In-vitro Androgenesis in Rice: Advantages, Constraints and Future Prospects

Development and characterization of elite doubled haploid lines from two indica rice hybrids.

An improved procedure has been developed for high frequency androgenesis in an elite long duration indica rice hybrid. The effects of cold temperature pretreatment, duration of treatment and media with different plant growth regulators on callus induction and shoot regeneration were examined for generation of doubled haploids. N6 medium supplemented with 2.0 mg l−1 2,4-D, 0.5 mg l−1 BAP and 30 g l−1 maltose was found to be most effective for callusing when compared with MS and SK1. The N6 media grown calli showed maximum green shoot regeneration frequency in MS medium supplemented with 0.5 mg l−1 NAA, 0.5 mg l−1 Kinetin, 1.5 mg l−1 BAP and 30 g l−1 sucrose after 2 week of culture. The cold temperature treatment of spike at 10°C for 2 days alongside by 8 days was found to be most suitable conditions for callusing and green shoot regeneration producing 186 green plants from indica rice hybrid, CRHR32. The ploidy status assessed on the basis of morpho-agronomic characters revealed fertile diploids at a frequency of about 81.10%; 16.10%, 2.68% and 1.08% were polyploids, haploids and mixploids respectively. Microsatellite marker analysis showed 1 : 1 ratio of the alleles of CMS and restorer lines used for development of CRHR32. Homozygosity was detected for all the marker loci in 150 DHs and only one plant was identified as heterozygote. This investigation identified the favorable media composition and condition for callus induction and green plant regeneration which would further increase the knowledge and better understanding in rice hybrids for development of DHs.

https://www.jstage.jst.go.jp/article/plantbiotechnology/advpub/0/advpub_16.0719a/_pdf

Doubled Haploids generated through anther culture from an elite long duration rice hybrid, CRHR32: Method optimization and molecular characterization

The study was undertaken to identify the quantitative trait loci (QTLs) governing yield and its related traits using a recombinant inbred line (RIL) population derived from the popular rice hybrid, KRH-2 (IR58025A/KMR3R). A genetic map spanning 294.2 cM was constructed with 126 simple sequence repeats (SSR) loci uniformly distributed across the rice genome. QTL analysis using phenotyping and genotyping information identified a total of 22 QTLs. Of these, five major effect QTLs were identified for the following traits: total grain yield/plant (qYLD3-1), panicle weight (qPW3-1), plant height (qPH12-1), flag leaf width (qFLW4-1) and panicle length (qPL3-1), explaining 20.23–22.76% of the phenotypic variance with LOD scores range of 6.5–10.59. Few genomic regions controlling several traits (QTL hotspot) were identified on chromosome 3 for total grain yield/plant (qYLD3-1) and panicle length (qPL3-1). Significant epistatic interactions were also observed for total grain yield per plant (YLD) and panicle length (PL). While most of these QTLs were observed to be co-localized with the previously reported QTL regions, a novel, major QTL associated with panicle length (qPL3-1) was also identified. SNP genotyping of selected high and low yielding RILs and their QTL mapping with 1,082 SNPs validated most of the QTLs identified through SSR genotyping. This facilitated the identification of novel major effect QTLs with much better resolution and precision. In-silico analysis of novel QTLs revealed the biological functions of the putative candidate gene (s) associated with selected traits. Most of the high-yielding RILs possessing the major yield related QTLs were identified to be complete restorers, indicating their possible utilization in development of superior rice hybrids.

/pdf/molecular-mapping-of-qtls-for-yield-related-traits-in-3p0om7ny8i.pdf

Molecular mapping of QTLs for yield related traits in recombinant inbred line (RIL) population derived from the popular rice hybrid KRH-2 and their validation through SNP genotyping.

Present study was designed to evaluate the effect of cold pretreatment temperatures (4, 8 and 12 o C) and durations of treatment (5, 9 and 13 d) on anther culture efficiency among 13 genotypes. Anthers were cultured on N6 medium supplemented with 2, 4-D (2 mg/L) and Kinetin (0.5 mg/L). Anther inoculated media petri dish were incubated in the dark at 25 ± 1 ° C for callus induction. When calli were 1-2 mm in diameter, they were transferred to MS regeneration medium supplemented with Kinetin (1 mg/L), NAA (1 mg/L) and BAP (2.5 mg/L) and were incubated at 25 ± 1 ° C under 16 h/8 h light/dark condition. The cold treatment at 12 o C for 5 days was found to be the most effective in all experimental genotypes used for the study. Out of 13 genotypes evaluated, IR58025B (25eB) was highly responsive for both callus induction as well as green plant regeneration. Lovelin Kaushal 1,* , Richa Sharma 1,2 , Balachandran S M 3 , Ulaganathan K 4 and Vinay Shenoy 1

EFFECT OF COLD PRETREATMENT ON IMPROVING ANTHER CULTURE RESPONSE OF RICE (Oryza sativa L.)

Application of anther culture techniques for improvement of indica rices is a formidable task as they are known to be recalcitrant to culture unlike japonica rices. Since anther culture can effectively address the major problems associated with the adoption of hybrid rice in India, an effort was made to assess the influence of cold pretreatment and phyto hormones on the anther culture response of Rajalaxmi (CRHR 5) and Ajay (CRHR 7), two elite and popular indica rice hybrids. Cold pretreatment for 7-9 days at 10 o C was found to have a positive influence on the callus induction frequency irrespective of the media employed and prolonged treatment over the optimum proved to be inhibitory. Of the different auxins (2, 4-D, NAA) and cytokinins (Kinetin, BAP) and their combinations studied, a ratio of 1:4 for 2,4-D and NAA and 1:3:1 ratio of Kinetin: BAP: NAA ratio proved to be optimal for callus induction and green plant regeneration respectively. This information can be of use in the development of doubled haploids with superior yield and good grain quality from the elite hybrid cultivars.

G. J. N. Rao

Papers

Effect of cold pretreatment and phytohormones on anther culture efficiency of two indica rice (Oryza sativa L.) hybrids-Ajay and Rajalaxmi.