Crossbreeding between clearfield® rice with weedy rice under various conditions

Rice is an important crop in our country as it is our staple food. Due to huge productivity losses because of weeds, the imidazolinone-resistant Clearfield® rice was developed to control it. Its close genetic relation with the weedy rice makes it a good candidate for hybridization, producing super weeds. The main objective of this study was to determine whether gene flow from Clearfield® rice to weedy rice can occur. This study has three experiments. In the first experiment, Clearfield® rice varieties (CL1, CL2) and weedy rice variants (V1, V2, V3, V4) were planted to observe the morphological characteristics. The second experiment was conducted in rice field for two seasons. The first (dry) season, two variants of weedy rice (V1, V2) and four variants (V1, V2, V3, V4) were used in and the second (rainy) season and were planted at a distance of 1m, 2m, 3m 4m and 5m from the Clearfield® rice. Seeds (F1) from weedy rice were collected and germinated in trays before were sprayed with OnDuty™ at day fourteen with a rate of 220 g/ha. The third experiment was determining hybrids using Simple Sequence Repeat (SSR) primer RM251 using leaves for the DNA extraction. The first experiment showed that weedy rice was morphologically superior to Clearfield® rice whereby it had double the number of tillers (more than 30) and almost 50 cm taller. In the second study after spraying OnDuty™, CL2 has significant difference at 20.38% compared to CL1 at 13.00% in second season. V1 showed the highest survival percentage, at 11.15% and 22.45% in both season. CL2 and V2 were the best combination of parent with 28.91% seedlings survived. About 80% seedlings survived from CL2V1 at the distance of 1m in second season. Higher number of overlapping period and wind speed in the second season were considered to affect survival percentages. The third study shows that molecular analysis has determined seven hybrids among the seedlings using primer RM251 with hybrids producing three bands. In conclusion, Clearfield® rice can hybridize with weedy rice under field condition and the percentages could increase with days of overlapping and wind speed.

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