Anaerobic metabolism enzymes as markers of flooding stress in maize seeds

Maize (Zea mays L.) seeds differ in their relative tolerance to the anaerobic environment caused by flooding. Seed tolerance to flooding stress depends on cellular and metabolic processes since gross anatomical responses have not developed at the pre-emergence stage. The study reported here characterizes the activities of four anaerobic respiratory enzymes: pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH), lactate dehydrogenase (LDH), and malic enzyme (ME) in the flood-tolerant A632 and floodsusceptible Mo 17 inbred maize seeds during flooding at 10 and 25°C. Each inbred consisted of two seed lots possessing 95% and 75% germination levels. Flooding increased the activities of all four enzymes. However, no consistent correlation between anaerobic enzyme activity and flood tolerance was observed across genotype, seed quality and flooding temperature. The results indicate that it may not be feasible to use whole-seed anaerobic enzyme activities to predict maize seed performance under flooding stress. Contribution from the Soil Drainage Research Unit, USDA-ARS, Columbus, OH, in cooperation with the Ohio Agricultural Research and Development Center, The Ohio State University. OARDC Journal Article No. 66–86.     

Correlation studies on yield and fibre traits in upland cotton (Gossypium hirsutum L.)

Summary Two diverse parents of upland cotton namely J.34 and I.C. 1926 were crossed. A comparison between biparental intermated progenies and F₃ families indicated alteration of correlation coefficient between yield and halo length. The significant negative correlation in F₃ population between these two attributes changed to a positive but non significant one in biparental intermated progenies. A change in correlation coefficients was expected due to breakage of linkage upon intermating. An increase in the correlation coefficients could also be expected when linkages are predominantly in the repulsion phase. It is suggested that intermating in early generations coupled with selection of desirable segregants may prove a useful method for improving yield and quality simultaneously. The diallel selective mating system may also supplement intermating to improve yield and quality in cotton.Part of Ph.D. Thesis submitted to the Haryana Agricultural University. Hissar-125004, India     

Inheritance of resistance to potato y viruses in Phaseolus vulgaris L

Summary Resistance to watermelon mosaic virus-2 in Phaseolus vulgaris L. is conferred by two distinct dominant alleles at independent loci. Based on segregation data one locus is designated Wmv, the other, Hsw. The dominant allele Wmv from cv. Great Northern 1140 prevents systemic spread of the virus but viral replication occurs in inoculated tissue. In contrast, Hsw confers both local and systemic resistance to WMV-2 below 30C. At higher temperatures, plants that carry this allele in the absence of modifying or epistatic factors develop systemic veinal necrosis upon inoculation with the virus that results in rapid death. Patho-type specificity has not been demonstrated for either allele; both factors confer resistance to every isolate tested. A temperature-sensitive shift in epistasis is apparent between dominant alleles at these loci. Because Hsw is very tightly linked if not identical to the following genes for hypersensitivity to potyviruses I, (bean common mosaic virus), Bcm, (blackeye cowpea mosaic virus), Cam, (cowpea aphid-borne mosaic virus) and Hss (soybean mosaic virus), parental, reciprocal dihybrid F₁ populations, and selected F₃ families were inoculated with each of these viruses and held at 35 C. F₁ populations developed vascular necrosis completely or primarily limited to inoculated tissue, while F₃ families from WMV-2-susceptible segregates were uniformly susceptible to these viruses. The relationship between Hsw, Wmv and other genes for potyvirus resistance suggest patterns in the evolution of resistance and viral pathogenicity. Characterization of the resistance spectrum associated with each factor provides an additional criterion to distinguish genes for plant virus resistance.     

Herbicide tolerant regenerates of potato

Summary Culture-derived plants and cell cultures of potato (Solanum tuberosum L.) respond to the application of the herbicides SYS 67 ME (MCPA) and OMNIDEL (Na-2,2-dichloropropionate) in a comparable fashion. By gradually increasing the herbicide concentration, cell lines were developed which tolerated 50 mg/l of ME or 300 mg/l of OMNIDEL. Any further increase in concentration resulted in the death of all cell cultures. From cell cultures that had been able to grow on media supplemented with 30 mg/l of ME, regenerate plants were obtained that were also tolerant to this concentration. This new trait was retained even after repeated vegetative propagation of the plants.     

A new species of the genusLotus (Fabaceae) in North Africa

A new species,Lotus digii, has been found in Morocco growing on the coastal sandy soils. Further localities are from Algeria and Egypt. It should be expected also in Libya.     

Concentration gradients of free sterols,steryl esters and lipid phosphorus in the trunkwood of Scot's pine (Pinus sylvestris L.)

The amounts of free sterols, steryl esters and lipid phosphorus were determined in the sapwood and heartwood of mature, and in the outer and inner sapwood of young Pinus sylvestris trees. In the mature trees (up to 70 years old) the heartwood contains significantly higher amounts of free sterols than the sapwood. No radial gradient can be demonstrated in the amounts of steryl esters. Lipids extracted from the sapwood contain higher amounts of phosphorus than those from the heartwood. Stems of young Pinus sylvestris trees (up to 13 years old) show in the inner sapwood higher amounts of both free sterols and steryl esters than the peripheral younger wood zone. The inner sapwood of the young stems shows slightly higher amounts of lipid phosphorus than the outer sapwood. The results indicate that Pinus sylvestris accumulates both free sterols and steryl esters in the stems at a very early stage of the life cycle. Sterol accumulation in the innermost parts of the stems seems not to depend on heartwood formation.     

Effect of root environment on proton efflux in wheat roots

Proton net efflux of wheat (Triticum aestivum L.) roots growing in sand culture or hydroponics was determined by measuring the pH values of the solution surrounding the roots by pH microelectrodes, by base titration and by color changes of a pH indicator in solid nutrient media. The proton net efflux was dependent on light, aeration, and source of nitrogen (NH ₄ ⁺ , NO ₃ ^? ). Ammonium ions caused the highest proton efflux, whereas nitrate ions decreased the proton efflux. Iron deficiency had no significant effect on proton efflux. Replacement of ammonium by nitrate inhibited proton efflux, whereas the reverse enhanced proton extrusion. A lag period between changes in plant environment and proton efflux was observed. The proton net efflux occurred at the basal portion of the roots but not in the root tips or at the elongation zone. Under optimal conditions, proton efflux capacity reached a maximum value of 5.7 μmole H⁺ g^?1 fresh weight h^?1 with an average (between different measurements) of 3.4 μmole H⁺ g^?1 fresh wth^?1 whereas the pH value decreased to 3.2–3.7 and reached a minimal value of 2.9. Inhibition of ATPase activity by orthovanadate inhibited proton efflux. The results indicate that proton efflux in wheat roots is ammonium ion and light dependent and probably governed by ATPase activity.     

Effect of selection intensity and population size on percent oil in maize,Zea mays L

Summary The effect of selection intensity and population size on the response to selection for percent oil in the grain of maize (Zea mays L.) was evaluated in a replicated experiment over ten cycles of selection. An open-pollinated variety, Armel's Reid Yellow Dent, was divided into subpopulations of 6,10 and 50 plants. Selection proportions of 17% and 5% were imposed upon each subpopulation. Selection was based on the percentage of oil in individual kernels as determined by wide-line nuclear magnetic resonance spectroscopy. As expected, total response to selection increased with larger population sizes and selection intensities. The concave shape of the response curves suggested that an appreciable part of the genetic variance can be attributed to additive genes at high initial frequencies, dominance genes at low initial frequencies, or to the generation of negative linkage disequilibrium due to selection. The consistently greater loss of vigor experienced by the more intensely selected populations reflects the enhancement of inbreeding due to artificial selection, an effect that increases with the intensity of selection. The results indicate that combined selection, based on kernels and using within- and amongfamily information, will be more efficient than other conventional selection procedures, including the normal combined scheme where selection is based on plants.Deceased     

Physical map of chloroplast DNA of aerial yam,Dioscorea bulbifera L.

Summary A physical map of chloroplast DNA (ctDNA) of aerial yam, Dioscorea bulbifera L. was constructed using three restriction endonucleases, PstI, SalI, and SmaI. In addition, a clone bank of the BamHI-digested fragments were generated, and the locations of most BamHI fragments on the map were also determined. The ctDNA of D. bulbifera was found to be a circular molecule with a total size of ca. 152 kb involving two inverted repeats of ca. 25.5 kb, and small and large single copy regions of ca. 18.5 and 83.4 kb, respectively. The genes for the large subunit of the ribulose 1,5-bisphosphate carboxylase (rbcL) and the ATP-synthase subunits and (atpB/atpE) were mapped.Contribution from the Plant Germ-plasm Institute and the Laboratory of Genetics (No. 504), Faculty of Agriculture, Kyoto University, Japan. The work was supported in part by a Grant-in-Aid (No. 60400005) from the Ministry of Education, Science and Culture, Japan