Improvement of grain and nutritional qualities of rice varieties through breeding

Abstract

The study was conducted to identify promising rice cultivars for developing high yielding variety with superior grain and nutritional qualities. It included 109 local germplasm cultivars and 20 high yielding varieties. Out of 129 rice cultivars, there were 36 long, 62 medium and 31 short grain cultivars. The study provided information on the agronomic characters of long, medium and short grain cultivars. Seven long grain cultivars (Boradudhkalam, Dudhkalam, Gohatibinni, Harilaxmi, Kanaibansi, Patnai-231 and Shata) varied in rough rice yield (4.0-5.2 t/ha), plant height(110-180cm) and growth duration (120-160 days) as well as those five medium grain rough rice cultivars (Ganjia, Gojalgoria, Jhoshuoa, Kajalsail andTilokajal) varied in rough rice yield (4.0-4.5t/ha), plant height (137-161cm) and growth duration (142-155 days).Eleven short grain cultivars (Betudhan,Binniphul, Chinisagor, Dudsail, Gurdoi, Khasa, Lalsaru, Nariabochi, Pajam, Sorukamina and Tulsimala) varied inrough rice yield (3.0-3.9 t/ha), plant height (140-193cm) and growth duration (116-155days). The color of rough rice of these cultivars, dehulledbefore milling, was mostly brown. Only 46 cultivars had red pericarp. The dehulled rice was milled to remove 10% bran-polish. Milling yield and head rice recovery of long grain cultivars varied from 63% to 71% and 41% to 96% respectively. Seven long grain cultivars (Boradudhkalam,Dudhkalam, Gohatibinni, Harilaxmi, Kanaibansi, Patnai-231 and Shata) as well as seven medium grain cultivars (Ganjia, Gojalgoria, Jhoshuoa, Kajalsail,Kanaklota, Maloti and Tilokkajal) had acceptable (> 67%) milling yield. Among the 129 cultivars, 24 had aroma, 16 had long slender and 85 had translucent grains. The cultivars having long slender grain with translucent kernel are preferred all over. Cultivars of Karailadhan, Pakhisail and Neda had long slender and translucent grains. The milled rice length of these cultivars were more than 7.0 mm. Amylose content in rice cultivar is an important factor influencing cooking and eating qualities. Long slender grains with intermediate to high amylose (20-29%), giving soft cooked rice, are suitable for export market and medium grains with high amylose, giving fluffy cooked rice, are preferred by hardworking people. Cultivars with high elongation ratio (>1.9) are preferred all over. Results showed that cultivars varied in amylose content from 5% to 29% and elongation ratio from 1.5 to 2.2. None of the long slender grain had more than 2.0 elongation ratio in this study. Medium grain cultivars (Ganjia,Kanaklota, Maloti and Tilokkajal) had more than 1.9 elongation ratio. Analysis of mineral contents (phosphorous, calcium, magnesium, nitrogen, potassium, sodium, iron and zinc) of the total cultivars showed that phosphorous, sodium and iron content were higher in the tested local cultivars than the HYVs irrespective of grain size and shape. Zinc content was significant and positively correlated with iron content. Protein content, protein digestibility, fractionation of protein and amino acid composition of rice cultivars may provide substantial information on protein nutritional value. Protein content of total cultivars varied from 6.5% to 10.7%. Magoibalam, Harilaxmi and Tilokkajalcultivars had 10.7%, 9.2% and 8.8% protein respectively. Amino acid composition of protein from promising cultivars showed that the cultivars varied from 3.34-4.29g/100g lysine, 3.34-3.97g/100g threonine, 2.09-2.23 g/100g methionine and 1.36-2.40g/100g cysteine. The invitro protein digestibility of Magoibalam, Motichak, Neda, Molladigha and Boylam varied from 67% to 78%. The highest invitro protein digestibility was observed in Magoibalam. The in vitro starch digestibility of cultivars varied from 62.3% to 83.8%at 120 minutes digestion. Low amylose (6.0-18)% of long grain cultivars of Athabinni, Kalabinni-1 and Kanaibansi as well asmedium grain cultivar of Ledabinni had more than 80% starch digestibility.High amylose (>25%) long grain cultivars of Boradudkalam, Depa, Dudkalam, Karailadhan, Molladiga and Patnai-231 had starch digestibility between 62.3% and 66.6%. On the other hand, high amylose (>25.0%) medium grain cultivars of Magoibalam and Motichak had 70.6% and 75.5% starch digestibility respectively. Genetic diversity of Waxy gene in selected rice cultivars was evaluated by using microsatellite marker and cleaved amplified polymorphic sequence marker. Results showed that Microsatellite marker (RM190) and cleaved amplified polymorphic sequence marker (RM190F-GBSSW2R/AccI) had efficacy to differentiate amylose status on the basis of allelic variation and single nucleotide (G/T) polymorphism of the Waxy gene. The hybrid vigor of Motichak × BRRI dhan28 (F1 seed) had 103 cm plant height, 9.1% protein and 26.7% amylose compared with parent. Three crosses were made as successful F1 hybridization. Evaluation of F1 hybridization and its confirmation on the basis of morphological and nutritional performances was found promising.