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

A genome scan for quantitative trait loci affecting cyanogenic potential of cassava root in an outbred population

<p>Abstract</p> <p>Background</p> <p>Cassava (<it>Manihot esculenta </it>Crantz) can produce cyanide, a toxic compound, without self-injury. That ability was called the cyanogenic potential (CN). This project aimed to identify quantitative trait loci (QTL) associated with the CN in an outbred population derived from 'Hanatee' × 'Huay Bong 60', two contrasting cultivars. CN was evaluated in 2008 and in 2009 at Rayong province, and in 2009 at Lop Buri province, Thailand. CN was measured using a picrate paper kit. QTL analysis affecting CN was performed with 303 SSR markers.</p> <p>Results</p> <p>The phenotypic values showed continuous variation with transgressive segregation events with more (115 ppm) and less CN (15 ppm) than either parent ('Hanatee' had 33 ppm and 'Huay Bong 60' had 95 ppm). The linkage map consisted of 303 SSR markers, on 27 linkage groups with a map that encompassed 1,328 cM. The average marker interval was 5.8 cM. Five QTL underlying CN were detected. <it>CN08R1</it>from 2008 at Rayong, <it>CN09R1</it>and <it>CN09R2 </it>from 2009 at Rayong, and <it>CN09L1 </it>and <it>CN09L2 </it>from 2009 at Lop Buri were mapped on linkage group 2, 5, 10 and 11, respectively. Among all the identified QTL, <it>CN09R1 </it>was the most significantly associated with the CN trait with LOD score 5.75 and explained the greatest percentage of phenotypic variation (%Expl.) of 26%.</p> <p>Conclusions</p> <p>Five new QTL affecting CN were successfully identified from 4 linkage groups. Discovery of these QTL can provide useful markers to assist in cassava breeding and studying genes affecting the trait.</p

Validation of a reference gene for transcript analysis in cassava (Manihot esculenta Crantz) and its application in analysis of linamarase and α-hydroxynitrile lyase expression at different growth stages

Relative real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) is a well-established method for the precise quantification of gene expression. For accurate relative real-time RT-qPCR analysis, validation of the expression of an appropriate reference gene is required. In this study, the expression of six commonly used reference genes, namely 40S ribosomal protein (40S), actin (ACT), cyclophilin C (CYCC), EF-1 alpha (EF1), TATA box binding protein (TBP) and polyubiquitin (UBI) was investigated in leaf and root samples of cassava obtained at 6, 9 and 12 months after planting (MAP). A transcript stability analysis was undertaken in two different varieties of cassava, namely Huay Bong 60 which has high cyanogenic potential (CN) and Hanatee which has low CN. The results reveal that TBP was the most stable reference gene for expression studies. This information was applied to an analysis of linamarase and α-hydroxynitrile lyase gene expression in samples from six low and six high CN cassava plants collected at 6, 9 and 12 MAP. The results indicate that at 6 MAP, the linamarase transcript from leaf of the high CN group was significantly increased, and the α-hydroxynitrile lyase transcript was significantly increased at 12 MAP.  Key words: Cassava, housekeeping gene, hydroxynitrile lyase, linamarase, real-time polymerase chain reaction (PCR)