Control of chlorophyll formation and sprouting of tubers by oil dipping in five potato cultivars of Pakistan

Five potato cultivars of autumn crop, dipped in corn oil, were observed for 90 days at room temperature under natural light. Chlorophyll formation took place in minute quantities in treated tubers of ‘Désirée’ and ‘Prima’, and a little more in ‘Primura’, ‘Montana’ and ‘Multa’, whereas all control tubers became completely green after 90 days. Sugars were significantly lower and starch higher in treated tubers than in controls. No sprout-development was observed in treated tubers of all cultivars, but 50–70% control tubers had sprouted during this period. Peeling-losses were minimum in treated tubers and were 67.5–85.4% in controls. The oil-dipped potato tubers of all cultivars could safely be stored for 60 days without quality deterioration under ordinary conditions of temperature and light.     

黄瓜游离小孢子培养诱导成胚和植株再生

 以10个不同基因型黄瓜为试材进行游离小孢子培养,通过对成胚条件的系统研究,从‘7447’和‘Poinsett97’中获得了子叶形胚和再生植株。研究结果表明：基因型和小孢子发育时期是限制黄瓜游离小孢子成胚的关键因子。不同品种间胚状体产量差异显著,每皿产胚1.5～33.4个。单核靠边期是进行黄瓜游离小孢子培养的最佳时期。低温预处理有利于胚状体的诱导,4 ℃预处理2～4 d为宜,以处理2 d时胚状体产量最高。外源激素在诱导胚状体时并非必需,但低浓度的外源激素（0.5 mg·L^-1 2,4－D、0.2 mg·L^-1 6－BA）更能促进小孢子成胚。NLN和B5两种基础培养基在诱导胚状体上无显著差异。子叶形胚易分化成苗,而其它类型的胚状体不能获得再生植株。     

Dimensionality control of electronic phase transitions in nickel-oxide superlattices

The competition between collective quantum phases in materials with strongly correlated electrons depends sensitively on the dimensionality of the electron system, which is difficult to control by standard solid-state chemistry. We have fabricated superlattices of the paramagnetic metal lanthanum nickelate (LaNiO(3)) and the wide-gap insulator lanthanum aluminate (LaAlO(3)) with atomically precise layer sequences. We used optical ellipsometry and low-energy muon spin rotation to show that superlattices with LaNiO(3) as thin as two unit cells undergo a sequence of collective metal-insulator and antiferromagnetic transitions as a function of decreasing temperature, whereas samples with thicker LaNiO(3) layers remain metallic and paramagnetic at all temperatures. Metal-oxide superlattices thus allow control of the dimensionality and collective phase behavior of correlated-electron systems.     

Relationship between leaf gas exchange characteristics and productivity of potato clones grown at different temperatures

The rate of dark respiration (Rd) and net photosynthesis (Pn) at various leaf temperatures was examined in three potato clones (Solatium tuberosum L.) differing in heat tolerance. Plants were grown at low (25/12 C, day/night) and high (35/25 C) greenhouse air temperatures for five weeks, beginning two weeks after tuberization. Gas exchange characteristics were measured by manometric and infrared gas analyzer techniques. Respiration:photosynthesis ratios were calculated as indicators of leaf carbon balance. High greenhouse temperature reduced whole plant and tuber growth rate of all clones, however, the reduction was highest in the cultivar Russet Burbank (heat sensitive). Gas exchange characteristics did not explain differences in heat tolerance. The heat tolerant cultivar Desiree had Rd similar to Russet Burbank, while the clone DTO-28, also heat tolerant, had lower Rd of mature leaves than Russet Burbank or Desiree. However, all clones had similar Rd of immature leaves. There was no apparent relationship between heat tolerance and Pn for the three clones. DTO-28 had lower respirationrphotosynthesis ratios of immature and mature leaves than Russet Burbank 4 weeks after the start of the high temperature treatment. Desiree had respiration:photosynthesis ratios as high as Russet Burbank. At different sampling times, Rd increased in a linear and curvilinear manner with increasing leaf temperature up to 40 C. Heat tolerant and sensitive clones had similar rates of increase in Rd with increasing leaf temperature. Simultaneous measurement of Rd and Pn did not help explain differences in heat tolerance among clones. However, determination of respirationrphotosynthesis ratios may help explain the physiological basis for heat tolerance of some clones.     

Soil Moisture Simulation under Cropped Condition Using a Moisture Dependent Root Sink Function

Moisture dependent root sink function developed by F eddes et al. (1976) which incorporates linearly varying moisture availability proposal between field capacity and wilting point was embedded in the continuity equation for transient moisture flow in conjunction with Darcy's law and moisture contents in a homogeneous soil profile under wheat cropped condition were simulated numerically using implicit finite difference scheme. Simulated moisture contents were observed to be reasonably in good agreement with the observed moisture contents as the variations between the simulated and observed values varied from 2.97 to 21.76 percent.     

Novel quantitative trait loci for yield and yield related traits identified in Basmati rice (Oryza sativa)

Increasing crop productivity is one of the prime goals of crop breeding research. Rice grain yield is a complex quantitative trait governed by polygenes. Although several QTLs governing grain yield traits have been reported and limited attempts have been made to map QTLs for grain yield parameters in Basmati rice. A population from the cross Sonasal and Pusa Basmati 1121 comprising 352 RILs was generated through the single seed descent method. A total of 12 QTLs governing yield and yield-related traits were mapped on six chromosomes, namely, 1, 2, 3, 7, 8 and 9, of which five QTLs were novel. We identified a novel and robust epistatic QTL (qPH1.1 and qPL1.1) governing plant height and panicle length, flanked by the markers RM5336-RM1 on chromosome 1. The gene encoding brassinosteroid insensitive 1-associated receptor kinase 1 precursor is the putative candidate gene underlying this epistatic QTL. Another novel QTL, qNT3.1, governing tiller number was bracketed to a region of .77 Mb between the markers RM15247 and RM15281 on chromosome 3. Of the 57 annotated gene models, Os03g0437600 encoding alpha/beta-fold hydrolase, a homologous to AtKai2 is a putative candidate gene underlying the novel QTL qNT3.1. The other QTLs such as qDFF1.1 governing days to 50% flowering co-localizes with the gene Ghd7, QTL for plant height qPH1.2 co-localizes with the gene sd1, the QTLs for panicle length co-localizes with FUWA and DEP2, the QTL for tiller number co-localizes with OsRLCK57 and QTLs for thousand-grain weight co-localize with the major gene GS3. The QTLs identified in the current study can be effectively used in marker-assisted selection for developing Basmati rice varieties with a higher yield.     

Phenotypic variation and the relationships among mustard (Brassica juncea L.) germplasm from Pakistan

An investigation was conducted to determine the extent of diversity and relationships among the Brassica juncea germplasm from Pakistan using morphological characters. A total of 52 accessions, including the collected germplasm as well as commercial cultivars/improved lines, were studied under field conditions at Tsukuba, Japan during 1995 and 1996. All the accessions were characterized for 35 agro-morphological characters from seedling emergence to crop maturity. Morphological data were analyzed by numerical taxonomic techniques using two complementary procedures: cluster and principal component analyses. Phenograms based on Euclidean distance placed the accessions into six groups during both years. Landrace groups were primarily associated with morphological differences among the accessions and secondarily with the breeding objectives and horticultural uses. The mustard germplasm collected from Pakistan showed a comparatively low level of phenotypic variation amongst themselves and were genetically similar to the oilseed cultivars. However, the oilseed forms and vegetable cultivars were genetically distinct. This study revealed that the evaluated germplasm appears to have a narrow genetic base which undergoes a high level of genetic erosion. This is perhaps due to the use of the same ancestors in the selection of new lines for similar horticultural traits, replacement by major crops and changes in agricultural land uses. This revised version was published online in July 2006 with corrections to the Cover Date.     

A bottleneck in lentil: widening its genetic base in South Asia

This paper introduces the concept of a bottleneck in lentil (Lens culinaris Medikus) in South Asia and then reviews its rupture. South Asia is the largest lentil growing region in the world and where indigenous lentils show a marked lack of variability. This results from its introduction from Afghanistan around 2000 B.C. and it limits breeding progress. Three approaches to widening the genetic base in the region have been tried, namely plant introduction, hybridization and mutation breeding. Introductions from West Asia flower as indigenous material matures. The asynchrony in flowering has isolated the local pilosae ecotype reproductively. However, the introduction of ILL 4605, an early, large-seeded line, has resulted in its release as ‘Manserha 89’ for wetter areas of Pakistan and its widespread use as a parent in breeding programs in the region. Hybridization between pilosae and exotic germplasm, primarily at International Center for Agricultural Research in the Dry Areas (ICARDA) followed by selection in the sub-continent has resulted in cultivars with improved disease resistance and yield in Bangladesh and Pakistan. Mutation breeding has given new morphological markers and several promising lines. These examples illustrate not only the widening of the genetic base of the lentil in South Asia, but also the evolution of a breeding program of an international center and national programs targeted toward specific adaptation. This revised version was published online in July 2006 with corrections to the Cover Date.