Abstract
Sixty cross combinations consisting of 15 intervarietal indica, 15 intervarietal japonica and 15 crosses each of inter-subspecific and three-way crosses were generated through different mating patterns in kharif 2008 and evaluated for hybrid sterility under two different agroecologies of Kashmir during kharif 2009. The estimates of pollen and spikelet sterility were very high in indica /japonica crosses followed by indica/indica andjaponica/japonica crosses. The magnitude of pollen and spikelet sterilities were observed high in L1 × T1followed by L4 × T3, L1 × T3, L5 × T3, L3 × T3 and so on all belonging to inter-subspecific group. The mean estimates of pollen and spikelet sterilities of different crossing blocks were very high when compared to their corresponding parental mean. Only inter-subspecific cross L1 × T2 yielded pollen and spikelet sterilities of less than 50% and another three crosses revealed a range between 50 and 70% for these traits. Five crosses were grouped as highly sterile by depicting sterility estimates greater than 70%. The mean estimates of pollen sterility and spikelet sterility for inter-subspecific crosses got reduced to the level of 30.80 and 25.75% respectively through three-way crosses by deploying wide compatibility cultivar (WCV) (Dular) as bridging parent. The estimated mean percentage overcome was 36.62% for pollen sterility and 63.92% for spikelet sterility. Such kind of modest attempt has widened the genetic variability by combining the genetic background across the two sub species and tailors the new genotypes. This in turn has paved way for the concept of ideotype breeding for unique cold temperate agroecologies. Key words: Hybrid sterility, inter-subspecific crosses, intra-subspecific crosses, rice, wide compatibility cultivar (WCV).
Highlights
The strong hybrid vigor in the F1s between indica and japonica subspecies of Asian cultivated rice (Oryza sativa L.) has attracted a large amount of research interest, with the hope for developing hybrid rice by making use of such heterosis (Yang et al, 1962; Yuan, 1994)
Sixty cross combinations consisting of 15 intervarietal indica, 15 intervarietal japonica and 15 crosses each of inter-subspecific and three-way crosses were generated through different mating patterns in kharif 2008 and evaluated for hybrid sterility under two different agroecologies of Kashmir during kharif 2009
The mean estimates of pollen sterility and spikelet sterility for inter-subspecific crosses got reduced to the level of 30.80 and 25.75% respectively through three-way crosses by deploying wide compatibility cultivar (WCV) (Dular) as bridging parent
Summary
The strong hybrid vigor in the F1s between indica and japonica subspecies of Asian cultivated rice (Oryza sativa L.) has attracted a large amount of research interest, with the hope for developing hybrid rice by making use of such heterosis (Yang et al, 1962; Yuan, 1994). Hybrid sterility frequently occurs in such inter-subspecific crosses (Ikehashi, 1982), the fertility of indica-japonica hybrids varies widely from fully fertile to almost completely sterile, with the majority of such hybrids showing significantly reduced fertility (Oka, 1988; Liu et al, 1996; Zhang et al, 1997). Wide compatibility cultivars (WCVs) produce fertile hybrids when crossed to both indica and japonica cultivars. The discovery of WCVs brought hope by breaking the fertility barriers between indica and japonica subspecies and provided possibility for exploiting the very strong heterosis demonstrated in cross between the two subspecies. A modest effort in this direction was to assess and estimate the magnitude of hybrid sterility in intra- and inter-subspecific crosses viz-a-viz to determine the level of overcome by deploying wide compatibility cultivar (WCV) as bridging parent through three-way crosses and to get the most suitable recombinants for two different agroecologies of Kashmir
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