Genetic polymorphism for cyanogenesis and linkage at the linamarase locus in Trifolium nigrescens Viv. subsp. nigrescens

Polymorphisms at two genetic loci conditioning the cyanogenic glucoside linamarin (Ac) and the glucosidase linamarase (Li) are reported for the first time in Trifolium nigrescens Viv. subspecies nigrescens (2n=2x=16). T. nigrescens is one of several possible ancestral species that may have donated a genome to the allotetraploid species white clover (T. repens L., 2n=4x=32). T. nigrescens is a strong candidate because it is the only very close relative that, like white clover, is cyanogenic. Genetic analysis showed that in T. nigrescens, cyanogenesis was inherited as a two-locus genetic system in a similar way to that in white clover. Furthermore, Li, which is linked to the locus Sdh (shikimate dehydrogenase, SDH) at a distance of 6 cM in one genome of white clover, also showed linkage (12 cM) in T. nigrescens. It is concluded that one of the subspecies of T. nigrescens is a likely donor of a genome to white clover. Received: 27 December 2000 / Accepted: 12 April 2001     

Molecular markers linked to white rust resistance in mustard Brassica juncea

 White rust, caused by Albugo candida (Pers.) Kuntze, is an economically important disease of Brassica juncea (L.) Czern. and Coss mustard, particularly in India. The most efficient and cost-effective way of protecting mustard plants from white rust disease is through genetic resistance. The objective of this study was to identify RAPD markers for white rust resistance in an F₁-derived doubled-haploid (DH) population originating from a cross between white rust-susceptible and white rust-resistant breeding lines of B. juncea from the canola-quality B. juncea breeding project of the Agriculture and Agri-Food Canada-Saskatoon Research Centre. The DH population was used to screen for RAPD markers associated with white rust resistance/susceptibility using bulked segregant analysis. Two markers, WR2 and WR3, linked to white rust resistance, flanked the resistance locus Ac2 ₁ and were highly effective in identifying the presence or absence of the resistance gene in the DH population. These two markers were shown to be specific to the Russian source of white rust resistance utilized in this project. It is concluded that the availability of these RAPD markers will enhance the breeding for white rust resistance in B. juncea. Received: 17 December 1997 / Accepted: 7 April 1998     

Novel variants in the KIT and PAX3 genes in horses with white‐spotted coat colour phenotypes

Variants in the EDNRB, KIT, MITF, PAX3 and TRPM1 genes are known to cause white spotting phenotypes in horses, which can range from the common white markings up to completely white horses. In this study, we investigated these candidate genes in 169 horses with white spotting phenotypes not explained by the previously described variants. We identified a novel missense variant, PAX3:p.Pro32Arg, in Appaloosa horses with a splashed white phenotype in addition to their leopard complex spotting patterns. We also found three novel variants in the KIT gene. The splice site variant c.1346+1G>A occurred in a Swiss Warmblood horse with a pronounced depigmentation phenotype. The missense variant p.Tyr441Cys was present in several part‐bred Arabians with sabino‐like depigmentation phenotypes. Finally, we provide evidence suggesting that the common and widely distributed KIT:p.Arg682His variant has a very subtle white‐increasing effect, which is much less pronounced than the effect of the other described KIT variants. We termed the new KIT variants W18–W20 to provide a simple and unambiguous nomenclature for future genetic testing applications.     

Orange, yellow and white-cream: inheritance of carotenoid-based colour in sunflower pollen

Inheritance of pollen colour was studied in sunflower (Helianthus annuus L.) using three distinct pollen colour morphs: orange, yellow and white‐cream. Orange is the most common colour of sunflower pollen, while the yellow morph is less frequent. These two types were observed in the inbred lines F11 and EF2L, respectively. White‐cream pollen is a rare phenotype in nature, and was identified in a mutant, named white‐cream pollen, recovered in the R₂ generation of an in vitro regenerated plant. The F11 inbred line was used as starting material for in vitro regeneration. The carotenoid content of these three pollen morphs differed, and was extremely reduced in white‐cream pollen. The phenotype of F₁ populations obtained by reciprocal crosses revealed that the orange trait was dominant over both white‐cream and yellow. Segregation of F₂ populations of both crosses, orange × yellow and orange × white‐cream, approached a 3:1 ratio, indicating the possibility of simple genetic control. By contrast, a complementation cross between the two lines with white‐cream and yellow pollen produced F₁ plants with orange pollen. The F₂ populations of this cross‐segregated as nine orange: four white‐cream: four yellow. A model conforming to the involvement of two unlinked genes, here designated Y and O, can explain these results. Accessions with yellow pollen would have the genotype YYoo, the white‐cream pollen mutant would have yyOO and the accession with orange pollen would have YYOO. Within F₂ populations of the cross white‐cream × yellow a new genotype, yyoo, with white‐cream pollen was scored. The results of the cross yyoo × YYoo produced only F₁ plants with yellow pollen, supporting a recessive epistatic model of inheritance between two loci. In this model, yy is epistatic on O and o. In F₂ populations, the distributions of phenotypic classes suggested that the genetic control of carotenoid content is governed by major genes, with large effects segregating in a background of polygenic variation. These three pollen morphs can provide insight into the sequence in which genes act, as well into the biochemical pathway controlling carotenoid biosynthesis in anthers and the transfer of these different pigments into pollenkitt.     

The Belt mutation in pigs is an allele at the Dominant white (I/KIT) locus

A white belt is a common coat color phenotype in pigs and is determined by a dominant allele (Be). Here we present the result of a genome scan performed using a Hampshire (Belt)/Pietrain (non-Belt) backcross segregating for the white belt trait. We demonstrate that Belt maps to the centromeric region of pig Chromosome (Chr) 8 harboring the Dominant white (I/KIT) locus. Complete cosegregation between Belt and a single nucleotide polymorphism in the KIT gene was observed. Another potential candidate gene, the endothelin receptor type A gene (EDNRA), was excluded as it was assigned to a different region (SSC8q21) by FISH analysis. We argue that Belt is a regulatory KIT mutation on the basis of comparative data on mouse KIT mutants and our previous sequence analysis of the KIT coding sequence from a Hampshire pig. Quantitative PCR analysis revealed that Belt is not associated with a KIT duplication, as is the case for the Patch and Dominant white alleles. Thus, Belt is a fourth allele at the Dominant white locus, and we suggest that it is denoted I ^Be . Received: 5 May 1999 / Accepted: 3 August 1999     

The genetics of brown coat color and white spotting in domestic yaks (Bos grunniens)

Domestic yaks (Bos grunniens) exhibit two major coat color variations: a brown vs. wild‐type black pigmentation and a white spotting vs. wild‐type solid color pattern. The genetic basis for these variations in color and distribution remains largely unknown and may be complicated by a breeding history involving hybridization between yaks and cattle. Here, we investigated 92 domestic yaks from China using a candidate gene approach. Sequence variations in MC1R, PMEL and TYRP1 were surveyed in brown yaks; TYRP1 was unassociated with the coloration and excluded. Recessive mutations from MC1R, or p.Gln34*, p.Met73Leu and possibly p.Arg142Pro, are reported in bovids for the first time and accounted for approximately 40% of the brown yaks in this study. The remaining 60% of brown individuals correlated with a cattle‐derived deletion mutation from PMEL (p.Leu18del) in a dominant manner. Degrees of white spotting found in yaks vary from color sidedness and white face, to completely white. After examining the candidate gene KIT, we suggest that color‐sided and all‐white yaks are caused by the serial translations of KIT (Cs₆ or Cs₂₉) as reported for cattle. The white‐faced phenotype in yaks is associated with the KIT haplotype S^wf. All KIT mutations underlying the serial phenotypes of white spotting in yaks are identical to those in cattle, indicating that cattle are the likely source of white spotting in yaks. Our results reveal the complex genetic origins of domestic yak coat color as either native in yaks through evolution and domestication or as introduced from cattle through interspecific hybridization.     

Effects of bud phenology and foliage chemistry of balsam fir and white spruce trees on the efficacy of Bacillus thuringiensis against the spruce budworm, Choristoneura fumiferana

Abstract 1 Efficacy of commercial formulations of Bacillus thuringiensis ssp. kurstaki (Btk) against spruce budworm Choristoneura fumiferana was investigated in mixed balsam fir‐white spruce stands. Btk treatments were scheduled to coincide with early flaring of balsam fir shoots, and later with flaring of white spruce shoots. Btk efficacy on the two host trees was compared and examined according to the foliar content of nutrients and allelochemicals and the insect developmental stage at the time of spray. 2 Larvae fed white spruce foliage were less vulnerable to Btk ingestion than larvae fed balsam fir foliage. Higher larval survival on white spruce, observed 10 days after spray, was related to higher foliage content in tannins and a lower N/tannins ratio, which might have induced inactivation of Btk toxins. 3 Larval mortality due to Btk did not depend on spruce budworm larval age. 4 Foliage protection of both host trees was similar in plots treated with Btk: larval mortality due to Btk treatment reduced insect grazing pressure on balsam fir trees; meanwhile, suitability of white spruce foliage seemed to decrease very rapidly, which induced high larval mortality among spruce budworm fed on white spruce trees. Nevertheless, following Btk sprays, 50% more foliage remained on white spruce than on balsam fir trees, because of the higher white spruce foliage production. 5 Both spray timings achieved similar protection of white spruce trees, but Btk treatments had to be applied as early as possible (i.e. during the flaring of balsam fir shoots to optimally protect balsam fir trees in mixed balsam fir‐white spruce stands).     

On the distribution of the time required to remove white balls from an URN

Balls are removed one-at-a-time at equal time intervals from an urn initially containingw ₀ white balls and a large number b of black balls and each black or white ball is immediately replaced by a black ball. The distribution of the number of white balls remaining aftert iterations (under certain limiting operations) is taken from the literature. The problem is to use this result to find the time required to remove a fixed number of white ballsw ₁ from the urn. We then find the mean and variance of this distribution and also look at the special case whenw ₁ =w ₀.     

In a world of white,flower colour matters: A white–purple transition signals lack of reward in an alpine Euphrasia

The New Zealand alpine flora displays a range of unusual characteristics compared with other alpine floras, in particular the high frequency of species with small white flowers. The presence of both white and bright purple flowers on the same plant in the New Zealand alpine annual creeping eyebright (Euphrasia dyeri Wettst.) provides an ideal opportunity to investigate the significance of flower colour in an environment where coloured flowers are rare. The relationships among flower age, gender phase, reward availability and petal colour were assessed in natural populations of E. dyeri. The effect of pollination on flower colour was tested using hand pollination of bagged flowers. Direct observations and videos of flowers were used to assess patterns of flower visitation by native and introduced pollinators. Unpollinated white E. dyeri flowers changed from white to purple within 6 days. However, pollination of white flowers triggered a significantly faster colour change, typically within 1–2 days. White flowers had receptive stigmas, large amounts of lipid‐rich pollen and small amounts of nectar, whereas stigmas of purple flowers are not receptive and flowers did not provide pollen or nectar rewards. Flowers were mainly visited by native syrphid flies. Both native syrphids and introduced Bombus bees showed a marked avoidance of purple flowers, tending to preferentially visit white flowers. Our study suggests that flower colour change from white to bright purple in E. dyeri functions to direct pollinators to rewarding, receptive flowers. As many Euphrasia L. species are described as having variably coloured flowers, this mechanism may be more widespread in the genus. Furthermore, our results add to the growing evidence that the dominance of white flowers in the New Zealand alpine is not simply due to a lack of colour discrimination among pollinators.     

Synergistic action of white spotting genes in the Syrian hamster (Rodentia,Cricetidae)

The phenotypic interaction of three mutant genes Ba, Ds and Wh are quantatively analysed for proportion of white areas in the coat. Each of the genes individually induces a characteristic amount of white spotting which is synergistically enhanced in combination. So much so, that the genotypes Ba+Ds+Wh+ has an almost or completely white coat.     

Michelia sonlaensis Q.N. Vu,sp. nov. (Magnoliaceae) from northern Vietnam

Michelia sonlaensis Q.N. Vu, a new species of Michelia from Son La province, northern Vietnam is described. The new species is assigned to the genus Michelia (separated from Magnolia), subfamily Magnolioideae based on general morphology. It is closely similar to M. xianianhei and M. mannii, but differs mainly in having a leaf‐lamina that is elliptic, thinly leathery, larger, with lower surface yellowish white villous (easily visible by eyes and feeling by hand), brachyblasts and outside bracts yellowish‐white sericeous, flowers light green to cream white in colour, and nine tepals with the outside of all tepals silky hairy at base.     

Ultrastructural observations and pH-measurements on red and white muscle from Antarctic fish

Summary Red and white muscle in the two Antarctic notothenioid fishes Dissostichus mawsoni and Pagothenia borchgrevinki show a rate of postmortem fall of 0.2 pH units per hour, which is close to the rate reported for mammalian muscle at 30°C, but the plateau value is reached several hours earlier in the Antarctic fish, indicating significantly lower stores of initial glycogen. A few particles, most likely representing glycogen, were seen in P. borchgrevinki white muscle and D. mawsoni red muscle, whereas predictably fewer glycogen still was evident in D. mawsoni white muscle. When large numbers of mitochondria and lipid stores were encountered in combination with a small amount of glycogen, we concluded that aerobic metabolism is dominant and that the two species examined would not use white trunk muscle for sustained or slow swimming. Rapid contractions of white trunk muscle as in prey capture or predator evasion are more likely.     

Cytomorphometry of sarcoplasmic reticulum in extrinsic eye muscles of the teleost (Tinca tinca L.)

Summary The sarcoplasmic reticulum of the white and red muscle fibers in the extrinsic eye muscle of the tench (Tinca tinca L.) differs in its organization. The SR of the white fibers is organized according to the Z type, the SR of the red fibers according to the A/I type. In order to estimate the volume and surface of the SR component in both types of muscle fibers, a stereological analysis was carried out.The volume of the SR expressed as a volume density (Vv _SR) is twofold greater in the white than in the red muscle fibers. The surface of the SR, expressed as surface density (Sv _SR) is 20,5% larger in the white muscle fibers.I extend my sincerest thanks to Prof. E. R. Weibel for helpful discussion and instructions in the use of his method and to Mrs. Anna Mleczko-Michalik for skillfull technical assistance. — This work was supported by Polish Academy of Science, project number 09.4.1.4.5.     

Alterations in photosynthesis in <Emphasis Type="Italic">Arabidopsis</Emphasis> lacking IMMUTANS,a chloroplast terminal oxidase

Green and white variegation in the Arabidopsis immutans (im) mutant is caused by a nuclear recessive gene. The green sectors contain cells with normal-appearing chloroplasts, while cells in the white sectors have photooxidized plastids lacking organized lamellae. In the present experiments, we found that the green im sectors have enhanced rates of carbon assimilation (monitored by ¹⁴CO₂ uptake) and that there are corresponding increases in the activities of Rubisco and SPS, elevated starch and sucrose pool sizes, and an altered pattern of carbohydrate partitioning that favors sucrose over starch. We hypothesize that these increases are due, at least in part, to interactions with white sectors, perhaps to compensate for reductions in total source tissue. Consistent with this idea, the im white sectors accumulate low levels of sucrose and acid invertase activities are markedly increased in the white versus green cells. This suggests that there is a sucrose gradient between the green and white sectors, and that sucrose is transported from the green to white cells in response to sink demand. The expression of photosynthetic genes is not appreciably altered in the green im sectors versus wild type, but rather there is an up-regulation of genes involved in defense against oxidative stress and down-regulation of genes involved in cell wall biosynthesis. We postulate that changes in photosynthesis in the im green cells are driven by a need for photoprotection (especially early in chloroplast biogenesis) and due to source-sink interactions. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Are European White Butterflies Aposematic?

It has been suggested that the white coloration of Pieridae butterflies is a warning signal and therefore all white Pieridae could profit from a mimetic resemblance. We tested whether green-veined white (Pieris napi) and orange-tip (Anthocharis cardamines) butterflies benefit from white coloration. We compared their relative acceptability to wild, adult pied flycatchers (Ficedula hypoleuca) by offering live A. cardamines and P. napi together with two non-aposematic butterflies on the tray attached to birds' nesting boxes. Experienced predators equally attacked white and non-white butterflies, and the order of attack among the Pieridae was random. If anything, there was a slight indication that the female A. cardamines was the least favoured prey. Since birds did not avoid white coloration, we compared the palatability of these two species against known palatable and unpalatable butterflies by presenting them to great tits (Parus major). Pieris brassicae, which has been earlier described as unpalatable, was also included in the palatability test. However, there were no significant differences in the palatability of the butterflies to birds, and even P. brassicae was apparently palatable to the great tits. Our results do not unambiguously support the hypothesis that the white coloration of Pieridae would signal unpalatability. Nevertheless, in our last experiment, pied flycatchers often rejected or left untouched free flying P. napi and A. cardamines. This suggests that other features in a more natural situation, such as the agile flight pattern or odours might still make them unprofitable to birds. This revised version was published online in July 2006 with corrections to the Cover Date.     

丛枝菌根真菌和根瘤菌对白三叶氮同化的影响

为揭示丛枝菌根真菌(AMF)和根瘤菌在白三叶氮(N)同化中的作用,该研究对白三叶进行单一或联合接种隐类球囊霉(Paraglomus occultum)和三叶草根瘤菌(Rhizobium trifolii),分析其对白三叶的生长、光合作用、叶片N和氨基酸含量以及N同化相关酶活性的影响。结果表明:(1)单一接种AMF或根瘤菌以及联合接种AMF和根瘤菌均显著增加了白三叶的株高、匍匐茎长度、叶片数、地上部生物量、总生物量、叶绿素b和总叶绿素含量、稳态光量子效率和叶片N含量,这种增强效应是联合接种>单一AMF>单一根瘤菌>未接种处理。(2)联合接种AMF和根瘤菌显著增加了白三叶叶片中丙氨酸、精氨酸、天冬酰胺、天冬氨酸、谷氨酰胺、谷氨酸和组氨酸的含量,显著提升了叶片N同化相关酶如硝酸还原酶、亚硝酸还原酶、谷氨酰胺合成酶、谷氨酸合成酶、谷氨酸脱氢酶、天冬酰胺合成酶和天冬氨酸转氨酶的活性,显著促进AMF对白三叶根系的侵染。综上认为,联合接种AMF和根瘤菌通过激活N同化相关酶活性有效促进N同化,产生更多氨基酸,进一步促进白三叶植株生长; 联合接种AMF和根瘤菌具有协同作用,有效促进了白三叶的N同化。