Identification of novel plant architecture mutants in barley

In grasses, biomass and grain production are affected by plant architecture traits such as tiller number, leaf size and orientation. Thus, knowledge regarding their genetic basis is a prerequisite for developing new improved varieties. Mutant screens represent a powerful approach to identify genetic factors underpinning these traits: the HorTILLUS population, obtained by mutagenesis of spring two-row cultivar Sebastian, is a valuable resource for this purpose in barley. In this study, 20 mutant families from the HorTILLUS population were selected and evaluated for tiller number, leaf angle and a range of other plant architecture and agronomic traits using an unreplicated field design with Sebastian as a check cultivar. Principal Component Analysis revealed strong relationships among number of tillers, upper canopy leaf angle, biomass and yield-related traits. Comparison to the Sebastian background revealed that most mutants significantly differed from the wild-type for multiple traits, including two mutants with more erect leaves and four mutants with increased tiller number in at least one phenological stage. Heatmap clustering identified two main groups: the first containing the two erect mutants and the second containing Sebastian and the high-tillering mutants. Among the high-tillering mutants, two showed significantly higher biomass and grain yield per plant compared to Sebastian. The selected mutants represent promising materials for the identification of genetic factors controlling tillering and leaf angle in barley.

Isoetes laurentiana, sp. nov. (Isoetaceae) endemic to freshwater tidal marshes in eastern Quebec, Canada

Morphological, phytogeographic, ecological, preliminary genetic, and C-value evidence indicates that populations of Isoetes confined to freshwater tidal marsh habitats along the St. Lawrence River in Quebec, Canada, represent an undescribed endemic species, proposed here as Isoetes laurentiana sp. nov. The combination of short velum coverage (ca. 10%) over a plain (unstreaked) sporangium, broad (ca. 1.0 mm) erect leaves, small megaspores (ca. 459 μm) with more densely convoluted-reticulate, almost echinate ornamentation, and its occurrence within an exceptional habitat, readily distinguish I. laurentiana from I. tuckermanii A.Braun with which it was formerly combined. Isoetes laurentiana is one of a series of endemic taxa of the floristically extraordinary St. Lawrence River estuary. Some populations of I. laurentiana are immense; in cultivation it demonstrates the capacity for prolific production of new individuals, which is presumably necessary to sustain such local abundance. Isoetes laurentiana is of national and global phytogeographic significance, but is not considered to represent a species at risk according to standards from the International Union for Conservation of Nature.

Austronea patersoniae (Asparagaceae, Scilloideae), a new species from the Eastern Cape Province in South Africa

Our fieldwork in the Eastern Cape province of South Africa revealed an undescribed species of Austronea which was named by Schonland as “Urginea Patersoniae Schonl. Ms.”, but never validly published. We here describe Austronea patersoniae to include plants showing bulbs with loose scales; 5–9 narrowly linear erect leaves with papillate margins; elongate peduncle; lowermost bracts with a broad, flat, papery spur and reddish flowers with papillate filaments. We provide a complete morphological description as well as data on ecology and distribution.

La importancia del intervalo de la floración en el mejoramiento para la resistencia a sequía en maíz tropical

The length of the Interval between anthesis and silking (ASI) is increased by drought which coincides with flowering. Four elite CIMMYT lowland tropical populations are undergoing recurrent selection (S1 or full-sib) for improved grain yield and several other traits under drought and well watered conditions. Data collected from more than 200 families per population grown In single row plots under three water stress levels (pre and post-flowering stress; post-flowering stress; normal irrigation, all in the absence of rain) showed weak or no correlation between grain yield and traits related to plant water status, such as leaf rolling and senescence, photooxidation, leaf chlorophyll concentration, shoot elongation rate, canopy temperature and predawn water potential. Yield under all levels of stress was significantly negatively correlated with AST, and as AST increased due to drought, kernels and ears per plant were significantly reduced. In all populations yield decreased by approximately 10 % per day increase in AST up to 8 days. In several stress situations broad-sense heritability of AST was greater than that of grain yield and the genetic correlation between grain yield and AST approached -1.00. Synthetics formed from one population following bidirectional selection and tested under drought showed adaptive advantage of cool canopy temperature, delayed leaf senescence, reduced AST and erect leaves, especially when all were combined with grain yield in a single index during selection. Selection for reduced AST and high grain yield under drought can be an effective means of improving drought tolerance in tropical maize.

The Biology of Canadian Weeds. 143. Apocynum cannabinum L.

Hemp dogbane, Apocynum cannabinum (Apocynaceae), is a perennial herb with white to greenish flowers in terminal clusters that produces pencil-like pods 12-20 cm long. A highly variable plant, A. cannabinum may be distinguished from spreading dogbane (Apocynum androsaemifolium) by its shorter corolla (2-6 mm compared with 5-10 mm), erect greenish-white petals (compared with recurved or spreading pinkish petals), seeds more than 3 mm long (compared with seeds less than 3 mm), and more erect leaves (compared with spreading or drooping leaves), although frequent hybridization between the two species obscures the identity of some individuals. Hemp dogbane is native to the United States and southern Canada, but most abundant in the upper Mississippi River Valley and east to the Atlantic coast. It has been increasing in other areas, and becoming more of a problem where conservation tillage is adopted. It infests crops such as corn (Zea mays), soybeans (Glycine max), wheat (Triticum aestivum), sorghum (Sorghum bicolor) and forages, and may cause livestock poisoning due to cardiac glycosides within its milky sap (but livestock generally avoid it). Potential medicinal uses of these compounds have been investigated, and the roots are a source of fibre. Control of A. cannabinum with various herbicides is difficult due to a thick cuticle, and one solution may be to target susceptible stages, such as seedlings or early spring growth. Cultivation may also control A. cannabinum, but care must be taken not to promote the proliferation of the plant through regrowth from fragmented roots and rhizomes. Rotation with alfalfa also reduces populations of A. cannabinum.Key words: Hemp dogbane, APCCA, Apocynum cannabinum, Apocynaceae, weed biology