alumnos. Como podemos observar en los datos ofrecidos por el centro hay dos grupos que superan

Modern sorghum breeding in China started in the 1920s, when cultivar trials managed by Jinling University in Nanjing were conducted at experimental stations in Beijing, Taigu in Shanxi Province, Dingxian in Hebei Province, and Kaifeng in Henan Province. Other northern agricultural institutes began to perform similar studies, and in 1933, cultivars Longnan 330 and Longnan 403 were selected at the Longnan Research Station in Gansu Province; 26-12 at the Kaifeng Experiment Station; 26-24 at Suzhou in Jiangsu Province; and 6-1 in Beijing. During the Japanese occupation in the 1930s and 1940s, Japanese scientists established experiment stations for yield trials in Gongzhuling and Xiongyuecheng in northeastern China.

Reselection and cross-breeding, initiated in 1939 and 1941, respectively, focused on improving cultivars such as Nixinbang and Heikesheyanhong.

Since the founding of the People’s Republic of China in 1949, sorghum improvement progressed in four phases: germplasm collection, landrace reselection, cross-breeding, and hybrid breeding.

Germplasm collection began in 1951, when the government called on people to collect and evaluate good landraces. Scientists cooperated with farmers and selected many superior genotypes, such as Daluobang and Guandongqing in Liaoning Province, Hongbangzi and Huboxiang in Jilin, Dabaye in Heilongjiang, Pingdingguan in Hebei, Zhuyeqing in Shandong, Luyiwaitou in Henan, Sanchisan in Shanxi, Xiheliu in Anhui, Dahongpao in Jiangsu, and Jinghehong in Xinjiang.

Some cultivars were also bred through reselection, including Xiongyue 334 and 360 by the Xiongyue Agricultural Sciences Institute of Liaoning Province;

Hejianghong 1 by the Hejiang Agricultural Science Institute in Heilonjiang Province; and Zhaonong 303 by the Chifeng Agricultural Experiment Station in Inner Mongolia. Through reselection, the Xiongyue Agricultural Sciences Institute bred the high yielding cultivar Xiongyue 253 in 1957. In 1966, other

cultivars were released, such as Jinliang 9-2, Yuejin 4 and Xiongyue 191, by the Xiongyue Agricultural Sciences Institute and Jinzhou Agricultural Science Institute in Shanxi; Fenxiaodahongsui by Shenyang Agricultural College; Kangya 2 by the Agricultural Institute of Shandong; Hu 2, Hu 4, and Hu 22 by the Agricultural Institute of Jilin; Pingyuanhong by the Agricultural Science Institute of Heilongjiang; and Zhaonong 300 by Chifeng Agricultural Experiment Station in Inner Mongolia.

Cross-breeding of sorghum started quite late in China. In the late 1950s and early 1960s, Liaoliang 119 was bred by Agricultural Science Institute of Liaoning Province, Jinliang 5 by Jinzhou Agricultural Science Institute, and Jiuliang 5 by Jilin Agricultural Science Institute.

Hybrid breeding started in 1956 when CMS line TX3197A and its maintainer TX3197B were introduced into China by Dr. Xu Guanren. Hybrid breeding in China has gone through three phases:

direct use of introduced CMS lines, development of new CMS lines by introducing the male-sterility trait into local cultivars, and development of maintainer and restorer lines.

With regard to fertility restoration of TX3197A cytoplasmic sterility, most local cultivars were classified as half-fertile or fertile, and only a few could achieve sterility. Therefore, sterile hybrids were used to breed new sterile lines, and the fertile ones were used to select the best maintainer lines.

In 1958, the Chinese Academy of Sciences and the Chinese Academy of Agricultural Sciences, both located in Beijing, released two series of hybrids, the Yiza series and the Yuanza series, based on TX3197A cytoplasm and using local cultivars as maintainer and restorer lines. They were the first generation of Chinese hybrid sorghums. These hybrids had many advantages and yielded 20-60% more than the parents. Their growth period lasted from 110 to 120 days, and average height was more than 200 cm, and as much as 295 cm. Excessive height and weak straw limited their planting over large areas.

Due to the short frost-free periods and the long vegetative growth stage of male-sterile sorghums, they could not be grown in northern China. For that reason, new hybrids were bred using local genotypes as maintainer lines. For example, the Agricultural Science Institute of Jilin Province produced Hongbangzi A, Hu 2A, and Cuo 1A using Hongbangzi, Hu 2, and Cuobazi as parents. Because

the advantages of hybrids derived from kaoliang sterile and maintainer lines were not significant, they were not planted over large areas. Breeding short hybrid cultivars started in the early 1970s. The first breakthrough was achieved by using the local cultivar Sanchisan as the restorer line, and crossing it with TX3197A. The resulting hybrid, Jinza 5, yielded 6,000 kg/ha and was widely accepted by farmers.

Later, when the Jinza and Xinza hybrids were released, sorghum production in China entered a new stage. In 1975, the area sown to hybrid sorghum rose to 2.7 million ha or 50% of the total sorghum area. Although their yields were very high, hybrids contained very high tannic acid levels, low protein content, and a disagreeable taste. As a result, the hybrid sorghum area rapidly declined. In 1976, the Ministry of Agriculture formulated specific criteria for selecting and breeding sorghum, emphasizing the development of hybrids with high yields, high quality, and resistance to diseases and insects.

Subsequently, many hybrids such as Jinza 1, Tieza 1, Shenza 3, and Jiza 1 were developed that met the specified criteria for high yield and good quality (including low tannic acid).

The Agricultural Science Institute of Liaoning Province introduced more male-sterile lines from the USA in 1979, including TX622A, TX623A, and TX624A. Subsequent evaluations showed that these strains performed much better than TX3197A in terms of hybrid vigor, stable fertility, and immunity from smut. These lines were distributed to breeding units, which subsequently produced many high yielding, good quality hybrids, such as Liaoza 1, Shenza 5, Tieza 7, Jinza 83, and Qiaoza 2.

After adopting more open policies, China introduced thousands of sorghum cultivars from India

(ICRISAT), USA, and Australia. This provided a greatly expanded range of germplasm for breeding throughout the country. Some hybrids based on these materials were released directly, whereas others were developed through breeding. By the 1990s, cross-breeding of local sterile and maintainer strains had become routine, with increasing numbers of local hybrids being produced, including Liaoza 10, Shenza 5, and Xiongza 4. Others, such as Jinza 12 from the Agricultural Science Institute in Shanxi Province, Jiza 80 and Jiza 83 from the Agricultural Science Institute of Jilin, and Siza 25 from Siping Agricultural Science Institute in Jilin, combined the Texas male-sterile A₂TAM428 with local maintainer lines; these hybrids have become leading cultivars.

Before the 1990s, almost all sorghum hybrid varieties developed had Milo cytoplasm, which endangered sorghum production due to its susceptibility to some diseases (Lu et al., 1997). New CMS lines with different cytoplasms were developed in the USA and India. Schertz et al. (1997) defined Milo cytoplasm as A1, and the others were named A2-A6, and 9E. Of these, A1 and A2 are widely used in grain sorghum hybrid production, and A3 cytoplasm is used in forage sorghum breeding. In the 1990s, varieties with A2 cytoplasm, viz., Jinza 12 (in Shanxi), Liaoza 10 (in Liaoning), and Jiza 80, Jiza 83, and Siza 25 (in Jilin), were developed and released.

The A3 CMS line, described in 1980 (Worstell et al., 1984), was derived from a cross with the cytoplasm of IS1112C (belonging to the Durra-Subglabrescens group of the Durra-bicolor race native to India). Only a very few Chinese kaoliang genotypes can restore their fertility, but can retain their sterility; hence they cannot be used directly in hybrid breeding. However, their use in forage sorghum breeding shows great potential. Several A3 cytoplasm hybrid varieties have been developed and released in more than 20 provinces. The new forage sorghum variety Jincao No. 1 was the first one with A3 cytoplasm in the world.

4. Breeding objectives

Kaoliang is a distinct crop with unique

characteristics such as white vein, dry stem, and a strong aerial root system. For it to remain an important crop, kaoliang has to be improved to meet special needs such as adaptation to lower rainfall and poorer soils, and suitability for increased mechanization; genotypes should also be developed that tolerate grass herbicides while retaining their special quality traits and high yield potential.

4.1 Special needs to be met by sorghum improvement

High yield potential. High yields can be achieved in two ways: (1) through further improvement of hybrids, and (2) by modifying the plant to enable it to better utilize the physical environment; for example, morphological changes will lead to greater light interception and higher photosynthetic efficiency.

Quality. Quality must be targeted to the intended uses of the crop. For food and feed, the objectives

must include protein content, improved protein digestibility, and reduced tannic acid content. For brewing, the objectives are to maximize carbohydrate content and minimize fat content. However, starch component requirements are different for each brand (Song et al., 1996). For Moutai and Luzhou flavors, higher amylopetine contents are required.

Resistance to diseases and pests. Sorghum must be resistant to the main diseases, including smut (Sphacelotheca reiliana), blotch (Exserohilum turcicum), anthracnose (Colletotrichum spp.), and purple blotch (Cercospora spp.), as well as to the main pests:

European corn borer (Ostrinia furnacalis (Guence)), sorghum aphid (Melanaphis sacchari (Zehntner)), and armyworm (Mythimna separata (Walker)). Some introduced sorghums have good resistance to diseases (e.g., TX626B and NK-133) and pests (e.g., TAM 428 and NK-133), but their agronomic traits need to be improved to suit Chinese conditions.

Finding kaoliang cultivars with adequate pest and disease resistance, in combination with good agronomic performance, will be a major challenge in the future.

Tolerance to environmental stress. Sorghum is a drought tolerant crop, but further tolerance will always be sought in order to address climate change, extend the range of the crop to drier areas, and increase production utilizing limited water resources, particularly in locations where the crop is transplanted. Sorghum also has advantages over maize in areas subject to waterlogging, alkaline soils, and low temperatures.

Herbicide resistance. Herbaceous weeds such as barnyardgrass (Echinochloa crusgalli) goosefoot (Chenopodium scrotinum L.), pigweed (Acalypha stralis), and cocklebur (Xanthium sibiricum) are major challenges to sorghum production. Unfortunately, kaoliang is highly sensitive to many herbicides, and the choice of available selective herbicides is extremely limited. Genetic engineering to introduce glyphosate resistance would be a worthwhile objective.

Suitability for mechanical harvesting. With the increasing migration of the labor force from rural to urban areas, mechanization of agriculture has become a significant trend in China, especially in areas with low populations. Mechanized harvesting is already a common practice on state-owned farms in Heilongjiang Province. For this, short dense plant types are preferred.