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[en] The present studies report the genotypic responses of 61 rice (Oryza sativa L.) genotypes (35 aromatic and 26 non aromatic) against the infestation of rice stem borers under natural field conditions. The data obtained on these genotypes on larval infestation in combination with yield were the criteria to assess the resistance depicted by them. The studies showed that among aromatic genotypes, 'Khushboo-95' gave the best yield of grain and harboured the least pest infestation (2.81% dead hearts and 1.85% white heads); on the other hand variety 'Sonahri Sugdasi (P)' harboured the highest borers attack (10.37% and 19.30%) and yielded the lowest grain yield. Regarding non-aromatic genotypes, IR8-2.5-11 received least infestation (1.32% and 0.26% dead hearts and white heads, respectively) generating highest yield showing its tolerance to borer's attack, in contrast, genotype IR6-252 harboured the highest infestation (5.65%, 4.28%) and yielded minimum grain indicating its susceptibility. These results demonstrate the expression of resistance gene in the genome of tolerant rice genotypes that can provide season-long protection from the natural infestation of insect pests. (author)

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[en] Rice is the most preferred staple food in Zanzibar. It is grown by most household in rural areas and forms a very important crop terms of food security. The main ecology of its production is rain fed condition which is faced with so many constraints such as low yield potential (with an average yield of 1.5t/ha), weed infestations, stem bores attack, RYMV and rice blasts. The objective of this trial was to evaluate rice mutant lines to determine suitable varieties for recommendation to farmers. On-station and on-farm field experiments were conducted both in Pemba and Unguja to evaluate rice mutant materials under rain fed lowland conditions. This trial was part of rice improvement programme through IAEA/URT/5/020 project 'enhancing crop productivity through radiation technology'. Twenty-four mutant lines of Supa and Salama were obtained from Sokoine University of Agriculture (SUA) and were grown in the first season when twelve lines were selected for a second season evaluation. Six superior lines were then evaluated under farmers' fields in Pemba and Unguja. The results of yield and yield components showed that Supa BC line ( a back cross of mutant 100 with Supa) was the best line (p=0.05). Many farmers in the tested rice irrigated schemes are now using Supa BC as their new preferred variety even though it has not been released officially. It is therefore recommended that more sites are tried with the variety so that it can be officially released as a new variety and therefore recommended to be used nationwide.(author)

[en] Germinated parboiled rice (GPR) is recognized as a functional food because it is rich in bioactive compounds, especially gamma-aminobutyric acid (GABA).GPR was produced by soaking, incubating, steaming, and then drying using a high-precision hot air dryer. The results indicated that air flow mode and drying temperature had significant effects on the quality of GPR. Drying at higher temperatures and shorter times conserved GABA content. Using through-flow mode decreased drying time and prevented color change. However, a slightly lower percentage of head rice yield was observed.Moreover, using through-flow mode negatively affected the hardness loss after cooking. (Author)

[en] In this work the new process of producing parboiled rice (PB) by combination of microwave and hot air fluidized bed (MWFB) was proposed and investigated. Results showed that the drying time was shorter with smaller bed depth, higher drying temperature and higher microwave power. The initial grain temperature, drying temperature, bed depth and microwave power strongly affected the gelatinization of rice starch. The PB produced by MWFB caused a very small broken kernel (1-2%). The whiteness was decreased with increase in drying time, initial grain temperature, drying temperature and microwave power. The specific energy consumption was increased with increasing such operating parameters. (Author)

[en] Seeds of the rice variety Krispo-38 were irradiated with 0, 100, 200, 300 and 400 Gray (Gy) and sown in the greenhouse. From each treatment, others containing uninucleate pollen grains were collected and cultured on a N6 agar medium with 5% sucrose concentration and supplemented with mg/l naphthalene acetic acid (NAA), 1 mg/l kinetin and 1 mg/l 2,4 dichlorophenoxyacetic acid (2,4-D). The pollen grains were induced to develop callus. The percentage of others that produced calli varied from 0.8 for the 400-Gy treatment to 3.3% for the control. The calli were transferred to N6 medium with 3% sucrose concentration, supplemented with 0.5 mg/l NAA and 1 mg/l kinetin. The percentage of calli that produced green plants varied from 1.9 for the 300-Gy treatment to 10.5 for the 200 Gy treatment. Plants developed in 2-5 weeks after callus transplant. A total of 101 green plants was obtained

[en] To examine whether the sensitivity of growth and yield of rice (Oryza sativa L.) to ozone (O₃) varies under different nitrogen (N) fertilization conditions, rice cultivar ‘Koshihikari’ was exposed to O₃ under either standard N (SN) fertilization or no N (NN) fertilization. The rice plants were subjected to three gas treatments (charcoal-filtered air (CF) and O₃ at 1.0 (1.0×O₃) and 1.5 (1.5×O₃) times the ambient concentration) in combination with two conditions of N fertilization. At five time points throughout the growth period, plant samples were collected to measure the leaf area and dry mass of each plant organ. At the final harvest, yield, yield components, and harvest index were measured. There was a significant interactive effect of O₃ and N on leaf, stem, root, and whole-plant dry mass at the final harvest. The dry mass of each plant organ and the whole-plant dry mass of rice plants grown in 1.5×O₃ were significantly lower than those in the plants grown in CF and 1.0×O₃ under SN, whereas there were no significant differences in the dry mass among the three gas treatments under NN. Brown rice yield was significantly reduced by the exposure to O₃ under SN, but not under NN. Relative yield loss rate based on the AOT40 (accumulated exposure over a threshold of 40 nmol mol⁻¹) was pronounced under SN, whereas relative yield was almost unchanged at different AOT40 levels under NN. We concluded that the sensitivity of growth and yield of rice to O₃ is dependent on N levels in the soil; the exposure to ambient levels of O₃ has a negative effect on rice under SN, but not under NN.

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No abstract available