizing the storage conditions of grains favoring a greater contribution of carotenoids from these staple foods.     

Simultaneous selection for stem borer resistance and forage related traits in maize (Zea mays ssp. mays L.) × teosinte (Zea mays ssp. mexicana L.) derived populations

Maize spotted stalk borer (Chilo partellus Swinhoe Pyralidae) (MSSB) is a serious pest of the maize (Zea mays ssp. mays L.) crop in Pakistan. This study was conducted to introgress resistance in maize against MSSB by exploring wild sources of resistance for the development of a resistant maize variety. To achieve this, teosinte (‘PI566674’) × maize (‘Sargodha-2002’) crosses were conducted and three populations (F₁, F₂ and F₃) were established. These populations were screened at various locations and in a contrasting artificial insect infestation experiment. Teosinte species ‘PI566674’, following screening, was shown to be highly resistant to MSSB and had the ability to produce a high biomass (5 times higher than susceptible genotypes) under high temperatures (36–40 °C). The biomass of the F₁ hybrid, which was highly susceptible to MSSB, was significantly reduced (P ≤ 0.05) following infestation by MSSB in all experiments. The introgression from teosinte for genes conferring resistance to MSSB was screened in segregating F₂ and F₃ generations. Despite a susceptible F₁ population, F₂ was resistant to MSSB. Twenty new recombinant plants with resistance to MSSB and a high leaf soluble solid (16 °Brix) content were identified. They were selected to grow the F₃ population. Mean values of F₃ progenies showed similar resistance to the F₂ population but a high percentage (60%) of resistant plants was recovered.     

Nuclear and chloroplast diversity and phenotypic distribution of rice (Oryza sativa L.) germplasm from the democratic people’s republic of Korea (DPRK; North Korea)

Background

Rice accounts for 43% of staple food production in the Democratic People’s Republic of Korea (DPRK). The most widely planted rice varieties were developed from a limited number of ancestral lines that were repeatedly used as parents in breeding programs. However, detailed pedigrees are not publicly available and little is known about the genetic, phenotypic, and geographical variation of DPRK varieties.

Results

We evaluated 80 O. sativa accessions from the DPRK, consisting of 67 improved varieties and 13 landraces. Based on nuclear SSR analysis, we divide the varieties into two genetic groups: Group 1 corresponds to the temperate japonica subpopulation and represents 78.75% of the accessions, while Group 2 shares recent ancestry with indica varieties. Interestingly, members of Group 1 are less diverse than Group 2 at the nuclear level, but are more diverse at the chloroplast level. All Group 2 varieties share a single Japonica maternal-haplotype, while Group 1 varieties trace maternal ancestry to both Japonica and Indica. Phenotypically, members of Group 1 have shorter grains than Group 2, and varieties from breeding programs have thicker and wider grains than landraces. Improved varieties in Group 1 also show similar and/or better levels of cold tolerance for most traits, except for spikelet number per panicle. Finally, geographic analysis demonstrates that the majority of genetic variation is located within regions that have the most intensive rice cultivation, including the Western territories near the capital city Pyungyang. This is consistent with the conscious and highly centralized role of human selection in determining local dispersion patterns of rice in the DPRK.

Conclusions

Diversity studies of DPRK rice germplasm revealed two genetic groups. The most widely planted group has a narrow genetic base and would benefit from the introduction of new genetic variation from cold tolerant landraces, wild accessions, and/or cultivated gene pools to enhance yield potential and performance.