E. A. Siddiq

Review of methods for the detection and quantification of adulteration of rice: Basmati as a case study

Rice is a staple and widely grown crop endowed with rich genetic diversity. As it is difficult to differentiate seeds of various rice varieties based on visual observation accurately, the harvested seeds and subsequent processed products are highly prone to adulteration with look-alike and low quality seeds by the dishonest traders. To protect the interests of importing countries and consumers, several methods have been employed over the last few decades for unambiguous discrimination of cultivars, accurate quantification of the adulterants, and for determination of cultivated geographical area. With recent advances in biotechnology, DNA based techniques evolved rapidly and proved successful over conventional non-DNA based methods to purge the problem of adulteration at commercial level. In the current review, we made an attempt to summarize the existing methods of adulteration detection and quantification in a comprehensive manner by providing Basmati as a case study to enable the traders to arrive at a quick resolution in choosing the apt method to eliminate the adulteration practice in the global rice industry.

Bulked Segregant Analysis to Detect Main Effect of QTL Associated withSheath Blight Resistance in BPT-5204/ARC10531 Rice (Oryza sativa L)

The population consisting of 210 F2:3 individuals from the cross between BPT-5204 (highly susceptible to sheath blight) and ARC-10531 a land race from Assam (moderately resistant to sheath blight) was analyzed to identify the markers associated with sheath blight resistance and to study any association of any morphological trait to disease incidence. The frequency distribution curve of F2:3 progenies for disease trait were continuous, indicating the polygenic control over the trait. The range of relative lesion height was 21-75% with a mean of 38.59%.No significant association between sheath blight disease and other morphological traits were detected in F2:3 populations. Parental polymorphisms were surveyed with 500 primer pairs of simple sequence repeats (SSR), revealed 70 polymorphic markers between the parents. In order to detect the major effect, QTL associated with sheath blight resistance, a strategy of combining the DNA pooling from selected segregants and genotyping was adopted. The association of putative markers identified based on DNA pooling from selected segregant was established by Single Marker Analysis (SMA).The results of SMA revealed that SSR markers, RM336 (chromosome#7) and RM205 (chromosome#9) showed significant association with sheath blight and accounted for 21.8% and 17.3% of total variation respectively. The results obtained from the DNA pooling of phenotypic extremes could be a useful strategy to detect the genetic loci with major effects of the complex trait such as disease resistance in rice.

Genetic Variability and DNA Fingerprinting of Elite Mango Genotypes of India Using Microsatellite Markers

Genetic variability of 20 promising Indian mango genotypes which include juicy and table types was studied employing 143 simple sequence repeats (SSRs). Of 143 SSRs, 80 were found to be polymorphic among the genotypes. Characterization of the 20 genotypes resulted in the detection of 236 alleles from 80 polymorphic loci with an average of 2.87 alleles per locus and polymorphism information content (PIC) of 0.63. UPGMA cluster analysis grouped all the genotypes into two major groups with a genetic similarity range of 37–66%. The genotypes were grouped into clusters based on the utility type. DNA fingerprinting of 20 genotypes was done using four hyper-variable SSRs, viz. SSR1, SSR11, SSR58 and SSR78, because of their unique cultivar-specific allele sizes that distinguish all the 20 popular mango genotypes by capillary electrophoresis. Cultivar-specific codes were developed based on allelic size of the amplified products for identification of the 20 genotypes. The study shows high genetic variability among promising genotypes and allele codes assigned for each mango genotype to confirm the genetic identity and genetic purity of variety. The authors conclude that this study developed unique allele-specific codes for the 20 mango genotypes in India.