Chromosome Behaviour and Fertility in Induced Polyploids of Grain Amaranths

Abstract

Polyploidy was induced in four species and two F₁ hybrids of grain amaranths of the genus Amaranthus (Amaranthaceae) by colchicine treatments of apical buds in seedlings. The induced polyploids were shorter, thicker and dark leaves, larger perianth, larger seed size and lesser number of seeds/panicle as compared to the diploids. The inflorescences of the induced polyploids were shorter but thicker and darker than those of diploid species. The grain yield/plant was also low in induced polyploids as compared to diploids. Cytological analyses of diploid, F₁ hybrid and colchiploid plants were made. The autotetraploids were inferior to their respective diploids. Induced polyploids exhibited less pollen grain fertility than their diploids. The amphidiploids showed increase in pollen grain fertility as compared to F₁ hybrids. While diploids and F₁ hybrids exhibited only bivalent formation at metaphase-I and anaphase was normal, induced tetraploids showed varying frequencies of univalents, bivalents, trivalents and quadrivalents at first metaphase and few lagging chromosomes at anaphase-I. The multivalents were mostly ring or chain type having four or three chiasmata. The possibility of utilization of polyploidy has been discussed.

Key words:

• Amaranthus
• amphidiploid
• autotetraploid
• chromosomes
• colchicine
• pollen fertility
• polyploidy
• quadrivalent