Morphological and molecular analysis of androgenetic, selfed and backcrossed plants produced from a Hordeum vulgare x H, bulbosum hybrid

Anther culture (AC) was carried out on a fertile triploid hybrid between Hordeum vulgare L. (cultivated barley) and H. bulbosum L, (bulbous barley grass) to determine whether AC-derived regenerants differed from progeny obtained through selfing and backcrossing. Chromosome counts were carried out on all plants and DNA was extracted from them to prepare Southern blots for molecular analysis. To identify true recombinants, the blots were probed with rye repetitive sequence probes (pSc119.1 and pScl19.2). which hybridize strongly and specifically to H. bulbosum DNA. Twenty probes that detect single- or low-copy sequences were hybridized with Southern blots containing restricted DNA extracted from 25 AC-derived plants, 11 selfed and six backcrossed progeny that showed hybridizations with pScll9. Although restriction fragment length polymorphisms (RFLPs) were only observed using probes that map to four of the possible 14 chromosome arms, an introgression associated with chromosome 6HS was frequently observed among plants derived from AC. selfing and backcrossing. Plants from AC differed from selfed and backcrossed progeny in their chromosome number; unique RFLP bands that were occasionally observed may indicate chromosomal rearrangements.     

Holocene deglaciation of Marie Byrd Land,West Antarctica

Surface exposure ages of glacial deposits in the Ford Ranges of western Marie Byrd Land indicate continuous thinning of the West Antarctic Ice Sheet by more than 700 meters near the coast throughout the past 10,000 years. Deglaciation lagged the disappearance of ice sheets in the Northern Hemisphere by thousands of years and may still be under way. These results provide further evidence that parts of the West Antarctic Ice Sheet are on a long-term trajectory of decline. West Antarctic melting contributed water to the oceans in the late Holocene and may continue to do so in the future.     

Renal T-cell lymphoma with cerebral metastasis in a dog with chronic canine ehrlichiosis

A renal T-cell lymphoma with exclusive cerebral metastasis was diagnosed in a 5-year-old Staffordshire bull terrier bitch euthanased for aggression. This is the first recorded case of primary renal lymphoma in a dog. Immune suppression, due to chronic canine monocytic ehrlichiosis, may account for the unusual primary site and metastatic pattern of the tumour.     

Influence of variety on the within-plant distribution of cassava green spider mite (Acari: Tetranychidae), and leaf anatomical characteristics and chemical components in relation to varietal resistance

The within-plant distribution of the cassava green spider mite, Mononychellus tanajoa Bondar, and the anatomical characteristics and the chemical components relating to varietal resistance of cassava, were studied using 11 cassava genotypes with varying levels of resistance for two dry seasons and one wet season. The results show that M. tanajoa aggregates on the top leaves of cassava at low levels of resistance as compared with a more even within-plant distribution at higher levels of resistance. Thus, for accurate sampling of mite populations, it might be important to consider young and old leaves, not just the young leaves, in fields containing resistant and susceptible cassava genotypes. Correlations between the anatomical characteristics and mite population density and damage scores were not consistent across months, either within or over seasons. This suggests that leaf anatomical characteristics may not be important in the varietal resistance of cassava to M. tanajoa. During the dry season, mite population density was positively correlated with leaf nitrogen, potassium and phosphorus and negatively correlated with leaf calcium and fat. Only calcium was negatively associated with mite damage at the peak of the dry season (January 1993 and 1994). Breeding cassava genotypes with high levels of leaf calcium and fat, and low levels of leaf nitrogen, potassium and phosphorus, may improve the level of resistance to M. tanajoa.     

Agroforestry techniques for the rehabilitation of degraded salt-affected lands in India

The development of appropriate technologies for the judicious use of India's 8.11 million ha of salt-affected lands would give increased food, fodder and fuelwood production. A sizeable portion of the salt-affected lands of the Indo-Gangetic plain have been reclaimed through chemical amendments and are being commercially used for arable farming. However, large areas of salt-affected common lands, village and government lands and waste lands near cities, along railway tracks and roads do not have any productive use. Owing to their sparse vegetative cover such lands are vulnerable to further degradation and can be a source of runoff causing floods, especially where cows congregate. Research at the Central Soil Salinity Research Institute, Karnal has generated agroforestry techniques which could enable the economic exploitation of such marginal lands. This paper deals with various aspects of these techniques, which have been applied to over 50 000 ha by 1994. Based on eight to ten years of growth and biomass figures, the most salt-tolerant woody species identified were: Prosopis juliflora, Acacia nilotica, Casuarina equisetifolia, Tamarix articulata, Leptochloa fusca (a palatable forage grass which was found to be a promising primary colonizer of salt lands). Agronomic practices for the successful establishment of trees such as planting methods, amendment use, irrigation, spacing and lopping schedules are discussed. A Prosopis juliflora-leptochloa fusca silvipastoral model was found to be excellent for fuelwood and forage production and for the amelioration of high pH soils. This system, when followed for little more than four years, reclaims alkali soils to such an extent that normal agriculture crops such as Trifolium alexandrinum and T. resupinatum can be grown successfully. A ridge-trench system of tree planting was found to be helpful in alkali soils, the in situ rainwater conservation it led to assisting biomass production. Eucalyptus tereticornis, Populus deltoides and Tectona grandis based agroforestry were promising for reclaimed salt-affected lands. The short- and long-term effects of various tree plantations on the physicochemical properties of the soil and on soil-water relations are also discussed. Agroforestry options for the development of salt-affected lands found in various agroclimatic zones of India are explored.