Genetic diversity and structure of Capsicum annuum as revealed by start codon targeted and directed amplified minisatellite DNA markers

Sweet pepper yield modeling via deep learning and selection of superior genotypes using GBLUP and MGIDI

Intelligent knowledge about Capsicum annuum L. germplasm could lead to effective management of germplasm. Here, 29 accessions of sweet pepper were investigated in two separate randomized complete block design with three replications in the field condition. Fruit yield accompanied by 13 agro-morphological traits were recorded in two experiments. Genomic fingerprinting of accessions was done by using 10 ISSR primers. The convolutional neural network (CNN) models via outputs of both correlation coefficients and stepwise regression showed the high accuracy of CNN model through correlation coefficients (R2 = 0.879) in predicting fruit yield of sweet pepper. Fruit thickness and fruit width were identified simultaneously as significant components in both models. Genomic best linear unbiased prediction through 65 amplified ISSR loci showed positive and high value of additive gene effect as breeding value for traits identified in the deep learning models. Among studied germplasm, G12, G13, G14, and G25 with positive and high value of breeding value especially for traits constructed the CNN models, recognized as superior genotypes. Regardless of breeding value, multi-trait genotype-ideotype distance index by utilizing all recorded agro-morphological traits simultaneously, revealed G11, G12, G13, and G15 as promising genotypes. So, G12 and G13 which have ideal values of studied traits simultaneously and also positive breeding value could be considered as promising parents for future breeding programs. The study concludes that a CNN model focusing on morphological traits with additive genetic control, combined with the MTSI index, can effectively enhance parental selection in sweet pepper.

Genome-Wide Identification and Characterization of SNPs and InDels of Capsicum annuum var. glabriusculum from Mexico Based on Whole Genome Sequencing

Capsicum annuum var. glabriusculum is an economically important horticultural crop and is considered the wild genetic ancestor of chili peppers. The distribution range extends from southern North America, through Central America, to South America. Approximately 226 million 150 paired-end reads were generated from CHMX_Ch1 (a C. annuum from Chihuahua, Mexico). To compare with the CHMX_Ch1 genome, high-quality reads from QO (a C. annuum from Querétaro, Mexico) were downloaded from the NCBI database. A total of 210,324 variants were detected in CHMX_Ch1, whereas 169,718 variants were identified in QO, all compared to the domesticated C. annuum reference genome, UCD10Xv1.1. This comprised 203,990 SNPs and 6334 InDels in CHMX_Ch1 and 164,955 SNPs and 4763 InDels in QO. The variants with high and moderate impact were identified as missense, splice acceptor, splice donor, start lost, stop gain, stop lost, frameshift, insertion, and deletion effects. The candidate genes with the highest fold enrichment values among the SNPs were predominantly involved in gene regulation and metabolic processes. InDels were associated with nuclear and transcriptional regulator activity in both genomes. Overall, a greater number of variants were found in CHMX_Ch1 compared to QO. This study provides knowledge of the principal functions associated with high- and moderate-impact variants and supplies a resource for further investigations of the genetic characteristics of these chiltepin peppers.

Start codon targeted (SCoT) polymorphism marker in plant genome analysis: current status and prospects

The present review illustrates a comprehensive overview of the start codon targeted (SCoT) polymorphism marker and their utilization in various applications related to genetic and genomic studies. Start codon targeted (SCoT) polymorphism marker, a targeted fingerprinting marker technique, has gained considerable importance in plant genetics, genomics, and molecular breeding due to its many desirable features. SCoT marker targets the region flanking the start codon, a highly conserved region in plant genes. Therefore, it can distinguish genetic variations in a specific gene that link to a specific trait. It is a simple, novel, cost-effective, highly polymorphic, and reproducible molecular marker for which there is no need for prior sequence information. In the recent past, SCoT markers have been employed in many commercially important and underutilized plant species for a variety of applications, including genetic diversity analysis, interspecific/generic genetic relationships, cultivar/hybrid/species identification, sex determination, construction of linkage map, association mapping/analysis, differential gene expression, and genetic fidelity analysis of tissue culture-raised plants. The main aim of this review is to provide up-to-date information on SCoT markers and their application in many commercially important and underutilized plant species, mainly progress made in the last 8-10 years.

Conservation of floral, fruit and chromosomal diversity: a review on diploid and polyploid Capsicum annuum complex in India

Capsicum as a spice crop, has wild and cultivated forms admired globally, including Indian subcontinent with vast climatic ranges. Systematic representation of the Indian Capsicum is required to address species relationships and sustainable agriculture, in face of unpredictable climatic conditions. We have updated the catalogue of Indian 'C. annuum complex' with 28 landraces and populations from different agro-climatic regions. The agro-climatic influence on the origin of stable chili landraces in India is remarkable, especially in the North East. The floral and fruit morphotype standards and chromosomal attributes have been considered for four distinct 'C. annuum complex' members under three species. The highlights of study are: (1) comparative profiling of Indian Capsicum species revealing less infraspecific variation within C. frutescens and C. chinense than C. annuum, at par with cultivation status, (2) karyotype analysis of some unique diploid landraces of C. annuum, (3) karyotypic confirmation of the polyploid Dalle Khursani landraces exclusive to India. To obtain more information, we attempted to correlate diversity of fruit and floral morphotype with chromosomal diversity. Existence of elite and rare germplasm found in the regional pockets offer great scope for enriching the agricultural tradition. The present dataset may serve as a template to be continuously upgraded by taxonomists, genomicists and breeders.

Exploring Genetic Variability among and within Hail Tomato Landraces Based on Sequence-Related Amplified Polymorphism Markers

Landraces are valuable sources of genetic characteristics, which are of plant breeders’ interest to include in breeding programs for crop improvement. We assess the inter- and intra-genetic variability among 96 accessions representing three Hail tomato landrace using DNA-based marker sequence-related amplified polymorphism (SRAP). Seven SRAP primer combinations generated 55 alleles with a polymorphism of 100%, and an average of 7.86 polymorphic alleles per pair of primers. All primers showed an average of 0.68 polymorphic information content (PIC) value and discrimination power (DP) of 14.29. Principal coordinate analysis (PCoA) confirmed the clustering produced via the UPGMA similarity dendrogram allowed for the grouping of the 96 accessions according to its gene bank accession numbers and showed relatively good separation between landraces. A similarity value ranged from 0.04 to 1.0 among accessions of Hail 747, 0.05 to 1.0 in Hail 1072, and from 0.16 to 0.92 in Hail 548. These results showed the landraces harbor a wide range of genetic diversity at both inter and intra-variation levels. AMOVA showed that most of the genetic variation was because of differences within populations (87%). Tomato Hail landraces have well-differentiated genetic populations and admixtures, where Hail 747 formed their separate group, and both Hail 548 and Hail 1072 were admixed, and some accessions showed more diversity pattern. We have to take the SRAP technique’s effectiveness in the study of genetic variability among and within landraces into consideration in the tomato-breeding programs through marker-assessed selection.

Whole genome resequencing of four Italian sweet pepper landraces provides insights on sequence variation in genes of agronomic value

Sweet pepper (Capsicum annuum L.) is a high value crop and one of the most widely grown vegetables belonging to the Solanaceae family. In addition to commercial varieties and F₁ hybrids, a multitude of landraces are grown, whose genetic combination is the result of hundreds of years of random, environmental, and farmer selection. High genetic diversity exists in the landrace gene pool which however has scarcely been studied, thus bounding their cultivation. We re-sequenced four pepper inbred lines, within as many Italian landraces, which representative of as many fruit types: big sized blocky with sunken apex ('Quadrato') and protruding apex or heart shaped ('Cuneo'), elongated ('Corno') and smaller sized sub-spherical ('Tumaticot'). Each genomic sequence was obtained through Illumina platform at coverage ranging from 39 to 44×, and reconstructed at a chromosome scale. About 35.5k genes were predicted in each inbred line, of which 22,017 were shared among them and the reference genome (accession 'CM334'). Distinctive variations in miRNAs, resistance gene analogues (RGAs) and susceptibility genes (S-genes) were detected. A detailed survey of the SNP/Indels occurring in genes affecting fruit size, shape and quality identified the highest frequencies of variation in regulatory regions. Many structural variations were identified as presence/absence variations (PAVs), notably in resistance gene analogues (RGAs) and in the capsanthin/capsorubin synthase (CCS) gene. The large allelic diversity observed in the four inbred lines suggests their potential use as a pre-breeding resource and represents a one-stop resource for C. annuum genomics and a key tool for dissecting the path from sequence variation to phenotype.