Genetic variation for grain yield, straw yield and straw quality traits in 132 diverse rice varieties released for different ecologies such as upland, lowland, irrigated and salinity prone areas in India

A total of 132 rice varieties released for different ecologies such as upland (25) and lowland (26), irrigated (65) and salinity (16) affected areas were investigated over two consecutive years for grain (GY) and straw (SY) yield, straw nitrogen (N), neutral (NDF) and acid detergent fiber (ADF), acid detergent lignin (ADL), silica and in vitro organic matter digestibility (IVOMD). Highly significant (P < 0.0001) differences were found between the cultivars for GY and SY and all straw fodder quality traits. Considerable ranges were observed for GY and SY which varied by 3.4 and 7.1-fold, respectively, and straw N that varied twofold. Neutral and acid detergent fibre the two major fibre components varied by 8.8 and 6.2 percent units, respectively, and IVOMD varied by 7.4 percent units; ADL and Silica varied by 2 and 5.2 percent units respectively. Except for NDF, year had highly significant effects on yields and straw fodder quality traits. Interactions between cultivars and years were consistently significant. Broad sense heritabilities (H2) were higher for SY than for GY (H2 = 0.71 vs 0.4). Neutral and acid detergent fibre had intermediate H2 of 0.50 to 0.52 and IVOMD a moderate H2 of 0.3. Broad sense H2 for ADL and Silica were close to zero. Grain yield and SY were significantly positively associated but GY accounted for only about 31% of the variation in SY and high GYs in the range of 6000 to 6500 kg/ha could be associated with SYs ranging from about 5000 kg/ha to more than threefold that. Of all the straw quality traits, N was most strongly and inversely associated with GY, though straw N accounted for only 18% of the variation in GY and high GYs in the range of 6000 to 6500 kg/ha could be associated with straw N contents ranging from approximately 0.7 to 1.0%. Similarly, straw N was statistically strongly and inversely associated with SY, with straw N accounting for 32% of the variation in SY through high SYs ranging from approximately 12 000 to 14 000 kg/ha could be associated with straw N ranging from about 0.7 to 0.9%. Neutral detergent fiber (NDF), an estimate of the plant cell wall content, was significantly positively associated with GY, though at most levels of GYs NDF content could vary by 4 to 5 percent units and more. Similar findings apply to the relationship between NDF and SY. In vitro organic matter digestibility was poorly correlated with GY suggesting that varieties can be bred simultaneously for both. In fact, the cultivar with the highest straw IVOMD was among the 10 highest grain yielders.