การคัดเลือกเพื่อลักษณะไม่ไวต่อช่วงแสงและปริมาณฟีนอลในเมล็ดสูงในประชากรรุ่นลูกระหว่างข้าวก่ำพันธุ์พื้นเมือง (ข้าวแสง 5) และพันธุ์ปรับปรุงสมัยใหม่ (ปทุมธานี 1)

Abstract

Purple rice is a local black glutinous rice that is popular in the north and northeast of Thailand. The prevalent of grain pericarp is purple or black colors, presenting high phenolic compounds, that is beneficial antioxidant for human health. Phenolic compounds are water-soluble, it is well-known as antioxidant properties that helps to prevent and reduce the risk of various diseases. However, a local purple rice mostly observed in Thailand is sensitivity to photoperiod that it can be grown once a year. This experiment was evaluated and selected for photoperiod insensitivity and high grain phenol concentration in progenies. The two rice varieties comprising of Kao Sang 5 variety; a local glutinous purple rice having a high grain phenol concentration and Pathum Thani 1; a modern rice with high grain yield but low grain phenol concentration was crossed for a hybrid rice variety with high phenol and photoperiod insensitive. Thus, the objective of this study was to evaluate photoperiod insensitive trait and grain phenol concentration in the hybrid populations. The study was comprised of three experimental series. First experiment was to assess the traits of the F, population compared to their parents. Rice plants were grown in a pot experiment at Faculty of Agriculture Chiang Mai University during wet season between July to October 2017. The experimental design was arranged in a completely randomized design (CRD) with 3 replications. Fifteen day old-seedlings were germinated in a petri- dish and transplanted into plastic pots. The hybrid population and their parents were tested for ten and five pots, respectively. The results showed that the first hybrid had the similar morphological characteristics as their parents. For instance, the hybrid seeds had the brown husk and black pericarp colors, which are similar to the mother parent. Agronomical characteristics of hybrid were found to have genetic variations, excepted in the numbers of tillers and panicles per plant. The flowering date of hybrid plants was earlier than their parents. Culm length was 20 cm higher than the parents. Although, the lower percentage of filled grain was found in the hybrids compared to the parents., No significant difference of grain yield was found between hybrid and parent plants. Second experiment, 280 plants of F2 plants and 50 plants of each parent were grown to determine the F2 population in the field experiment in the dry season during February to July 2018. The fertilizers of 15-15-15 was equally applied at the rate of 25 kg/rai as basal and at 60 days after transplanting, and 46-0-0 fertilizer was applied at the rate of 10 kg/rai at flowering stage. The results showed that the grain color distribution exhibited three colors including black, brown and white. There were 151 plants presenting a black grain pericarp and those 129 plants with enough seeds were analyzed for phenol concentration. The F2 generation of hybrids had a continuous distribution on the grain phenol centration with the average of 96.8 mg/100 g, which the concentration was quite similar in the farther plant. Interestingly, there were two rice plants exhibiting higher phenol concentration compared with the mother plant. The starch of hybrid determined by iodine test showed the distribution of starch types, non-glutinous, glutinous rice and both types was found in the same rice plant with the proportions of 34.9%, 24.0% and 41.1%, respectively. For the grain yield trait, the second hybrids were ranged from 6.2 to 56.5 g/plant with an average of 16.4 g/plant, even though the most grain yield was quite similar to the mother plant (14.0 g/plant). In addition, the distribution was found in grain weight trait. There was no relationship between grain phenol concentration and grain yield found in F2 population. Third experiment was arranged by selecting the seeds of F2 generation with top five highest grain phenol concentration as represent plants to evaluate theF, generations. About 5 families were planted in the plot experiment in the wet season of 2018, 12 plants per family per row were tested. The results showed that there were 26 rice plants presenting black pericarp color and then it was used to determine phenol concentration. The phenol concentration of F3 generations had a distribution ranging from 170.6 to 419.2 mg/100 g, which the concentration was between parents. For grain yield trait, the F3 generation ranged from 15.9 to 40.4 g/plant, which was among the parents. The relationship between grain phenol concentration and grain yield was not found in F3 generation. From the result, there were 14 rice plants that having high grain phenolic concentration with various starch types. All selected F3 plants will be used as the representative line for the F4 generations. Therefore, the distribution of phenol concentration and non-photosensitive traits from this study will be very useful for breeding program as the genetic resource for developing new variety, which should be going on