MSC

Rice (Oryza sativa L.) popularly known as ‘Global grain’ is the staple food for over half the world’s population. In Kerala, rice occupies the prime place among the food crops cultivated. Diversity of cropping systems, the edaphic and climatic variations found among and within different cropping regions have resulted in a cafeteria of variable genotypes.

Concerted efforts by breeders in Kerala Agricultural University to conserve the diversity in rice crop, have resulted in formation of a germplasm collection of over 1000 accessions. Such large variability, though essential for crop improvement programmes, reduces the accessibility of germplasm and poses difficulty in making effective choice of parental material for breeding programmes. The concept of core collection proposed by Frankel (1984) provides a solution to this problem. According to him, core collection is defined as a representative sample of the entire collection with minimum repetitiveness and maximum genetic diversity of a crop species and its relatives.

Considering the advantages in obtaining a subset that retains maximum diversity of the large germplasm collection, an effort was made to form a core set from a base collection of 160 short duration accessions (Base collection). The 160 accessions were raised in an Augmented Blocks Design, at College of Horticulture, Vellanikkara with 16 blocks during kharif 2011 -12. Each block comprised of 10 accessions (unreplicated) and 3 checks. The accessions were characterized and evaluated for 41 qualitative traits and 24 quantitative traits as per the descriptor of rice (Rani et al., 2004; IRRI 2007).

Results revealed that wide variability existed in the Base collection for all the traits studied. A core set of 34 accessions was developed by using PowerCore (v.1.0) software based on 24 quantitative traits. The representativeness of diversity in base collection in the core set was evaluated through comparison of, i) estimates of mean for the quantitative trait through One sample‘t’ test, and ii) Levene’s F-test for variances. Chi-square test was employed to examine the parity in frequency distribution of morphological traits in the core set and Base collection. All the above tests proved that both the core set and Base collection did not differ significantly from each other. This indicated that variability in core set was on par with that found in the Base collection.

Shannon-Weaver diversity index between Base collection and the core set was compared to assess the extent of diversity present in the two populations. Results revealed that core set comprising of 34 accessions has captured 100.54% of total diversity of the Base collection (160 accessions) which it was derived from. Thus, the core set proved to be a true representative of the diversity present in the Base collection. The reduced number greatly enhances accessibility of germplasm collection for breeding programmes aiming at improving yield and yield contributing traits.