A novel environment-induced genic male sterile (EGMS) mutant in indica rice
SummaryMale-sterile mutants were isolated from M2 and M3 generations of indica rice variety 26 Zhaizao, dry seeds of which had been exposed to 60Co-γ rays at a dose of 290 Gy. The mutants were planted in early season and ratooned in late season for two successive years for identification of fertility conversion in different growing seasons. One of the mutant lines was further observed in a growth chamber and in the field. Results showed that daily average temperature might be the major factor conditioning the male fertility conversion at a moderate daylength. The critical temperature for the male fertility conversion of the mutant grown under 12.5 h and 14.0 h daylength is about 23°C, below which the plant becomes completely male sterile. Its male fertility conversion character differs from other EGMS lines so far developed. The performance of the hybrids between the mutant and some other indica varieties demonstrated its good combining ability and its potential value in hybrid rice production. The obtained mutant line still sheds KI-stainable pollen grains under male sterilizing conditions. Nevertheless, pollen grains shed from the male sterile plants were much more vulnerable than from normal plants. At sucrose concentration below 1.5 M, the pollen grains from the mutant grown under male sterilizing conditions almost completely broke down, while above 1.5 M they became plasmolysed and shrunken. This is indicative of poor development of the membrane and walls of the pollen grains from the male sterile mutant, causing the pollen grains to be unfunctional. NBT test also clarified the abortion of the pollen grains from the mutant, which were formed in the male sterilizing environment.
Cytogenetic Analysis of Thermosensitive Genic Male Sterility (TGMS) Recovered from a Pennisetum glaucum (L.) R. Br.×P. violaceum (Lam.) L. Rich Cross
One male-sterile plant was recovered from a cross between pearl millet (Pennisetum glaucum) and its wild progenitor P. violaceum. The behavior of male sterility was temperature dependent, as the development of pollen mother cells to pollen grains was found to be dependent on temperature. The plant showed sterility at lower temperatures while it was fertile at higher temperatures during seasonal variations. This thermosensitive male sterility trait was found to be genetically controlled based on the segregation data of backcross generation. Segregation was observed for ca. 50% of the population expressing this trait. These TGMS plants exhibited transition from fertility to sterility when mean daily temperature reduced to ca. 20°C or below, and fertility was restored above this temperature. The period of 4 to 5 d prior to anthesis was found to be most sensitive to temperature variations. Chromosomal studies on the parent plant as well as segregants showed 2n=14 with regular meiosis during non-sensitive phase (period exhibiting male-fertility) ruling out aneuploidy and/or gross chromosomal structural aberrations as a cause of male sterility. Fertility characters were also studied for TGMS and non-TGMS plants during sensitive and non-sensitive phases. Pollen grains shed from the TGMS plants were much more vulnerable than from normal plants during sensitive phase indicating poor development of the membrane and walls of the pollen grains during sterility inducing conditions. Transition characteristics from male sterility to male fertility during sensitive and non-sensitive phases for TGMS and non-TGMS plants are discussed.
Natural Radioactivity of Intrusive-Metamorphic and Sedimentary Rocks of the Balkan Mountain Range (Serbia, Stara Planina)
Stara Planina (also known as the Balkan mountain range) is known for numerous occurrences and deposits of uranium and associated radionuclides. It is also famous for its geodiversity. The geologic framework is highly complex. The mountain is situated between the latitudes of 43° and 44° N and the longitudes from 22°16′ to 23°00′ E. Uranium exploration and radioactivity testing on Stara Planina began back in 1948. Uranium has also been mined in the zone of Kalna, within the Janja granite intrusive. The naturally radioactive geologic units of Stara Planina are presented in detail in this paper. The main sources of radioactivity on Stara Planina can be classified as: 1. Granitic endogenous—syngenetic–epigenetic deposits and occurrences; 2. Metamorphogenic—syngenetic; and 3. Sedimentary, including occurrences of uranium deposition and fluctuation caused by water in different types of sedimentary rocks formed in a continental setting, which could be classified under epigenetic types. The area of Stara Planina with increased radioactivity (higher than 200 cps), measured by airborne gamma spectrometry, is about 380 square kilometers. The highest values of measured radioactivity and uranium grade were obtained from a sample taken from the Mezdreja uranium mine tailing dump, where 226Ra measures 2600 ± 100 Bq/kg and the uranium grade is from 76.54 to 77.65 ppm U. The highest uranium (and lead) concentration, among all samples, is measured in graphitic schist with high concentrations of organic (graphitic) material from the Inovska Series—99.47 ppm U and 107.69 ppm Pb. Thorium related radioactivity is the highest in granite samples from the Janja granite in the vicinity of the Mezdreja granite mine and the Gabrovnica granite mine tailing dump, and it is the same—250 ± 10 Bq/kg for 232Th, while the thorium grade varies from 30.82 to 60.27 ppm Th. In gray siltstones with a small amount of organic material, the highest radioactivity is related to potassium—2080 ± 90 Bq/kg for 40K.