Differential amplification of rDNA repeats in barley translocation and duplication lines: role of a specific segment

Variation in restriction pattern, relative amounts of the two ribosomal DNA (rDNA) repeats, and the overall content of rDNA were compared among twelve segmental duplications and eleven parental translocations involving NOR6 and NOR7 of cultivated barley. Southern blot hybridization revealed two rDNA repeats of 9.9 kb and 9.0 kb. While all duplications snowed dimers for these rDNA repeats, the duplication lines D29 and D47 displayed trimers in addition to a higher proportion of rDNA repeats as dimers. The rDNA of Dl, D29 and D47 showed resistance to Bam HI and Taq I digestion, indicating possible melhylation of cytosine and adenine. Densitometric scans of autoradiographs revealed variations in the relative amounts of the 9.0 kb and 9.9 kb rDNA repeats among different karyotypes. Dot blot hybridizations indicated variation in the overall rDNA content. Comparison of the 9.0/9.9 kb ratios and the percentage of genomic DNA hybridizing to an rDNA clone of barley illustrates differential amplification for the two rDNA repeats. When the segmental composition of these deviating lines were compared, it was evident that the relative position of the segment 12-16 of chromosome 6 determines differential amplification while duplication of the same segment controls the overall rDNA content

Resistance to Early Leaf Spots in Peanuts

Early leafspot caused by Cercospora arachidicola Hari is a serious disease of peanuts in Malawi. Disease survey in the 1982/83 crop season showed that early leafspot was causing severe damage to peanut

Proceedings of the Fifth Regional Groundnut Workshop for Southern Africa 9-12 March 1992

Eighteen scientists representing national programs and agricultural universities in the Southern African Development Coordination Conference (SADCC) region participated in this regional workshop. Angola and Lesotho were the only countries of the region not represented. Also participating were five groundnut scientists from four other African countries(Ethiopia, Kenya, Nigeria, and Uganda), representatives from the Southern African Centre for Cooperation in Agricultural Research and Training(SACCAR) and Deutsche Gesellschaft fur Technische Zusammenarbeit(GTZ), and 10 ICRISAT delegates. Papers reviewed various aspects of groundnut research, particularly agronomy and physiology. Country reports summarized the state of groundnut research in each country represented. The recommendations made at the Workshop's plenary session provide valuable guidelines for regional project activities

Effect of high-temperature heat treatment duration on the purity and microstructure of MWCNTs

The effect of high-temperature heat treatment on purity and structural changes of multiwalled carbon nanotubes (MWCNTs) were studied by subjecting the raw MWCNTs (pristine MWCNTs) to 2600∘C for 60 and 120 min. Thermogravimetric analysis (TGA), X-ray diffraction, Raman spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to study the effect of heat-treatment duration on the purity and structural changes of MWCNTs. Results show that high-temperature heat treatment can be used to purify MWCNTs with proper optimization of treatment time. It was observed that 60 min heat treatment of raw MWCNTs imparts high purity and structural perfection to MWCNTs, while 120 min heat treatment imparts structural degradation to MWCNTs with collapse of the innermost shells. The present study indicates that metal impurities act as moderators in controlling the degradation of MWCNTs up to certain duration, and once the metal impurities escape completely, further heat treatment degrades the structure of MWCNTs

Improving Scheelite Recovery from Gold Tailings

Tungsten occupies a very important place amongst the strategic metals. However, resources available in India are scarce and lean in grade. Various physical methods of beneficiation have been tried to beneficiate such, low grade ores, but these have not been generally efficient in terms of high recoveries and concentrate grades. Tungsten minerals, wolframite and scheelite being friable, tend to slime during size reduction stages. Because of this, high loss in slimes occurs during conventional gravity opera-tions. Flotation techniques too have not been very succe-ssful though some excellent results have been reported by Mercade (1) on direct flotation of scheelite from low grade ores. Recently special gravity concentration equi-pment such as Bartles Mozley Separator (MIS)and Cross Belt Concentrator (CBC) have been used in separation of a wide variety of fine heavy minerals including scheelite (2, 3, 4, 5). To obtain a high grade concentrate, a combination of gravity and flotation and/or magnetic separation method is generally employed

Cohesion Factor Relations for Cubic Equations of State: Soave-Redlich-Kwong Equation of State

Cubic Equations of States (CEOS), a well celebrated tool for predicting phase equilibrium, can be compared based on the accuracy of the prediction of vapor pressure. Accurate vapor pressure prediction is completely dependent on cohesion factor used in CEOS. In the present work, six cohesion function models for Soave Redlich Kwong (SRK) Equations of State (EOS), available in literature have been compared. 313 compounds, compromising of 29 different classes of families, have been selected for the study. The reduced temperatures were studied in three regions; (i) Tr=0.7 and (iii) entire range from freezing point to critical point. It was observed that all the models compared here show the acceptable behavior except model proposed by Soave (Soave, 1992). Some families showed very high deviation in AAD, which can be attributed to more than one factor like polarity, acentricity, and association

Intergeneric hybridization in pigeonpea. I. Effect of hormone treatments

Attempts to cross Cajanus cajan with Atylosia albicans, A. cajanifolia, A. grandifolia, A. mollis, A. platycarpa, A. sericea and A. volubilis resulted in varying degrees of success. Hormone treatment (gibberellic acid and kinetin) increased pod-set and the number of seeds per pod. Hormone treatment among the unsuccessful crosses delayed bud drop by 3–4 days, which prolonged ovule development. Our results indicate that treatment with hormones helps post-fertilization development and leads to improvement in the rate of crossing succes

Intergeneric hybridization in pigeonpea. II. Effect of cultivar on crossability and hybrid fertility

Eight species of Atylosia hybridized with Cajanus cajan L. Millsp. with varying degrees of success when Cajanus was the female parent. The cultivar of the Cajanus parent influenced both the species crossability and hybrid fertility. Variation in the extent of species crossability and hybrid fertility was less pronounced in Cajanus × Atylosia crosses involving Cajanus cultivars derived from a common female background

Nucleolar variation in a pigeon pea intergeneric hybrid: evidence for allosyndetic recombination

Cytological study of a hybrid between Cajanus cajan and Atylosia albicans revealed regular bivalent formation and disjunction. Nevertheless, high pollen sterility and low seed set were evident. An examination of pollen mother cells revealed variation in nucleolar number at telophase-I (four to eight) and at telophase-II (zero to four in daughter nuclei), although each genome contained two nucleolar organizers. Variation was also recorded for nucleolar size and distribution at telophase-II. Variation in nucleolar number and distribution are interpreted to have originated from pairing and recombination between nucleolar organizer chromosome(s) of one parental species with the nonnucleolar organizer chromosome(s) of the other. Size variation is attributed to nucleolar dominance. These results explain the high degree of pollen sterility in the hybrid in spite of normal meiosis, and also suggest that the karyotypes of C. cajan and A. albicans have differentiated through structural heterozygosity