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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.

Over the past decades, numerous efforts were made towards the improvement of cereal crops mostly employing traditional or molecular breeding approaches. The current scenario made it possible to efficiently explore molecular understanding by targeting different genes to achieve desirable plants. To provide guaranteed food security for the rising world population particularly under vulnerable climatic condition, development of high yielding stress tolerant crops is needed. In this regard, technologies upgradation in the field of genome editing looks promising. Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 is a rapidly growing genome editing technique being effectively applied in different organisms, that includes both model and crop plants. In recent times CRISPR/Cas9 is being considered as a technology which revolutionized fundamental as well as applied research in plant breeding. Genome editing using CRISPR/Cas9 system has been successfully demonstrated in many cereal crops including rice, wheat, maize, and barley. Availability of whole genome sequence information for number of crops along with the advancement in genome-editing techniques provides several possibilities to achieve desirable traits. In this review, the options available for crop improvement by implementing CRISPR/Cas9 based genome-editing techniques with special emphasis on cereal crops have been summarized. Recent advances providing opportunities to simultaneously edit many target genes were also discussed. The review also addressed recent advancements enabling precise base editing and gene expression modifications. In addition, the article also highlighted limitations such as transformation efficiency, specific promoters and most importantly the ethical and regulatory issues related to commercial release of novel crop varieties developed through genome editing.

The grain size is one of the complex trait of rice yield controlled by a plethora of interaction of several genes in different pathways. The present study was undertaken to investigate the influence of seven known grain size regulating genes: DEP1, GS7, GS3, GW8, GL7, GS5 and GW2. A wide phenotypic variation for grain length, grain width and grain length-width ratio were observed in 89 germplasm. The correlation analysis showed a strong association among these three grain traits viz. GL, GW, GLWR and TGW which play important roles in determining the final rice grain size. Except for GW2, all six genes showed strong association with grain size traits. A total of 21 alleles were identified with an average of 2.1 allele/locus in 89 germplasm of which seven alleles were found to be favourable alleles for improving the grain size with the frequency range of 24 (26.97%) to 82 (92.13%); the largest was found in GS5 followed by GW8, GL7, DEP1, GS3 and GS7 genes. Through ANOVA, four markers (GS3-PstI, S9, GID76 and GID711) of three genes (GS3, DEP1 and GL7) were found significantly associated with all the three traits (GL, GLWR and TGW). Concurrent results of significant associations of grain size traits with other markers were observed in both analysis of variance and genetic association through the general linear model. Besides, the population structure analysis, cluster analysis and PCoA divided the entire germplasm into three sub-groups with the clear-cut demarcation of long and medium grain types. The present results would help in formulating strategies by selecting suitable candidate markers/genes for obtaining preferred grain shape/size and improving grain yield through marker-assisted breeding.