Abstract
Advanced backcross introgression lines (BILs) developed from crosses of Oryza sativa var. Swarna/O. nivara accessions were grown and evaluated for yield and related traits. Trials were conducted for consecutive three seasons in field conditions in a randomized complete block design with three replications. Data on yield traits under irrigated conditions were analyzed using the Additive Main Effect and Multiplicative Interaction (AMMI), Genotype and Genotype × Environment Interaction (GGE) and modified rank-sum statistic (YSi) for yield stability. BILs viz., G3 (14S) and G6 (166S) showed yield stability across the seasons along with high mean yield performance. G3 is early in flowering with high yield and has good grain quality and medium height, hence could be recommended for most of the irrigated locations. G6 is a late duration genotype, with strong culm strength, high grain number and panicle weight. G6 has higher yield and stability than Swarna but has Swarna grain type. Among the varieties tested DRRDhan 40 and recurrent parent Swarna showed stability for yield traits across the seasons. The component traits thousand grain weight, panicle weight, panicle length, grain number and plant height explained highest genotypic percentage over environment and interaction factors and can be prioritized to dissect stable QTLs/ genes. These lines were genotyped using microsatellite markers covering the entire rice genome and also using a set of markers linked to previously reported yield QTLs. It was observed that wild derived lines with more than 70% of recurrent parent genome were stable and showed enhanced yield levels compared to genotypes with higher donor genome introgressions.
Highlights
Improving rice production per unit area and per unit time will be a major challenge in future due to the expanding population of rice consumers in the world
In three seasons; broad genotypic variation was observed and genotypic average ranged for days to fifty percent flowering (DFF) (77.37 to 133.04); grain yield (GY) (4.73 to 24.63); bulk yield (BY) (0.33 to 2.10); plant height (PH) (65.98 to 148.43); tiller number (TN) (6.12 to 20.70); GN (93.70 to 314.55); panicle length (PL) (18.09 to 25.19); panicle weight (PW) (0.98 to 3.87); 1000 grain weight (TGW) (12.50 to 26.07); spikelet fertility (SF) (60.57 to 97.57); BM (11.26 to 54.12); harvest index (HI) (0.20 to 0.55) and per day productivity (0.04 to 0.19) among the backcross introgression lines (BILs) under study (Table 3)
G2 was of shortest duration and showed desirable yield traits such as panicle length, 1000 grain weight, spikelet fertility and plant height compared with checks
Summary
Improving rice production per unit area and per unit time will be a major challenge in future due to the expanding population of rice consumers in the world. The average yield of existing cultivars reached a plateau and research is directed toward wild relatives of Oryza to explore novel genes that can improve yield traits. Wild relatives were widely explored as donors for stress resistance and less exploited for yield improvement because of non-preferable agronomic traits linked with them. Wild rice genotypes provide a diverse range of allelic variation due to their adaption to a wide range of environmental conditions. Wild and related genotypes are valuable resources to explore novel variations to widen the genetic background of cultivated rice (Brar and Khush, 1997; Tanksley and McCouch, 1997; Swamy and Sarla, 2008; Wickneswari et al, 2012). Introgression of chromosomal segments from wild species into cultivated species can generate de-novo variations in the new genetic background (Wang et al, 2005)
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