Potato (Solanum tuberosum L.) is the world’s number one non-cereal food crop and ranks fourth among most important crops grown worldwide in terms of acreage, yield and value. In order to maintain greater protection against environmental stresses, we developed transgenic potato overexpressing Arabidopsis thaliana glutathione reductase gene (AtGR1). The transgenic potato maintained up to 6.5 folds higher GR activity, 5.8 folds glutathione (GSH) contents and up to 2.2 folds higher glutathione S-transferase activity compared to non transformed plants (NT). Interestingly, while the transgenic plants exhibited decreased dehydroascorbate reductase (DHAR) activity, the relative reduced ascorbate (AsA) contents were higher while the relative dehydroascorbate (DHA) were lower compared to NT which provide a support to the hypothesis that an active glutathione-independent pathway for DHA reduction might exists in vivo. The transgenic plants maintained an enhanced tolerance to methylviologen, and cadmium. When subjected to drought stress, the transgenic plants exhibited faster recovery with less visual injury compared to NT. These results suggest that manipulation of glutathione levels provides reliable strategy for the development of industrial transgenic potato plants with enhanced tolerance to multiple environmental stresses.
According to the modified ABC model, class B genes are expressed in whorl 1 as well as in whorls 2 and 3, therefore the organs of whorls 1 and 2 have the same petaloid structure in many monocots. The viridiflora tulip, a well-known cultivar group, has flowers in which the tepals in whorls 1 and 2 have greenish stripes. This phenotype could be expected as class B mutant by the modified ABC model. In this study, we discovered that tepal phenotypes correlated with that of stamens. We isolated two class A genes (TGSQA and TGSQB) from wild type tulip. Northern hybridization of these two class A genes, and the class B genes (TGDEFA, TGDEFB and TGGLO), showed that the expression of TGDEFA and TGDEFB in the viridiflora tulips were weaker than those in wild type cultivars, whereas the expression patterns of the rest genes were almost identical. From our results, we suggest that reduced expression of the two DEF-like genes, TGDEFA and TGDEFB, is involved in the development of the viridiflora phenotype. This reduced expression could be caused by the amino acid difference.
We recently presented a method for simultaneous estimation of relative biological effectiveness (RBE) of alpha particles and protons. Here, we evaluate RBE for chlorophyll mutation rate and four M1 effects in thermal neutron exposure of barley (Hordeum vulgare L.) seeds. RBEs of both alpha particles and protons were low for germination rate, seedling height, and number of spikes, and high for seed fertility and mutation rate. Thus, M1 effects are not necessarily accurate as a proxy for mutation rate in comparisons of different types of radiation. RBE of alpha particles for mutation rate was 130.3, much higher than values so far reported in plant materials. RBE of protons for mutation rate was 106.4; as far as we are aware, this is the first value reported for thermal neutron exposure of plant materials. RBEs of alpha particles and protons were significantly correlated (r = 0.939, P < 0.05).
Radish is an important vegetable, and displays a wide variation in root shape. To understand the mechanisms controlling development and/or inheritance of different root shapes, we attempted to identify the genes expressed differentially in roots of two cultivars with different root shapes; long and thick type (Lt) cv. Taibyousoubutori and skinny type (St) cv. Kosena. Morphological studies revealed that significant differences in thickness of roots began at 4 weeks after sowing. By suppression subtractive hybridization using roots at this stage, 140 and 70 non-redundant ESTs were identified from subtraction of St (tester) × Lt (driver) and reverse subtraction, respectively. Of these ESTs, 102 and 52 showed high similarity to previously identified genes, and the remaining 38 and 18 showed no matches to known genes. Quantitative RT-PCR analysis for selected eleven genes demonstrated that they are differentially expressed in roots of two radish cultivars according to the direction of subtraction. These results will contribute to a better understanding of the mechanisms and inheritance of radish root shape.
We investigated the correspondence between classifications based on simple sequence repeat (SSR) markers and on morphological traits for 30 bunching onion (Allium fistulosum L.) varieties. We also examined applicability of an assignment test for variety identification in bunching onion. Cluster analysis based on the allele frequency data at 29 SSR loci classified most of the varieties except for ‘Iwatsuki-2’ into the predicted variety groups, ‘Kaga’, ‘Senju’ or ‘Kujo’, which were categorized based on morphological traits. Although ‘Iwatsuki-2’ has been regarded as a member of ‘Kaga’ group, molecular data suggested the variety belonging to ‘Kujo’ rather than ‘Kaga’. In the assignment test at the individual level, 89.1% of the individuals were assigned to their original variety. When the assignment was conducted based on groups each consisting of four individuals, the percentage of correct assignments was considerably improved (99.3%). These results suggested that the assignment test approach will be useful for variety identification in allogamous bunching onions, which have large within-variety genetic diversity. On the other hand, it was also suggested that sampling of true source varieties will be fundamental to avoid misjudgment.
Quantitative trait loci (QTLs) for resistance to whitebacked planthopper (WBPH), Sogatella furcifera, were determined using 202 backcrossed inbred lines derived from a cross between the recurrent parent Xieqingzao B and an accession of Oryza rufipogon, and then tested using chromosome segment substitution lines (CSSLs) selected from BC3F3 populations of the same cross. Seedling mortality with WBPH infestation was measured to evaluate the resistance. Three QTLs were detected and the wild alleles always had the effect for decreasing seedling mortality. There were qWph2 located in the interval RM1285-RM555 on the short arm of chromosome 2, qWph5 in RM3870-RZ70 on the long arm of chromosomes 5, and qWph9 in RG451-RM245 on the long arm of chromosomes 9, among which qWph9 had the most stable effect. Duplicate lines of seven CSSLs carrying homozygous alleles of O. rufipogon at qWph9 were tested with WBPH infestation. Significant effects at P = 0.01 were observed for all the 14 lines. On the average, the seedling mortality was decreased by 55.2%. Validation of the major effect of qWph9 on enhancing WBPH resistance not only provides a useful QTL but also a series of breeding materials for rice improvement.
Aside from a report claiming that soybean seeds contain less than 1% starch, little is actually known about the genetic variation of the starch content in this important crop species. We used a starch-iodine test to identify varieties with high starch content in a soybean germplasm collection and found a total of 34 cultivars that showed a strongly positive reaction (dark color). For a more accurate quantitation of starch contents, we established a new method using a heat-resistant α-amylase and dinitrosalicylic acid (DNS) reagent. We compared the DNS method and the standard method using glucose-oxidase (GOD) with a known amount of starch as a standard. We showed that the DNS method generated results that were very highly correlated with the GOD method. In addition, we found the new method to be easier and faster to implement than the GOD method. Using the DNS method, we found several accessions in our soybean germplasm whose starch contents were 2–7%.
The Brassica species displays great variation with regard to morphology. However, the genetic mechanisms that underlie this variability are mostly unknown. We generated 188 F2 plants derived from a cross between a Chinese cabbage and a vegetable turnip, and scored several morphological traits (head formation, leaf lobe, pubescence, and turnip formation) twice (2005 and 2007) in two subsets of 94 individuals. With the exception of pubescence, we did not find any typical discrete segregation of these traits in F2 plants, suggesting that they are controlled by multiple genes. We constructed a linkage map to conduct quantitative trait locus (QTL) analysis, and detected eight and 14 QTLs in 2007 and 2005, respectively, for head formation, leaf lobe, pubescence, turnip size, and turnip weight. The amplified fragment length polymorphism (AFLP) fragments linked to the QTLs were converted into sequence-tagged site (STS) markers. The QTLs detected here and their linkage markers may provide useful information for the selection of traits during the breeding of Chinese cabbage and turnip cultivars.
Shiratae Nijo is a new two-rowed food barley cultivar bred at the National Agricultural Research Center for Kyushu Okinawa Region (KONARC) in collaboration with the National Institute of Crop Science (NICS) and released in 2009. Shiratae Nijo is a proanthocyanidin-free cultivar bred by backcross breeding using a leading cultivar Nishinohoshi as a recurrent parent and a foreign proanthocyanidin-free mutant ant28-494 as a non-recurrent parent. The agronomic characteristics of Shiratae Nijo are almost the same as those of Nishinohoshi which has high yield performance and high resistance to barley yellow mosaic virus (BaYMV) type I and powdery mildew. Like Nishinohoshi, Shiratae Nijo shows high resistance to Fusarium head blight (FHB) at the anthesis stage but is susceptible 10 days after anthesis. Shiratae Nijo exhibits significantly weaker seed dormancy than Nishinohoshi. Shiratae Nijo has excellent pearling quality, and the pearled grains show no discoloration and high whiteness after cooking because of the lack of catechin and proanthocyanidin in the grains.