Development of monosomic alien addition lines from the wild rice (Oryza brachyantha A. Chev. et Roehr.) for introgression of yellow stem borer (Scirpophaga incertulas Walker.) resistance into cultivated rice (Oryza sativa L.)

Abstract

Oryza brachyantha, the African wild rice which is resistant to yellow stem borer (YSB), was exploited as a source for introgression of YSB resistance trait into cultivated rice (O. sativa), through development of monosomic alien addition lines (MAALs). BC2F1 backcross hybrids (O. sativa cv Savitri/O. brachyantha//O. sativa cv Savitri///O. sativa cv Savitri) were produced employing embryo rescue, with a crossability of 0.12 %. Hybrid embryos that were collected at 10 and 12 days after pollination showed highest percentage of survival in culture with a germination percentage of 35.8 %. Cytological analysis of pollen mother cells (PMCs) of the BC2F1 hybrids revealed 15 hybrids with 2n + 1(2n = 25) chromosome number that exhibited typical trisomic chromosomal configurations. These aneuploids were putatively designated as MAALs and characterized morphologically and cytologically. Based on their morphological similarity to primary trisomics of the cultivated rice (O. sativa), 8 MAALs viz., MAALs-4 (Sterile), 5 (Twisted leaf), 7 (Narrow leaf), 8 (Rolled leaf), 9 (Stout), 10 (Short grain), 11 (Pseudonormal) and 12 (Tall) were isolated, each of which exhibited several distinct morphological features. Among the 505 PMCs analysed, 79.80 % had 12II, 5.45 % had 11II and 1.78 % PMCs had 1III configurations. The size of the extra chromosome was found to be smaller than those of O. sativa chromosomes and in 97.25 % of PMCs it remained unpaired and at a distance from the rest of the chromosomes. Of the 8 MAALs screened for YSB resistance, MAAL 11 was found to be moderately resistant. Undesirable morphological traits of O. brachyantha were found to be eliminated in the MAALs.