Influence of γ-PGA on greenhouse gas emissions and grain yield from paddy rice under different rice varieties.

BACKGROUND: Significant efforts have been devoted to assess the effects of the poly-gamma-glutamic acid (γ-PGA) on crop growth, yield and quality, soil water retention and fertilizer use efficiency. However, few studies have evaluated the effects of γ-PGA on greenhouse gas (GHG) emissions and grain yield from paddy fields with different rice varieties. METHODS: In the present study, a split-plot field experiment was performed to comprehensively evaluate the effects of γ-PGA concentrations (i.e., no application [P0] and 25.0 kg ha-1 of γ-PGA fermentation solution [P1]) and rice varieties (i.e., conventional rice [Huanghuazhan, H], red rice [Gangteyou 8024, R] and black rice [Black indica rice, B]) on the grain yield, GHG emissions, global warming potential (GWP), greenhouse gas intensity (GHGI), net ecosystem economic profit (NEEP) and carbon footprint (CF) during 2022 and 2023 rice-growing seasons in central China. RESULTS: Application of γ-PGA significantly affected the GHGs emissions, NEEP and CF. Compared with P0 treatments, P1 treatments significantly increased the NEEP by 1.2-11.2 %, and decreased the GWP by 12.9-35.4 %, the GHGI by 16.5-35.9 % and the CF by 13.8-26.2 % in 2022-2023. Application of γ-PGA showed a tendency to increase the yield. Under γ-PGA application condition, R treatment exhibited the lowest GWP, GHGI and CF, and the highest yield and NEEP compared with B and H treatments. CONCLUSION: Our results suggest that γ-PGA application is an ecological agricultural management to increase rice yield, reduce greenhouse gas emission and increase economic benefit, and its advantage is more significant for red rice than for other rice varieties.

Integrated effects of microbial decomposing inoculant on greenhouse gas emissions, grain yield and economic profit from paddy fields under different water regimes.

Few studies have comprehensively evaluated the impacts of microbial decomposing inoculants on greenhouse gas emissions and economic profit from paddy fields under different water regimes. Here, this study evaluated the effects of microbial decomposing inoculant treatments (straw returning without or with microbial decomposing inoculants (S and SMD)) on rice yield, CH4 and N2O emissions, economic profit and net ecosystem economic profit (NEEP) from paddy fields under different water regimes (continuous flooding (CF) and alternate wetting and drying irrigation (AWD)) in central China with a two-year field experiment. Compared with S treatment, SMD treatment significantly increased the rice yield and crop water productivity by 6.6-7.2% and 5.6-7.9%, respectively. AWD treatment significantly enhanced the crop water productivity by 56.9-73.7% while did not affect rice yield relative to CF treatment. Regardless of water regimes, SMD treatment did not affect N2O emissions, but significantly increased CH4 emissions by 13.8-39.6% relative to S treatment, resulting in a remarkable enhancement of global warming potential by 13.5-32.5%. Compared with S treatment, SMD treatment improved the economic profit and NEEP. By contrast, AWD treatment significantly increased N2O emissions by 19.1-64.8% compared with CF treatment, but significantly reduced CH4 emissions by 35.3-79.1%. Accordingly, AWD treatment significantly decreased the global warming potential by 33.4-73.9% compared with CF treatment. In addition, AWD treatment resulted in 39.9-96.4% higher economic profit and 48.0-124.4% higher NEEP relative to CF treatment. In summary, AWD treatment is a sustainable water regime that can maintain rice yield, mitigate global warming potential, and increase economic income. However, regardless of water regimes, SMD treatment led to higher rice yield and economic profit, as well as higher global warming potential than S treatment, suggesting that other appropriate treatments of crop straw are needed to mitigate CH4 emissions while improving economic profit for rice sustainable production.

Production and cytogenetic characterization of intertribal somatic hybrids between Brassica napus and Isatis indigotica and backcross progenies.

Intertribal somatic hybrids between Brassica napus (2n = 38, AACC) and a dye and medicinal plant Isatis indigotica (2n = 14, II) were obtained by fusions of mesophyll protoplasts. From a total of 237 calli, only one symmetric hybrid (S2) and five asymmetric hybrids (As1, As4, As6, As7 and As12) were established in the field. These hybrids showed some morphological variations and had very low pollen fertility. Hybrids S2 and As1 possessed 2n = 52 (AACCII), the sum of the parental chromosomes, and As12 had 2n = 66 (possibly AACCIIII). Hybrids As4, As6 and As7 were mixoploids (2n = 48-62). Genomic in situ hybridization analysis revealed that pollen mother cells at diakinesis of As1 contained 26 bivalents comprising 19 from B. napus and 7 from I. indigotica and mainly showed the segregation 26:26 at anaphase I (AI) with 7 I. indigotica chromosomes in each polar group. Four BC(1) plants from As1 after pollinated by B. napus resembled mainly B. napus in morphology but also exhibited some characteristics from I. indigotica. These plants produced some seeds on selfing or pollination by B. napus. They had 2n = 45 (AACCI) and underwent pairing among the I. indigotica chromosomes and/or between the chromosomes of two parents at diakinesis. All hybrids mainly had the AFLP banding patterns from the addition of two parents plus some alterations. B. napus contributed chloroplast genomes in majority of the hybrids but some also had from I. indigotica. Production of B. napus-I. indigotica additions would be of considerable importance for genome analysis and breeding.

Production and characterization of intergeneric somatic hybrids between Brassica napus and Orychophragmus violaceus and their backcrossing progenies.

Alien chromosome addition lines have been widely used for identifying gene linkage groups, assigning species-specific characters to a particular chromosome and comparing gene synteny between related species. In plant breeding, their utilization lies in introgressing characters of agronomic value. The present investigation reports the production of intergeneric somatic hybrids Brassica napus (2n = 38) + Orychophragmus violaceus (2n = 24) through asymmetric fusions of mesophyll protoplasts and subsequent development of B. napus-O. violaceous chromosome addition lines. Somatic hybrids showed variations in morphology and fertility and were mixoploids (2n = 51-67) with a range of 19-28 O. violaceus chromosomes identified by genomic in situ hybridization (GISH). After pollinated with B. napus parent and following embryo rescue, 20 BC(1) plants were obtained from one hybrid. These exhibited typical serrated leaves of O. violaceus or B. napus-type leaves. All BC(1) plants were partially male fertile but female sterile because of abnormal ovules. These were mixoploids (2n = 41-54) with 9-16 chromosomes from O. violaceus. BC(2) plants showed segregations for female fertility, leaf shape and still some chromosome variation (2n = 39-43) with 2-5 O. violaceus chromosomes, but mainly containing the whole complement from B. napus. Among the selfed progenies of BC(2) plants, monosomic addition lines (2n = 39, AACC + 1O) with or without the serrated leaves of O. violaceus or female sterility were established. The complete set of additions is expected from this investigation. In addition, O. violaceus plants at diploid and tetraploid levels with some variations in morphology and chromosome numbers were regenerated from the pretreated protoplasts by iodoacetate and UV-irradiation.

Chromosome elimination and fragment introgression and recombination producing intertribal partial hybrids from Brassica napus x Lesquerella fendleri crosses.

The intertribal sexual hybrids between three Brassica napus (2n=38) cultivars and Lesquerella fendleri (2n=12) with the latter as pollen parent were obtained and characterized for their phenotypes and chromosomal and genomic constitutions. F(1) plants and their progenies mainly resembled female B. napus parents, while certain characters of L. fendleri were expressed in some plants, such as longer flowering period, basal clustering stems and particularly the glutinous layer on seed coats related to drought tolerance. Twenty-seven F(1) plants were cytologically classified into five types: type I (16 plants) had 2n=38, type II (2) had 2n=38-42, type III (3) had 2n=31-38, type IV (5) had 2n=25-31, and type V (1) had 2n=19-22. Some hybrids and their progenies were mixoploids in nature with only 1-2 chromosomes or some chromosomal fragments of L. fendleri included in their cells. AFLP (Amplified fragments length polymorphism) analysis revealed that bands absent in B. napus, novel for two parents and specific for L. fendleri appeared in all F(1) plants and their progenies. Some progenies had the modified fatty acid profiles with higher levels of linoleic, linolenic, eicosanoic and erucic acids than those of B. napus parents. The occurrence of these partial hybrids with phenotypes, genomic and fatty acid alterations resulted possibly from the chromosome elimination and doubling accompanied by the introgression of alien DNA segments and genomic reorganization. The progenies with some useful traits from L. fendleri should be new and valuable resource for rapeseed breeding.