Abstract
Utilization of “hidden genes” from wild species has emerged as a novel option for enrichment of genetic diversity for productivity traits. In rice we have generated more than 2000 lines having introgression from ‘A’ genome-donor wild species of rice in the genetic background of popular varieties PR114 and Pusa44 were developed. Out of these, based on agronomic acceptability, 318 lines were used for developing rice hybrids to assess the effect of introgressions in heterozygous state. These introgression lines and their recurrent parents, possessing fertility restoration ability for wild abortive (WA) cytoplasm, were crossed with cytoplasmic male sterile (CMS) line PMS17A to develop hybrids. Hybrids developed from recurrent parents were used as checks to compare the performance of 318 hybrids developed by hybridizing alien introgression lines with PMS17A. Seventeen hybrids expressed a significant increase in yield and its component traits over check hybrids. These 17 hybrids were re-evaluated in large-size replicated plots. Of these, four hybrids, viz., ILH299, ILH326, ILH867 and ILH901, having introgressions from O. rufipogon and two hybrids (ILH921 and ILH951) having introgressions from O. nivara showed significant heterosis over parental introgression line, recurrent parents and check hybrids for grain yield-related traits. Alien introgressions were detected in the lines taken as male parents for developing six superior hybrids, using a set of 100 polymorphic simple sequence repeat (SSR) markers. Percent introgression showed a range of 2.24 from in O. nivara to 7.66 from O. rufipogon. The introgressed regions and their putative association with yield components in hybrids is reported and discussed.
Highlights
Rice is grown annually on more than 153 million hectares with an annual production of about 483 million tons globally [1]
The most successful examples of utilizing wild species include the use of O. spontanea as a source of wild abortive cytoplasmic male sterility [5], O. nivara genes to provide resistance against grassy stunt virus [6], and O. longistaminata gene Xa21 [7]–[8], O. rufipogon gene Xa23 [9] and O. nivara gene Xa38 [10] for resistance against bacterial blight
There are several indications that introgression lines served as dynamic entities to identify new genes [26], distinguish pleiotropy from linkage [27] and identify quantitative trait loci (QTL) contributing to heterosis, those showing overdominance [28]
Summary
Rice is grown annually on more than 153 million hectares with an annual production of about 483 million tons globally [1]. Global rice demand is estimated to rise from 676 million tons in 2010 to 763 million tons in 2020 and further increase to 852 million tons in 2035. Incorporation of potentially favorable alleles from wild ancestors of rice into improved genotypes for productivity traits has emerged as a promising strategy. Following the availability of advancedbackcross quantitative trait loci (AB-QTL) approach proposed by Tanksley and Nelson [12], discovery of favorable genes from wild species received impetus as a plant breeding strategy. Several yield-enhancing alleles from wild species of rice, such as O. rufipogon, were identified and introduced into highyielding elite cultivars [13]–[20]. Apart from O. rufipogon, search for yield-enhancing quantitative trait loci (QTL) alleles was successfully extended to O. glaberrima [21], O. grandiglumis [22], O. glumaepatula [23], O. longistaminata [24] and O. minuta [25]. There are several indications that introgression lines served as dynamic entities to identify new genes [26], distinguish pleiotropy from linkage [27] and identify QTL contributing to heterosis, those showing overdominance [28]
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