DUS Characterization of Tamil Nadu Traditional Rice (Oryza Sativa L.) Varieties

In the world, rice is the second most important cereal crop after the corn. Rice is grown in over one hundred countries and produces more than 700 million tonnages annually, with total harvested area of approximately 158 million hectares (470 million tons of milled rice). Asia produces almost 640 million tons of rice, which accounts for 90% of the world demand. Rice is the main staple food crop and the most competitive in India (Barua and Saikia 2018). Production reaches to 116.42 million tonnes in 2018-2019 and having an estimate of 120.48 million tonnes in 2019-2020 (Anonymous 2019). India has a rich and wide range of genetic wealth of rice (Anju and singhl 2003). Approximately, 425, 500 rice accessions stored in various gene banks on worldwide are possible genetic sources for improving guided crops Chakrabarty et al., (2012) Different studies suggest that India has over 70,000 germplasm accessions and also needs the selection and protection of a large number of wild species (Siddiq 1992). Indigenous rice varieties also have an impact for various conditions such as skin disorders, blood pressure, fever, paralyzes, rheumatism, leukorrhea and for increasing tone of lactation in the Indian states of Karnataka, Madhya Pradesh, Kerala, Tamil Nadu, Uttar Pradesh, Western Ghats and the Himachal Pradesh Ahuja et al., (2008). In addition to providing sources for clearly inherited traits such as resistance or the tolerance to biotic and abiotic stresses, traditional rice varieties also provide genes for complex properties for further improvements in grain quality and yield. Singh et al., (2010) Valuable rice germplasm in this region has rapidly disappeared over the last few years due to the change in the variety spectrum and the usage of paddy fields for non-agricultural purposes Latha et al., (2013). Hence, there is an urgent need for characterization and conservation of these traditional landraces. In this context, an attempt was made to characterize a set of twenty-seven rice landraces for different morphological and agronomic traits and identify the variability available in the collection.
       
Government of India has introduced Protection of Plant Varieties and Farmers’ Rights (PPV & FR) Act in 2001. DUS-based morphological characterization (Distinctness, Uniformity and Stability) is the criterion for variety registration under the PPVandFR Act. Hence the programme is aiming for DUS characterization of twenty-seven landraces of Tamil Nadu.

Study site
 
Twenty-seven traditional varieties of rice were grown in a Randomized block design with three replications in 2019 at the Department of Genetics and plant Breeding farm situated near Faculty of Agriculture, Annamalai, University. The experimental site has the co-ordinates of 11°24¢ N latitude and 79°41¢ E longitude at an altitude of 5.1 m above the main sea level.
 
Experiment materials
 
The present research experimental material consists of 27 local rice cultivars (Oryza sativa L.) of Tamil Nadu. Relevant common name was gathered from local farmers. (Table 1).


 
Field plot
 
Accessions were grown in a randomized block design with the three replications. Each entry was sown in three rows of 20 plants, at a spacing of 15 cm between plants and 20 cm between rows and 1mt isolation separation was maintained between two entries in each block. Crop was raised by following recommended package of practices. (Manjunatha et al., (2018).
 
Observations
 
The observations were taken for forty-nine morphological and agronomic characters. In these observations, Morphological characterization of twenty-seven landraces of rice was carried out using twelve DUS characters. Visual observations were recorded on remaining thirty-seven characters for single plant basis on ten randomly selected plants in each genotype at appropriate growth stages as reported by Umarani et al., (2017).

Fourty-nine traits were observed in twenty-seven germplasm to establish distinctiveness among germplasm and these are presented below.
 
Morphological characterization
 
Qualitative characters are important for the definition of plants and are mainly influenced by consumer preference, socio economic scenario and natural selection (Ismaeel et al., 2016). Frequency distribution for 39 qualitative traits is depicted in (Table 2). Most of the morphological characters display variability in different accessions, with the exception of Basal sheath colour, Leaf collar, Leaf collar anthocyanin colouration and Leaf Ligule. A majority of accessions possess green (96.30%) coleoptile colour, purple colour coleoptiles found in (karupu kavuni) 3.70% of plant as a unique genotype because more than 95% of the purple coleoptile colour plant is resistant to insect pest i.e. brown plant hopper (Bph) (Bennet 1994) while in wheat purple colour of coleoptile is reportedly related with resistance to bunt. (Shoeva and Elena, 2015).


       
The observations for leaf traits were recorded as leaf anthocyanin colouration (88% present), leaf distribution of anthocyanin colouration (81% Uniform), leaf sheath anthocyanin coloration (88% present), leaf auricles (85% Present), leaf anthocyanin coloration of auricles (85% colourless), leaf colour of ligule (96% white), leaf intensity of green colour (40% Medium, 33% light, 26% dark), leaf sheath intensity of anthocyanin coloration (44% medium, 30% weak, 26% strong), leaf pubescence of blade surface (52% medium, 33% strong, 14% weak,) leaf shape of ligule (52% acute, 30% split, 18% truncate), Similar type of work was also reported (Bisne and Sarawgi, 2008; Ahmed et al., 2016) and some of the accessions possessed various distributions were found in (Shrivastava et al., 2015). Culm attitude is an indicator of the growth habit of a particular species. During the current study valuable variation was observed among the accessions for culm angle. (Rawte and Saxena, 2018). Culm attitude (for floating rice) (81% procurement), culm attitude (40% erect, 19% semi erect, 4% spreading) (Fonseca et al., 2002). Time of heading 50% of plants with panicles were observed and noticed that 52% landraces are medium type, 44% landraces are very late type and 3% (Arupatham kuruvai) landraces were of early and a short duration variety. Flag leaf: attitude of blade (early observation) (48% semi erect, 30% horizontal, 18% erect, 3% drooping), Spikelet: density of pubescence of lemma (55% absent, 18% medium, 14% strong, 7% weak, 3% very strong), Spikelet: colour of stigma (30% light green, 7% yellow and purple) (Nascimento et al., 2011)  Stem: Thickness (59% thick, 29% thin, 11% medium), Panicle: length of main axis (19% medium, 15% very short, 7% long and very long), Flag leaf: attitude of blade (late observation) (19% semi erect, 15% erect, 3% horizontal and deflexed), panicle curvature of main axis (19 semi straight, 15% straight, 7% drooping), spikelet colour of tip of lemma (15% brown and black, 7% yellowish, 4% purple, 3% straw), Lemma and Palea: colour (11% purple and black, 3.40% reddish, gold and brown), Panicle: presence of secondary branching (30% present, 7% absent) (Ndour et al., 2016), Panicle: secondary branching (22% weak, 7% strong), In the traditional growing areas of Asia, rices of various colors-red, black, brown, yellow and green have been known and grown, but for the present day generation, rice connotes pearly white grain. Colored rices have been preferred in the past for their special features such as medicinal value and exclusive taste. Flavoured, black rices were the favourites of the royals of China, while red rices were preferred by people in many parts of India, Sri Lanka and Bhutan. (Rood, 2000) Decorticated grain: colour (44% light brown, 30% white, 11% dark brown and light red, 7% variegated brown) (Rao et al., 2013; Tirkey et al., 2013; Mondal et al., 2014; Manjunatha et al., 2016; Kalyan et al., 2017; Umarani et al., 2017) and similar results has been reported earlier and some morphological characters showed similar type of variations in different accessions such as Lemma: anthocyanin colouration of keel, Lemma: anthocyanin colouration of area below apex, Lemma: anthocyanin colouration of apex.
 
Agronomic characterization
 
The quantitative characters also showed wide variation among all varieties (Table 2). Most of the Agronomic characters exhibited variations in various accessions except grain length. A majority of accessions were found to possess Grain: width (92.59% very narrow) and the balance 7.40% narrow genotypes possess kattu yanam and karudan samba. Leaf: length of blade (48% medium, 33% long, 19% short), Leaf: width of Blade (59% narrow, 26% broad, 15% medium), Stem: length (excluding panicle; excluding floating rice) (55% short), Panicle: number per plant (22% few, 19% medium), Grain: weight of 1000 fully developed grains consist of 19% medium, 15% low, 7% high, 7% (Illaapai poo samba (14.59 gram) and Milagu samba (14.84 gram) very low) and 3% (Mapillai Samba (30.41 gram) very high). By compare with the hybrid varieties, hybrid had higher grain weight than inbred varieties but traditional rice varieties have more over high in inbred and hybrid varieties. (Lu et al., 2020).
       
According to the DUS protocol decorticated rice grain length and width have been grouped into three categories short grains, medium grain and long grain, in decorticated grain width 70% of the accessions possessed medium and others were found various distributions. Decorticated grain: length possessed 52% short, 44% medium, 3% long. Seed shape have been used to differentiate the rice genotypes by various researchers (Bhattacharya and sowbhagya 1980) Decorticated grain: shape (63% of the varieties are short slender, 22% long slender and 11% possess Long slender (For Basmati type) Extra-long slender variety (sorna masuri, kattue vallai and kuzhiadichan) (Komala et al., 2017).

The identified variability and unique characteristics can be utilized for the development of varieties. Unique genotypes can be registered in PPV and FRA. Qualitative features such as dark green leaf colour, heavy pubescence on the leaf blade or purple surface, margin leaf blade etc. have been identified (Karuppu kavuni) and utilized for developing rice varieties with tolerant to leaf surface, related insects and diseases.

Authors are thankful to the Department of Genetics and Plant
Breeding, Faculty of Agriculture, Annamalai University, Tamil Nadu, India for providing the Experimental farm facilities for the conduct of present study.

The authors declare that there is no competing interest.