Introduction to the Characteristics and Traits of the Rice Variety Peiza 67

Basic Information We used the low-temperature-sensitive genic male sterile line Pei'ai 64S and the self-selected high-quality indica-japonica hybrid progeny line G67 (Copslo17/Haogolao//Xinxiu 299) for test crossing, and bred the new two-line hybrid rice combination Peiza 67, which combines high quality, high yield and high resistance.

Characteristics and Traits Peiza 67 participated in the Guangdong Province two-line hybrid rice joint trial, with a yield of 6.84 t/ha, on par with the control Shanyou 63; in 1996 and 1997 it participated in the provincial hybrid rice joint regional trial, with yields of 6.29 and 6.08 t/ha respectively, showing a non-significant yield decrease and a just-significant decrease compared with the control. In 1997 it participated in the national "863" pilot test, with yields of 6.99 t/ha in the South China early rice regional trial and 6.55 t/ha in the late rice regional trial, showing non-significant and significant yield increases respectively compared with the control Shanyou 63. Starting in 1995, trial plantings and demonstrations were successively carried out in some counties and cities of Guangdong Province such as Yangjiang, Qingyuan and Meizhou, with yields generally around 6.75 t/ha, either equal to or significantly higher than locally promoted varieties; because of the combination's superior grain quality, it was well received by farmers. From 1996 to 1999, in Xinxing County, trial plantings over 4 consecutive years and 7 seasons covered more than 1300 ha, with yields of 7.05-7.50 t/ha, of which the high-yielding plots reached 9.78 t/ha. In the late season of 1998 it was planted in Guangning County, with an average yield per unit area of 7.56 t/ha; in 1999, 40 ha were planted for demonstration in Longchuan County, with an average yield of 7.25 t/ha, both significantly higher than locally promoted varieties. The promoted area of Peiza 67 expanded rapidly, and by the end of 1999 the cumulative promoted planting area had reached 6606.7 ha.

Peiza 67 is a temperature-sensitive medium-late maturing combination, with a maturity period comparable to Shanyou 63; the whole growth period is 129 d in the early season and 118 d in the late season. Plant height is 110 cm, the plant type is moderately compact, the stems are thick and strong, tillering ability is relatively weak, the leaves are stiff and upright, the leaf color is fresh green, cold resistance is relatively strong, and the late-stage ripening color is good. The total number of grains per panicle is 160-200, the seed-setting rate is about 80%, the 1000-grain weight is 19 g, and the grain quality in the early crop is appearance grade one. It is highly resistant to rice blast (whole-group resistance ratio 94%), moderately susceptible to bacterial leaf blight (whole-group resistance ratio grade 7), and field planting shows both rice blast and bacterial leaf blight to be mild. In ordinary-fertility fields the yield can reach 6.75 t/ha, and in high-fertility fields it can reach more than 9.5 t/ha.

Breeder: Department of Agronomy, South China Agricultural University

Region and Technical Cultivation Technical Points: a) Seed disinfection and breaking of the dormancy period. The Peiza series combinations all have a certain dormancy period, and Peiza 67 is no exception; especially for new seeds produced in spring for late-season use, it is best to soak the seeds with strong chlorinating agent for disinfection and to break dormancy, so that emergence is uniform and consistent and seed-borne disease is eliminated. b) Peiza 67 has slightly weak tillering ability and a small 1000-grain weight; to give full play to its high-yield potential, sufficient base fertilizer and early topdressing should be applied during cultivation. To create a high-yielding seedling framework, the number of effective panicles should be increased on the basis of ensuring its original large panicles; it is necessary to transplant enough basic seedlings at 900,000-1,200,000 per ha, and strong seedlings must also be cultivated, with early fertilization to promote early tillering. c) After enough seedlings are present, expose the field and dry it lightly more often to control the peak seedling number, and apply appropriate mid-season fertilizer (panicle-grain fertilizer); under low-temperature conditions in the late season, the leaves tend to senesce early in the later stage, so the field should be kept moist. In the early season the plants are slightly taller, and when planted under high-fertility conditions lodging must be prevented; timely and appropriately spraying chlormequat has a good effect.

d) For late-season reverse-autumn cultivation, the seedling age should not be too long, and 18-20 d is appropriate, to prevent early heading from affecting yield. Control of diseases and insect pests such as sheath blight, rice planthopper, rice false smut and ustilaginoidea should be strengthened.

Key Points of Seed Production Technology: Pei'ai 64S has advantages such as concentrated flowering time and a high stigma exsertion rate, but its stigma is small, stigma vigor declines quickly, the glume-opening time is short, the glume-opening angle is small, and it is especially insensitive to "920"; these characteristics bring certain difficulties to high-yield seed production. The male parent G67 has a small 1000-grain weight, large panicles with many grains, relatively weak tillering ability, a large amount of pollen, a long flowering duration per hill, and an ordinary response to "920". Therefore, the following technical measures are proposed.

Two-line hybrid rice seed production requires both an optimal heading and flowering period and an optimal safe young panicle differentiation period, to ensure that the female parent is safely sterile. The two safe periods should be determined according to local climatic conditions and years of seed production experience, and the sowing interval between the parents should be reasonably arranged. For spring seed production in Hainan, Pei'ai 64S is generally required to begin panicle initiation at the end of April to the beginning of May, so the female parent should be sown on February 10-15, the stage I male parent should be sown 10-13 d earlier than the female parent, and the stage II male parent should be sown 5-7 d earlier. For mid-summer seed production in Guangdong Province, the sowing interval between the parents is basically the same as for seed production in Hainan.

Pei'ai 64S grains are small; although its tillering ability is strong, the panicle-setting rate is relatively low, and stigma vitality declines quickly. Therefore, high seed production yields must be achieved through reasonable dense planting and increasing the number of basic seedlings; the general field seeding rate is 25-30 kg/ha. Because the male parent has relatively poor tillering ability, sparse sowing is required, strong seedlings with tillers should be cultivated, and 3-4 seedlings should be transplanted per hill. The male parent plants are tall, with large panicles and many grains and sufficient pollen, so the row ratio can be appropriately widened, with about 2:14 being suitable.

Pei'ai 64S is a fertilizer-tolerant variety, and sufficient base fertilizer should be applied. Per hectare, 450 kg of ammonium bicarbonate and 375 kg of phosphate powder can be used as base fertilizer; the first topdressing should be applied 3-4 d after transplanting, and the second topdressing 8-10 d after transplanting; panicle fertilizer should be applied around stage II of young panicle differentiation, and leaf-cutting and flower-preserving fertilizer should be heavily applied at stages V-VI of young panicle differentiation. The male parent should receive 1-2 additional fertilizer applications, and water management should be strengthened to build a good seedling framework and ensure sufficient pollen amount and a longer flowering time. The male parent has relatively poor tillering ability, so strong seedlings should be cultivated, and fertilizer should be applied early to promote tillering and ensure the number of effective panicles.

Pei'ai 64S is especially insensitive to "920", and using "920" well is the key link to achieving high seed production yields. Generally, 330 g/ha of "920" is used, sprayed continuously for 3 d when 3%-5% of panicles have headed. During spraying, growth regulators such as k2HP04 should also be sprayed to advance the flowering time of the female parent and improve stigma vitality and the seed-setting rate.