Onkar Nath Singh

Phenotypic and Marker-Assisted Genetic Enhancement of Parental Lines of Rajalaxmi, an Elite Rice Hybrid

The cytoplasmic male sterile line system comprising CRMS 32A and its maintainer line CRMS 32B is a popular choice for the development of new hybrids in India as CRMS 32A, having Kalinga 1 cytoplasm (other than WA), is a viable alternative to WA cytoplasm. However, both lines are susceptible to bacterial blight (BB), a major disease on rice. As enhancement of host plant resistance is the most effective and economical strategy to control this disease, four resistance genes (Xa4, xa5, xa13, and Xa21) were transferred from a BB pyramid line of IR64, into the A and B lines using a marker-assisted backcrossing (MAB) breeding strategy. During the transfer of genes into CRMS 32B, foreground selection was applied using markers associated with the genes, and plants having resistance alleles of the donor, are selected. Selection for morphological and quality traits was practiced to select plants similar to the recurrent parent. The four gene and three gene pyramid lines exhibited high levels of resistance against the BB pathogen when challenged with eight virulent isolates. Using genome wide based SSR markers for background selection, pyramids having >95% of the recurrent parent genome were identified. With CRMS 32B gene pyramid as donor, the four resistance genes were transferred into the A line through repeated backcrosses and the A line pyramids also exhibited high level of resistance against BB. Through a combination of selection at phenotypic and molecular levels, four BB resistance genes were successfully introduced into two parental lines (CRMS 32 B and A) of Rajalaxmi, an elite popular hybrid. The pyramided B lines did exhibit high levels of resistance against BB. Selection for morphological and quality traits and background selection hastened the recovery of the recurrent parent genome in the recombinants. Through repeated backcrosses, all the four resistance genes were transferred to CRMS 32A and test crosses suggest that the maintenance ability of the improved CRMS 32B lines is intact. These improved maintainer and CMS lines can directly be used in hybrid rice breeding and the new hybrids can play an important role in sustainable rice production in India.

Oryza officinalis Complex

Oryza officinalis complex is the largest species complex within the genus Oryza, consisting of both diploid and allotetraploid species. It contains at least ten reported perennial species (O. officinalis, O. rhizomatis, O. eichengeri, O. minuta, O. malampuzhaensis, O. punctata, O. latifolia, O. alta, O. grandiglumis, O. schweinfurthiana and O. australiensis) distributed throughout the tropics. Most of the allotetraploid species in this group have originated recently, and their progenitors are also naturally available in many cases. This provides a unique opportunity to study evolution of polyploidy within the genus Oryza. Classical cytogenetic techniques like karyotyping, meiotic pairing have provided valuable information in this regard. Most of the diploid and allotetraploid species contain ‘C’ genome except diploid O. punctata (BB) and O. australiensis (EE). Till date, whole genome sequence is available only for O. punctata and rest are under progress. Considerable success has been achieved in terms of developing genetic stock through wide hybridization and mapping agronomically important genes from the species of O. officinalis complex. Successful introgressions of brown plant hopper resistance and bacterial leaf blight resistance to the cultivated varieties have been achieved from these genetic stocks. Molecular marker resources to facilitate such alien gene introgression events are becoming more and more available. In order to address the problem of world food security, global importance has been laid on utilization of wild resource in rice. With focused objectives and rapidly emerging scientific and technological know-how, we can expect much more efficient utilization of the O. officinalis complex in future rice improvement.

Combining Ability Analysis for Yield and Quality Related Traits in Non- Basmati Aromatic Rice (Oryza sativa L.)

Aromatic rice occupies a prime position in Indian culture not only because of their high quality but also of its auspicious nature. India had an immense wealth of aromatic rice; many have been lost during the last four decades as an aftermath of the green revolution where main emphasis was given on yield rather than quality (Yoshihashi et al., 2004 and Singh et al., 2011). Among aromatic rice, basmati rice is known as ‘Crown Jewel’ of South Asian gift of India and Pakistan to the world, prized for its exquisite aroma and taste. Basmati is highly valued in the international market due to its unique combination of aroma, grain, cooking and eating qualities (Singh et al., 1988, 2000). International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 7 Number 10 (2018) Journal homepage: http://www.ijcmas.com