Screening of water-efficient rice genotypes for dry direct seeding in South Asia

<p>Rice genotypes having high crop water productivity in dry direct-seeded rice (DDSR) need to be assessed while promoting labor- and water-saving technology. The objective of this study was to evaluate the ability of several selection indices to identify genotypes with high crop water productivity in DDSR. A set of 16 genotypes [13 recombinant inbred lines (RILs) and three genotypes as check for control] were evaluated under DDSR for two consecutive years (2013 and 2014) using two irrigation regimes [-10 kPa (non-stress) and -20 kPa (stress)]. Grain yield varied from 5.3 to 8.4 t ha^-1 and 5.9 to 8.7 t ha^-1 for irrigation regimes of -20 and -10 kPa, respectively. Yield reductions caused by water stress ranged from 2.9 to 25.1%; being lowest in RIL1649 and highest in hybrid SVH-127. The genotypes with high stress-tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP) and harmonic mean productivity (HAR) were identified as the most productive genotypes for high crop water productivity in DDSR. The results implied that selection based on stress tolerance indices likes STI, MP, GMP and HAR was useful in identifying genotypes with high crop water productivity under DDSR and RIL 1649 and SVH-127 were identified as superior genotypes in this regard.</p

Yield-Enhancing Heterotic QTL Transferred from Wild Species to Cultivated Rice <i>Oryza sativa</i> L

<div><p>Utilization of “hidden genes” from wild species has emerged as a novel option for enrichment of genetic diversity for productivity traits. In rice we have generated more than 2000 lines having introgression from ‘A’ genome-donor wild species of rice in the genetic background of popular varieties PR114 and Pusa44 were developed. Out of these, based on agronomic acceptability, 318 lines were used for developing rice hybrids to assess the effect of introgressions in heterozygous state. These introgression lines and their recurrent parents, possessing fertility restoration ability for wild abortive (WA) cytoplasm, were crossed with cytoplasmic male sterile (CMS) line PMS17A to develop hybrids. Hybrids developed from recurrent parents were used as checks to compare the performance of 318 hybrids developed by hybridizing alien introgression lines with PMS17A. Seventeen hybrids expressed a significant increase in yield and its component traits over check hybrids. These 17 hybrids were re-evaluated in large-size replicated plots. Of these, four hybrids, viz., ILH299, ILH326, ILH867 and ILH901, having introgressions from <i>O. rufipogon</i> and two hybrids (ILH921 and ILH951) having introgressions from <i>O. nivara</i> showed significant heterosis over parental introgression line, recurrent parents and check hybrids for grain yield-related traits. Alien introgressions were detected in the lines taken as male parents for developing six superior hybrids, using a set of 100 polymorphic simple sequence repeat (SSR) markers. Percent introgression showed a range of 2.24 from in <i>O. nivara</i> to 7.66 from <i>O. rufipogon</i>. The introgressed regions and their putative association with yield components in hybrids is reported and discussed.</p></div

Performance of 17 introgression lines for important yield contributing traits.

<p>^a Significantly higher and ^c lower than the recurrent parent Pusa 44 or PR114 at <i>P</i>≤0.01.</p><p>^b Significantly higher and ^d lower than the recurrent parent Pusa 44 or PR114 at <i>P</i>≤0.05.</p

Mean values of the ILHs for important agronomic traits and extent of heterosis (%) over parents check hybrids and recurrent parents in 17 hybrids.

<p>*, **significant at <i>P≤0.05</i> and <i>P≤0.01</i>, respectively.</p><p>CH1 = PMS17A/Pusa44; CH2 = PMS17A/PR114;</p><p>∧ILH developed from Pusa44 derived IL.</p>∼<p>ILH developed from PR114 derived IL;</p>a<p>details of the hybrids are presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096939#pone-0096939-t001" target="_blank">table 1</a>.</p

Mean grain yield and standard heterosis of 17 ILHs evaluated in the year 2008.

<p>*, **significant at P≤0.05 and P≤0.01, respectively. IRGC and CR refer to International Rice Germplasm Centre and CRRI Cuttack, accession numbers, respectively.</p

Development of alien introgression lines.

<p>Development of alien introgression lines.</p

Graphical genotypes of six alien introgression lines generated after analyzing these with polymorphic SSR markers.

<p>Regions in blue are homozygous alien segments and gray are heterozygous alien segments introgressed from <i>O. rufipogon</i> in IL299, IL326, IL867 and IL901 and <i>O. nivara</i> in IL901 and IL951. Numbers on the right of linkage group are the cM distances as per Temnykh et al <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096939#pone.0096939-Temnykh1" target="_blank">[32]</a>. Numbers at the bottom are the chromosomes. Details of the ILHs in parentheses are presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096939#pone-0096939-t001" target="_blank">Table 1</a>.</p

Field photograph of IL921 (left), ILH921 (middle) and on right hand side showing panicle characteristics.

<p>Field photograph of IL921 (left), ILH921 (middle) and on right hand side showing panicle characteristics.</p

Development of Test and Check hybrids.

<p>Development of Test and Check hybrids.</p