MSc

Cashew (Anacardium occidentale L., Anacardiaceae), a foreign exchange earning
horticultural plantation crop, native of north east Brazil and was introduced into India by
Portuguese travellers during 16th century. Since its introduction, cashew has very well
adapted to the Indian climatic conditions and is grown both in the east coast and west coast
regions. India was the first country to exploit the international trade of cashew kernels in the
early part of 20th Century. Now India is the largest producer, processor, consumer and
exporter of cashew in the world. It is famous for its delightful nutritious kernels and apple,
and it by-product like cashew nut shell liquid (CNSL), is commercially used in polymer and
paint industries.
More than 46 high yielding varieties of cashew released in India, Kerala
Agricultural University holds the credit for 16 varieties. The varieties selected for this
study include three hybrids (Poornima, Priyanka and Dhana) and two selections (Sulabha
and Madakkathara-1) based on their unique characteristics such as Poornima with
medium nut size, best shelling percentage (31%), Priyanka large sized nut and yellowish
red apple, Dhana large sized nut, better shelling percentage, and wide acceptability,
Sulabha large sized nut and kernel, light orange colour apple and late flowering,
Madakkathara-1 for small sized nut and early flowering.
The present study entitled ―Molecular characterization and DNA fingerprinting of
selected cashew (Anacardium occidentale L.) varieties of KAU‖ was carried out at the
Centre for Plant Biotechnology and Molecular Biology, College of Horticulture,
Vellanikkara during the period 2012-2014. The objective of the study was to characterize
the five selected cashew varieties of KAU using ISSR and SSR molecular markers, and to
develop a DNA fingerprint specific to each variety.
Morphological characters were recorded from three mature plants per variety of
almost same age, at Cashew Research Station, Madakkathara as per the IBPGR minimal
descriptor for cashew. Grafts of selected cashew varieties were obtained from Cashew
Research Station, Madakkathara and maintained at CPBMB, College of Horticulture.
Genomic DNA of good quality was extracted from cashew genotypes using CTAB
method (Rogers and Bendich, 1994) with slight modifications. PCR components and
thermal profiles were optimized for ISSR and SSR assay. Thirty nine ISSR primers and
twenty five SSR primer pairs were screened for amplification of genomic DNA out of them,
eleven each of ISSR and SSR primers were selected for further analysis, based on the
reliable distinct amplification pattern. In ISSR and SSR analyses, selected primers produced
total of 149 and 19 amplicons, respectively. Out of which 69 and 12 were polymorphic with
an average of 6.27 and 1.09 polymorphic bands per primer and polymorphic percentage
were 46 and 63, respectively. The resolving power (Rp) worked out for the different primers
ranged from 1.4 to 7.0 in ISSR analysis, indicating the capacity of the primers selected to
distinguish the varieties. The polymorphic information content (PIC) ranged from 0.256 to
0.42 for ISSR analyses indicating the variability among the genotypes. While, the PIC value
for SSR primers ranged from 0 to 0.50.
The ISSR and SSR banding pattern was scored and analysed for their similarity, using
the software NTSys pc (version 2.02i). The dendrogram generated with ISSR, SSR and
combined profiles grouped the selected cashew varieties in separate clusters. The varieties
Priyanka and Dhana were found more closer with 98 per cent similarity but a field grown
graft of Poornima was the most distinct one from other cashew genotypes.
Distinct amplicons developed through ISSR and SSR analyses were used to develop
the DNA fingerprint of cashew genotypes. Sharing of amplicons for each primer with other
genotypes was also analyzed and demarcated with different colour codes in the fingerprint
developed. In ISSR assay, each primer gave a unique amplification pattern for each variety.
Separate fingerprints were developed for all the five varieties through ISSR and SSR
analysis. The DNA fingerprints developed could be utilized for the variety identification and
to solve IPR issues.