2 Reasons for wheat winter freeze damage and late lodging and their relationship with varieties
2.1 Freezing damage of wheat in spring
2.1.1 Genetic factors
The cold resistance of wheat varieties is a comprehensive problem affected by genetics, ear differentiation process, and environmental conditions. From a genetic point of view, the cold resistance of wheat is a quantitative trait controlled by multiple genes, mainly additive effect, and the interaction between genotype and environment is greater. The cold resistance of spring varieties is poor. The heritability of cold resistance is low, ranging from 30.7% to 81.4%, and the offspring of hybrids have the phenomenon of superparent separation. For example, the cold resistance of wheat hybrid F1 tends to be strong relatives or intermediate inheritance, and the cold resistance of F2 is continuously separated, and super-parental separation can occur. Because wheat has higher heredity in the early generation and lower heritability in the offspring, the cold resistance of varieties with stronger cold resistance will also decrease after planting for several generations.
2.1.2 Spike differentiation process and meteorological factors
The wheat ear differentiation process directly affects its cold resistance. When the growth cone begins to elongate and enter the ear differentiation, the tolerance to low temperature begins to decline, but the decline is not obvious; when entering the two-edge period, it will obviously decrease, and the freezing rate after the two-edge period is extremely high, especially young When the ear length is 5 ~ 10mm, it is most vulnerable to frost damage and infertility. The spring in 2007 was warmer and warmer, and some wheat fields experienced spring growth on the basis of the vigorous growth before winter. The stages of greening, rising, and jointing were correspondingly advanced by 7-10 days, and the ear panicle differentiation process was extremely advanced. The ability to "invert the spring cold" decreased significantly, so that when the temperature dropped significantly on March 6 and April 3, severe early spring frost damage and late frost damage occurred successively, which caused the wheat leaves, young ears, spikelets, and stamens to freeze successively.
2.1.3 Cultivation management
The reasons for the pre-winter and spring growth of wheat are that in addition to the high temperature before winter and winter, and the temperature rises too fast in early spring, some wheat fields are planted too early (some are planted on September 23), and the planting amount is too large (150 ～ 225kg / hm2 ), Which leads to the vigorous growth of wheat fields, early ear differentiation and reduced cold resistance. Frost damage and frost damage weather occurred on March 6 and April 3, 2007, which caused damage to the premature, semi-winter wheat, which formed prematurely, excessively large amount of fertilizer, and excessive fertilization. However, the normal wheat field with suitable sowing period, proper sowing amount and reasonable fertilization is basically not damaged or is very harmless. There is a clear difference between Wangchang and non-wangchang wheat fields. In summary, the cold resistance of wheat varieties is restricted and influenced by various factors. In addition to the variety's strong cold resistance, the main factors are human factors and meteorological factors. Catastrophic cold spring weather is inevitable, but artificial cultivation measures can be used to prevent catastrophic weather and enhance the variety's resistance to cold. Wheat spring freezing damage has a certain relationship with the variety, but the main problem is not the variety, but the combination of prosperity caused by human factors, early growth period and catastrophic weather. Practice has shown that controlling the growth of semi-winter varieties through proper sowing and reasonable fertilization can effectively reduce the degree of freezing injury in spring and even avoid freezing injury. On the contrary, blindly planting winter varieties early will also lead to prosperous growth and early ear differentiation, reducing their cold resistance. Therefore, the cold resistance of varieties cannot be evaluated by the premature planting and the growth and freezing damage of wheat seedlings caused by large fertilizer, large water and large sowing volume.
2.2 Late wheat lodging
2.2.1 Variety tolerance
Lodging resistance of wheat is an indispensable characteristic of high-tolerance product varieties. Fertilization resistance is the response characteristics of wheat to fertilizers, especially nitrogen fertilizers. Lodging resistance is closely related to fertilizer tolerance. Wheat's fertilizer resistance is mainly related to nitrate reductase in plants. Nitrate reductase is a rate-limiting enzyme and an inducing enzyme, which plays a key role in nitrogen metabolism. Its vitality is inversely related to wheat's fertilizer tolerance, namely The stronger the vitality, the weaker the fertilizer resistance, the weaker the vitality, the stronger the fertilizer resistance. Therefore, excessive nitrogen fertilizer application, nitrate reductase activity and nitrogen metabolism in wheat plants are enhanced, and the ability to resist lodging is reduced.
2.2.2 Stalk traits
Lodging resistance of wheat also has a complex relationship with other traits, such as plant height, physical and physiological strength of the stalk, it is related to the weight acting on the base of the stem and the strength of the base of the stem, crushing resistance, toughness and elasticity, and root The relationship between size and depth is greater. The physical and physiological strength of stems is related to the inner and outer stems, stem wall thickness, internode length, leaf sheath coverage, number, shape, size and arrangement of vascular bundles. In addition, the distribution and accumulation of the photosynthetic products of the lodging-resistant and high-yielding species in the stalks and ear grains are relatively balanced and reasonable.
2.2.3 Cultivation conditions and meteorological factors
From the cultivation point of view, the lodging resistance of wheat has a great relationship with the sowing amount, sowing date, fertilization amount and group size, whether it is prosperous. For example, from 2006 to 2007, many wheat fields in Jining City were severely vigorously grown before winter and early spring due to cultivation, the total number of stems and the number of panicles per unit area were too large, the internodes at the base were too long, the stalk wall became thin, and the ability to resist wind disasters in the later period was significantly reduced . Large winds and heavy rains occurred on May 20-22, and a large area of ​​lodging occurred. In short, the lodging resistance of wheat is a complex issue, which is directly related to the internal factors such as the fertility and stalk characteristics of the variety, as well as the cultivation factors and meteorological factors. Variety lodging resistance has a certain limit, it can show lodging resistance under reasonable cultivation management and normal weather conditions, but under bad cultivation management (large fertilizer, large water, large sowing volume, blind early sowing, etc.) and bad weather ( Under the conditions of strong wind and heavy rain, the lodging resistance is weakened or even lost. Therefore, the large area of ​​lodging in some plots is not only a problem of varieties, but more importantly is caused by cultivation and meteorological factors.
Goat Hair Makeup Brush Set,Makeup Brush Set,Professional Painting Brush Set,Goat Hair Brush
SAMINA FORAM (SHENZHEN) CO., LIMITED. , https://www.saminamakeuptools.com