Characterization of simple sequence repeat markers derived in silico from Brassica rapa bacterial artificial chromosome sequences and their application in Brassica napus

A collaborative Brassica rapa genome sequencing project is currently in progress to aid the identification of agronomically important traits in Brassica species. As an initial stage, the ends of over 110 000 bacterial artificial chromosome clones were sequenced and mined for simple sequence repeats (SSRs). We present the characterization of 40 of these SSRs and their application in Brassica napus. The markers were screened against six Brassica species and Arabidopsis, and demonstrated reliable amplification, genome specificity, cross‐amplification and significant polymorphism. These SSRs will be useful for genetic analysis of Brassica germplasm.     

Effect of water stress on the enzymes of nitrogen metabolism in mung bean (Vigna radiata Wilczeck) nodules

Abstract. Water stress created by withholding irrigation in mung bean resulted in decreased leaf water potential and nodule moisture content. Decreased leaf water potential was associated with decreased activity of nitrogenase, glutamine synthetase (GS), asparagine synthetase (AS), aspartate amino transferase (AAT), xanthine dehydrogenase (XDH) and uricase. However, the activity of glutamate dehydrogenase increased three-fold under severe stress. The activity of allantoinase and allantoicase was not affected by moderate stress but decreased under severe stress. The in vitro production of allantoic acid from allantoin and uric acid in the cytosol fraction decreased more than its production from xanthine and hypoxanthine. The production of NADH also decreased under stress.
During recovery from severe stress, the activity of XDH and uricase further decreased, whilst that of allantoinase and allantoicase increased compared to the control. This corresponded with the higher content of ureides during recovery. The recovery in other enzymes was not complete although leaf water potential and nodule moisture content recovered fully within 24 h.     

Disc Electrophoretic Studies of IAA Oxidases and their Relationship with Rooting of Etiolated Stem. Segments of Populus nigra

Stem segments of Populus nigra did not root in water but rooted in glucose + IAA. Rooting was completely inhibited by cyclobeximide or actinomycin-D, added to the medium. The synthesis of two existing and one new isoenzyme was repressed at 24 h in segments cultured in glucose + IAA, but that of two new ones was induced in water. Cycloheximide and actinomycin-D induced the synthesis of some new isoenzymes although they inhibited the fresh turn-over of some others.     

The family Lomariopsidaceae (Filicopsida) and its probable ancestors

The family Lomariopsidaceae includes eight genera of tropical ferns– Arthrobotrya, Bolbitis, Egenolfia, Elaphoglossum, Lomagramma, Lomariopsis, Teratophyllum and Thysanosoria. Salient morphological features of the Lomariopsidaceae have been enumerated. Views of various authors postulating evolution of this family from Thelypteroid, Dryopteroid, Polystichoid or Dennstaedtioid stocks are discussed and it is concluded that they do not seem to be the ancestors of the Lomariopsidoid ferns. On the other hand, it appears, on the basis of various characters, that the Tectarioid ferns could possibly be the ancestors of the Lomariopsidaceae.     

Cytoembryology of some Malaysian dipterocarps, with some evidence of apomixis

KAUR, A., JONG, K., SANDS, V. E. & SOEPADMO, E., 1986. Cytoembryology of some Malaysian dipterocarps, with some evidence of apomixis. Embryological and cytological studies on some members of the Dipterocarpaceae were undertaken. Of the dipterocarps investigated 83% were diploids. Two new polyploids were observed, namely Shorea resinosa (2 n = 3x = 21) and Hopea subalata (2 n = 3x = 21). Multiple seedlings were observed in H. subalata, Shorea agami, S. argentifolia, S. ovalis, S. pauciflora and S. resinosa. For the first time embryological studies have conclusively demonstrated reproduction by agamospermy in 5. ovalis and S. agami. Considerable evidence leads to the inference that H. subalata, S. resinosa and 5. macroptera are also agamosperms. Each of these produces multiple seedlings. Of these apomictic species three are polyploids, namely S. ovalis (2 n = 4x = 28), H. subalata (2 n = 3x = 21) and S. resinosa (2 n = 3x = 21), whereas S. agami (2 n = 14) and S. macroptera (2 n = 14) are diploids.