Grading is an important post-harvest operation where the seeds are homogenized based on size, weight and color to upgrade the quality of the seeds. Rice bean is one of the underutilized crops with hidden multipurpose utility. Hence, studies were carried out to upgrade the quality of seeds through sequential dual grading using size and color of the seeds. The seeds were size-graded using BSS 5  5, 6  6 and 7  7 wire mesh sieves and each of the size grades was further graded based on color as yellowish green, light brown and brown and were evaluated for the seed and seedling quality characters. The results revealed that the seeds size-graded using BSS 5  5 recorded the maximum seed quality characters in terms of germination and vigor, but it was on a par with BSS 6  6 which recorded the maximum recovery. Further, grading based on the color revealed that yellowish green seeds of both BSS 5  5 and 6  6 sieve recorded the highest germination of 90%, though the recovery was only 10 and 8%. Hence in rice bean, this type of dual grading could be adopted for nuclear and breeder seed production where seeds are to be with higher initial quality. But for commercial seed production both yellowish green and light brown seeds retained in grade BSS 6  6 (includes BSS 5  5 retained sieve) could be selected as the recovery of seed would be more than 80% combined with seed quality characters which were higher with these dual grading.

Rice bean is domesticated in Southeast Asia, while wild forms of rice bean are distributed in Northeastern India, Burma, Thailand, Laos and Vietnam (Ohashi et al. 1988). In India, its distribution is mainly confined to tribal regions of North Eastern hills, Western and Eastern Ghats in peninsular India, often in hilly tracts. Rice bean is an annual food legume belonging to the subgenus Ceratotropis in the genus Vigna. The genus Vigna, together with the closely-related genus Phaseolus, forms a complex taxonomic group, called Phaseolus- Vigna complex. It is described that the cultivation is popular in Southeast Asia and Pacific islands (Duke 1981).

In their monograph, two varieties are recognized in V. umbellata. One is V. umbellata var. umbellata which is rice bean, and another is V. umbellata var.gracilis which is a wild ancestor of rice bean. Generally, morphology of rice bean is similar to azuki bean. Seed is slender and hilum is protruding. Flower color is golden yellow. Pod attaches to the peduncle downward. The duration of the rice bean ranges from 65 to 110 days in India and it yields 8-10 quintals per ha. The seed protein varies from 18-21%, wherein methionine and tryptophan are considerably high, as compared to other Vigna species. It is rich in calcium with 302 mg/100g and low in fat with 1.4 g/100g among other traditional pulses. Regarding the uses of rice bean, dry seed is boiled and eaten with rice. It can be utilized as whole rice bean, rice bean dhal and flour in various pulse-based products by adopting different methods of cooking like roasting, steaming, frying, etc. To encourage large-scale production of this underutilized economic crop, seed production techniques are much warranted, as quality seed is the base for successful production. On standardization of seed production techniques, grading is an important post-harvest operation where the seeds are homogenized for better seed quality characters. Researchers recommended various grading techniques based on size, weight and color to upgrade the quality of the seeds. Size grading is the basic grading, but this crop is characterized with a mixture of various colored seeds. Hence studies were carried to upgrade the quality of seeds through sequential dual grading using size and color of the seeds and the results are discussed in this paper.

Genetics & Evolution Journal, CEL-I Endonuclease, Heterozygous Mutants, Homozygous Mutants, Biological Processes, Plant Mutants, Solanum Lycopersicon, Microcentrifuge Tubes, Homozygous Plants, Plant Genes, Cross Pollination, Heteroduplex Formation.