Cross-genera transferability of (simple sequence repeat) SSR markers among cassava (Manihot esculenta Crantz), rubber tree (Hevea brasiliensis Muell. Arg.) and physic nut (Jatropha curcas L.)

Cross-genera transferability of simple sequence repeat (SSR) markers among three economically important plants of family Euphorbiaceae has been proposed. A set of SSR loci generated from cassava (199), rubber tree (49) and physic nut (42) were used to determine transferability with five accessions each of cassava, rubber tree and physic nut. The results revealed that cross-genera transferability among these species was observed. Of the 290 markers, 144 could amplify DNA of at least one nondonor species and 34 markers could amplify DNA of all tested species. A total of 57, 120 and 59 alleles were detected in cassava, rubber tree and physic nut, respectively, by transferable markers. The highest transferability (59.18%) was observed from cassava to rubber tree, followed by from rubber tree to cassava. Low transfer rates were found between cassava and physic nut, and between rubber tree and physic nut. These identified transferable markers for cassava, rubber tree and physic nut (37, 61 and 46, respectively) will be useful for comparative mapping and genomic studies. In addition, this finding is an important initial knowledge on cross-genera transferability of SSR markers in these three commercial species.Key words: Microsatellites, transferability, Euphorbiaceae, cassava, rubber tree, physic nut

DNA methylation in diploid inbred lines of potatoes and its possible role in the regulation of heterosis

Self-incompatible diploid potatoes were altered to self-compatible ones by a function of S-locus inhibitor gene and continued selfing generated highly homozygous inbreds. In this study, this process was investigated for the status of DNA methylation by a simple method using genomic DNA digested by methylation-sensitive restriction enzymes prior to RAPD analysis. We detected 31 methylation-sensitive RAPD bands, of which 11 were newly appeared in the selfed progenies, and 6 of them stably inherited to subsequent generations. Aberrant segregations and paternal- or atavism-like transmission were also found. Segregating methylation-sensitive bands in initial populations became fixed in the advanced selfed progenies by 75.0–93.8%, of which 41.7% were fixed to all present and 58.3% to all absent. Because DNA methylation is generally recognized to suppress gene expression as regulatory factors, homozygosity/heterozygosity of methylated DNA may be involved in inbreeding depression/heterosis

Genetics and cytogenetics of the potato

Tetraploid potato (Solanum tuberosum L.) is a genetically complex, polysomic tetraploid (2n = 4x = 48), highly heterozygous crop, which makes genetic research and utilization of potato wild relatives in breeding difficult. Notwithstanding, the potato reference genome, transcriptome, resequencing, and single nucleotide polymorphism (SNP) genotyping analysis provide new means for increasing the understanding of potato genetics and cytogenetics. An alternative approach based on the use of haploids (2n = 2x = 24) produced from tetraploid S. tuberosum along with available genomic tools have also provided means to get insights into natural mechanisms that take place within the genetic load and chromosomal architecture of tetraploid potatoes. This chapter gives an overview of potato genetic and cytogenetic research relevant to germplasm enhancement and breeding. The reader will encounter findings that open new doors to explore inbred line breeding in potato and strategic roads to access the diversity across the polyploid series of this crop’s genetic resources. The text includes classical concepts and explains the foundations of potato genetics and mechanisms underlying natural cytogenetics phenomena as well as their breeding applications. Hopefully, this chapter will encourage further research that will lead to successfully develop broad-based potato breeding populations and derive highly heterozygous cultivars that meet the demands of having a resilient crop addressing the threats brought by climate change