Inheritance of resistance to bacterial blight in 21 cultivars of rice

Genetic analysis for resistance to bacterial blight (Xanthomonas oryzae pv. oryzae) of 21 rice (Oryza sativa L.) cultivars was carried out. These cultivars were divided into two groups based on their reactions to Philippine races of bacterial blight. Cultivars of group 1 were resistant to race 1 and those of group 2 were susceptible to race 1 but resistant to race 2. All the cultivars were crossed with TN1, which is susceptible to all the Philippine races of X. oryzae pv. oryzae. F1 and F2 populations of hybrids of group 1 cultivars were evaluated using race 1 and F1 and F2 populations of hybrids of group 2 cultivars were evaluated using race 2. All the cultivars showed monogenic inheritance of resistance. Allelic relationships of the genes were investigated by crossing these cultivars with different testers having single genes for resistance. Three cultivars have Xa4, another three have xa5, one has xa8, two have Xa3, eight have Xa10, and one has Xa4 as well as Xa10. Three cultivars have new, as yet undescribed, genes. Nep Bha Bong To has a new recessive gene for moderate resistance to races 1, 2, and 3 and resistance to race 5. This gene is designated xa26(t). Arai Raj has a dominant gene for resistance to race 2 which segregates independently of Xa10. This gene is designated as Xa27(t). Lota Sail has a recessive gene for resistance to race 2 which segregates independently of Xa10. This gene is designated as xa28(t)

Farmers' management of rice varietal diversity in the mid-hills of Nepal: implications for on-farm conservation and crop improvement

Season-long monitoring of on-farm rice (Oryza sativa, L.) plots in Nepal explored farmers' decision-making process on the deployment of varieties to agroecosystems, application of production inputs to varieties, agronomic practices and relationship between economic return and area planted per variety. Farmers deploy varieties [landraces (LRs) and modern varieties (MVs)] to agroecosystems based on their understanding of characteristics of varieties and agroecosystems, and the interaction between them. In marginal growing conditions, LRs can compete with MVs. Within an agroecosystem, economic return and area planted to varieties have positive relationship, but this is not so between agroecosystems. LRs are very diverse on agronomic and economic traits; therefore, they cannot be rejected a priori as inferior materials without proper evaluation. LRs have to be evaluated for useful traits and utilized in breeding programmes to generate farmer-preferred materials for marginal environments and for their conservation on-farm

Primary trisomic of rice: orgin, morphology, cytology and use in linkage mapping

Twelve primary trisomics of Oryza sativa L. were isolated from the progenies of spontaneous triploids and were transferred by backcrossing to the genetic background of IR36, a widely grown high yielding rice variety. Eleven trisomics can be identified morphologically from one another and from diploids. However, triplo 11 is difficult to distinguish from diploid sibs. -The extra chromosome of each trisomic was identified cytologically at pachytene stage of meiosis, and the chromosomes were numbered according to their length at this stage. The major distinguishing features of each pachytene chromosome were redescribed. -The female transmission rates varied from 15.5% for triplo 1, the longest chromosome, to 43.9% for triplo 12, the shortest chromosome. Seven of the 12 primary trisomics transmitted the extra chromosome through the male. The low level of chromosomal imbalance tolerated by rice and other evidence are interpreted to indicate that this species is a basic diploid. -Genetic segregation for 22 marker genes in the trisomic progenies was studied. Of a possible 264 combinations, involving 22 genes and 12 trisomics, 120 were examined. Marker genes for each of the 12 chromosomes were identified. The results helped establish associations between linkage groups and cytologically identifiable chromosomes of rice for the first time. Relationships between various systems of numbering chromosomes, trisomics, linkage groups and marker genes are described, and a revised linkage map of rice is presented

Phylogenetic relationships among Oryza species revealed by AFLP markers

The genus Oryza to which cultivated rice belongs has 22 wild species. Seventy-seven accessions of 23 Oryza species, five related genera, and three outgroup taxa were fingerprinted using amplified fragment length polymorphism (AFLP). A total of 1191 polymorphic markers were obtained using five AFLP primer combinations. AFLP data were analyzed to study species relationships using different clustering algorithms, and the resulting phenograms were tested for stability and robustness. The findings suggest a common ancestry to the genus Oryza. Moreover, the results demonstrate that: (1) evolution in Oryza has followed a polyphyletic path wherein multiple lineages underwent independent divergence after separation early in the evolution from a common ancestor/pool of related taxa; (2) newly assigned genomes, GG for O. meyeriana and HHJJ for O. ridleyi complexes, are among the most diverged in the genus; (3) CCDD tetraploids have a relatively ancient origin among the Officinalis complex; (4) O. malampuzhaensis, O. indandamanica, O. alta, and O. grandiglumis are diverged enough to deserve species status; (5) O. officinalis and O. eichingeri (CC) are putative progenitors of O. minuta/O. malampuzhaensis and tetraploid O. punctata, respectively, (6) O. brachyantha is most diverged species in the genus. AFLP is reliable molecular technique and provides one of the most informative approaches to ascertain genetic relationships in Oryza, which may also be true for other related species/organisms

Heterosis in traits related to low temperature tolerance in rice

The manifestation of heterosis for 17 traits related to low-temperature tolerance and productivity in rice in 102 F1 hybrids (42 for germination coefficient) at 5 growth stages is reported. Average heterosis of 163.0% for cold tolerance index at final survival, 61.24% for germination coefficient, 50.62% and 39.92% for cold tolerance indices based on revival 10 days and 5 days after treatment at the seedling stage, and 69.32% and 54.59% for cold tolerance indices at 22 and 15 days survival, at the early seedling stage was recorded over the mid-parent. Heterosis for cold hardiness was greater for the japonica/indica group of hybrids at the early seedling stage and for the indica/indica group at the seedling stage. Number of fertile spikelets and fertility showed negative average heterosis at booting and flowering stages of low-temperature treatment. They hybrids were intermediate in blooming and showed no advantage for seedling height on the 15th and 22nd days of cold stress. Intercharacter correlations among hybrids indicated that the parental averages for tolerance indices at revival 10 days and 5 days after treatment were most highly associated with percent fertility at both booting and flowering stages of cold stren in low temperature tolerance evaluation studies. Correlations between the mid-parent mean and hybrid performance were highly significant for 13 of the 17 traits. The coefficients for cold tolerance indices at 15 days survival, revival 10 days and 5 days after treatment, at 22 days survival and at final survival, and flowering duration were of sufficient magnitude to indicate that mid-parent values would be highly effective indicators of hybrid performance

Drosophila immunity: two paths to NF-kappaB

Recent studies of Drosophila immune responses have defined the immune deficiency (IMD) signaling pathway that mediates defense against Gram-negative bacterial infection. Like the Toll pathway, the IMD pathway regulates antimicrobial peptide gene expression via a Rel/nuclear factor (NF)-kappaB-like transcription factor. However, the two pathways do not appear to share any intermediate components. Maintaining distinct immune response pathways might be one mechanism by which flies mount adapted immune responses

Genetics of resistance of rice cultivar ARC10550 to Bangladesh brown planthopper teletype

Resistance to brown planthopper in rice cultivar ARC 10550 was found to be governed by a single recessive gene which was designated bph 5. It conveys resistance to brown planthopper populations in South Asia but not to the populations in East and Southeast Asia. This gene segregated independently of four other known genes for brown planthopper resistance. It should be possible to combine this gene with any of the other four genes to develop rice cultivars with a broad spectrum of resistance

RAPD and RFLP mapping of the bacterial blight resistance gene xa-13 in rice

Bacterial blight (BB) caused by Xanthomonas oryzae pv oryzae (Xoo) is one of the most serious diseases of rice. The recessive gene xa-13 confers resistance to Philippine race 6 of Xoo. To tag xa-13 with molecular markers, RAPD analysis was conducted with the combined use of near-isogenic lines and bulked segregant analysis. From the survey of 260 arbitrary 10-nucleotide primers, one primer (OPAC05) was detected to amplify specifically a 0.9-kb band from the DNA of susceptible plants. The distance between the RAPD marker OPAC05-900 and xa-13 was estimated to be 5.3 cM. The RAPD marker was then mapped on chromosome 8 using a mapping population of doubled haploid lines derived from the cross of IR64/Azucena. The linkage between RFLP markers and the RAPD marker was analyzed using an F2 population of 135 plants derived from a cross between a near-isogenic line for xa-13, IR66699-5-5-4-2, and IR24. No recombinants were found between RZ28 and CDO116 and their distance from xa-13 was estimated to be 4.8 cM. RG136 was located at 3.7 cM on the other side of xa-13. The mapping of xa-13 with closely linked DNA markers provides the basis for marker-aided selection for rice improvement

Issues in the Differential Diagnosis of Uterine Low-grade Endometrioid Carcinoma, Including Mixed Endometrial Carcinomas: Recommendations from the International Society of Gynecological Pathologists

This article provides practical recommendations developed from the International Society of Gynecological Pathologists Endometrial Carcinoma Project to address 4 issues that may arise in the diagnosis of uterine corpus low-grade endometrioid carcinoma: (1) The distinction between atypical hyperplasia and low-grade endometrioid carcinoma. (2) The distinction between low-grade endometrioid carcinoma and serous carcinoma. (3) The distinction between corded and hyalinized or spindle cell variants of low-grade endometrioid carcinoma and carcinosarcoma. (4) The diagnostic criteria for mixed endometrial carcinomas, a rare entity that should be diagnosed only after exclusion of a spectrum of tumors including morphologic variants of endometrioid carcinoma, dedifferentiated endometrial carcinoma, carcinosarcoma, and endometrial carcinomas with ambiguous morphology