Shyama R. Weerakoon

By Shyama R. Weerakoon, Seneviratnage Somaratne, E. M. Sachini I. Ekanayaka and Sachithri Munasighe

Since studies on herbicide-resistant rice (HRR) are limited in Sri Lanka, the present study conducted to screen the naturally existing glyphosate and glufosinate resistance in traditional and inbred rice varieties. Six traditional varieties and nineteen inbred lines were selected for the study. Complete randomized design with three pots with 10 replicates for each herbicide concentration was employed. Optimal concentrations of glyphosate (0.5 gl−1) and glufosinate (0.05 gl−1) were applied at 3–4 leaf stages. Varieties ≥50% survival percentage was considered as resistant to respective herbicides. Twelve varieties showed resistance (≥50%) at 0.5 gl−1 glyphosate concentration. Survived plants were monitored and agro-morphological and yield characters/parameters were measured. Fifteen varieties were to glufosinate at 0.05 gl−1. Even though no significant differences (p > 0.05) were observed in growth parameters across control and treated plants, there was a yield penalty. Nine varieties (At362, Bg352, Bg359, Bg366, Bg369, Bg379-2, Bg403, Bg454, and Pachchaperumal) indicated moderate resistance to both glyphosate and glufosinate. The emerged HRRs indicated varying responses of agro-morphological and yield characters across the type of herbicide and the variety. Glyphosate reduced the growth parameters and yield penalty compared to glufosinate treated varieties. These HRR varieties have a higher potential in rice breeding programs and in developing HR rice varieties in future.

Part of the book: Rice Crop

By Shyama R. Weerakoon

Rice is the staple food crop in Sri Lanka, which occupies 34% (0.77/million ha) of the total cultivated area. Sri Lanka currently produces 2.7 million tonnes of rough rice annually and satisfies around 95% of the domestic requirement. In Sri Lanka, genus Oryza consists of two species complexes, O. sativa (AA) and O. officinalis (CC). These two complexes are both pan tropical and have very similar overall distribution. Five wild rice species are reported in Sri Lanka, (O. nivara [AA], O. rufipogan (AA) O. eichengeri [CC], O. rhizomatis (CC) and O. granulate (GG). O. rhizomatis has been reported only in Sri Lanka and considered endemic to Sri Lanka. Recent studies demonstrated, the reliance on single source of information could mislead results in the phylogenetic inferences due to analytical inconsistency and biological processes. Therefore, exact number of wild rice species in Sri Lanka becomes uncertain and the necessity arises to assess Oryza species complexes in Sri Lanka using morphological, anatomical, and molecular information to enumerate number of species within each Oryza complex and characterization of species and species complexes. The study revealed, characterization of wild rice species, to a certain extent, can be made through morphological and anatomical characters, specially lamina anatomical characters. Molecular information is more reliable in delimitation of wild rice species complexes in Sri Lanka. O. rhizomatis and O. eichingeri (CC) are well separated from the rest of wild rice species (AA). Molecular data revealed, O. nivara and O. rufipogon have undergone independent evolution within Sri Lanka. Well separated five wild rice species are existing in Sri Lanka. Studies on ecological resilience of morphological, anatomical, and molecular studies are very useful for species enumeration of wild rice complexes in Sri Lanka. The findings led to conclude that wild rice species in Sri Lanka are “ecological swarms” and represents allopatric or sympatric populations. A comprehensive knowledge on genetic diversity and population structure of wild rice germplasm in Sri Lanka provides useful information to include these locally adapted and evolved wild rice species in rice crop improvement/breeding.

Part of the book: Cereal Grains