nan Atique-ur-Rehman

BORON NUTRIPRIMING IMPROVES THE GERMINATION AND EARLY SEEDLING GROWTH OF RICE (ORYZA SATIVA L.)

Boron (B) is one of the important micronutrient required for rice in particular during reproductive growth. A laboratory study was conducted to explore the potential of boron nutripriming in improving the germination and early seedling growth of rice. Seeds of fine grain aromatic rice cultivar Super Basmati were primed in aerated B solution (0.001, 0.01, 0.1 and 0.5% w/v) while untreated dry seeds were taken as control. Seed priming in 0.001 and 0.1% B solutions improved the time to 50% germination, germination energy, final germination percentage, mean germination time, and germination index. Beyond this concentration either there was no effect or an adverse effect on rice seeds. In the cases of radicle length, plumule length and secondary roots priming more diluted B solution, i.e., 0.001% proved better than rest of the treatments as suppression in these three traits was observed by other B treatments than control. Seed priming in relatively concentrated B solution, i.e., 0.5% completely suppressed the germination and growth.

ROLE OF BORON IN LEAF ELONGATION AND TILLERING DYNAMICS IN FINE-GRAIN AROMATIC RICE

This study was conducted to explore the role of boron (B) in seedling emergence, leaf elongation, and tillering dynamics. Boron was applied as seed priming. For priming seeds of two rice cultivars (Super Basmati and Shaheen Basmati) were soaked in B solutions having 0.001, 0.01, 0.1 and 0.5% concentrations. Substantial improvement in seedling emergence was observed from hydropriming and seed priming in 0.001 and 0.01% solutions; beyond this B concentration, emergence potential was suppressed. Seeds primed in 0.5% B solution even did not emerge. A linear increase in plant height was recorded up to 30 days from seeds primed in 0.001% solution. Similarly rate of leaf emergence and elongation and rate of tiller appearance were substantially improved in seedlings raised from seeds primed in 0.001% B solution. Overall B plays a significant role in leaf appearance, elongation and tillering dynamics of rice when used in very low concentration.

Soil Application of Boron Improves the Tillering, Leaf Elongation, Panicle Fertility, Yield and its Grain Enrichment in Fine-Grain Aromatic Rice

Boron (B) is one of the essential micronutrients having a specific role, particularly during reproductive phase, in rice. In a previous experiment on aerobic rice, panicle sterility was noted as one of the major challenges. This experiment was conducted to evaluate the influence of soil-applied B on tillering, panicle sterility, water relations, and grain enrichment in fine-grain aromatic rice cultivars ‘Super Basmati’ and ‘Shaheen Basmati’. Boron was soil applied at 0.50, 0.75, 1, 1.25, and 1.50 kg ha−1 while the control treatment did not receive B. Rate of leaf emergence and elongation and tiller appearance were significantly improved by B application. Likewise, B application also improved the leaf chlorophyll contents and water relations in both rice cultivars. Substantial improvement in kernel yield and yield contributing traits was also observed by B application owing to decrease in panicle sterility. A linear increase in leaf and kernel B contents was observed with increase in B application rate. However, the range for an optimum B application rate is very narrow and increase of B application beyond 1 kg ha−1 was toxic. In conclusion, soil application of B is an effective way to decrease panicle sterility and increase the kernel yield and grain B enrichment in rice.

Boron nutrition of rice in different production systems. A review

Half of the world’s population—more than 3.5 billion people—depend on rice for more than 20% of their daily energy requirements. Rice productivity is under threat for several reasons, particularly the deficiency of micronutrients, such as boron (B). Most rice-based cropping systems, including rice–wheat, are facing B deficiency as they are often practiced on high pH and alkaline soils with low B contents, low soil organic matter, and inadequate use of B fertilizer, which restricts the availability, uptake, and deposition of B into grains. Farmers’ reluctance to fertilize rice fields with B—due to the lack of cost-effective B-enriched macronutrient fertilizers—further exacerbates B deficiency in rice-based cropping systems. Here we review that, (i) while rice can tolerate excess B, its deficiency induces nutritional disorders, limits rice productivity, impairs grain quality, and affects the long-term sustainability of rice production systems. (ii) As B dynamics in the soil varies between flooded and aerobic rice systems, different B deficiency management strategies are needed in rice-based cropping systems. (iii) Correct diagnosis of B deficiency/toxicity in rice; understanding its interaction with other nutrients including nitrogen, phosphorus, potassium, and calcium; and the availability and application of B fertilizers using effective methods will help to improve the sustainability and productivity of different rice production systems. (iv) Research on rice-based systems should focus on breeding approaches, including marker-assisted selection and wide hybridization (incorporation of desirable genes), and biotechnological strategies, such as next-generation DNA and RNA sequencing, and genetic transformations to develop rice genotypes with improved B contents and abilities to acquire B from the soil. (v) Different B application strategies—seed priming and foliar and/or soil application—should be included to improve the performance of rice, particularly when grown under aerobic conditions.