Cytogenetical investigations on newly synthesized diploid hybrids of section Arachis

Groundnut (or peanut) is one of the major oil seed crops and a valuable cash crop of the world that is planted by millions of small-scale farmers around the globe. It’s a valuable source of proteins, vitamin E, K, and B (ref…). It’s worthy to note that 70% of global groundnut production is in the semi-arid tropics.

Groundnut is susceptible to range of diseases caused by viruses, bacteria, fungi and insect pests. Sources of resistance to these constraints are not there in a big way in the cultivated germplasm. Whereas wild relatives of groundnut have shown resistance to these constraints.

Transfer of resistance genes/traits from wild species is not a straightforward process due to ploidy differences and compatibility barriers. To develop new sources of tetraploid groundnut diploid hybrids were produced not only between putative genome donors but a range of diploid species.

Cultivated groundnut i.e., Arachis hypogaea is an allotetraploid (4x=40). Arachis is reported to be cytologically difficult on account of small chromosomes and inadequate spreading of the chromosomes. This has made elaborate cytological analysis difficult. Nevertheless it is possible to study the meiosis of groundnut hybrids. Main objective of this dissertation work is to perform a cytological analysis, which involves studying meiosis as well as tetrad analysis to find out the homology of the parents and reason for the pollen sterility in the hybrids and to check pollen fertility of the hybrids.

In the present study a range of diploid hybrids with variable pollen fertility are being used as the study material for cytogenetical studies. Study of meiotic chromosome configuration, anaphase analysis and tetrad analysis give an insight into the genome homology/homeology, which have gone to make diploid hybrids.

Selected F1 hybrids were used for the cytological analysis. For the cylotological study, the young buds are collected and first treated with Carnoy’s Fluid-II for 48 hours and then transfered to Carnoy’s Fluid-I containing a little ferric chloride for 24 hours. Anthers from fixed buds are squashed in acetocaramine dye and then a coverslip is placed. For a better view and study of chromosomes the slide should be destained using acetic acid solution. Gently warm the slide and press the coverslip to facilitate further spreading of chromosomes.

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