Advances in Breeding of Peach, Plum and Apricot

Research on the expression of fruit specific genes may allow breeders in the future to selectively manipulate through gene transfer in certain aspects of fruit development/quality in their advanced breeding lines thus reducing the time necessary for cultivar development. This would be particularly useful in breeding programmes, hybridizing standard cultivars with exotic germplasm of low fruit quality. The use of exotic germplasm will be important for the expansion of the peach germplasm base and the development of stress resistant cultivars. More immediate results of research on fruit specific gene expression will provide a better understanding of fruit development and quality. It is required to learn how the differences at the gene level correlate with quality characteristics. With the continued cooperation of fruit biochemists it is expected to obtain a better definition of fruit quality and a better understanding of fruit biochemistry. The potential will exit to generate a range of “anti-sense mutants” i.e. transgenic plants expressing anti-sense gene contstructs that reduce or nullify the effects of the normal gene. The phenotypes of these mutants could help to define the biochemistry, genetics and quality of peach fruit. The development of efficient regeneration and transformation system in peach will be useful not only for the modification of fruit characteristics, but also for the transfer and manipulation of genes affecting stress resistance and other economically important characters.

Prospects for Trifolium Improvement Through Germplasm Characterisation and Pre-breeding in New Zealand and Beyond

Trifolium is the most used pastoral legume genus in temperate grassland systems, and a common feature in meadows and open space areas in cities and parks. Breeding of Trifolium spp. for pastoral production has been going on for over a century. However, the breeding targets have changed over the decades in response to different environmental and production pressures. Relatively small gains have been made in Trifolium breeding progress. Trifolium breeding programmes aim to maintain a broad genetic base to maximise variation. New Zealand is a global hub in Trifolium breeding, utilising exotic germplasm imported by the Margot Forde Germplasm Centre. This article describes the history of Trifolium breeding in New Zealand as well as the role and past successes of utilising genebanks in forage breeding. The impact of germplasm characterisation and evaluation in breeding programmes is also discussed. The history and challenges of Trifolium breeding and its effect on genetic gain can be used to inform future pre-breeding decisions in this genus, as well as being a model for other forage legumes.

Genetic Basis for Lentil Adaptation to Summer Cropping in Northern Temperate Environments

ABSTRACTThe continued success of lentil (Lens culinaris Medik.) genetic improvement relies on the availability of broad genetic diversity and new alleles need to be identified and incorporated into the cultivated gene pool. Availability of robust and predictive markers greatly enhances the precise transfer of genomic regions from unadapted germplasm. Quantitative trait loci (QTLs) for key phenological traits in lentil were located using a recombinant inbreed line (RIL) population derived from a cross between an Ethiopian landrace (ILL 1704) and a northern temperate cultivar (CDC Robin). Field experiments were conducted at Sutherland research farm in Saskatoon and at Rosthern, Saskatchewan, Canada during 2018 and 2019. A linkage map was constructed using 21,634 SNPs located on seven linkage groups (LGs) which correspond to the seven haploid chromosomes of lentil. Eight QTL were identified for six phenological traits. Flowering related QTL were identified at two regions on LG6. FLOWERING LOCUS T (FT) genes were annotated within the flowering time QTL interval based on the lentil reference genome. Similarly, a major QTL for post-flowering developmental processes was located on LG5 with several senescence-associated genes annotated within the QTL interval. The flowering time QTL was validated in a different genetic background indicating the potential use of the identified markers for marker-assisted selection to precisely transfer genomic regions from exotic germplasm into elite crop cultivars without disrupting adaptation.Core IdeasStable QTL were located for key phenological traits in lentil that lead to regional adaptation.FT genes are candidates for controlling flowering time in lentil grown in temperate environments.A major locus controlling post-flowering developmental processes was located on lentil LG5 with several senescence-associated genes annotated within the QTL interval.Markers identified in this study can be useful for marker-assisted selection to precisely transfer genomic regions from exotic germplasm into elite lentil cultivars without disrupting adaptation.

ALLELES ASSOCIATED TO DISEASE SEVERITY INDEX OF MAL DE RÍO CUARTO DISEASE IN MAIZE EXOTIC GERMPLASM

Mal de Río Cuarto (MRC) is one of the most important viral diseases of maize in Argentina. The disease severity index (DSI) allows to combine the incidence and severity of a disease in a single metric. The genotypic reaction to MRC has been extensively studied in biparental populations. However, this complex trait has not been analyzed by genome-wide association studies (GWAS). The aim of this work is to identify new resistance alleles associated with DSI of MRC in an exotic germplasm from the International Maize and Wheat Improvement Center (CIMMYT). A population of maize lines from CIMMYT was phenotypically evaluated in environments in the area where the disease is endemic. The predictors of genetic effects (BLUP, best linear unbiased predictor) and 78,376 SNP markers (Single Nucleotide Polymorphism) were used to perform the GWAS in 186 maize lines. The values of variance components and mean-basis heritability suggest a wide genotypic variability in the population. The GWAS allowed to identify 11 putative QTL of resistance to MRC. The incorporation of exotic germplasm into local maize breeding programs could contribute favorably to the creation of hybrids with a higher level of resistance to MRC. The predictive ability of associated markers with MRC resistance indicates that marker-assisted selection is an advisable tool for selecting MRC resistant genotypes. Key words: Disease severity index; genome-wide association study; QTL; SNP

Population structure of Nepali spring wheat (Triticum aestivum L.) germplasm

Background Appropriate information about genetic diversity and population structure of germplasm improves the efficiency of plant breeding. The low productivity of Nepali bread wheat (Triticum aestivum L.) is a major concern particularly since Nepal is ranked the 4th most vulnerable nation globally to climate change. The genetic diversity and population structure of Nepali spring wheat have not been reported. This study aims to improve the exploitation of more diverse and under-utilized genetic resources to contribute to current and future breeding efforts for global food security. Results We used genotyping-by-sequencing (GBS) to characterize a panel of 318 spring wheat accessions from Nepal including 166 landraces, 115 CIMMYT advanced lines, and 34 Nepali released varieties. We identified 95 K high-quality SNPs. The greatest genetic diversity was observed among the landraces, followed by CIMMYT lines, and released varieties. Though we expected only 3 groupings corresponding to these 3 seed origins, the population structure revealed two large, distinct subpopulations along with two smaller and scattered subpopulations in between, with significant admixture. This result was confirmed by principal component analysis (PCA) and UPGMA distance-based clustering. The pattern of LD decay differed between subpopulations, ranging from 60 to 150 Kb. We discuss the possibility that germplasm explorations during the 1970s–1990s may have mistakenly collected exotic germplasm instead of local landraces and/or collected materials that had already cross-hybridized since exotic germplasm was introduced starting in the 1950s. Conclusion We suggest that only a subset of wheat “landraces” in Nepal are authentic which this study has identified. Targeting these authentic landraces may accelerate local breeding programs to improve the food security of this climate-vulnerable nation. Overall, this study provides a novel understanding of the genetic diversity of wheat in Nepal and this may contribute to global wheat breeding initiatives.

Development and Evaluation of Promising Popcorn Hybrids Developed from Local and Exotic Germplasm

Popcorn is considered as one of the oldest forms of field corn and mainly used as a snack food. In the time being, no local popcorn registered hybrids are available in Egypt and all country needs are imported hybrids. Therefore, there is a dire need to develop local popcorn hybrids. Using local and exotic germplasm, eighty-six promising yellow F1- hybrids were developed at Nubaria research station (30°54' N, 29°30' E) maize program, Field Crops Research Institute, ARC, Egypt. These hybrids were split into two groups (A and B); each one along with two exotic hybrid checks were evaluated under irrigation in 2019 at two environmentally different locations, one in north of Egypt and the other one in south of Egypt. Purpose of this investigation was to evaluate these promising hybrids for grain yield, number of days to mid-silk, plant height, resistance to late wilt disease and two quality traits i.e. popping volume and percentage of unpopped kernels. Randomized complete block design with 4 replications was used. All technical recommendations for maize production were applied. Highly significant differences were found among tested hybrids for all studied traits except number of wilted plants in trial A. Seven hybrids were selected, 5 from trial A and two from trial B. Hybrids # 11, 12, 17, 20 and 28 from trial A and 15, 33 from trial B. Results revealed that germplasm of Serbian origin was more beneficial to the national popcorn breeding program than other germplasm sources since most selected hybrids were of Serbian origin. Further evaluation of selected hybrids across multiple different locations is necessary before submission of selected hybrids to Variety Registration Committee.

Understanding photothermal interactions will help expand production range and increase genetic diversity of lentil (Lens culinaris Medik.)

SummaryLentil (Lens culinaris Medik.) is cultivated under a wide range of environmental conditions, which led to diverse phenological adaptations and resulted in a decrease in genetic variability within breeding programs due to reluctance in using genotypes from other environments.We phenotyped 324 genotypes across nine locations over three years to assess their phenological response to the environment of major lentil production regions and to predict days from sowing to flowering (DTF) using a photothermal model.DTF was highly influenced by the environment and is sufficient to explain adaptation. We were able to predict DTF reliably in most environments using a simple photothermal model, however, in certain site-years, results suggest there may be additional environmental factors at play. Hierarchical clustering of principal components revealed the presence of eight groups based on the responses of DTF to contrasting environments. These groups are associated with the coefficients of the photothermal model and revealed differences in temperature and photoperiod sensitivity.Expanding genetic diversity is critical to the success of a breeding program; understanding adaptation will facilitate the use of exotic germplasm. Future climate change scenarios will result in increase temperature and/or shifts in production areas, we can use the photothermal model to identify genotypes most likely to succeed in these new environments.