Taichung Native 1 Research Articles

Relative resistance of paddy varieties to Sitotroga cerealella (Lepidoptera: Gelechiidae)

Relative resistance of paddy varieties to the Angoumois grain moth, Sitotroga cerealella was investigated in the laboratory at a temperature of 28 ± 1.0°C and relative humidity of 65 ± 1.5%. The study was carried out on Indian Agricultural Research Institute (IARI), New Delhi, India varieties and a Taiwan variety. The larvae of S. cerealella were allowed to feed and developed inside the grain while adults did not feed. Results showed that the performance of S. cerealella was least in T (N)-1 (Taichung Native-1), with the longest developmental time (26.3 days) and egg to adult survival of 38% making the variety the most resistant. The performance was best in Pusa 44 with the shortest developmental time (23.0 days) and egg to adult survival of 68.7% making the variety the least resistant. The heaviest females and males with 4.04 g and 2.38 g, respectively, were reared on Pusa sugandh 3, which are large seeds. Moths reared on T (N)-1 had the lowest weights for males and females. Unmated females lived longer than their mated counterparts while females generally lived longer than males. Fecundity was highest (164.2 eggs/female) in Pusa 44 and lowest (108.1 eggs/female) in T (N)-1. Hatchability ranged from 81.2% in T (N)-1 to 96.2% in Pusa 834. Generally, grain characters tested in this study influenced moth herbivore performance but the influence was not significant except for grain width which appeared to be the most important trait. With advances in biotechnology, it is possible to transfer desirable characters to other varieties to improve their resistance to S. cerealella and other stored products insects. However, care must be taken since this could change the grains susceptibility to some pests affecting pest-host relationships.

Suppression of Two Tungro Viruses in Rice by Separable Traits Originating from Cultivar Utri Merah

Rice tungro disease (RTD) is caused by Rice tungro spherical virus (RTSV) and Rice tungro bacilliform virus (RTBV) transmitted by green leafhoppers. Rice cv. Utri Merah is highly resistant to RTD. To define the RTD resistance of Utri Merah, near-isogenic lines (NIL, BC(5) or BC(6)) developed from Utri Merah and susceptible cv. Taichung Native 1 (TN1) were evaluated for reactions to RTSV and RTBV. TW16 is an NIL (BC(5)) resistant to RTD. RTBV was able to infect both TN1 and TW16 but the levels of RTBV were usually significantly lower in TW16 than in TN1. Infection of RTSV was confirmed in TN1 by a serological test but not in TW16. However, the global gene-expression pattern in an RTSV-resistant NIL (BC(6)), TW16-69, inoculated with RTSV indicated that RTSV can also infect the resistant NIL. Infection of RTSV in TW16 was later confirmed by reverse-transcription polymerase chain reaction but the level of RTSV was considerably lower in TW16 than in TN1. Examination for virus accumulation in another NIL (BC(6)), TW16-1029, indicated that all plants of TW16-1029 were resistant to RTSV, whereas the resistance to RTBV and symptom severity were segregating among the individual plants of TW16-1029. Collectively, these results suggest that RTD resistance of Utri Merah involves suppression of interacting RTSV and RTBV but the suppression trait for RTSV and for RTBV is inherited separately.

Abscisic acid-induced hydrogen peroxide is required for anthocyanin accumulation in leaves of rice seedlings

The role of hydrogen peroxide (H(2)O(2)) in abscisic acid (ABA)-induced anthocyanin accumulation in detached and intact leaves of rice seedlings was investigated. Treatment with ABA resulted in an accumulation of anthocyanins in detached rice leaves. Dimethylthiourea, a chemical trap for H(2)O(2), was observed to be effective in inhibiting ABA-induced accumulation of anthocyanins. Inhibitors of NADPH oxidase (diphenyleneiodonium chloride and imidazole), phosphatidylinositol 3-kinase (wortmannin and LY 294002), and a donor of nitric oxide (N-tert-butyl-alpha-phenylnitrone), which have previously been shown to prevent ABA-induced H(2)O(2) accumulation in detached rice leaves, inhibited ABA-induced anthocyanin increase. Exogenous application of H(2)O(2), however, was found to increase the anthocyanin content of detached rice leaves. In terms of H(2)O(2) accumulation, intact (attached) leaves of rice seedlings of cultivar Taichung Native 1 (TN1) are ABA sensitive and those of cultivar Tainung 67 (TNG67) are ABA insensitive. Upon treatment with ABA, H(2)O(2) and anthocyanins accumulated in leaves of TN1 seedlings but not in leaves of TNG67. Our results, obtained from detached and intact leaves of rice seedlings, suggest that H(2)O(2) is involved in ABA-induced anthocyanin accumulation in this species.

Toxicity in leaves of rice exposed to cadmium is due to hydrogen peroxide accumulation

The production of H2O2 in detached rice leaves of Taichung Native 1 (TN1) caused by CdCl2 was investigated. CdCl2 treatment resulted in H2O2 production in detached rice leaves. Diphenyleneiodonium chloride (DPI) and imidazole (IMD), inhibitors of NADPH oxidase (NOX), prevented CdCl2-induced H2O2 production, suggesting that NOX is a H2O2-genearating enzyme in CdCl2-treated detached rice leaves. Phosphatidylinositol 3-kinase inhibitors wortmanin (WM) or LY294002 (LY) inhibited CdCl2-inducted H2O2 production in detached rice leaves. Exogenous H2O2 reversed the inhibitory effect of WM or LY, suggesting that phosphatidylinositol 3-phosphate is required for Cd-induced H2O2 production in detached rice leaves. Nitric oxide donor sodium nitroprusside (SNP) was also effective in reducing CdCl2-inducing accumulation of H2O2 in detached rice leaves. Cd toxicity was judged by the decrease in chlorophyll content. The results indicated that DPI, IMD, WM, LY, and SNP were able to reduce Cd-induced toxicity of detached rice leaves. Twelve-day-old TN1 and Tainung 67 (TNG67) rice seedlings were treated with or without CdCl2. In terms of Cd toxicity (leaf chlorosis), it was observed that rice seedlings of cultivar TN1 are Cd-sensitive and those of cultivar TNG67 are Cd-tolerant. On treatment with CdCl2, H2O2 accumulated in the leaves of TN1 seedlings but not in the leaves of TNG67. Prior exposure of TN1 seedlings to 45oC for 3 h resulted in a reduction of H2O2 accumulation, as well as Cd tolerance of TN1 seedlings treated with CdCl2. The results strongly suggest that Cd toxicity of detached leaves and leaves attached to rice seedlings are due to H2O2 accumulation.

A RAPD marker identified a susceptible specific locus for gall midge resistance gene in rice cultivar ARC5984

Gall Midge ( Orseolia oryzae) is one of the serious insect pests of rice in Asia and South East Asia. In India, gall midge has been a particular problem because of the presence of five different biotypes in different geological regions. The annual yield losses due to gall midge have estimated to be in a range of 28–35%. The present study covers phenotyping of recombinant inbred lines (RILs) for gall midge resistance/susceptibility, bulked segregant analysis (BSA) to identify putative marker(s) and individual analysis to confirm linkage between putative marker(s) and gene-controlling gall midge resistance/susceptibility. Phenotyping of 120 RILs-F 9 derived from a cross between ARC5984, Resistant parent and Taichung Native1 (TN1), susceptible parent were screened against gall midge biotype 2. A total of 58 lines showed resistance, 56 lines were susceptible while only 6 showed segregation. Genomic DNA of 30 homozygous RILs (15 homozygous resistant and 15 homozygous susceptible) were taken for BSA with 33 random oligonucleotide primers by RAPD marker analysis and successfully amplified a total of 256 loci. Out of which only one primer i.e. OPQ05 has shown polymorphism in 1150 bp locus in susceptible parent and susceptible bulk. The OPQ05 1150 used for co-segregation analysis for those 30 RILs individually out of which 9 were recombinant. The marker OPQ05 1150 was found to be linked to the susceptible specific gene at the distance of 30 cM.

Multiple isoforms of UDP‐glucose pyrophosphorylase in rice

Uridine diphosphate (UDP)‐glucose pyrophosphorylases (UGPases, EC 2.7.7.9) are key enzymes in plant carbohydrate metabolism and cell‐wall biosynthesis, catalyzing the reversible production of glucose‐1‐phosphate and uridine triphosphate from UDP‐glucose and pyrophosphate. In the study presented here, two‐dimensional gel electrophoresis followed by peptide sequencing analysis using nanospray electrospray ionization tandem mass spectrometry showed that rice (Oryza sativa L.) UGPase undergoes N‐terminal acetylation, which may be a conserved modification of plant UGPases. We also obtained indications, using two‐dimensional gel electrophoresis in combination with western blot analysis, that multiple isoforms of UGPase are present in rice in vivo and are regulated tissue‐specifically. The rice genome contains two homologous UGPase genes, OsUgp1 and OsUgp2. We present evidence that both OsUgp1 and OsUgp2 are ubiquitously expressed throughout rice development, and that OsUgp1 is expressed at much higher levels than OsUgp2. In accordance with the gene expression patterns, the UGPase isoform derived from the OsUgp1 gene predominated in various rice tissues and exhibited qualitative variations (position shifts and presence/absence) between rice varieties B5 and Taichung native 1 (TN1). Our results demonstrate that these qualitative variations are attributable to a single amino acid substitution of Asp‐462 in B5 by His in TN1, corresponding to the allelic difference in the OsUgp1 gene between B5 and TN1.

The participation of hydrogen peroxide in methyl jasmonate-induced NH 4+ accumulation in rice leaves

Ammonium is a central intermediate in the nitrogen metabolism of plants. We have previously shown that methyl jasmonate (MJ) not only increases the content of H(2)O(2), but also causes NH(4)(+) accumulation in rice leaves. More recently, H(2)O(2) is thought to constitute a general signal molecule participating in the recognition of and the response to stress factors. In this study, we examined the role of H(2)O(2) as a link between MJ and subsequent NH(4)(+) accumulation in detached rice leaves. MJ treatment resulted in an accumulation of NH(4)(+) in detached rice leaves, which was preceded by a decrease in the activity of glutamine synthetase (GS) and an increase in the specific activities of protease and phenylalanine ammonia-lyase (PAL). GS, PAL, and protease appear to be the enzymes responsible for the accumulation of NH(4)(+) in MJ-treated detached rice leaves. Dimethylthiourea (DMTU), a chemical trap for H(2)O(2), was observed to be effective in inhibiting MJ-induced NH(4)(+) accumulation in detached rice leaves. Scavengers of free radicals (sodium benzoate, SB, and glutathione, GSH), nitric oxide donor (N-tert-butyl-alpha-phenylnitrone, PBN), the inhibitors of NADPH oxidase (diphenyleneiodonium chloride, DPI, and imidazole, IMD), and inhibitors of phosphatidylinositol 3-kinase (wortmannin, WM, and LY 294002, LY), which have previously been shown to prevent MJ-induced H(2)O(2) production in detached rice leaves, inhibited MJ-induced NH(4)(+) accumulation. Similarly, changes in enzymes responsible for NH(4)(+) accumulation induced by MJ were observed to be inhibited by DMTU, SB, GSH, PBN DPI, IMD, WM, or LY. Seedlings of rice cultivar Taichung Native 1 (TN1) are jasmonic acid (JA)-sensitive and those of cultivar Tainung 67 (TNG67) are JA-insensitive. On treatment with JA, H(2)O(2) accumulated in the leaves of TN1 seedlings but not in the leaves of TNG67. Ethylene action inhibitor, silver thiosulfate, was observed to inhibit MJ- and abscisic acid-induced accumulation of NH(4)(+) and changes in enzymes responsible for NH(4)(+) accumulation in detached rice leaves, suggesting that the action of MJ and ABA is ethylene dependent.

Hydrogen peroxide is involved in methyl jasmonate‐induced senescence of rice leaves

The role of H2O2 in the senescence of detached rice leaves induced by methyl jasmonate (MJ) was investigated. MJ treatment resulted in H2O2 production in detached rice leaves, which was prior to the occurrence of leaf senescence. Dimethylthiourea, a chemical trap of H2O2, was observed to be effective in inhibiting MJ‐induced senescence and MJ‐increased malondialdehyde (MDA) content in detached rice leaves. Diphenyleneiodonium chloride (DPI) and imidazole (IMD), inhibitors of NADPH oxidase, prevented MJ‐induced H2O2 production, suggesting that NADPH oxidase is a H2O2‐generating enzyme in MJ‐treated detached rice leaves. DPI and IMD also inhibited MJ‐promoted senescence and MJ‐increased MDA content in detached rice leaves. Phosphatidylinositol 3‐kinase inhibitors wortmannin (WM) or LY 294002 (LY) inhibited MJ‐induced H2O2 production and senescence of detached rice leaves. Exogenous H2O2 reversed the inhibitory effect of WM or LY. In terms of leaf senescence, it was observed that rice seedlings of cultivar Taichung Native 1 (TN1) are jasmonic acid (JA)‐sensitive and those of cultivar Tainung 67 (TNG67) are JA‐insensitive. On treatment with JA, H2O2 accumulated in the leaves of TN1 seedlings but not in the leaves of TNG67. Evidence was also provided to show that MJ‐induced H2O2 production in detached rice leaves is abscisic acid (ABA)‐independent. Ethylene action inhibitor, silver thiosulfate, was observed to inhibit MJ‐ and ABA‐induced H2O2 production and senescence of detached rice leaves, suggesting that the action of MJ and ABA is ethylene‐dependent.

A Novel Function of Abscisic Acid in the Regulation of Rice (Oryza sativa L.) Root Growth and Development

Plant roots retain developmental plasticity and respond to environmental stresses or exogenous plant growth regulators by undergoing profound morphological and physiological alteration. In this study, we investigated the effects of exogenous ABA on root growth and development in Taichung native 1 (TN1) rice. Exogenous application of 10 microM ABA leads to swelling, root hair formation and initiation of lateral root primodia in the tips of young, seminal rice roots. Cortex cells increased in size and were irregularly shaped. ABA treatment significantly increased 2, 3, 5-triphenyl tetrazolium chloride (TTC) reductase ability in the root tips and the exudation rate of xylem sap. In addition, the K(+) ion content in xylem sap increased nearly 2-fold, but not that of Ca(2+) or Mg(2+). Analysis of proteins expressed in the root tips identified several ABA-induced or -repressed proteins, including actin depolymerization factor (ADF), late embryo abundant protein (LEA), putative steroid membrane-binding protein, ferredoxin thionine reductase and calcium-binding protein. The effects of ABA on root morphogenesis change were Ca(2+) dependent and required the participation of calmodulin and de novo protein synthesis. A model is presented that illustrates how ABA acts through a potential cellular and signal transduction mechanism to induce morphological and physiological changes in rice roots.

Evaluation of rice allelopathy in hydroponics

SummaryThe inhibitory activity of water extracts from the shoots and roots of three rice cultivars, Taichung native 1 (TN1) and IAC165 (both allelopathic rice) and AUS196 (non‐allelopathic rice), grown in hydroponics was evaluated. The release of germination inhibitors by allelopathic rice plants into hydroponic solution was also determined with freshly collected solution and XAD‐4 resin desorbate. The degree of the inhibition was quantified in terms of root growth in Echinochloa colona, Echinochloa crus‐galli, Echinochloa crus‐galli var. oryzicola, Triantema portulacastrum and Lactuca sativa. The allelopathic activity of rice was species specific, and depended on source and concentration. Root length of all test species was inhibited by the different concentrations of shoot extract of allelopathic and non‐allelopathic rice. However, of the three cultivars, TN1 showed higher inhibition than IAC165 and AUS196 in all test species. Water extracts of shoots and roots significantly inhibited root growth in E. crus‐galli but the shoot extract gave a greater inhibitory effect on E. crus‐galli than the root extract. Root exudate of TN1 inhibited root elongation of E. crus‐galli from 2 weeks after transplanting (WAT) and the inhibition continued for 4 WAT. The results confirmed the previous finding of a laboratory bioassay that the TN1 had allelopathic activity and produced allelochemicals that inhibit growth of some weed species.

Changes in level of virus accumulation and incidence of infection are critical in the characterization of Rice tungro bacilliform virus (RTBV) resistance in rice.

Analysis by enzyme-linked immunosorbent assay showed that Rice tungro bacilliform virus (RTBV) accumulated in a cyclic pattern from early to late stages of infection in tungro-susceptible variety, Taichung Native 1 (TN1), and resistant variety, Balimau Putih, singly infected with RTBV or co-infected with RTBV + Rice tungro spherical virus (RTSV). These changes in virus accumulation resulted in differences in RTBV levels and incidence of infection. The virus levels were expressed relative to those of the susceptible variety and the incidence of infection was assessed at different weeks after inoculation. At a particular time point, RTBV levels in TN1 or Balimau Putih singly infected with RTBV were not significantly different from the virus level in plants co-infected with RTBV + RTSV. The relative RTBV levels in Balimau Putih either singly infected with RTBV or co-infected with RTBV + RTSV were significantly lower than those in TN1. The incidence of RTBV infection varied at different times in Balimau Putih but not in TN1, and to determine the actual infection, the number of plants that became infected at least once anytime during the 4 wk observation period was considered. Considering the changes in RTBV accumulation, new parameters for analyzing RTBV resistance were established. Based on these parameters, Balimau Putih was characterized having resistance to virus accumulation although the actual incidence of infection was >75%.

Biological Variants of Rice Tungro Viruses in the Philippines

Tungro is a composite disease of rice induced by dual infection with rice tungro bacilliform virus (RTBV) and rice tungro spherical virus (RTSV). Four strains of RTBV, designated L, G1, G2, and Ic, were isolated on the basis of their characteristic symptoms on rice cultivars FK135 and Taichung Native 1 (TN1). On FK135, strain Ic caused severe stunting, reduced tillering, narrow leaves, and distinct interveinal chlorosis (striping and/or mottling) on the leaf blades, while G1 and G2 caused only mild stunting and foliage was a normal green. On TN1, G1 and Ic caused mild stunting but no discoloration of the foliage; G2 caused severe stunting and yellow to orange discoloration similar to that caused by the type strain L. Thus, G1 and Ic can be readily differentiated by the reaction of cultivar FK135, while G1 and G2 can be differentiated by that of TN1. Cross-inoculation experiments showed that strains G1 and Ic were cross protective. In other studies, a virulent strain of RTSV (Vt6) was isolated from tungro-infected plants collected from Mindanao, Philippines. The cultivar TKM6, like many other cultivars resistant to type strain A, was susceptible to strain Vt6. TKM6 plants infected with both RTBV and strain Vt6 showed severe stunting and discoloration

Behavioral responses of the whitebacked planthopperSogatella furcifera (Homoptera: Delphacidae) on rice plants whose odors have been masked

In a two-choice test, moreS. furcifera females settled more often on exposed plants than on parafilm-masked ones, regardless of the susceptibility of rice varieties. This indicates that rice volatiles play an important role in the insect's short-range orientation to its host. The fact that more insects settled on exposed resistant Rathu Heenati (RHT) than to masked susceptible Taichung Native 1 (TN1) suggests that there must be certain common volatiles released by both varieties. Few females landed on masked plants of either RHT or TN1. This implies that the insect could not recognize at a distance that a plant was resistant or susceptible without olfactory stimuli.S. furcifera excreted less honeydew on masked plants than on exposed ones for both varieties and more on masked TN1 than on exposed RHT. The electronic monitoring of feeding behavior demonstrates that the insect made more frequent probes and had shorter phloem ingestion durations on exposed RHT than on exposed TN1 and on masked RHT than on masked TN1. Moreover, the insect had longer phloem ingestion durations on masked TN1 than on exposed RHT. These results suggest that volatile chemicals given off by resistant RHT plants have a negative effect on feeding.

Resistance Gene of Rice Cultivar, Taichung Native 1 to Philippine Races of Bacterial Blight Pathogens

In the inoculation tests on rice cultivars using Philippine races of bacterial blight (BB) caused by Xanthomonas campestris pv oryzae, we found that Taichung Native 1 (TN1) was resistant only to race 5 (PXO112) and susceptible to races 1, 2, 3, 4, and 6. This kind of reaction pattern to BB pathogens has not been found in any other rice cultivar resistant to BB in Japan and at the International Rice Research Institute in the Philippines. Therefore, it was suggested that TN1 has a new gene for resistance to BB. The mode of inheritance of resistance in TN1 to race 5 was studied. The analysis of the F 1 plants, the F 2 populations, and the backcross progeny from the crosses between TN1 and susceptible cultivars revealed that the resistance of TN1 was controlled by a single dominant gene. Thus this new resistance gene was designated as Xa-14.

Iron, Silica, and Aluminum Stresses and Varietal Resistance in Rice: Effects on Whitebacked Planthopper

Certain physicochemical stresses affect the susceptibility of plants to insects. The objective of this study was to determine the effects of different levels of Fe, Si, and Al on the establishment of Sogatella furcifera (Horváth) on resistant IR2035‐117‐3 (IR2035) and susceptible Taichung Native 1 (TN1) rice (Oryza saliva L.) cultivars under glasshouse conditions in natural daylight of 12 h, 29/21 °C (day/night), and minimum 70% relative humidity. Insect population increased on rice plants grown in culture solution containing low (0.02 mg L−1) or high (40 mg L−1) Fe than on plants grown in standard culture solution (Fe at 2 mg L−1). Increased Si (400 mg L−1) reduced intake and assimilation of food, growth, adult longevity, fecundity, and population increase by S. furcifera on susceptible TN1 plants. Addition of Al to culture solution at 90 mg L−1 adversely affected insect biology. Regardless of the mineral stress, the difference between the resistance of IR2035 and susceptibility of TN1 cultivars remained distinct. Plants affected with low or high Fe stress had apparently less allelochemicals than did control (unstressed) plants. Mortality of S. furcifera first instars was greater on TN1 plants painted with steam‐distillate extract of Fe‐stressed or control IR2035 plants than on TN1 plants painted with TN1 extract or acetone. Iron and Al stresses significantly decreased the growth and biomass of rice plants. Resistance of rice plants to S. furcifera can be improved by application of Fe at optimum (2 mg L−1) and Si at high (400 mg L−1) rates.

Tolerance of the Rice Variety Triveni to the Brown Planthopper, Nilaparvata lugens1

Seedling screening and survival and population growth studies on 30-day-old plants indicated similar degrees of susceptibility on Taichung Native 1 (TN1) and Triveni rice to Nilaparvata lugens (Homoptera: Dilphacidae). However, studies in the screenhouse and field indicated that at both the vegetative and mature stage, Triveni possesses tolerance to insect damage, expressed as the ability to survive and produce a higher percentage of productive tillers than TN1 at similar N. lugens populations. Yield reduction caused by feeding of N. lugens was ca. 40% when infested with 400 N. lugens on 35, 50, or 75 day-old plants, whereas it was almost 100% on TN1 at the same ages. Photosynthetic activity of seedling-stage Triveni was less affected than that of TN1 when severely damaged by the feeding of N. lugens .

Selection of Biotype Populations 2 and 3 of Nilaparvata lugens1 by Exposure to Resistant Rice Varieties

The release of an insect pest-resistant variety and subsequent adaptation of the insect species to that variety through the process of biotype selection has occurred on many cultivated crops. The present study was designed to obtain detailed information on some of the processes involved in the selection of biotypes of Nilaparvata lugens (Stal) on two rice varieties with different major genes for resistance. The N. Lugens population selected for the study, which had originally been collected in the field and reared on a susceptible variety for 12 years (ca. 140 generations), initially had a low survival on the resistant rice varieties Mudgo (Bph 1 gene) and ASD7 (bph 2 gene) and high survival on the susceptible variety, Taichung Native 1 (TN1). Monitoring the survival and length of the developmental period for seven generations indicated a progressive increase in the survival and shortening of the nymphal period in each generation on the heretofore resistant varieties until they were similar to those on TN1. The shift in the population to a more virulent biotype was also confirmed by the seedling bulk test. The selected populations reared on Mudgo or ASD7 were not able to kill Mudgo or ASD7, respectively, in the fifth generation but by the eighth generation were able to do so. In addition, adult longevity and fecundity on the resistant varieties increased during the selection process.

Inheritance of Bacterial Blight Resistance in Rice

We studied the inheritance and allelic relationships of the genes for resistance to bacterial blight in three rice breeding lines IR1330-3-2, IR944-102, IR1698-241, and in three cultivars, Pelita I/1, Kele, and Chinsurah Boro II. The study of F1, F2, F3, and reciprocal backcross populations of crosses between resistant parents and the susceptible cultivar Taichung Native 1 (TN-1) revealed that resistance in these rices is under monogenic control. The resistance of IR 1330-3-2 and Pelita I/1 is incompletely dominant, whereas that of Kele and Chinsurah Boro II is recessive. The genes that govern resistance in IR944-102 and IR1698-241 show recessive gene action with the method of inoculation used in this study. Evidence from allele tests with known genes for resistance indicates that Xa4 governs resistance in IR1330-3-2 and Pelita I/1, and xa5 in Kele and Chinsurah Boro II. Rice breeding lines IR944-102 and IR1698-241 have the same gene for resistance which is closely linked to Xa4.

Genetic divergence among rice strains

For screening better types among 10 strains with the help of the D (2) statistic, an experiment was conducted in randomized block design with three replications. 10 plants in each plot were randomly selected and observations were recorded on final plant height, heading duration, effective tillers, number of grains per panicle, yield per plant and 100 grain weight.The observations were analyzed and found to be significant at 1% level.In the study of distance relations the contribution of grain number per panicle to D (2) values was found to be maximum. Again, this technique also helped in grouping the 10 strains into four clusters, viz. A, B, C and D, of which B possessed six strains out of 10; A possessed two and C and D one each.Group A comprised 2 selections from the same cross. Group D was composed of a selection from a cross involving Dular and Taichung Native-1 as parents. Group B possessed Dular, two selections from a cross involving Dular as one of the parents, Dharial and N.C.-1626. The constituents of A are expected to be transgressive segregates.Group A was maximally distantly related with D followed in order by C and B. The distance between B and C was small.Group D was found to be the best of all strains studied, followed by B, C and A.

Yield of a tall and a dwarf indica rice as affected by fertilizer nitrogen, with and without nitrification inhibitors

SUMMARYTwo varieties of irrigated rice N.P. 130 (a tall variety) and Taichung Native-1 (a dwarf variety of indica rice) were compared in 1966 and 1967 when grown with several amounts of sodium nitrate and ammonium sulphate. Comparisons of ammonium sulphate treated with ‘N-Serve’ or with ‘AM’ against untreated ammonium sulphate were made.Applying more than 60–80 kg N/ha did not increase the number of panicles per m with N.P. 130 but lowered the number of spikelets and filled grain percentage. Up to 120 kg N/ha, panicle number and the number of spikelets of Taichung Native-1 increased significantly but the filled grain percentage was not increased; yield of grain responded significantly up to 120 kg N/ha. Taichung Native-1 yielded more grain and less straw than N.P. 130. Increasing the nitrogen applied significantly increased the yield of straw from both varieties.Ammonium sulphate increased panicle number and reduced the percentage of filled grain compared to sodium nitrate but the increase in panicle number was higher with Taichung Native-1 than with N.P. 130; as a result ammonium sulphate consistently increased the grain yield of Taichung Native-1. When the ammonium sulphate was treated with either inhibitor it gave more grain of Taichung Native-1 than untreated fertilizer; treated fertilizer gave more straw of both varieties.