Combining ability and heterosis study in maize (Zea mays L.) Hybrids at different environments in Bangladesh

The aim of this study was to isolate superior inbred lines and better combining parents for suitable hybrids and to determine percent of heterosis using standard commercial checks in a 7 × 7 diallel analysis excluding reciprocals over five environments. The mean sum of square obtained from combined analysis of variance showed the presence of genetic variability among the crosses, environment and crosses × environment interaction for all of the characters under study. The variances for general combining ability (GCA) and specific combining ability (SCA) of variance were found significant for all the characters. However, relative magnitude of variances indicated that additive gene effects were more prominent for all the characters studied. GCA and SCA effects both showed significant interaction with environment for all the traits. This clearly suggested the need of selecting different parental lines for hybrids for different ecological situations. Parents P3, P5 and P6 were the best general combiner for high yield; parents P6 for earliness; and P1, P2 and P3 for dwarf plant type. The range of heterosis expressed by different crosses was from -13.04 to 5.25 % percent for grain yield. The better performing six crosses (P1 × P2, P1 × P5, P3 × P4, P3 × P6, P3 × P7 and P4 × P5) can be utilized for developing high yielding hybrid varieties as well as for exploiting hybrid vigour. These crosses also need to be evaluated further in multilocations.Bangladesh J. Agril. Res. 43(1): 125-134, March 2018

Hereditary dwarfism in yellow lupin (Lupinus luteus L)

A dwarf plant was found in the F₄ generation of a hybrid between two yellow lupin subspecies. Genetic analysis demonstrated that the dwarf grwoth is conditioned by one recessive factor which was named nanus. This factor acts pleiotroipically since it reduces the height, changes the morphological structure and some anatomical traits and reduces fertility in the dwarf plants. It is believed that in the chromosome with translocation a gene block arose in the F₄, plant. These genes acting as a compact system cause dwarfism, changes in the anatomical structure and reduce fertility.

New species and notes on Hesperantha (Iridaceae) in southern Africa

Field studies of the sub-Saharan African and largely southern African Hesperantha conducted since 2003 have resulted in the discovery of three new species in this genus, bringing the total to 82. Hesperantha longistyla J.C.Manning Goldblatt. known from one collection from the mountains of SW Namibia, is a dwarf plant with moderately long-tubed, purple flowers and unusually long style branches, possibly allied to the Kamiesberg species, H. latifolia. A second species, H. helmei Goldblatt J.C.Manning, also known from a single collection from the interior mountains of Eastern Cape near Graaff- Reinet, has terete leaves and small flowers with tepals ± 8 x 2.5 mm, about as long as the perianth tube. It is apparently most closely allied to the Roggeveld species, H. cliolata. A third novelty, H. lithicola J.C.Manning Goldblatt. restricted to the Swartruggens range in the eastern Cold Bokkeveld, has bell-shaped corms with toothed margins, leaves 1-2 mm wide, and white flowers with a tube 10-12 mm long, and appears most closely allied to the widespread H. falcata. A new collection of H karooica from northeast of the Hantamsberg represents a small but significant range extension for this local endemic previously known from just two collections near Calvinia, south of these mountains. The flower size, especially dimensions of the tepals, confirms its status as a separate species allied to H. vaginata. Lastly, new collections o f the relatively uncommon, yellow-flowered variant of H. acuta show that this plant, confined to the eastem portion of the range of the species, differs consistently from the white-flowered form in several floral features, and it is raised to subspecies rank as H. acuta subsp. tugwelliae.