Qisong Miao

This study investigated the role of the sugar transporter OsSWEET11 during the early stage of rice caryopsis development using β-glucoronidase (GUS) to represent its expression, together with clustered regularly interspaced short palindromic repeats-CRISPR-associated protein 9 (CRISPR-Cas9)-mediated knockout, cross-fertilization and RNA sequencing (RNA-seq) analyses. The results showed that OsSWEET11 was expressed strongly in developing caryopsis, particularly in the ovular vascular trace, nucellar epidermis and cross cells. The knockout of OsSWEET11 significantly decreased the sucrose concentration in the mutant embryo sacs and led to defective grain filling compared with that of the wild-type (WT) plant. Moreover, the expression of 2,549 genes in the mutant caryopsis was affected. The grain weight and seed setting percentage were also decreased in the mutants. The cross-fertilization of the mutant and WT rice revealed that the mutated maternal donor induced defective grain filling. These results strongly suggested that OsSWEET11 played an important role in sucrose release from maternal tissue to the maternal-filial interface during the early stage of caryopsis development. It might also induce sucrose release from the ovular vascular trace and cross cells of developing caryopsis. These findings bridge the gap in the understanding of post-phloem sugar transport during the early stage of rice caryopsis development.

OsNRT1.1a is a low-affinity nitrate (NO3 (-) ) transporter gene. In this study, another mRNA splicing product, OsNRT1.1b, putatively encoding a protein with six transmembrane domains, was identified based on the rice genomic database and bioinformatics analysis. OsNRT1.1a/OsNRT1.1b expression in Xenopus oocytes showed OsNRT1.1a-expressing oocytes accumulated (15) N levels to about half as compared to OsNRT1.1b-expressing oocytes. The electrophysiological recording of OsNRT1.1b-expressing oocytes treated with 0.25 mM NO3 (-) confirmed (15) N accumulation data. More functional assays were performed to examine the function of OsNRT1.1b in rice. The expression of both OsNRT1.1a and OsNRT1.1b was abundant in roots and downregulated by nitrogen (N) deficiency. The shoot biomass of transgenic rice plants with OsNRT1.1a or OsNRT1.1b overexpression increased under various N supplies under hydroponic conditions compared to wild-type (WT). The OsNRT1.1a overexpression lines showed increased plant N accumulation compared to the WT in 1.25 mM NH4 NO3 and 2.5 mM NO3 (-) or NH4 (+) treatments, but not in 0.125 mM NH4 NO3 . However, OsNRT1.1b overexpression lines increased total N accumulation in all N treatments, including 0.125 mM NH4 NO3 , suggesting that under low N condition, OsNRT1.1b would accumulate more N in plants and improve rice growth, but also that OsNRT1.1a had no such function in rice plants.

Sheath blight, which is caused by Rhizoctonia solani, is a disease that majorly impacts rice production. A biocontrol agent used for control rice sheath blight must be sprayed on the stem at specific times during rice growth, a process that is labour-intensive and renders the antagonist vulnerable to environmental factors. In this study, Trichoderma asperellum T12 was used to produce preparation by solid-state fermentation using a surface-response method. Rice hull was selected as a carrier based on its ability to sustain the T12 floating in the water and protect T12 from ultraviolet irradiation. The production of a T12-based preparation required 32% wheat bran, 7% inoculum, 2.3 g kg−1 (NH4)2SO4 and 65% water content, with fermentation at 27.5°C for 30 days and agitation every six days. The preparation demonstrated 90% biocontrol efficacy and significantly (P > 0.05) increased the seed-set rate and 1000-grain weight as compared with the pathogen treatment. The population of Trichoderma on the surface of rice leaf sheath in the treatment applied with T12 preparation increased from 232 cfu (colony forming units) g−1 fw (fresh weight) to 436 cfu g−1 fw during rice growth stage, which was significantly (P > 0.05) higher than pathogen treatment. The population of R. solani on the leaf sheath increased from 41 cfu g−1 fw to 271 cfu g−1 fw in the pathogen treatment, while remained stable (P > 0.05) at level of 10–23 cfu g−1 fw in T12 preparation applied treatment. Biocontrol of sheath blight by the addition of the preparation to the soil is effective and decreases the costs of agro-industrial waste disposal.

Effective microorganism biochar-based fertilizer (EMBF) can improve the physiological properties of tobacco (Nicotiana tabacum L.) In this study, the irrigation and EMBF rates were applied as factors that influence the photosynthetic characteristics and chlorophyll content of tobacco. The experiment involved 12 treatments: CK1-CK3, T1-T3, T4-T6, and T7-T9; these four groups represented 0, 100, 300, and 600 g EMBF pot -1 , respectively. Each group was irrigated at rates of 40, 80, and 120 L pot -1 . When comparing with the control treatment CK, results showed that net photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci), transpiration rate (Tr), and soil plant analysis development (SPAD) increased by 8.21%-107.03%, 18.78%-118.27%, 18.78%-118.27%, 7.24%-104.15%, and 3.47%-69.09%, respectively, after EMBF application. The Pn, gs, Ci, and Tr at the growth and maturity stages were highly significant (P < 0.01) and positively correlated with EMBF application. The Pn, gs, and Tr were significant (P < 0.05) and positively correlated with irrigation, and Ci was less affected by irrigation (P > 0.05). The SPAD value of flue-cured tobacco at three growing stages was highly significant (P < 0.01) and positively correlated with the irrigation and fertilization rates. The SPAD values at the growth and maturity stages were higher than those at the rooting stage by 46.73%-79.2% and 2.21%-46.17%, respectively. Furthermore, the 80 L pot -1 irrigation rate combined with 300 g EMBF pot -1 is the best water and fertilizer combination. The results of this study might provide theoretical and practical guidance for growing flue-cured tobacco in production areas.

This study aimed to determine the effect of irrigation amount and irrigation frequency on drip-irrigated flue-cured tobacco evapotranspiration (ETa), yield, and water use efficiency. Four irrigation treatment levels were imposed: 100% IRT (fully irrigated treatment, no stress), 85% IRT, 70% IRT, RFT (rainfed treatment), and high, medium, and low irrigation frequencies were set. The relationship between irrigation volume and yield is a quadratic curve. The evapotranspiration had a positive relationship with the irrigation amount. The yield of flue-cured tobacco was the highest in 2016 (wet year), and the corresponding ETa was the smallest. The irrigation water use efficiency (IWUE) in the driest year, 2017, was lower than IWUE in the wet years 2015 and 2016, and the crop water use efficiency (CWUE) had similar results for the three years. IWUE increased with irrigation amount. The effect of irrigation frequency on CWUE was not significant. The CWUE had a positive relationship with yield. No significant differences due to irrigation frequency were found for yield.