Summary• Recent years have seen rapid advances in our knowledge of the transcriptomic consequences of allopolyploidy, primarily through the study of polyploid crops and model systems. However, few studies have distinguished between homoeologs and between tissues, and still fewer have examined young natural allopolyploid populations of independent origin, whose parental species are still present in the same location.• Here, we examined the expression of 13 homoeolog pairs in seven tissues of 10 plants of allotetraploid Tragopogon mirus from two natural populations formed by independent polyploidizations between Tragopogon dubius and Tragopogon porrifolius c. 40 generations ago. We compare these with patterns of expression in the diploid parental species from the same locality.• Of the 910 assays in T. mirus, 576 (63%) showed expression of both homoeologs, 63 (7%) showed no expression of either homoeolog, 186 (20%) showed nonexpression of one homoeolog across all tissues of a plant, and 72 (8%) showed non-expression of a homoeolog in a particular tissue within a plant. We found two cases of reciprocal tissue-specific expression between homoeologs, potentially indicative of subfunctionalization.• Our study shows that tissue-specific silencing, and even apparent subfunctionalization, can arise rapidly in the early generations of natural allopolyploidy.

These approaches can be easily and inexpensively applied to many other plant species-making any evolutionarily provocative system a new "model" system.

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This study describes an efficient in vitro method using colchicinetreated triploid seedlings of Napiergrass and Pearl millet hybrids to produce hexaploid hybrids and their subsequent identification with flow cytometry. It also describes chromosome count and stomatal morphology and their use to ploidy analysis. Four-hundred and eighty triploid seeds, representing 12 different hybrids were sterilized and transferred to MS media to induce chromosome doubling. Surviving plants were analysed by flow cytometry. From six triploid (control) and hexaploid plants, the stomata sizes and frequency were analysed. Chromosome count was performed only in the plants identified as hexaploid. Seventeen plants were identified as hexaploid by flow cytometry analysis. Further confirmation of the hexaploid condition was performed with stomatal morphology (stomatal frequency reduction and stomatal length increase) and chromosome count (2n = 6x = 42). Chromosome doubling has numerous applications in Pennisetum breeding. It can be used to restore the fertility of interspecific hybrids and to improve seed size.The genus Pennisetum is one of the important genera of the family Poaceae. Pennisetum purpureum Schum. (Napiergrass) and Pennisetum glaucum (L.) R.Br. (Pearl millet) are important species widely used as forage. Pennisetum glaucum is a diploid species with 2n = 2x = 14 chromosomes and P. purpureum is tetraploid with 2n = 4x = 28 chromosomes (Martel et al. 2004). Napiergrass has been successfully crossed with Pearl millet to produce high quality and high yielding perennial interspecific forage hybrids (Hanna 1981). However, the sterility of this hybrid due to its triploid condition (2n = 3x = 21 chromosomes) has been pointed as a difficulty for its use in breeding programmes. The fertility of this hybrid can be restored with chromosome doubling. Colchicine is an alkaloid widely used for chromosome doubling and for the induction of polyploidy in plants (Pasakinskiene´2000). The technique of exposing explants to colchicine in vitro has been used in a number of cases (Kadota and Niimi 2002). Chromosome counts and stomatal morphology have been used routinely for polyploidy screening. However, these methods make the analysis of a great number of plants difficult and time-consuming. Flow cytometry represents a technology gain and has been increasingly used for highthroughput ploidy screening (Roy et al. 2001). This study describes an efficient in vitro method using colchicine-treated triploid seedlings of Napiergrass and Pearl millet hybrids to produce hexaploid hybrids and their subsequent identification with flow cytometry. It also describes chromosome count and stomatal morphology and their use for ploidy analysis. Plant materials and in vitro induction of chromosome doublingFour-hundred and eighty triploid seeds, representing 12 different hybrids (40 per hybrid), were sterilized and transferred to MS media to induce seedling development. The treatments (hybrids) have been arranged in a completely random design with four repetitions. Each...

The Guzerat breed is well adapted to the tropical conditions of Brazil. After 1940, the widespread use of Guzerat cattle for crossing has reduced its population size. In 1994, a selection program for milk production traits was initiated in some purebred herds. However, its success is compromised by genetic drift and an increased inbreeding coefficient (F). The objective of this study was to evaluate the genetic status of the Guzerat population under selection for milk production in order to monitor genetic variability. Genealogical data from 10,051 animals were used to estimate genetic parameters. The average F for all animals and for inbred animals in the pedigree was 0.009 and 0.025, respectively. Average relatedness was 0.011. The average generation interval was 7.48 years and the linear increase in F per generation was 0.0051. There was no trend of changes in the effective population size along generations, with the observation of an effective size of 98 in the last generation evaluated. The effective number of founders and ancestors was 318 and 101, respectively. Only 47 of 2106 ancestors contributed to 50% of the reference population. The bottleneck effect was 3.15. Average F and relatedness values are still low despite non-random mating. However, the reduced effective population size and effective number of ancestors indicate a risk of an increase in the inbreeding coefficient and genetic drift and consequent loss of variability.