Genetic Diversity Analysis Using Resistance Gene Analog-Based Markers to Support Morphological Characterization of Shallots

<p>Shallot (Allium cepa var. aggregatum) is one of the most important vegetable crops grown in Indonesia. The limited knowledge available on the genetic diversity and the threat of plant disease have been major problems to maintain high shallot production in Indonesia. Development of molecular markers linked to disease resistance is required for molecular breeding activity in this crop. This study aimed to assess the genetic diversity at conserved domain of resistance gene analog (RGA) in a set of 36 Indonesian shallot genotypes to complement morphological characterization. Twelve morphological and fifteen molecular markers traits were investigated in an attempt to characterize and to discriminate the Indonesian shallots genotypes. Characterization at orphological level indicated that phenotypic variance was highest for total bulb weight (TWB, cv = 99.39%) and the least for the plant height (PH, cv = 28.16%). The correlation analysis between traits showed that TWB and number of bulb (NB), TWB and bulb weight per plant (WB), NB and WB, and WB and PH were positively correlated. Molecular analysis revealed a total of 1,512 alleles with an average of 1.946 alleles per locus. The Polymorphism Information Content (PIC) values ranged from 0.253 to 0.676 and six out of 15 RGA markers were highly informative with PIC values ≥0.50. Based on cluster analysis, the 36 Indonesian shallot genotypes were clearly discriminated into six major groups. These results revealed that the RGA-based markers could support the morphological characterization in evaluating the genetic diversity of shallots. </p>

Genotyping Lupinus angustifolius cultivars with SRAP molecular markers and degenerate primers

We examined 18 combinations of SRAP primers with resistance gene analog (RGA) and chitinase degenerate primers in order to determine their utility for genotyping L. angustifolius. Primer pairs ResAn51-f/Me8, p-loop/Em5, TM/Me8, Chit3-r/Em5 were the most effective for detection of genetic polymorphism of different narrow-leaved lupine varieties.

Application of resistance gene analog markers to analyses of genetic structure and diversity in rice

Plant disease resistance gene analog (RGA) markers were designed according to the conserved sequence of known RGAs and used to map resistance genes. We used genome-wide RGA markers for genetic analyses of structure and diversity in a global rice germplasm collection. Of the 472 RGA markers, 138 were polymorphic and these were applied to 178 entries selected from the USDA rice core collection. Results from the RGA markers were similar between two methods, UPGMA and STRUCTURE. Additionally, the results from RGA markers in our study were agreeable with those previously reported from SSR markers, including cluster of ancestral classification, genetic diversity estimates, genetic relatedness, and cluster of geographic origins. These results suggest that RGA markers are applicable for analyses of genetic structure and diversity in rice. However, unlike SSR markers, the RGA markers failed to differentiate temperate japonica, tropical japonica, and aromatic subgroups. The restricted way for developing RGA markers from the cDNA sequence might limit the polymorphism of RGA markers in the genome, thus limiting the discriminatory power in comparison with SSR markers. Genetic differentiation obtained using RGA markers may be useful for defining genetic diversity of a suite of random R genes in plants, as many studies show a differentiation of resistance to a wide array of pathogens. They could also help to characterize the genetic structure and geographic distribution in crops, including rice, wheat, barley, and banana.