Heterosis for yield and yield attributes in rice (Oryza sativa L.)

The present study was carried out to study the extent of heterosis, heterobeltiosis and standard heterosis for yield and yield parameters in rice. Analysis of variance indicated significant difference among the genotypes for various traits. Estimation of heterosis for various yield contributing traits indicated that out of nine crosses studied, Pusa sugandh-2 X BPT-5204 (27.93) and Pusa sugandh-2 X Kasturi (24.71) were identified as promising. These hybrids may be recommended for commercial cultivation after further evaluation

Heterosis for yield and quality traits in rice (Oryza sativa L.)

Twenty F1 hybrids from three CMS lines and eight pollen parents were evaluated to study the heterosis for various yield and quality traits in rice (Oryza sativa L.). The findings suggested that the magnitude of heterosis differed from character to character and cross to cross. Majority of the hybrids recorded desirable heterosis for grain yield. Among the rice hybrids exhibiting high heterosis for grain yield, IR-68897A x Pusa Sugandh-3, IR-58025A x HUR-JM-59221 and IR-58025A x Pusa Sugandh-5 were top performers. The hybrid, IR-68897A x Pusa Sugandh-3 recorded highest yield per plant, and was among the best three performers for traits, days to 50% flowering, days to maturity and number of effective tillers per plant. Thus, IR-68897A x Pusa Sugandh-3 may be considered as the best heterotic combination for yield and yield traits. Among the three high yielding hybrids, IR-58025A x Pusa Sugandh-5 was found to be relatively better performing for majority of the quality traits. Thus, IR-58025A x Pusa Sugandh-5 may be considered as the best cross combination if both yield and quality traits are taken into consideration

Combining ability analysis for various yield and quality traits in rice (Oryza sativa L.)

An investigation was undertaken to assess the combining ability for yield and quality traits in rice. Three WA cytoplasmic male sterile lines of rice i.e., IR-58025A, IR-68897A and Pusa 6A were crossed with six restorer genotypes i.e., Sanwal Basmati, Pusa Sugandh-2, Pusa Sugandh-3, Pusa Sugandh-5, Pusa 2517-2-51-1 and HURJM- 59221 in line x tester design to generate 18 hybrids. Among the female parents, IR-58025A revealed significant desirable value of GCA effect for yield per plant and most of the quality traits. Among the pollen parents, Pusa Sugandh-3 revealed significant desirable value of GCA effect for most of the yield traits. However, Pusa Sugandh-5 revealed significant desirable value of GCA effect for most of the quality traits. Pusa 6A x Pusa Sugandh-2 evinced the highest significant value of SCA effect for grain yield followed by IR-58025A x Pusa Sugandh-5. However, IR- 68897A x Pusa 2517-2-51-1 followed by IR-58025A x Sanwal Basmati revealed the significant desirable value of SCA effect for most of the quality traits. For both yield and quality traits, IR-58025A x Pusa Sugandh-5, IR-68897A x HUR-JM-59221 and Pusa 6A x Pusa Sugandh-2 were found to be relatively better performing. Thus, present study aims to develop hybrids performing better for both yield and quality traits

Search for astrophysical sources of neutrinos using cascade events in IceCube

The IceCube neutrino observatory has established the existence of a flux of high-energy astrophysical neutrinos inconsistent with the expectation from atmospheric backgrounds at a significance greater than $5\sigma$. This flux has been observed in analyses of both track events from muon neutrino interactions and cascade events from interactions of all neutrino flavors. Searches for astrophysical neutrino sources have focused on track events due to the significantly better angular resolution of track reconstructions. To date, no such sources have been confirmed. Here we present the first search for astrophysical neutrino sources using cascades interacting in IceCube with deposited energies as small as 1 TeV. No significant clustering was observed in a selection of 263 cascades collected from May 2010 to May 2012. We show that compared to the classic approach using tracks, this statistically-independent search offers improved sensitivity to sources in the southern sky, especially if the emission is spatially extended or follows a soft energy spectrum. This enhancement is due to the low background from atmospheric neutrinos forming cascade events and the additional veto of atmospheric neutrinos at declinations $\lesssim-30^\circ$.Comment: 14 pages, 9 figures, 1 tabl

Measurement of the multi-TeV neutrino cross section with IceCube using Earth absorption

Neutrinos interact only very weakly, so they are extremely penetrating. However, the theoretical neutrino-nucleon interaction cross section rises with energy such that, at energies above 40 TeV, neutrinos are expected to be absorbed as they pass through the Earth. Experimentally, the cross section has been measured only at the relatively low energies (below 400 GeV) available at neutrino beams from accelerators \cite{Agashe:2014kda, Formaggio:2013kya}. Here we report the first measurement of neutrino absorption in the Earth, using a sample of 10,784 energetic upward-going neutrino-induced muons observed with the IceCube Neutrino Observatory. The flux of high-energy neutrinos transiting long paths through the Earth is attenuated compared to a reference sample that follows shorter trajectories through the Earth. Using a fit to the two-dimensional distribution of muon energy and zenith angle, we determine the cross section for neutrino energies between 6.3 TeV and 980 TeV, more than an order of magnitude higher in energy than previous measurements. The measured cross section is $1.30^{+0.21}_{-0.19}$ (stat.) $^{+0.39}_{-0.43}$ (syst.) times the prediction of the Standard Model \cite{CooperSarkar:2011pa}, consistent with the expectation for charged and neutral current interactions. We do not observe a dramatic increase in the cross section, expected in some speculative models, including those invoking new compact dimensions \cite{AlvarezMuniz:2002ga} or the production of leptoquarks \cite{Romero:2009vu}.Comment: Preprint version of Nature paper 10.1038/nature2445

Search for astrophysical sources of neutrinos using cascade events in IceCube

The IceCube neutrino observatory has established the existence of a flux of high-energy astrophysical neutrinos inconsistent with the expectation from atmospheric backgrounds at a significance greater than $5\sigma$. This flux has been observed in analyses of both track events from muon neutrino interactions and cascade events from interactions of all neutrino flavors. Searches for astrophysical neutrino sources have focused on track events due to the significantly better angular resolution of track reconstructions. To date, no such sources have been confirmed. Here we present the first search for astrophysical neutrino sources using cascades interacting in IceCube with deposited energies as small as 1 TeV. No significant clustering was observed in a selection of 263 cascades collected from May 2010 to May 2012. We show that compared to the classic approach using tracks, this statistically-independent search offers improved sensitivity to sources in the southern sky, especially if the emission is spatially extended or follows a soft energy spectrum. This enhancement is due to the low background from atmospheric neutrinos forming cascade events and the additional veto of atmospheric neutrinos at declinations $\lesssim-30^\circ$.Comment: 14 pages, 9 figures, 1 tabl

Book Reviews

With the observation of high-energy astrophysical neutrinos by the IceCube Neutrino Observatory, interest has risen in models of PeV-mass decaying dark matter particles to explain the observed flux. We present two dedicated experimental analyses to test this hypothesis. One analysis uses 6 years of IceCube data focusing on muon neutrino ‘track’ events from the Northern Hemisphere, while the second analysis uses 2 years of ‘cascade’ events from the full sky. Known background components and the hypothetical flux from unstable dark matter are fitted to the experimental data. Since no significant excess is observed in either analysis, lower limits on the lifetime of dark matter particles are derived: we obtain the strongest constraint to date, excluding lifetimes shorter than $10^{28}$ s at 90% CL for dark matter masses above 10 TeV