Drought is the major constraint limiting rainfed rice production. The ability of rice roots to penetrate compacted soils and therefore to increase water extraction capacity, osmotic adjustment and dehydration tolerance of leaves enables the plant to tolerate drought. Experiments were conducted to determine the extent of genetic variation in root penetration index, osmotic adjustment and dehydration tolerance among indica accessions adapted to rainfed lowlands as well as traditional varieties from rainfed uplands. Root penetration index was evaluated in a system using wax–petrolatum layers to simulate soil compaction. Osmotic adjustment and dehydration tolerance were studied under slow development of water stress. Substantial genetic variation was found for root penetration index, osmotic adjustment and dehydration tolerance among indica ecotypes from lowlands, and the study of several traditional varieties from uplands showed variation in root penetration index and related root traits. An indica accession, IR58821‐23‐B‐1‐2‐1 had a high root penetration index of 0.38. The accessions, IR61079‐33‐1‐2‐2‐3, IR62266‐42‐6‐2 and IR63919‐38‐B‐1 had high osmotic adjustment capacities (1.91, 1.90 and 1.78 MPa, respectively); IR61079‐33‐1‐2‐2‐3 also had high dehydration tolerance. Good osmotic adjustment and dehydration tolerance were associated with poor root system. The traditional varieties ‘Kallurundaikar’ and ‘Norungan’ had higher root penetration indices (0.46 and 0.43, respectively), than even the japonica accessions. The study identified indica accessions and traditional varieties with superior root‐ and shoot‐related drought resistance traits that could be used in breeding for drought resistance in rice.
Green cybrids with a new nucleus-chloroplast combination cannot be selected after protoplast fusion in the intersubfamilial Nicotiana-Solanum combination. As an approach to overcome the supposed plastomegenome incompatibility, a partial plastome transfer by genetic recombination has been considered. After fusions of protoplasts of a light-sensitive Nicotiana tabacum (tobacco) plastome mutant and lethally irradiated protoplasts of wild-type Solanum tuberosum (potato), a single green colony was recovered among 2.5×10(4) colonies. The regenerated plants had tobacco-like (although abnormal) morphology, but were normally green, and sensitive to tentoxin, demonstrating chloroplast markers of the potato parent. Restriction enzyme analysis of the chloroplast DNA (cpDNA) revealed recombinant, nonparental patterns. A comparison with physical maps of the parental cpDNA demonstrated the presence of a considerable part of the potato plastome flanked by tobacco-specific regions. This "potacco" plastome proved to be stable in backcross and backfusion experiments, and normally functional in the presence solely of N. tabacum nucleus.
Cassava witches' broom (CWB) is an important disease of Manihot esculenta Crantz that is widely cultivated across South East Asia. In 2010, more than 60,000 ha were affected in Vietnam with crop losses as high as 80%, and reductions in yield and starch content reached 30%. The disease was observed in Quang Ngai, Dong Nai and Yen Bai provinces of Vietnam, also affecting the availability of clean planting material. Studies were then carried out on the etiology of this disease to acquire information about its management. Aster yellows phytoplasmas were detected and restriction fragment length polymorphism analyses of nested PCRamplified fragments from Vietnamese CWB phytoplasmas indicated the presence of differentiable strains all related to the 16SrI group. Sequence analyses of partial 16S rDNA fragments showed that Vietnamese CWB phytoplasmas have 99% similarity with 'Candidatus Phytoplasma asteris'. To our knowledge, this is the first report of cassava infection with phytoplasmas related to the 16SrI group in Vietnam.
Two groups of TiO 2 thin films were deposited onto Corning glass substrates by the RF magnetron sputtering in reactive argon gas containing 20% oxygen and by the sol-gel technique combined with dip coating. The films prepared by RF sputtering were annealed for 15 min at 650 • C with different rates of increase of temperature with the aim to search for the TiO 2 anatase phase formation. Besides, with the same aim, a set of the TiO 2 films prepared by sol-gel technique was doped with Co in the concentration range from 0 to 8% by weight. Influence of the rate of increase of temperature and Co doping on the anatase phase formation have been observed and estimated by x-ray diffraction and Raman scattering. Structure deformation induced by rapid heating and Co doping is considered as the main reason affecting the anatase phase formation in TiO 2 thin films.
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