การคัดเลือกสายพันธุ์ก้าวหน้าเพื่อลักษณะสารประกอบฟีนอลในเมล็ดสูงและไม่ไวต่อช่วงแสงในลูกผสมชั่วที่ 4 และชั่วที่ 5 ระหว่างข้าวพันธุ์แสง 5 และพันธุ์ปทุมธานี 1

Abstract

Local rice varieties were characterized by their high special nutrient concentration, especially rice that had a black pericarp. This type of rice was commonly referred to as "purple rice." It was particularly grown in the northern and northeastern regions of Thailand. One of its distinct features from ordinary rice was the presence of purple color in various parts of the plant, such as the leaf blade, leaf sheath, stem, and rice husk, including the purple appearance on the seed coat. The purple color in these native rice varieties was caused by the accumulation of anthocyanin, which was a part of the flavonoid group, similar to phenols that had antioxidant properties. These properties were believed to boost the body's immune system against various diseases. However, most local black rice varieties were recognized for their low yield and photoperiod sensitivity, limiting its cultivation to once a year. Plant breeding group at Division of Agronomy, Chiang Mai University has developed a hybrid by crossing between "Saeng 5" variety, the black rice with high phenol concentration in the seeds, and the "Pathumthani 1" variety, a high-yielding rice that was photoperiod insensitivity. The aim was to produce new variety with high phenol concentration, high yield, and photoperiod insensitivity. Selection and seed multiplication were practiced in F2 and F3 generations. This research was a continuation of prior efforts. Hence, the study aimed to assess and select the F4 to F5 generations to obtain the advanced lines with a black pericarp, high phenol concentration, high yield and photoperiod insensitivity. F3 generations were received from the Genetic Resources and Plant Nutrition Research and Development Unit of the Faculty of Agriculture at Chiang Mai University (CMUPNlab). A total of 54 populations were provided. From each population, five seeds were randomly sampled, and their pericarp colors were examined. Populations with black pericarp covering ¾ of the seed or completely black were identified, and a total of 43 populations were selected. The phenol concentration and antioxidant levels in the seeds were then assessed. It was found that the average phenol concentration in the seeds of the parent varieties was 0 and 226.8 mg gallic/100 g, respectively, and the average antioxidant concentration was 46.6 and 218.0 mg trolox/100 g, respectively. Families with higher phenol and antioxidant concentrations in seed than the parent variety were chosen as represent F4 lines for further cultivation and selection in the next generation. A total of 14 lines were selected, with phenol concentration in seeds ranging between 260.9 – 711.6 mg gallic/100g and antioxidant concentration between 252.2 – 594.0 mg Trolox/100 g. F4 generation was evaluated in pots in dry season. Each line was sown in two pots with 5 plants per pot, totaling 10 plants per line. Agronomical and morphological characteristics were recorded. However, when reaching maturity, not all the plants could be harvested due to high temperatures during the panicle initiation through flowering. Out of the 140 plants, only 42 plants could be harvested. The seeds harvested from each plant were not sufficient for analyzing their phenolic and antioxidant concentration. As a result, data on the phenol and antioxidant concentration from the F3 generation was used to assist in the selection. Four plants were selected that had a black pericarp and a F3 generation seed phenol concentration higher than the parent varieties. The selected lines had phenol concentration in the seeds ranging from 566.5 – 711.6 mg gallic/100 g, day to flowering between 74 – 88 days, culm height ranging from 68.6 – 95.5 centimeters, and total of 7 – 12 panicles per plant. In the F5 generation, varieties were planted and selected during the rainy season in experimental agricultural research at Mae Hia Agricultural Research and Training Station, Faculty of Agriculture, Chiang Mai University. Parental lines were placed in every fifth row, using the transplanted plants with a spacing of 25 x 25 cm and one plant per hill. Four lines were transplanted, two rows with 12 plants per row. Fertilizer was applied as 15-15-15 (N:P:K) fertilizer at 25 kg/rai at 30 days after transplanting and 46-0-0 at the rate of 10 kg/rai. At anthesis, the agronomic traits and colors of different parts of the plants were recorded. At maturity, similar agronomic characteristics as in the fourth generation were observed and recorded. Plants with seeds that were ¾ black or entirely black for each variety were selected. Seed samples from the selected plants were combined, taking 5 grams per plant, for a bulk analysis of phenol concentration. The phenol concentration of the F5 population were between 209.4 to 722.7 mg gallic/100g. The check variety, Saeng 5, was determined to have a phenol concentration of 431.2 mg gallic/100g. Two lines were selected with a phenol concentration higher than the parental lines, ranging between 575.4 and 722.7 mg gallic/100g. Individual plants within two selected lines were analyzed for phenol concentrations. Seven plants with higher phenol concentration than the parental lines, ranging between 753.0 - 1237.4 mg gallic/100g were selected and represent F6 lines. These lines also exhibited black pericarp and higher yield than the parental lines, with yield ranging from 20.2 – 24.6 grams per plant. These represented the selected F6 line, which can be used as significant genetic resources for plant breeding and genetic base for selection for new varieties with high phenol concentration, black pericarp, and the potential for high yields in the future.