Rice seeds germinating in flooded soils encounter hypoxia or even anoxia leading to poor seed germination and crop establishment. Introgression of AG1 and AG2 QtLs associated with tolerance of flooding during germination, together with seed pre-treatment via hydro-priming or presoaking can enhance germination and seedling growth in anaerobic soils. This study assessed the performance of elite lines incorporating AG1, AG2 and their combination when directly seeded in flooded soils using dry seeds. The QTLs were in the background of two popular varieties PSB Rc82 and Ciherang-Sub1, evaluated along with the donors Kho Hlan On (AG1) and Ma-Zhan Red (AG2) and recipient parents PSB Rc82 and Ciherang-Sub1. In one set of experiments conducted in the greenhouse, seedling emergence, growth, and carbohydrate mobilization from seeds were assessed. Metabolites associated with reactive oxygen species (ROS) scavenging including malondialdehyde (MDA) as a measure of lipid peroxidation, ascorbate, total phenolic concentration (TPC), and activities of ROS scavenging enzymes were quantified in seeds germinating under control (saturated) and flooded (10 cm) soils. In another set of experiments conducted in a natural field with 3-5 cm flooding depths, control and pretreated seeds of Ciherang-Sub1 introgression lines and checks were used. Flooding reduced seedling emergence of all genotypes, though emergence of AG1 + AG2 introgression lines was greater than the other AG lines. Soluble sugars increased, while starch concentration decreased gradually under flooding especially in the tolerant checks and in AG1 + AG2 introgression lines. Less lipid peroxidation and higher α-amylase activity, higher ascorbate (RAsA) and TPC were observed in the tolerant checks and in the AG1 + AG2 introgression lines. Lipid peroxidation correlated negatively with ascorbate, TPC, and with ROS scavengers. Seed hydro-priming or pre-soaking increased emergence by 7-10% over that of dry seeds. Introgression of AG2 and AG1 + AG2 QTLs with seed pretreatment showed 101-153% higher emergence over dry seeds of intolerant genotypes in the field. Lines carrying AG1 + AG2 QtLs showed higher α-amylase activity, leading to rapid starch degradation and increase in soluble sugars, ascorbate, and TPC, together leading to higher germination and seedling growth in flooded soils. Seed hydro-priming or pre-soaking for 24 h also improved traits associated with flooding tolerance. Combining tolerance with seed management could therefore, improve crop establishment in flooded soils and encourage large-scale adoption of direct seeded rice system.

No abstract

No abstract

No abstract

1 An experiment was conducted at the research farm of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) during May to September 2008 to investigate the effect of alley widths of Gliricidia sepium and different nitrogen levels on yield of Aus rice (BR24). The experiment was laid out in a split-plot design with three replications. Three alley widths 3.0, 4.5, and 6.0 m and a control, without tree were compared under five N doses 0, 18.75, 37.5, 56.25 and 75 kg ha -1 . G. Sepium species gave the highest (20.24 t ha -1 ) pruned materials from closer alley width (3m). The highest grain yield (3.54 t ha -1 ) of rice was obtained at 75 kg N from urea and pruned materials (PM) in 4.5 m alley width. The study suggests that G. sepium can contribute to increase rice yield and increase N use efficiency.

Nitrogenous fertilizer has remarkably improved rice (Oryza sativa L.) yield across the world since its discovery by Haber-Bosch process. Due to climate change, future rice production will likely experience a wide range of environmental plasticity. Nitrogen use efficiency (NUE) is an important trait to confer adaptability across various abiotic stresses such as flooding, drought and salinity. The problem with the increased N application often leads to a reduction in NUE. New solutions are needed to simultaneously increase yield and maximize the NUE of rice. Despite the differences among flooding, salinity and drought, these three abiotic stresses lead to similar responses in rice plants. To develop abiotic stress tolerant rice varieties, speed breeding seems a plausible novel approach. Approximately 22 single quantitative trait loci (QTLs) and 58 pairs of epistatic QTLs are known to be closely associated with NUE in rice. The QTLs/genes for submergence (SUB1A) tolerance, anaerobic germination (AG, TPP7) potential and deepwater flooding tolerance (SK1, SK2) are identified. Furthermore, phytochrome-interacting factor-like14 (OsPIL14), or loss of function of the slender rice1 (SLR1) genes enhance salinity tolerance in rice seedlings. This review updates our understanding of the molecular mechanisms of abiotic stress tolerance and discusses possible approaches for developing N-efficient rice variety.

Fruit tree vegetable-based agroforestry systems (FVAS) are being introduced in highland cropping systems of Bangladesh. This combined production system is applicable against changing climate, ensuring nutritional requirements along with food security, ecological balance, and economic profitability. The present study explored the performance of cauliflower as lower story crop in aonla based multistoried agroforestry system. The experiment was laid out in randomized complete block design (RCBD) with four replication. The treatments were T1= Aonla + carambola + lemon + dragon fruit + cauliflower, T2= Aonla + dragon fruit + cauliflower, T3= Dragon fruit + cauliflower, T4= Cauliflower in the open field (Control). Among different combinations of agroforestry systems, the highest curd yield of cauliflower (15 t ha-1) was recorded under dragon fruit-based system (T3) whereas most of the morphological parameters were maximum in the aonla + carambola + lemon + dragon fruit-based system (T1). The highest benefit–cost ratio (2.95) was noted in aonla+dragon+cauliflower-based system (T2) followed by dragon fruit based system (T3), while the highest land equivalent ratio (3.78) was calculated in the aonla + carambola + lemon + dragon fruit-based system (T1). This study revealed that, aonla + dragon + cauliflower based agroforestry system showed relatively higher economic returns and maximum land use efficiency in the upland cropping system.

Field experiments were conducted during [2007][2008][2009][2010] . In case of rice equivalent yield (REY), Tomato-Mungbean-BRRI dhan33 cropping pattern produced comparatively high average REY (29.95 t ha -1 ) followed by Tomato-Mungbean-BRRI dhan39 (27.33 t ha -1 ) cropping pattern. Among the tested cropping patterns, Tomato-Mungbean-BRRI dhan33 and Tomato-Mungbean-BRRI dhan39 were more profitable than other patterns.