Chromosomal Association and Meiotic Behaviour of Four Triploid Varieties of Mulberry (Morus sp.)

Abstract

Chromosomal association and behaviour during microsporogenesis were studied in 4 triploid (2n=3x=42) varieties of mulberry. The meiosis of these varieties was irregular and indicated the typical features met within triploids. The average frequency of chromosomal associations observed were 0.06IV+11.97III+1.83II+2.22I, 13.25III+0.75II+0.75I, 12.79III+1.18II+ 1.25I and 0.04IV+11.42III+2.31II+2.94I in FGDTR-9, TR-8, Thailobed and KPG-1 respectively. The high frequency of trivalents suggested autotriploid nature of these varieties. Due to random assortment of loosely paired chromosomes of trivalents and the regular univalents, anaphasic separation was unequal leading to the formation of aberrent pollen grains. These features are discussed in relation to the importance of triploid mulberries in sericulture.