Analysis On Development And Evolvement Of Early Indica Rice Varieties In Zhejiang Since 1949

On the base of the origin and differentiation of rice, the characteristic and history status of early indica rice, the paper summarized and studied the production development, change of status, istributing characteristic and variety evolvement about early indica rice of different period in China including Zhejiang by collecting and coordinating the information and statistical data of early indica rice since 1949. The growth period, concentration of chlorophyl, blast resistance and agronomy traits of 35 early indica rice varieties planted in Zhejiang in different period were studied, and the study showed the change and problem of these characters of early indica rice. The paper also proposed the ideals of breeding objective, such as yield, mature time, plant type, character and resistance about early indica rice in Zhejiang. The results listed as follow:1. Both area and yield of early indica rice increased in early ages and decreased in later time in Zhejiang since 1949. The yield of unit area also presented four different periods namely it increased in the beginning and then declined and keeping finally waving. Due to many factors, planting area of early indica rice presented difference between different regions in Zhejiang. There were four phases for the varieties evolvement history, namely estimating and selecting farmhouse variety, shortening cultivars, multiplying rice cultivars with high yield, resistance and different mature times, and breeding new varieties with high yield, good quality and resistance. These varieties were such developed more and more.2. The biological feature evolvement of early indica rice in Zhejiang during different phases were studied as followed: (a) Growth duration were resemble to these rice varieties of 1950s-1960s, 1970s, 1980s, 1990s and to date; (b)The chlorophyl concentration in leaves increased from tillering stage to heading period, however, the chlorophyl concentration of the varieties from 1950s to 1970s decreased, then increased from 1980s from heading period to grain filling stage. Except breeded varieties in 1970s, the chlorophyl concentration of other varieties after heading increased as the year went ahead, so did the amount of chlorophyl content; (c) Plant height shortened during 1950s-1980s, and increased from then; (d)Effective panicles per plant were more in 1950s-1960s, almost maintain unchanged during 1970s to 1990s but slightly decreased to newly breeded varieties; (e) Although newly breeded vartieties had less effective panicles per plant, the amount of grains, amount of filled grains and grain density increased as time pushed; (f) Panicle length, empty spikelets, burliness ratio and 1000-grain weight changed with no any laws, but panicle length for newly breeded vartieties was shorter while grain density was higher than for earlier breeded vartieties; (g)Yield per plant of the varieties released after 1970s increased 10.2-25.3% higher than these from 1950s to 1960s, but yield per plant dropped slightly down in 1990s;(h) Grain width descended, but grain length and the ratio of length and width appeared the opposite trend from 1950s to 1990s, however, the three traits of newly breeded cultivars decreased; (i)Average and highest degrees and resistant spectrum for rice leaf blast increased from 7.6, 8.3 and 2.0% to 3.8, 4.4 and 36.3%, respectively, as time pushed. Meanwhile, the earlier rice were planted, the stronger single bacterium impacted on rice and the new bacterium influenced also more stronger.3. This paper brings forward the ideotype for early indica rice in Zhejiang.These traits included high tillering capacity of eight to ten tillers per plant; high grain filling percentage; big panicle with more 120 grains per panicle; 1000-grain weight of 25 to 30g; about 112d growth duration; a plant height of 80 to 90cm under high fertility; a vigorous root system with deep; thick and sturdy stems controlling the length of low part of panicles, panicle neck and the first section; leaves that were straight and dark green, and erect; no premature senility; a high effective panicle ratio, a high grain filling percentage; breeding new varieties to meet demands for industries or market; paying more attention to collecting and identifying and using the resistance rice germplasm to enhance rice resistance, exhuming and creating novel resistance gene and improved rice through biological technology.4. The Strategies for continual development about Zhejiang are listed as follow: The government should pay more attention to the production of early indica rice; It modulated to region arrangement, planting mode, variety match and management organization; It should extend the early indica rice market, decreas its production cost, increase its quality and quantity to enhance competitive capacity;It also should optimize variety distribution and industrialize management.