Secondary Chromosomal Association in Kidney Bean ( Phaseolus Vulgaris L. )

Abstract

The present study documents the mutagenic efficacy of gamma ray and sodium azide on the chromosomal association pattern of bivalents and meiotic behavior in Phaseolus vulgaris L. The seeds were irradiated with different doses of gamma rays viz.10 krad, 20 krad, and 30 krad from a 60 Co source and thereafter, the seeds were treated with 0.3% of freshly prepared sodium azide solution for three hours, respectively. The results clearly show the formation of various types of secondary chromosomal association among bivalents. Secondary association is defined as the tendency of bivalents to lie in pairs having diffused connections. The phenomenon of secondary pairing manifested from metaphase I stage and persisted upto metaphase II stage. The bivalents lie side by side and end to end to form secondary pairing. A secondary association between bivalents is considered to be of great significance as it is being taken as an indicator of ploidy in plants. Apart from secondary chromosomal association, other meiotic abnormalities were also noticed. These include precocious movement of chromosomes at metaphase I/II (2.83%), stickiness at metaphase I/II (3.45%), stickiness at anaphase I/II (2.20%), bridge (1.25%), unorientation (0.94%), micronuclei (1.88%) etc. This phenomenon, along with other meiotic aberrations affects the pollen fertility considerably.

Meiotic analysis and FISH with rDNA and rice BAC probes of the Thai KPS 01-01-25 sugarcane cultivar

“…Secondary associations were first described by Lawrence (1931) and were thereafter regularly referred to in meiotic studies of several plant species, most of them about polyploid species (Gustafsson 1935;Kempanna and Riley 1964;Kumar and Singhal 2013), including sugarcane (Sreenivasan and Jagathesan 1975). Such associations were also described in haploids (Sadasivaiah and Kasha 1971;Jelenkovic et al 1980), in material exposed to ionizing radiation and mutagenic treatments (Kumar and Chaudhary 2014) and even in the ancestral polyploid Brassica oleracea (Wills 1966;Ji et al 2014). Although the nature for such associations may be different in the examples mentioned above, the general clarification for this phenomenon points at residual homology or duplicated segments between homeologous and non-homologous chromosomes as found in (ancestral) polyploids and haploids, respectively (Kempanna and Riley 1964).…”

“…Klášterská (1976) argued that such threads in multivalent-like associations as found in Rosa meiosis are the result of a disturbed recondensation of the chromosomes after the diffuse diplotene stage and do not reflect any kind of structural hybridity. However, as strong variation in such associations was found between the samples from different seasons it may suggest that environmental conditions play a role in the occurrence of such secondary associations, an explanation that is also favored by Kumar and Chaudhary (2014). Alternatively, Thomas andRevell (1946), andJelenkovic et al (1980) suggested that duplications in the heterochromatic segments favors associations between non-homologous parts, which find support in the recent FISH study of Brassica oleracea meiosis (Ji et al 2014) showing that such inter-bivalent connections contain stretches of 45S rDNA and centromere tandem repeats.…”

Secondary associations in ‘Himalayan pink’ (Dianthus angulatus Royle ex Benth., Caryophyllaceae) from cold deserts of Lahaul-Spiti

“…More than century ago the phenomenon of secondary associations was discovered by TAHARA (1909) in Morus (1909). Subsequently, this phenomenon had been reported by many other workers (KUWADA, 1910;ISHIKAWA, 1911;MARCHAL, 1912;DARLINGTON, 1928;LAWRENCE, 1931;HEILBORN, 1936;JACOB, 1957;GUPTA and ROY, 1973;AGARWAL, 1983;ARGIMYN et al, 1999;KUMAR et al, 2013;KUMAR and CHAUDHARY, 2014). Different views applied by different authors to explain the basis of secondary associations include, the fusion between heterochromatic regions of the involved bivalents (THOMAS and REVELL, 1946), homology of paired bivalents, and artefact induced due to squash technique (HEILBORN 1936;BROWN, 1950) or fixation (PROPACH, 1937).…”