Evaluate The Aluminum Tolerance Resources In Sichuan And Tibet Wheat And Genetic Improvement Of Aluminum Tolerancein Australian Durum Wheat

Acid soils are widely distributed in the world. Acid soils limit crop yields due to nutrient deficiencies and mineral toxicities and have become one of the major limiting factors affecting agricultural production around the worldwide. The root system of sensitive plants grown on acid soils were severely injured and typically were shorter and thicker because of high concentrations of soluble aluminum (Al3+) inhibit root elongation and destroy the root tips. This restricts plant’s ability to acquire water and nutrients and reduces the production. Improving the aluminum tolerance of crops in acid soils is an alternative way to improve the yield losses. A widely screening and evaluation is necessary for finding crops with aluminum tolerance. There is large area of acid soils distributed in Sichuan and its surrounding areas. It is necessary to find aluminum tolerance wheat germplasms from wheat distributed in these areas and use them to breed new wheat cultivars with improved aluminum tolerance. Durum wheat is extremely sensitive to Al3+ toxicity, severely limiting its production in acid soils. In order to improve the aluminum tolerance of durum wheat, the TaMATE1B gene which located on 4BL chromosome and the TaALMTl gene originated from 4D chromosomes were introduced into Australia (?)te durum wheat cv. Jandaroi, and its aluminum tolerance ability were assessed. The main results were as follows:1) The aluminum tolerance of 40 Sichuan bread wheat cultivar and 52 Sichuan wheat landrace were evaluated by soil experiment, TaALMTl gene upstream sequence clone and Malate efflux test. Using aluminum tolerance wheat Chinese spring and ET8 as controls, some aluminum tolerance wheat were identified., For example, Chuanmai 44, Chuanmai 45. Chuanmai 32 and Chuanyu16 in cultivar wheat. As1596, As1572, As1576. As1580, As1592, As1589and Chengduguangtou in landrace wheat were similar aluminum tolerance to aluminum tolerance control Chinese Spring (CS). There are five types of upstream sequences in TaALMTl gene in Sichuan bread wheat cultivars and three types of upstream sequences in Sichuan wheat landraces. Chinese spring is a bread wheat with unique type Ⅲ upstream sequences in TaALMT1 gene reported so far, however, in this study, six other Sichuan bread wheat cultivars (Chuanmai 35, Chuanmai 33, Chuanmai 41, Chuanmai 42, Chuanfu 5 and Mianyang 29)and two other Sichuan wheat landraces (As1635 and As1641)share the same type Ⅲ upstream sequences in TaALMT1 gene as Chinese spring. It is necessary to study the relationships among the type Ⅲ upstream sequences in TaALMT1 gene, the aluminum tolerance and the quantity of malate secret.2) The aluminum tolerance of Tibet bread wheat were evaluated by soil experiment, TaALMT1 gene upstream sequence clone and malate efflux test. Some aluminum tolerance wheat (for example As1242) were identified, The root regrowth lengths of some Tibet bread wheat were closer to the aluminum tolerance control CS. The upstream sequence compositions in TaALMT1 gene of the Tibet wheat were more simple, mostly of them were type Ⅰ and Ⅱ except for one type Ⅳ and one type Ⅴ. The upstream sequence compositions in TaALMT1 gene were highly related to aluminum tolerance. The aluminum tolerance Tibet wheat often have type Ⅱ upstream sequences, whereas the aluminum sensitive ones often have type Ⅰ upstream sequences. The Al-tolerance Tibet wheat often secret more malate than the aluminum sensitive ones. In some cases, no malate was secreat from the root tips of aluminum sensitive ones.3) Twenty-seven Chinese endemic wheat including Yunnan hulled wheat, Xinjiang rice wheat and semi-wild Tibet wheat were evaluated for aluminum tolerance by soil experiment, TaALMT1 gene upstream sequence clone and malate efflux test. Xinjiang rice wheat AS360 exhibit the best aluminum tolerance among all of the Chinese endemic wheat, though its posses type Ⅰ upstream sequence in TaALMT1 gene. In our experiments, the root regrowth lengths of As360 were longer than that of the aluminum tolerance control ET8 but shorter than that of the CS. To our interesting that As360 secret more malate acid, just like most of the aluminum tolerance wheat. Therefore, AS360 can be used as a aluminum tolerance source in aluminum tolerance genetics and breeding. The aluminum tolerance of Yunnan hulled wheat, xinjiang rice wheat and semi-wild Tibet wheat were not the same. Among them, Yuanan hulled wheat showed better aluminum tolerance than Xinjiang rice wheat and semi-wild Tibet wheat. However, there is no difference for the aluminum tolerance between Xinjiang rice wheat and semi-wild Tibet wheat..4) Longdon 4D (4B) substitution lines were used as TaALMTl gene donors to improve the aluminum tolerance of the semi-dwarf durum wheat cultivar Jandaroi. The F1 crosses of Jandaroi×Longdon 4D (4B) substitution lines were made using Jandaroi as female parent and the F1 hybrids were backcrossed using Jandaroi as recurrent parent till get the BC3F3 homozygous lines. Notably, introgression lines with 4D chromosome fragments inserted in durum wheat cv. Jandaroi improved the aluminum tolerance and the salt tolerance. Specially, the aluminum tolerance capacity of semilar root has been enhanced, but the lateral resistance remains unchanged. Analysis of plant characteristics in the absence of Al3+ toxicity showed that the insertion of 4D fragment into durum wheat did not affect the total grain yields except for reduced the weight of individual grains.5) In order to minimum the 4D chromosomal fragments into durum wheat Jandaroi, the Longdon 4D (4B) substitution lines were crossed with durum wheat cv. Cappelli, a ph1 gene lost mutant, and then backcrosses 2 times with Cappelli till obtaining BC2F2 homozygous lack of ph1 gene locus. The BC2F2 seeds were then selfed till obtain BC2F10. The BC2F10 plants were crossed with Jandaroi and the aluminum tolerance plants were selected. The D genome sizes of the homozygous F3 lines in aluminum tolerance locus TaALMT1 were evaluated by quantitative PCR using D genome-specific Dgas markers and fluorescence in situ hybridization. It is indicated that the 4D chromosomal fragment sizes in these lines were much smaller than its parent Longdon 4D (4B) substitution lines and the aluminum tolerance of these durum wheat lines were improved.. In the F2 populations, the sergergation of the aluminum tolerance gene TaALMTl were meet the 3:1 Mendelian laws.6) In order to improve the aluminum tolerance of durum wheat, the TaMATE1B gene on chromosome 4B of hexaploid wheat were introduced into durum wheat through the crosses of common wheat with durum wheat. Indeed, introducing of TaMATE1B into durum wheat improved the ability of aluminum tolerance. The hydroponic experiments also shown that it can protect the root growth either at high Al3+ concentrations or at low Al3+ concentrations, however, it is less effect in protecting the root regrowth than that of the TaALMTl gene at high Al3+concentrations. In the soil experiment, it can protects both the semilar root and fine root growth especially at low concentrations of Al3+ in acidic soils, but the TaALMTl gene only protect the semilar root growth.