All-optical control of ferromagnetic thin films and nanostructures

The interplay of light and magnetism has been a topic of interest since the original observations of Faraday and Kerr where magnetic materials affect the light polarization. While these effects have historically been exploited to use light as a probe of magnetic materials there is increasing research on using polarized light to alter or manipulate magnetism. For instance deterministic magnetic switching without any applied magnetic fields using laser pulses of the circular polarized light has been observed for specific ferrimagnetic materials. Here we demonstrate, for the first time, optical control of ferromagnetic materials ranging from magnetic thin films to multilayers and even granular films being explored for ultra-high-density magnetic recording. Our finding shows that optical control of magnetic materials is a much more general phenomenon than previously assumed. These results challenge the current theoretical understanding and will have a major impact on data memory and storage industries via the integration of optical control of ferromagnetic bits.Comment: 21 pages, 11 figure

Biotechnological Approaches to Evolve Sorghum (Sorghum bicolor (L.) Moench) for Drought Stress Tolerance and Shoot fly Resistance

Sorghum is a model tropical grass that uses C4 photosynthetic activity. But its yield is affected by many abiotic stresses likeheat, drought, cold, salt and also biotic stresses such as shoot fly, midges, and stem borerfromseedling stages to maturity. This article summarizes the terminal drought stress tolerance mechanism with staygreen phenotype expression during postflowering and also mechanisms of early shoot fly resistance during seedling stages of crop growth. The trait stay-green is extensively studied and its correlation to yield makes the stay-green trait more special for research and in marker assisted back cross programs. Under terminal drought stress conditions, stay-green trait is expressed with a complex mechanism involving many transcription factors, chlorophyll retention and nitrogen remobilization from leaves to maintain longer photosynthetic activity. Shoot fly resistance on the other hand, involves manyphysico-chemical, biologicaland morphological traits. Out of the many morphological traits, seedling leaf blade glossiness and trichome density are well characterized at genetic level and can assist as shoot fly resistance sources in marker-assisted breeding programs as they are highly negatively correlated with shoot fly dead heart formation. However, quantitative trait loci (QTL) mapping studies and candidate genes identified for the stay-green and shoot fly component traits need to be further validated with fine mapping, gene cloning and expression level studies. Pyramiding these two traits into a high yielding sorghum variety may lead to multiple stress resistance which could ultimately benefit the marginal farmers in India

Different isoforms of starch-synthesizing enzymes controlling amylose and amylopectin content in rice (Oryza sativa L.)

Starch, composed of amylose and amylopectin, greatly influences rice cooking and textural quality, which in turn is controlled by various isoforms of several enzymes. Activity of one or more isoforms of starch synthesizing enzymes results in various forms of starch structure based on the amylopectin chain length, average external, internal and core chain length distribution and hence result in varying physicochemical and cooking quality. Since the synthesis of starch is highly complex, it is crucial but essential to understand its biosynthetic pathway, starch structure and its effects on the physicochemical properties that control eating and cooking quality; and alongside conduct research on gene/QTL mapping for use in marker-assisted selection (MAS) with a view to improve and select cultivars with most desirable range and class of rice starch properties. This article presents the updates on current understanding of the co-ordination among various enzymes/isoforms towards rice starch synthesis in endosperm and their effect on rice grain physico-chemical, cooking and eating qualities. The efforts in identifying regions responsible for these enzymes by mapping the gene/QTLs have provided a glimpse on their association with physic-chemical and cooking properties of rice and hence, improvement is possible by modifying the allelic pattern, resulting in down or nil regulation of a particular enzyme. The clear understanding of the tissue specific co-ordination between enzyme isoforms and their subsequent effect in controlling eating and cooking properties will enhance the chances to manipulate them for getting desired range of amylose content (AC) and gelatinization temperature (GT) in improved cultivars through combining desired alleles through MAS

Seed microflora of five ICRISAT mandate crops

International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) supplies seeds of sorghum, pearl millet, pigeonpea, chickpea, and groundnut for research globally. The export of seeds of these crops is channelized through the regional station of the National Bureau of Plant Genetic Resources (NBPGR), Rajendranagar, Hyderabad. However, the tests for quarantine clearance of seeds for export are done at the Export Certification Laboratory at the ICRISAT Center. During the period from June 1989 to December 1997, ICRISAT exported 371,818 samples of its mandate crops to 136 countries. The largest number of exported samples were of sorghum (140,143) followed by chickpea (119,308). A total of 1786 samples (sorghum, 571; pearl millet, 120; pigeonpea, 311; chickpea, 199; Groundnut, 585) were detained due to heavy seed infection by fungi and/or bacteria (>80% seed infection). Pigeonpea appeared to be the most popular crop exported to 105 countries followed by sorghum (91 countries) and groundnut (88 countries). A total of 182 fungal spp. belonging to 71 genera were recorded. Largest number of fungi-132 fungal species across the years, were found associated with sorghum crop. The corresponding figures for pearl millet, chickpea, pigeonpea, and groundnut were 94, 91, 96, and 60, respectively. Aspergillus spp. were more on pulses and groundnut than on sorghum and pearl millet; however, Curvularia spp. showed the reverse trend. Fusarium and Alternaria spp. occurred most frequently on pigeonpea followed by on sorghum. Also, there was a total absence of three graminicolous fungi - Dreschlera, Biopolaris and Exserohilum spp. on groundnut. There were 31 fungi associated with all the five crops. Aspergillus niger (3.8%) and Cladosporium spp. (3.6%) were the most commonly occurring fungi being most predominant on groundnut and sorghum, respectively

Detection, seedborne nature, disease transmission and eradication of seedborne infection by rhizoctonia bataticola (Taub) butler in groundnut

A study was conducted to determine the seedborne nature, disease transmission and eradication of seedborne infection by Rhizoctonia bataticola in groundnut. In case of 10 groundnut accessions, infection percentage of R. bataticola, ranged between 13.3 to 73.3. Component-plating method indicated that the pathogen is located mainly on the seed coat and rarely in the endosperm and embryo. Infection in embryo and endosperm was always associated with seed coal infection. All accessions showed pre-emergence damping-off in the form of seed rot. Post- emergence damping-off was noticed in three accessions. The per cent infection ranged between 9.5 to 42.9 in case of pre-emergence damping-off. while it was 4.8 to 19.1 for post-emergence damping-off. The latent infection of R. bataticola from healthy seedlings was proved using Potato carrot agar medium. Infected seeds of 10 groundnut accessions were gi~own and no apparent symptoms were observed on the plants for one season, but seeds harvested from such plants resulted in seed infection of 6.1 - 33.3 % indicating the seed transmission nature of the pathogen from one generation to the next. Carbendazim + tin ram @ 2g a.i / kg seed can be used as a routine treatment in quarantine laboratories to eliminate R. bataticola from groundnut seed

Improvement of two traditional Basmati rice varieties for bacterial blight resistance and plant stature through morphological and marker-assisted selection

Bacterial blight (BB) is a major production threat to Basmati, the aromatic rice prized for its unique quality. In order to improve the BB resistance of two elite, traditional BB-susceptible Basmati varieties (Taraori Basmati and Basmati 386), we utilized the strategy of limited marker-assisted backcrossing for introgression of two major BB resistance genes, Xa21 and xa13, coupled with phenotype-based selection for improvement of their plant type and yield. Improved Samba Mahsuri, an elite high-yielding, fine-grain-type BB-resistant rice variety served as donor for BB resistance. Backcross-derived improved Basmati lines at BC1F5 possessing a single resistance gene (i.e. either Xa21 or xa13) displayed moderate resistance to BB, while lines possessing both Xa21 and xa13 showed significantly higher levels of resistance. Two-gene pyramid lines (Xa21 + xa13) possessing good grain and cooking quality similar to their respective traditional Basmati parents, short plant stature (<110 cm plant height) and higher grain yield than the recurrent parent(s) were identified and advanced. This work demonstrates the successful application of marker-assisted selection in conjunction with phenotype-based selection for targeted introgression of multiple resistance genes into traditional Basmati varieties along with improvement of their plant stature and yield