No abstract

screening of 25 SSR markers, revealed 23 clear and consistent amplification profiles in the entire walnut germplasm set. A total of 54 alleles were amplified by SSR primers and the number of alleles range from 2 to 3. The PIC value ranged from 0.36 to 0.68. The dendrogram classified all genotypes into two main clusters with various degrees of subclustering. Estimated genetic dissimilarity coefficient ranged from 0.36 to 0.85. Through model-based cluster analysis all genotypes were grouped into 5 genetically distinct subpopulations. The expected heterozygosity at a given locus was found to range from 0.520 to 0.5477. Similarly, population differentiation measurements (Fst) ranged from 0.2286 to 0.2909. These findings would be helpful for decision making in future walnut breeding studies, germplasm management activities to maximize genetic diversity in walnut germplasm and may also prove useful in future for conducting association mapping in walnut for different traits.

Persian walnut populations have tremendous morphological and allelic diversity in their germplasm due to heavy outcrossing and years of seed multiplication. These variations are assessed by morphological, cytological, biochemical and molecular markers. Various researchers have used different tree, foliage, flower, nut, and kernel traits to evaluate morphological/phenotypic diversity. In walnut, morphological indices are considered the first to describe and classify the germplasm, but the environment influences them. In comparison, DNA-based markers can detect genetic diversity at any stage of plant development and have been shown to be a potential tool for assessing variation at the DNA level and deciphering genetic relationships within and between species. Microsatellites are very powerful and informative among DNA-based markers in studying genetic relationships and genetic identity at different levels. They are neutral, highly frequent, uniformly distributed, hypervariable, codominant, highly reproducible, produce many alleles per locus, and require a small amount of DNA for analysis. Current breeding objectives can be achieved by selecting superior genotypes from the germplasm, supplemented by molecular characterization in the selection of parents for each breeding program. Therefore, the use of morphological and molecular markers is recommended for efficient exploration and utilization of germplasm resources and to improve diversity among genetic resources. The published literature on morphological and molecular markers, especially SSRs, is presented in this review to provide current insights into the level of genetic diversity in walnut.

Fifteen autochthonous walnut (Juglans regia L.) genotypes of the North-western Himalayan region were evaluated for biochemical composition. The moisture content in them ranged from 2.98 to 8.69 % whereas, the oil content varied from 40.00 to 62.43 %. The linoleic acid was found most abundant among the fatty acids values which ranged between 48.50 and 67.30 %. Furthermore, linolenic acid and oleic acid content ranged from 5.70 to 18.58% and 12.14 to 20.60 %. The protein and carbohydrate content extended from 15.00 to 23.00% and 9.03 to 12.96 g/100 g, respectively. Vitamin B1 was the amplest vitamin ranging from 0.74 to 0.52 mg/100g. Results of the present study revealed that the genotype JWSD-59 contained highest percentage of fats, oils and nutrients and genotype JWSP-06 in proteins. These genotypes can be utilized for breeding of nutrient rich cultivars and serve as reserve gene pool for the future walnut improvement programme efforts. Bangladesh J. Bot. 51(1): 93-101, 2022 (March)

Persian walnut populations have tremendous morphological and allelic diversity in their germplasm due to heavy outcrossing and years of seed multiplication. These variations are assessed by morphological, cytological, biochemical and molecular markers. Various researchers have used different tree, foliage, flower, nut, and kernel traits to evaluate morphological/phenotypic diversity. In walnut, morphological indices are considered the first to describe and classify the germplasm, but the environment influences them. In comparison, DNA-based markers can detect genetic diversity at any stage of plant development and have been shown to be a potential tool for assessing variation at the DNA level and deciphering genetic relationships within and between species. Microsatellites are very powerful and informative among DNA-based markers in studying genetic relationships and genetic identity at different levels. They are neutral, highly frequent, uniformly distributed, hypervariable, codominant, highly reproducible, produce many alleles per locus, and require a small amount of DNA for analysis. Current breeding objectives can be achieved by selecting superior genotypes from the germplasm, supplemented by molecular characterization in the selection of parents for each breeding program. Therefore, the use of morphological and molecular markers is recommended for efficient exploration and utilization of germplasm resources and to improve diversity among genetic resources. The published literature on morphological and molecular markers, especially SSRs, is presented in this review to provide current insights into the level of genetic diversity in walnut.