Applied mutagenesis could improve economically important traits in bitter gourd (Momordica charantia L.).

Mutants with unique characters have played a key role in discovery of gene, mapping, functional genomics and breeding in many vegetable crops, but information on bitter gourd is lacking. Induction of mutation by gamma rays (Co60 source) at five different doses (50 Gy, 100 Gy, 150 Gy, 200 Gy and 250 Gy) was studied in four widely divergent bitter gourd genotypes BG-1346501, Meghna-2, Special Boulder and Selection-1 in M1 generation. Reduction in seed germination percentage, vine length and pollen fertility occurred in M1 generation with the increasing doses of mutagens. LD50 dose for BG-1346501, Meghna-2, Special Boulder and Selection-1 corresponded to 290.76 Gy, 206.12 Gy, 212.81 Gy and 213.49 Gy ᵞ radiation, respectively suggested low to medium doses (200-250 Gy) of gamma rays would be helpful in producing useful and exploitable mutants for further breeding. No remarkable effect of ᵞ radiation on fruit physicochemical characters in M1 generation were observed. M2 generation, raised from two widely divergent genotypes, BG-1346501 and Meghna-2, were screened critically and observed no significant reduction in seed germination and pollen viability, however little damage occurred particularly in vine length. There is possibility of isolating segregates in M2 generation with enhanced nutrient contents at low radiation dose. Highest mutation frequency resulted by treating Meghna-2 at 200 Gy and BG-1346501 at 100 Gy. Both genotype and mutagenic doses influenced mutagenic effectiveness. Spectrum of mutation was very low; number of putative mutants isolated from M2 generation was five in Meghna-2 and three in BG-1346501. Among six putative macro mutants isolated from M3 generation, we could identify two putative mutants, namely Meghna-2 with gynoecious sex form and BG-1346501 with high charantin, appreciable ß-carotene and high ascorbic acid contents having ample promise for further utilization in bitter gourd breeding after critical testing in subsequent generations for estimation of genetic gain and trait heritability to confirm the mutant stability.

Revisiting the physical mutagenesis for sugarcane improvement: a stomatal prospective.

This study was conducted to investigate the influence of gamma rays on stomatal parameters and the interaction of these traits with agronomy of the sugarcane crop. Three genotypes of sugarcane (NIA-0819, NIA-98, and BL4) were exposed to four doses of gamma radiation (10, 20, 30, and 40 Gy) and then subjected to field trials. Stomatal length, width, and density were observed using scanning electron microscopy. Moreover, agronomic and sugar-related characteristics of the crop were determined at maturity. The stomatal parameters augmented at two lower doses of gamma radiation (10 and 20 Gy) and declined under higher doses (30 and 40 Gy). The maximum stomatal length was observed in NIA-0819 at 10 Gy (63.71 µm), whereas NIA-98 and BL4 demonstrated highest stomatal length under 20 Gy (54.11 and 57.40 µm, respectively), indicating a role of genetic factors in varietal response. Similar trend was noticed for stomatal width and density as well. The lowermost treatment (10 Gy) of NIA-0819 produced maximum stomatal density (115.31 stomata mm-2 on the abaxial surface). Adaxial stomatal density was significantly lower than the abaxial one. Sugar quality attributes revealed a different tendency. Sucrose contents of BL4 increased gradually from 12.33% at control to 14.54% at 40 Gy. Yield and yield-contributing traits of genotypes indicated a strong positive correlation with the stomatal parameters. The present study suggested that gamma radiations cause variations in stomatal characteristics of sugarcane. These changes further influence the photosynthetic activity and instigate a direct impact on the agronomic performance of the crop.

Quantitative Trait Loci for Light Sensitivity, Body Weight, Body Size, and Morphological Eye Parameters in the Bumblebee, Bombus terrestris.

Bumblebees such as Bombus terrestris are essential pollinators in natural and managed ecosystems. In addition, this species is intensively used in agriculture for its pollination services, for instance in tomato and pepper greenhouses. Here we performed a quantitative trait loci (QTL) analysis on B. terrestris using 136 microsatellite DNA markers to identify genes linked with 20 traits including light sensitivity, body size and mass, and eye and hind leg measures. By composite interval mapping (IM), we found 83 and 34 suggestive QTLs for 19 of the 20 traits at the linkage group wide significance levels of p = 0.05 and 0.01, respectively. Furthermore, we also found five significant QTLs at the genome wide significant level of p = 0.05. Individual QTLs accounted for 7.5-53.3% of the phenotypic variation. For 15 traits, at least one QTL was confirmed with multiple QTL model mapping. Multivariate principal components analysis confirmed 11 univariate suggestive QTLs but revealed three suggestive QTLs not identified by the individual traits. We also identified several candidate genes linked with light sensitivity, in particular the Phosrestin-1-like gene is a primary candidate for its phototransduction function. In conclusion, we believe that the suggestive and significant QTLs, and markers identified here, can be of use in marker-assisted breeding to improve selection towards light sensitive bumblebees, and thus also the pollination service of bumblebees.

QTL for survival to UV-C radiation in Drosophila melanogaster.

PURPOSE: The aim of this study was to investigate tolerance to UV-C (ultraviolet C, 280-100 nm) radiation in Drosophila melanogaster, implementing a quantitative trait locus (QTL) mapping approach. This is of interest to test for genetic variation in survival to UV (ultraviolet) radiation. MATERIALS AND METHODS: We performed a QTL scan in D. melanogaster recombinant inbred lines (RIL) constructed from parental stocks derived from a crossing between northern and southern hemisphere populations that segregated substantial genetic variation in thermal resistance in a previous study. Here, two experimental treatments were implemented: Continuous and cyclic UV-C radiation. RESULTS: Significant QTL were detected on all three major chromosomes. Among these, multiple trait composite interval mapping revealed a significant QTL in the pericentromeric region of chromosome 2, a genome region consistently implicated in thermotolerance in previous studies. CONCLUSIONS: This study shows substantial genetic variation for UV-C radiation resistance in D. melanogaster, with QTL for survival to UV-C radiation generally overlapping with major thermotolerance QTL. The genetic architecture of UV-C radiation resistance appears to be more complex in continuously irradiated individuals.

[Genetic consequences of irradiation in a scots pine Pinus sylvestris L. population].

The genetic consequences of irradiation were studied in a Scots pine population from a region contaminated as a result of the Chernobyl meltdown. Mutations of isozyme loci were not detected in seeds collected from trees of the first post-meltdown generation in 2004. The frequency of cells with chromosome aberrations in the root meristem of seedlings grown from the seeds did not differ from the control level. A deviation from the expected ratio 1:1 was observed for some isozyme alleles in endosperms of seeds obtained from heterozygous trees.

Upregulation of c-myc gene accompanied by PU.1 deficiency in radiation-induced acute myeloid leukemia in mice.

OBJECTIVE: High-dose radiation exposure induces acute myeloid leukemia (AML) in C3H mice, most of which have a frequent hemizygous deletion around the D2Mit15 marker on chromosome 2. This region includes PU.1, a critical candidate gene for initiation of leukemogenesis. To identify novel cooperative genes with PU.1, relevant to radiation-induced leukemogenesis, we analyzed the copy number alterations of tumor-related gene loci by array CGH, and their expressions in primary and transplanted AMLs. MATERIALS AND METHODS: For the induction of AMLs, C3H/He Nrs mice were exposed to 3 Gy of x-rays or gamma-rays. The genomic alterations of 35 primary AMLs and 34 transplanted AMLs obtained from the recipient mice transplanted the primary AMLs were analyzed by array CGH. According to the genomic alterations and mutations of the 235th arginine of PU.1 allele, we classified the radiogenic AMLs into three types such as Chr2(del) PU.1(del/R235-) AML, Chr2(del) PU.1(del/R235+) AML and Chr2(intact) PU.1(R235+/R235+) AML, to compare the expression levels of 8 tumor-related genes quantitatively by real-time polymerase chain reaction and cell-surface antigen expression. Results. In addition to well-known loss of PU.1 with hemizygous deletion of chromosome 2, novel genomic alterations such as partial gain of chromosome 6 were recurrently detected in AMLs. In this study, we found similarity between cell-surface antigen expressions of bone marrows and those of spleens in AML mice and significantly higher expressions of c-myc and PU.1 expression, especially in the PU.1-deficient (Chr2(del) PU.1(del/R235-)) AML and Chr2(del) PU.1(del/R235+) compared to Chr2(intact) PU.1(R235+/R235+) AMLs. CONCLUSION: The new finding on upregulation of c-myc and PU.1 in both and hemizygous PU.1-deficient AMLs and different genomic alterations detected by array CGH suggests that the molecular mechanism for development of radiation-induced AML should be different among three types of AML.

Analysis of natural allelic variation controlling Arabidopsis thaliana seed germinability in response to cold and dark: identification of three major quantitative trait loci.

Light and temperature are key external factors in the control of Arabidopsis thaliana seed germination and dormancy mechanisms. Perception and response to these stimuli have to ensure that seedling emergence and growth occur at the most advantageous time for correct establishment. Analysis of over 300 Arabidopsis accessions identified 14, from 12 different geographical locations, that were able to germinate to greater than 20% at 6 degrees C in the dark. This natural variation was exploited to identify genetic loci responsible for cold-tolerant, dark germination. A quantitative trait loci approach was used on recombinant inbred line progeny of a cross between Bay-0 and Shahdara. Six distinct quantitative trait loci were identified, three of which were major loci, each responsible for 17-25% of the phenotypic variability in this trait. Parental phenotypes indicated that the majority of the cold-tolerant, dark-germination characteristics are related to light responses. Validation of the three major loci using heterogeneous inbred families confirmed the feasibility of fine mapping and cloning the genes at the quantitative trait loci responsible for cold-tolerant, dark germination.