Molecular characterization and SNP identification using genotyping-by-sequencing in high-yielding mutants of proso millet.

Proso millet (Panicummiliaceum L.) is a short-duration C4 crop that is drought tolerant and nutritionally rich and can grow well in marginal lands. Though the crop has many climate-resilient traits like tolerance to drought and heat, its yield is lower than that of common cereals like rice, wheat, and maize. Being an underutilized crop, the molecular resources in the crop are limited. The main aim of the present study was to develop and characterize contrasting mutants for yield and generate functional genomic information for the trait in proso millet. Gamma irradiation-induced mutant population was screened to identify high-yielding mutants, which were evaluated up to M4 generation. One mutant with a dense panicle and high yield (ATL_hy) and one with a lax panicle and low yield (ATL_ly) along with the wild type were sequenced using the genotyping-by-sequencing approach. The variants detected as single nucleotide polymorphisms (SNPs) and insertions-deletions (InDels) were annotated against the reference genome of proso millet. Bioinformatic analyses using the National Center for Biotechnology Information (NCBI) and UniProt databases were performed to elucidate genetic information related to the SNP variations. A total of 25,901, 30,335, and 31,488 SNPs, respectively, were detected in the wild type, ATL_hy mutants, and ATL_ly mutants. The total number of functional SNPs identified in high-yielding and low-yielding mutants was 84 and 171, respectively. Two functional SNPs in the high-yielding mutant (ATL_hy) and one in the low-yielding mutant (ATL_ly) corresponded to the gene coding for "E3 ubiquitin-protein ligase UPL7". Pathway mapping of the functional SNPs identified that two SNPs in ATL_ly were involved in the starch biosynthetic pathway coding for the starch synthase enzyme. This information can be further used in identifying genes responsible for various metabolic processes in proso millet and in designing useful genetic markers.

Novel and stable QTL regions conferring resistance to MYMV disease and its inheritance in blackgram (Vigna mungo (L.) Hepper).

Mungbean yellow mosaic virus (MYMV) disease is a significant constraint for blackgram production. The present study employed a mapping population derived from a cross between susceptible (MDU 1) and resistant (TU 68) genotypes to identify quantitative trait loci (QTL) associated with MYMV disease resistance in addition to bruchine resistance loci identified from the previous study. Phenotyping was carried out in F2 generation under the disease spreader row method at field condition. Disease score observations were carried out 60 days after sowing (DAS). The chi-square goodness of fit test revealed inhibitory gene action with two genes controlling the expression of resistance to MYMV disease. However, QTL analysis revealed one major QTL region, i.e. qMYMVD_60 at LG 10 responsible for MYMV disease score at 60 DAS, accounted for 21 per cent of variation. The identified QTL has the flanking markers as CEDG180 and CEDG116. Hence, the QTL, qMYMVD_60 may be utilized in the breeding of MYMV disease resistance. Further, the marker-assisted introgression of both the MYMV and bruchine resistance QTLs can be performed in the near future.

Gamma irradiation to induce beneficial mutants in proso millet (Panicum miliaceum L.): an underutilized food crop.

PURPOSE: Proso millet is a potential crop for food, nutritional security, and sustainable agriculture, particularly in the context of climate change. It is one of the traditional millet crops in cultivation in Tamil Nadu and India. Self-pollinated nature of this crop makes evolutionary process a terminal one and creating variability to broaden the genetic base is important. The objective of the study was to optimize mutagenic dose of gamma mutagen, document types of mutations and identify mutants for high grain yield (GY) and fodder yield (FY), hence to determine the feasibility of gamma mutagenesis in proso millet crop improvement. MATERIALS AND METHODS: A mutation breeding program with 10 doses of gamma irradiation, i.e. 100, 200, 300, 400, 500, 600, 700, 800, 900 and 1000 Gy were imposed on seeds of variety ATL 1, a popular variety in India. Roll paper method, tray method and field evaluation were carried out to determine the LD50 and GR50 doses. Based on viable mutation frequency in M2 generation, mutagenic effectiveness and efficiency was estimated. Targeted selection for yield and yield contributing traits was carried out in M2, M3 and M4 generation to identify high yielding mutants. RESULTS: The LD50 and GR50 doses of gamma were estimated to be 418 Gy and 542 Gy, respectively. Based on results from probit analysis, mutagenic effectiveness, mutagenic efficiency and mutation spectrum, the optimum treatment dose of gamma was concluded to be 400 Gy. High frequency, i.e. 10.96% of phenotypic mutants was identified in the M2 generation. The broad range of mutants identified in M2 generation had mutations for plant height, plant habit, panicle shape, compactness, and length, days to 50% flowering (DFF), lodging resistance, tillering, leaf phenotype, apiculus color, culm branching, stem and leaf hairiness, sheath pigmentation, seed color and shape and seed coat attachment. Eight high yielding mutant families were isolated in M4 generation. The mean single plant GY and FY of these mutants ranged between 25 to 51 g and 40 to 68 g respectively while in control it was 15 g and 30 g, respectively. CONCLUSIONS: The wide spectrum and high frequency of mutations both for qualitative and quantitative traits suggest mutation induction as a promising method for creating novel variations in proso millet. The high yielding mutants identified can be utilized for varietal development both for grain and fodder purpose after further stability and quality evaluations in the advanced generations.