Sri Lankan traditional rice germplasm (Oryza sativa indica) consists of a wide variety of morphology and days to flowering (DF). The objective of this research was to develop a mini core collection representing the DF variation of the total collection. Three hundred and eighty four rice accessions from 53 Sri Lankan traditional rice varieties were evaluated for morphological and flowering time variation. The experiment was carried at Rice Research and Development Institute, Bathalagoda, Sri Lanka during the late short day season (Maha), 2012/2013.Three hundred and forty five accessions flowered and 39 accessions did not flower during the experimental period of 210 days. Two principal component analyses (PCA) were performed and subsequently 2 dendograms were developed for flowered and not flowered accessions. Sixty eight percent of total observed variation was explained through 6 principal components (PC's) by DF and fourteen quantitative morphological characters of 345 flowered accessions. Seventy nine percent of total observed variation of not flowered 39 accessions was explained through 4 PC's by 9 quantitative morphological characters. Ninety accessions were selected from 2 dendograms for development of a mini core collection; out of which 85 accessions represented flowered accessions based on minimum and maximum DF variation in each cluster of the dendogram. Five randomly selected accessions represented each cluster of not flowered accessions. Minimum and maximum DF values of both total collection and mini core collection were 56 and 189 days, respectively. Average DF of total flowered collection and mini core collection was 79.16 ± 0.95 and 87.95 ± 3.1, respectively. A similar trend in the regression relationship between DF and plant height and, DF and leaf length of the leaf prior to flag leaf was observed in total flowered collection and mini core collection, indicating the representation of mini core collection for flowering time variation.

Breeding new varieties adaptable for changing climate is an essential need in sustainable rice production. Around 2000 Sri Lankan rice accessions at Plant Genetic Resources Centre (PGRC), Sri Lanka have not been fully characterized for the yield potential and sensitivity to mild photoperiodic differences for days to flowering (DF). DF is a candidate key determinant in yield components in rice and understanding the physiological and molecular nature for DF is important to manipulate crop yield through breeding programmes. The objective of this study was to assess the genetic diversity of 15 Hondarawala accessions from PGRC using selected 37 morphological characters and DF. DF varied from 58-189 days while accession number 3988 did not flower until 200 th day of seed germination. Principal Component Analysis (PCA) revealed that four principle components (PA) explained 86.5% of total observed variation. Variation of DF positively associated with most of morphological characters of vegetative growth while a few characters were negatively associated. In the dendogram, 10 clusters formed at rescale distance of 5. Widely variable DF accessions distributed among clusters.

Sri Lankan traditional rice is an important breeding resource for development of rice for ecological adaptation during the era of climate change. There are around 2000 accessions belonging to more than 500 varieties comprised of one to several accessions in each with wider morphological differences, flowering times and yield variations. Genetic identity of Sri Lankan traditional rice accessions belonging to each rice variety is not established at molecular level. Variety Sudu wee comprises of around 30 accessions at PGRC. Sudu wee could be useful in re-introduction programmes of traditional rice due to relatively shorter crop duration. The objective of the present study was to evaluate the diversity of 29 Sudu wee accessions from PGRC, based on days to flowering, (DF), 12 morphological and 2 physiological characters during non-inductive photoperiod season. DF varied from 62 to 106 days while accession 4193 did not flower during the experimental period of nearly 7 months. Leaf temperature at heading (LeT) and Leaf temperature difference at heading (LeTD), vegetative morphological characters and yield components varied among Sudu wee accessions. Seventy nine percent of total observed variation among accessions was explained through Principal Component Analysis. In the dendogram of accessions, 10 clusters were formed at the rescale distance of 5. Seed morphology indicated the genetic similarity among accessions while significantly different DF could be an indication of flowering time gene variation among similar genotypes. Increased DF reduced the grain yield increasing the vegetative growth among accessions of Sudu wee. Our results would be useful in future breeding for manipulating flowering time and yield within similar genetic backgrounds.

Sri Lankan traditional rice varieties consist of more than one accession mostly which, exhibit a wide variation in morphological characters, flowering time and yield. The objective of this study was to evaluate the diversity based on days to flowering (DF) and 12 morphological characters of two Sri Lankan traditional rice varieties Pachchaperumal and Suduru samba comprising of 13 and 7 accessions respectively. DF of Pachchaperumal and Suduru samba varied from 60 - 72 and 79 - 99 days respectively. Vegetative morphological characters and yield components also varied among Pachchaperumal and Suduru samba accessions while pericarp colour, grain width, and length were distinct characters between the two varieties. According to the hierarchical cluster analysis, 2 major clusters were identified at the rescale distance of 25 separating accessions of Pachchaperumal and Suduru samba except for accession 3136 of Pachchaperumal, which was located in Sudura samba cluster. Seven clusters were derived at rescaled distance of 5 where accessions of similar quantitative and qualitative morphological characters were clustered together. There were negative correlations between DF and selected yield components in contrast to positive correlations between DF and selected vegetative growth parameters. Our results may be useful in the determination of identity of accessions belonging to the same variety, which could be further supported by molecular analysis.

Photoperiod and temperature are two important environmental factors affecting vegetative growth and yield of rice. The varietal diversity based on the response to temperature and photoperiod during vegetative growth was determined in a core collection of 40 Sri Lankan traditional rice accessions (SLTRA) and 2 improved and 2 wild rice types in terms of days were imposed during 2 trials of high temperature (HT) and low temperature (LT) at under. Average DFL of the collection while photoperiod alone affected 1 accession. Average PHs by photoperiod or temperature. Temperature alone affected 12 accessions and photoperiod alone affected 2 accessions. Both photoperiod and temperature affected 4 accessions. In the SLTRA and improved rice were differentiated into 2 clusters at accessions of the same variety together. The differential varietal response to photoperiod and temperature in SLTRA would be useful in breeding for climate change adaptations after further experiments Oryza sativa