Distinctness of 110 rice ( Oryza sativa L . ) varieties of Bangladesh through morphological traits

A total of 110 rice varieties of which 108 local (From Bangladesh Rice Research Institute) and two hybrid varieties (From ACI Ltd. Bangladesh) were used to identify the morphological traits during July, 2008 to June, 2009. These varieties represented four types viz. T. Aman (n=92), B. Aman (n=15), Boro (n=2) and Jhum accession (n=1) as described by Bangladesh Rice Research Institute’s literature. Though all these materials were varied ecotypically but grown in one (T. Aman) season. Irrespective of groups of all, 90 varieties were appeared distinctly morphologically from others due to seed colour; stigma colour; anthocyanin colouration of leaf sheath, nodes and lemma:palea, presence of awn and nodal root. Among 90 distinct varieties 19 were distinctly different from others by four traits, nine by three traits, 24 by two traits and 38 varieties by only single trait. The rest 20 varieties were distinguished flag leaf: attitude of the leaf blade. This was done to assess the quality traits of distinctness as major concern and was noninfluenced by the environment.


Introduction
Rice, Oryza sativa (2n = 24) belongs to the family Gramineae and subfamily Oryzoidae.Rice is the most important human food crop, providing the staple food for nearly half of the global population, especially in Asia, Africa, and Latin America (FAO, 2004).Due to the great significance of this crop in food security and local culture, Asian farmers have selected a vast number of rice varieties over thousands of years (Jackson, 1995).There is wide genetic variability, leaving a wide scope for future crop improvement (Chakravarthi and Naravaneni, 2006).As the number of rice varieties increases, the ability to distinguish them on the basis of morphological and biochemical traits becomes more difficult, mostly due to genotype-environment interaction.Any developed variety requires distinctness for its identity and protection.Farmers select the best-performing plant from among the varieties bred by breeders, to compensate for environmental variation.Without a good method for maintaining genetic purity of varieties, there is the danger of losing varieties' identity.The advent of plant variety protection lends urgency to the search for solutions to the conservation of plant genetic diversity.Varieties that originated in farmer's fields may be legally protected, as many of those materials have been approved in Bangladesh and elsewhere by the regulating agencies in association with the institutional breeders for protection.This paper on the rice variety identification through distinct qualitative and quantitative traits is part of the morphological and molecular characterization of plant varieties in Bangladesh (Rahman et al. 2007;2008) where descriptors have widely been used.

Collection of seed and seedlings
Seedlings 29 days old of 108 local rice varieties were collected from Genetic Resource and Seed Division (GRSD), Bangladesh Rice Research Institute (BRRI) in August 2008.Seeds of varieties ACI 1 and Aalok 932024 were supplied by ACI Ltd.Bangladesh in August 2008.All were planted in the experimental farm on August 4, 2008 for studying morphological traits.

Observation, data collection and record keeping
The experimental plots were visited every day.The approved crop descriptors as given in the Volume 1 of PLANT varieties of Bangladesh (Rahman et al., 2007;2008) were used for documentation of these varieties.
1.All observations were made on at least 25-30 plants.
2. For the assessment of uniformity of characteristics on the line as a whole, visual assessment was done by a single observation of a group of plants or parts of plants.3.All observations on the leaf were made on the penultimate leaf.4. For the assessment of anthocyanin colour characteristics, recommended Breeder's descriptors codes were used.

Measurements
A few qualitative traits such as anthocyanin colouration of leaf sheath, lemma:palea, stigma and node, presence of awn, nodal root and seed shape were mainly utilized for distinctness of rice varieties.Plant height was measured from the base of the plants to the neck of the panicle.The panicle length was measured from the neck to the tip of the panicle of main tillers without awns.Longitudinal dimension was measured as the distance from the base of the lowest sterile lemma to the tip (apiculus) of the lemma or palea, whichever was longer.In the case of awned varieties, length was measured to a point comparable to the tip of the apiculus.Dorsiventral diameter was taken as the distance across the lemma and the palea at the widest point.A few quantitative traits were studied using number of effective tillers, days to 50% flowering and maturity, panicle length, 1000 grain weight and length: width ratio of grains.

Harvesting
The 110 rice varieties were harvested at different times from 27 th October, 2008 to 15 th January, 2009.This was due to their requirement of different days to reach maturity.

Data analysis
Mean, Standard deviation and Co-efficient of variation were analyzed using a total of six parameters: effective tillers, days to 50% flowering, panicle length (cm), days to maturity, 1000 grains weight and seed length/width ratio.

Results and Discussion
The quantitative results (Table 1) clearly indicate high variation.One of the major traits, the days 50% flowering is considered as the types are Aman and Boro.But one consideration is important that the rice varieties selected over long years but grown under one management conditions in one season will in fact give the expression of that trait as compared to others.This is where the case of distinctness is more important.
In the present study, 92 varieties were T. Aman, 15 B. Aman, 2 Boro, and 1 was classified as Jhum, as per information supplied by BRRI.The important traits for distinctness were anthocyanin colouration of seed, leaf sheath, lemma: palea, stigma, node and seed shape, presence of awn, nodal root.The study includes group-wise distinction as well as overall pooled (110 varieties) distinctness (Table 2).
One variety, Buna Dhan, was identified by anthocyanin colouration of leaf sheath, lemma:palea, presence of awn and seed colour.Based on anthocyanin colouration of lemma: palea, node, nodal root, presence of awn and seed colour two varieties, Tulo Sail and Jola Bhangh were distinct.According to presence of anthocyanin colouration of lemma:palea, node, presence of awn and seed colour one variety, Biropa, was distinct.Two varieties were identified by the presence of anthocyanin colouration of leaf sheath, lemma: palea and nodes, Ful Kari and Mukut Sail.Nag Pechi was distinct due to the presence of anthocyanin colouration of lemma: palea, node, nodal root and presence of seed colour.anthocyanin colouration of lemma: palea, node and presence of seed colour made Pani Torong distinct.2), Raj Bhog, Khoni Dhan, Bhor Gelam, Asham Baba, Lal Modonga, Lal Amon, Hasna Chikon, Kochu Dhola , Moisha Mida, Choia Mora, Thakor, Dharga Sail, Thakor dhan were distinct (Table 2).
B. B-Aman group: Among 15 B-Aman varieties 13 are distinct.Two varieties, Kali Cochr and Kala Gura, were distinct depending on anthocyanin colouration of leaf sheath, lemma: palea, nodes and seed colour.
Based on anthocyanin colouration of leaf sheath, lemma: palea and nodes, Jhaw Lota was distinct.One variety, Monura was distinct based on anthocyanin colouration of lemma:palea, node, presence of seed colour.Based on anthocyanin colouration of lemma:palea, presence of seed colour two varieties, Hiruyal and Chand Moni (3) were distinct.Based on anthocyanin colouration of nodes and presence of nodal roots Muar Sail and Bhoban were distinct.On the basis of seed colour, five varieties, Shil Pan, Pushon, Ghori Amon, Chapa Mali and Moisa Mira were distinct (Table 2).
C. Boro: Among two Boro varieties, ACI 1 was distinct from the other based on presence of anthocyanin colouration of leaf sheath, lemma:palea and nodes (Table 2).
D. Jhum: In this study, only one Jhum variety was included, Ful Badam, which was distinct based on the presence of seed colour (Table 2).In previous studies (Rahman et al., 2006;2007), 34 and 91 rice varieties were distinguished from each other on anthocyanin colouration of lemma:palea, colour of stigma, anthocyanin colouration of leaf sheath, colour of seed, presence of awn and penultimate leaf; shape of the ligule.

Overall Distinctness based on qualitative traits
Irrespective of groups of rice varieties out of 110, 90 varieties appeared to be distinct morphologically due to seed colour and presence of awn, lemma:palea, anthocyanin colouration of stigma, anthocyanin colouration of leaf sheath, nodes and the presence of nodal root.Among 90 distinct varieties some 19 were distinct by four traits, nine by three traits, 24 by two traits and 38 by a single trait (Table 2).Out of 110 varieties 90 were identified through qualitative traits while 20 were identified by four quantitative traits (Table 2).Those 20 were not distinguishable using the qualitative traits.

Quantitative traits
Data of 110 varieties related mostly to the quantitative traits (Table 1) indicated a high CV for effective tillers and seed shape (L/W) ratio, and for other traits.These results revealed considerable diversity in the total population.Even when the results were computed for individual groups, the variation was high (Table 4).

Table 1 .
Mean values of different Morphological traits of rice varieties
Two varieties, Jol Kumari and Hati Banda were distinct by anthocyanin colouration of lemma: palea, presence of awn and seed colour.Based on anthocyanin colouration of lemma: palea, presence of seed colour, seven varieties, Bhasha Manik, Horinkhur Panati, Paglakushyari, Kurki, Kanchon Mogi, Kali Jira (2), and Sundar Sail were distinct.One variety, Ban Kolom, was distinct by presence of anthocyanin colouration of leaf sheath and anthocyanin colouration of lemma:palea.Based on presence of anthocyanin colouration of nodes and presence of awn, Madhu Mala was distinct.Two varieties, Lal Patjat and Galong were distinct by anthocyanin colouration of node and seed colour.Five varieties, Tembur, Choro, Randar, Gutok and Jula Gudi were distinct by anthocyanin colouration of nodes, presence of nodal roots and presence of seed colour.Four varieties, Dudshar, Chakkol (Muta) Raozan, Chadlash, Porangi were distinct by seed colour and awn.Based on presence of nodal roots and seed colour two varieties, Bhua Dhan and Neel Huri were distinct.Four varieties, Lau Jan, Kamoni Sail, Jhual Kata and Mutonga (2) were distinct by anthocyanin colouration of nodes and presence of nodal roots.Muijuri was distinct by anthocyanin colouration of lemma:palea.Based on presence of awn, Sungawala, Konek Chul and Dhul Abiz were distinct.According to presence of seed colour22 varieties, Mulai, Tulsi Mala, Sandik Sail, Jhoria Sail,  Maitya Cheng, Kui Sail (2), Munsi Sail, Moina Sail, Butu Balam (

Table 2 .
Distinctness of 90 rice varieties based on qualitative traits

Table 3 .
Distinctness of 20 varieties, which could not be identified through qualitative traits individually or in combination

Table 4 .
Mean values of different quantitative traits of rice varieties