Naveen Singh

Yield-Enhancing Heterotic QTL Transferred from Wild Species to Cultivated Rice Oryza sativa L

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 O. rufipogon and two hybrids (ILH921 and ILH951) having introgressions from O. nivara 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 O. nivara to 7.66 from O. rufipogon. The introgressed regions and their putative association with yield components in hybrids is reported and discussed.

Yield and Nitrogen-Use Efficiency of Aromatic Rice Cultivars in Response to Nitrogen Fertilizer

Aromatic cultivars of rice respond differently to nitrogen application as compared to nonaromatic rice. Most of the aromatic rice cultivars are susceptible to disease and insect pest attack, and are more prone to lodging. Therefore, nitrogen is the key input for increasing the productivity of aromatic rice. Research analyzing the effects of N level on yield and nitrogen-use efficiency (NUE) of modern aromatic cultivars is not well documented. Therefore, the present study was conducted to optimize N levels for higher yield and NUE of modern aromatic rice cultivars. Across all genotypes, the mean nitrogen-fertilizer response was highest at 40 kg N/ha as compared to other N levels (0, 20, and 60 kg N/ha), indicating that further increase in N level had no effect on crop response to fertilizer. The mean grain yield increased by 64.2% when plots were supplemented with 40 kg N/ha as compared to control (unfertilized). Among cultivars, ‘Punjab Mehak 1’ registered highest yield (4.3 t/ha), followed by ‘Pusa 1121’ (4.0 t/ha) and ‘Punjab Basmati 2’ (3.9 t/ha). Interactive effect between N levels and cultivars revealed that ‘Punjab Mehak 1’ responded significantly up to 60 kg N/ha due to more NUE and higher N uptake as compared to ‘Pusa 1121’ and ‘Punjab Basmati 2’. Results from this study indicate that genotype differences in NUE existed in aromatic rice cultivars; therefore, NUE of different cultivars could be a useful tool to adopt the appropriate cultural practices for achieving high yield and N response exploration.

Validation of molecular markers linked to low glucosinolate QTLs for marker assisted selection in Indian mustard (Brassica juncea L. Czern & Coss)

Six earlier reported markers closely linked to low glucosinolate QTLs of Brassica juncea, spread across ‘A’ genome (A2, A3 and A9) were validated in a recombinant inbred line (RIL) population of a cross between Pusa Mustard-21 (low erucic acid) and EC-597325 (double low) genotypes, to utilize them in marker-assisted selection (MAS). Of them, four markers viz., GER 1 amplified alleles of 650 bp and of 950 bp, GER 5 amplified 310 bp and 350 bp, At5gAJ67 amplified 500 bp and 450 bp and Myb28 amplified alleles of size 900 bp and 920 bp in EC597325 and Pusa Mustard-21, respectively and therefore differentiated low and high glucosinolate parents. These four polymorphic markers were then used to genotype the phenotyped RIL population consisting 608 plants. Marker-trait association was tested for goodness of fit using 2 test. Of the four markers, GER1 and GER5 showed higher phenotypic variance (R2 value) compared to the others, indicating their significance in determination of glucosinolates and prospects for use in MAS for development of Indian mustard genotypes with low glucosinolates content.

Inheritance of low erucic acid in Indian mustard [Brassica juncea (L.) Czern. and Coss.]

Genetics of erucic acid content was studied using six generations viz., P1, P2, F1, F2, B1 and B2 derived from the crosses, Varuna × LES-39 and Varuna × LES-1-27. The trait high erucic acid content was partially dominant over low erucic acid content in both the crosses. In both the crosses, adequacy of additive – dominance model suggested absence of non-allelic interactions. The study revealed that selection for low erucic acid would result in isolation of plants with high oleic and linoleic acids and hence, it should be possible to develop high oleic acid lines having low erucic acid content in mustard.

Heterotic response of genomic regions derived from Oryza rufipogon and O. nivara in improving grain morphology and quality of indica rice (Oryza sativa L.)

Limited backcrossing was followed to introgress useful variability, needed for improving grain morphology and milling traits, from wild Oryza species into two indica cultivars PR114 and Pusa44.These alien introgressions lines (ILs), having similar grain quality parameters to the recurrent parent, were used for developing rice hybrids to assess the effect of these introgressions in the heterozygous state and to assess their grain quality parameters, as most of the hybrids commercialized in the tropics have inferior grain quality. These ILs and their recurrent parents, possessing fertility restoration ability for wide abortive cytoplasm, were crossed with CMS line PMS 17A to generate introgressions line hybrids (ILHs). Hybrids developed from recurrent parents were used as a check to compare the performance of ILHs. Based on yield and phenotypic acceptability, six ILHs having enriched genome of O. rufipogon and O. nivara were selected and analyzed for grain quality traits. All six hybrids observed significant improvement in milled rice recovery (up to 10%), head rice recovery (up to 25%) over ILs and check hybrids. Introgressions were analyzed using polymorphic SSR markers. The majority of O. rufipogon and O.nivara alleles identified in the study seems to be effective across recipient genotypes and could be used effectively in quality breeding programs.