It has the normal ploidy level, as such there are would not be any effect on its genetic improvement

Please have a look at these links.

http://www.fao.org/docrep/006/y4751e/y4751e0c.htm

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4807965/

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3706852/

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2610172/

1. If you are using genetic transformation method to improve your crop: In general,  the larger the genome, the harder the genetic transformation can be done, such as garlic, wheat...etc

2. It is also harder to perform some molecular analyses on plants with large genomes after genetic transformation, such as Southern assay. When the same amount of DNA is used for analysis, for 1 copy of the transgene presented in the larger genome, several to many copies of the same transgene can present in a  smaller genome. This leads to easier radioactive band detection on transgenic plants with smaller genome size.

3. Sequencing effort can also be hindered by a large genome with polyploidy. See attached paper:

"Why Assembling Plant Genome Sequences Is So Challenging (2012 Review)" 

Hello Yuan,

Please clear how the larger genome size hinder in genetic transformation procedure?

regards

vajinder

@  Vajinder Kumar,

That is a good question. Linking low genetic transformation efficiency to plant 'large genome' has been reported in some papers, such as the paper attached (yellow highlights, p.3487). However, the reasons/mechanisms of causing that are barely studied, or at least I haven't noticed that on literature/reports. Maybe someone on RG knows?

Large genome size can challenge CRISPR-based crop improvement:

Recent technology CRISPR/Cas9 is a powerful tool for targeted genome editing. Researchers use it to knock-out an allele, fix an allele and more. However, a larger genome can chanlenge its use due to its complexity, ex. 'duplication events', and slow down the process of a crop improvement. See this description (p.46) from the paper attached:

"(p.46) In maize, which has the largest genome and greatest number of annotated genes among the eight species that were analyzed, only 30% of the transcription units could be targeted by specific gRNAs. The lack of specific gRNAs for so many maize genes probably reflects the genome complexity (duplication events) and genomic sequence context. It is therefore anticipated that wheat and barley, with even larger genomes than maize, may present similar challenges for CRISPR/Cas9-mediated genome editing."

There is also a hypothesis called "The Large Genome Constraint Hypothesis".

See the attached paper**. From their studies, some evidence tentatively supports the large genome constraint hypothesis. The authors listed several constraints from their studies.

(1)  Genera with large genomes are less likely to be highly specious – suggesting a large genome constraint on speciation

(2)  Species with large genomes are under-represented in extreme environments – again suggesting a large genome constraint for the distribution and abundance of species

(3)  Species with large genomes have reduced maximum photosynthetic rates – again suggesting a large genome constraint on plant performance

**Title: The Large Genome Constraint Hypothesis: Evolution, Ecology and Phenotype

If the hypothesis does exist (more extensive studies still need), the genome size of your species-of-interest can affect the results of your project.

I suppose the smaller genome is more amenable for genetic engineering, disarming would be easier.

@ Kadhim,

What did you mean by 'disarm'? T-DNA of Agrobacterium?

Genomic shock of hybridization

When you perform interspecies cross such as diploid x tetraploid = triploids, then through 'chromosome doubling', you will obtain a new allopolyploidy species with hexaploid. This new species will encounter genome reorganization including size reduction. That means pieces of DNA/genes in the new genome will lost. Therefore, the DNA amount in the new genome won't be the same as the combined DNA amount of the two parents. This phenomena is called "Genomic shock" of hybridization (see attached paper). This has been reported in tobacco, wheat, and others. 

If your research project involves in this area, it is important for you to have the knowledge of the sizes of both the parents (diploid and tetraploid) and the new species.

It is clear that genome size is important in crop improvement analysis

based on method used. It affects sequence analysis and transformation studies. it may not have effect on MAB and some other crop improvement strategies