Multiple mutations in BADH2 gene reveal the novel fragrance allele in indica rice (Oryza sativa L.).

The aroma in rice is the most appreciable quality trait, controlled by the loss of function of the betaine aldehyde dehydrogenase 2 (BADH2) gene. In the present study, indica rice cultivars (basmati, nonbasmati aromatic, and nonaromatic) were screened to explore allelic differences in the BADH2 gene using two functional markers (badh2-p-5'UTR and FMbadh2-E7). Notably, the results of the present mutational analysis showed that both markers confirmed a different mutation in indica rice cultivars than earlier reported japonica accessions. It was found that there is 250-bp deletion in the promoter region of aromatic Kagesali and Kalakrishna as compared to nonaromatic Kolamb. The results of FMbadh2-E7 showed 8-bp deletion and six SNPs in exon 7 of the Kalakrishna cultivar. Interestingly, the nonbasmati aromatic Lalbhat rice cultivar did not harbour any reported mutation and showed a novel BADH2 allele carrying 1-bp deletion in exon 7. Among the selected aromatic rice cultivars, eight cultivars showed mutation in the 5' UTR region and interestingly 23 rice cultivars carried the mutation in both 5' UTR and exon 7 of a BADH2 gene. The 2-acetyl-1-pyrroline (2AP) biosynthesis related metabolites, enzyme assay and gene expression supported mutation in BADH2 gene and expression of 2AP in aromatic rice cultivars under study.

Genome Editing in Cereals: Approaches, Applications and Challenges.

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.

Mutation Breeding in Tomato: Advances, Applicability and Challenges.

Induced mutagenesis is one of the most effective strategies for trait improvement without altering the well-optimized genetic background of the cultivars. In this review, several currently accessible methods such as physical, chemical and insertional mutagenesis have been discussed concerning their efficient exploration for the tomato crop improvement. Similarly, challenges for the adaptation of genome-editing, a newly developed technique providing an opportunity to induce precise mutation, have been addressed. Several efforts of genome-editing have been demonstrated in tomato and other crops, exploring its effectiveness and convenience for crop improvement. Descriptive data compiled here from such efforts will be helpful for the efficient exploration of technological advances. However, uncertainty about the regulation of genome-edited crops is still a significant concern, particularly when timely trait improvement in tomato cultivars is needed. In this regard, random approaches of induced mutagenesis are still promising if efficiently explored in breeding applications. Precise identification of casual mutation is a prerequisite for the molecular understanding of the trait development as well as its utilization for the breeding program. Recent advances in sequencing techniques provide an opportunity for the precise detection of mutagenesis-induced sequence variations at a large scale in the genome. Here, we reviewed several novel next-generation sequencing based mutation mapping approaches including Mutmap, MutChromeSeq, and whole-genome sequencing-based mapping which has enormous potential to accelerate the mutation breeding in tomato. The proper utilization of the existing well-characterized tomato mutant resources combined with novel mapping approaches would inevitably lead to rapid enhancement of tomato quality and yield. This article provides an overview of the principles and applications of mutagenesis approaches in tomato and discusses the current progress and challenges involved in tomato mutagenesis research.