Brenda Brookes

Taxonomic circumscription and identification in theMedicago sativa-falcata (alfalfa) continuum

Medicago sativaincludes 2 polarly distinctive variants, subsp. sativa (M. sativa sensu stricto)and subsp. falcata (M. falcata),which are connected by intergrading variants commonly termed subsp. × varia (M. varia).Cultivated alfalfas and most wild and weedy relatives encountered are referable to this continuum of variation. Because of striking agronomic and ecological differences among the variants, it is desirable taxonomically to divide the continuum as precisely as possible. Towards an improved classification, canonical analysis was used to circumscribe the intermediate group of the M. sativa-falcatacomplex as inclusive of the middle range between the multivariate centres of the polar variants. The 3 most conservative characters examined, flower color, fruit coiling, and habit, were used in a discriminant function to create a simple tabular key.

Reduction of the geocarpic Factorovskya to Medicago

Summary Factorovskya (Trigonella) aschersoniana (Urb.) Eig is shown on the basis of a variety of features to be appropriately placed in Medicago, and is recognized as M. hypogaea E. Small. As with some other geocarpic legumes once recognized as monotypic genera, the presence of geocarpic adaptations has obscured close affinities apparent in other characteristics.

Allozyme variation in relation to morphology and taxonomy inMedicago sect.Spirocarpos subsect.Intertextae (Fabaceae)

Medicago intertexta andM. ciliaris have been controversially recognized as separate species. The only reliable diagnostic character, gland-tipped trichomes on the fruits inM. ciliaris, is controlled by presence of a single dominant allele, and such one-character taxonomies are debatable. Contributing to the difficulty,M. muricoleptis andM. granadensis, the other two species ofMedicago sectionSpirocarpos subsectionIntertextae, are sometimes confusingly similar toM. intertexta or to each other. Allozyme differences provided 95% verification of the suitability of the gland-tipped trichome character for separatingM. intertexta andM. ciliaris, thus corroborating their recognition as separate taxa. Several measures of allozyme variation indicated thatM. intertexta is more polymorphic than its sister species. Heterozygosity was also highest inM. intertexta, suggestive of a higher outcrossing rate, which is also consistent with larger floral size. Heterozygosity ofM. intertexta was concentrated in Sicily and nearby countries. Taxonomic difficulties in identifying SicilianM. intertexta are well known, and may be the result of interspecific hybridization and introgression.Medicago muricoleptis differed from the above two species in the frequency of several alleles, whileM. granadensis possessed numerous unique alleles consistent with its complete absence of genetic exchange with the other three substantially interfertile species.

Remarkable asymmetries in trifoliolate leaves with particular reference to Medicago

Abaxial pubescence of the trifoliolate leaves of numerous species is asymmetric, with a greater density of trichomes on the portions of the lateral leaflets between their midribs and outer margins (the margins closest to the base of the petiole) than on the remainder of the lateral leaflets or on the central leaflet. This pattern was evaluated statistically in 1250 plants representing 55 species of Medicago, 13 other genera of the Leguminosae, and 5 genera of other plant families. It was found that the magnitude of asymmetry of pubescence is higher in Medicago than in other legumes considered collectively, but the phenomenon is widespread in the Leguminosae. The generality of the pattern in other vascular plant families could not be assessed reliably because of the paucity of nonlegume species with pubescent trifoliolate leaves. However, the pattern is not universal because in Staphylea trifolia (Staphyleaceae) an opposite asymmetry was found. Young trifoliolate leaves of leguminous plants frequently are ...

Isozyme variation and alleged progenitor-derivative relationships in theMedicago murex complex (Fabaceae)

Chromosomal studies ofMedicago lesinsii (n = 8) and its close relativeM. murex (n = 7) have led to the competing hypotheses that the latter is derived directly from the former, or that both originated from a common ancestor. In contrast to the relatively variableM. murex, M. lesinsii proved to be almost uniform isozymically, except that most populations of Greece differed by one allele from plants of the remainder of the range. This Greek variant ofM. lesinsii was indistinguishable from one of the isozyme variants ofM. murex. The greater level of allozyme variation inM. murex was consistent with its greater ecological amplitude and competitive ability. Also, this suggests thatM. murex is unlikely to have originated directly from the less variableM. lesinsii. The data suggest that either both species originated from a common ancestor, or that the n = 8 species evolved from the n = 7 species, a mode of chromosome evolution not previously hypothesized for the genus.

Temperature and Moisture Content for Storage Maintenance of Germination Capacity of Seeds of Industrial Hemp, Marijuana, and Ditchweed Forms of Cannabis sativa

Cannabis sativa seeds of three industrial hemp cultivars, a medicinal strain of marijuana, and a ruderal strain were subjected to combinations of four temperatures (20°C, 5°C, −20°C, and −80°C) and three seed moisture contents (approximately 11%, 6%, and 4%) for 66 months. Storage of seeds with a moisture content of 11% at 20°C reduced the germinability of seeds of all varieties to zero in less than 18 months. Either reducing the temperature to at least 5°C or reducing the seed moisture content to at least 6% had a huge beneficial effect on maintaining seed viability. Additional reduction of temperature, but not additional reduction of moisture content had a small supplementary beneficial effect. No apparent benefit was noticed from oxygen-free seed storage.

Medicago truncatula f.laxicycla (Leguminosae), a new taxon with loose fruit coiling promoting rapid germination of the fruit-retained seeds

Medicago truncatula is a member ofMedicago sect.Spirocarpos, in which all 34 species have coiled fruit, usually tightly coiled, that permanently retain the seeds. A variant ofM. truncatula from Libya is unique for the species in possessing very loosely coiled fruits, and is here recognized as a new forma,M. truncatula f.laxicyclaE. Small. In germination tests of a number of species ofMedicago, the unusual Libyan variant proved to be the only one in which rapid and simultaneous germination of most of the seeds occurred while still within a fruit. The loose coiling of the fruit of the Libyan variety appears to facilitate water entry and seedling escape. Its rapid germination might adapt it to respond quickly to intermittently available moisture, but at the cost of abandoning the strategy of intermittent germination adopted by other populations ofMedicago sect.Spirocarpos.

Preferential infestation of fruits within theMedicago truncatula — M. littoralis (Leguminosae) complex by the bean weevilBruchidius bimaculatus

The bean weevilBruchidius bimaculatus was found in fruits of 68 of 217 populations of theMedicago truncatula — M. littoralis complex of Israel, Greece, Italy and Spain. Infestation was higher in fruits of somewhat larger than mean size, and in the more pubescent and tightly coiled fruits. Bean weevil size proved to be independent of fruit size, so that the “preference” for larger fruits does not seem due to adaptation to a larger food source or a larger domicile. Fruit size has been used to delimit the host “species”M. truncatula andM. littoralis, but the character proved to be unimodal, and it is apparent that the taxonomy of the plant complex requires further clarification. Of the 11 472 fruits examined, less than 4% were infested. Given that the plants have evolved indehiscent legumes in which typically only one of the approximately six seeds survives to reproduce, and that very few seeds of a fruit are destroyed, the bruchids infestation appears to be non-harmful, and indeed the association may be mutualistic.

A systematic comparison of morphology and seed proteins of early- and late-flowering forms of Medicago scutellata

Two hundred and thirty-nine germ plasm accessions of Medicago scutellata grown under greenhouse conditions exhibited a strongly bimodal distribution of flowering time. Numerical taxonomic analysis showed that the early- and late-flowering forms are substantially different morphologically. The early-flowering form is smaller and less vigorous, has fewer flowers in the inflorescence, and fewer serrations on the leaf blades and stipules than the late-flowering form. Analysis of seed proteins using polyacrylamide gel electrophoresis identified 11 seed proteins that can be used to distinguish the two forms and putative hybrids. Although both forms appear widespread in the circum-Mediterranean indigenous distribution area, only about one-third of the accessions represented the early-flowering form, which seemed to predominate only on isolated Mediterranean islands. The two forms may merit infraspecific taxonomic recognition. Key words: Medicago scutellata, Fabaceae, taxonomy, classification, systematics, seed p...