Classification Of Maturity Groups Of Soybean Varieties In High-latitude Cold Area Of North Region Of Northeast China

Under the natural conditions of Heihe Municipality, Heilongjiang Province, the early soybeanvarieties and the main varieties in the high-latitude north area of Northeast China were madedivision on maturity group (MG) with the North American standard varieties as references. Wearrive at the following review：The latest soybean varieties in the high-latitude cold area of Northeast China were in MG0and the earliest ones were earlier than MG000. We classified them into MG0000. The MG0000varieties in the three-year experiment were characteristic of stably ultra early maturing. Precociousamplitude of MG0000when it was compared with MG000reached interval standard (10-15d) ofNorth-America maturity group. The clustering and variance analysis of tested varieties’ growthperiod confirmed that MG0000was independent from other early MGs, indicating that theexpansion towards more precociousness of internationally-recognized MG system in the currentstudy was reasonable.Based on the findings of this study, we made some revisions on the previous classification ofsoybean MG in China. For examples, we found that Heihe12which was originally classified as anMG00variety should be in MG000, and Dongnong36which was originally classified into MG000should be included in MG0000. We proposed that when making divisions of MG, both photoperiodand temperature response should be considered; in addition, the locations where we would identifythe MGs of soybean varieties should meet the demand of temperatureWe found that there was obvious yearly difference in days to maturity and growth period ofsoybean varieties, caused by the inter-annual temperature difference. We found the greater thetemperature difference was, the greater the corresponding difference of days to maturity was. Inthis experiment, temperature sensitivity of reaction and maturity-promoting rates between thegroups of MG000and MG00were not significantly different, but their temperature sensitivitydifferences from other groups of reached extremely significant level. Maturity-promoting rateshowed no significant differences from other groups, but we got a trend that difference was lesssignificant when growth period was prolonged, suggesting that the shorter that the growth periodwas, the more sensitive the temperature response became.We found that the difference of vegetative growth period (V) was not obvious; that the lengthof reproductive growth period (R) was greatly different; and growth period structure differencereached a significant level. The experiment proved that days from flowering to maturity of thevarieties in the High-latitude cold area was the contributory cause of maturity group differenceamong soybean varieties.According to the MG and planting area of the tested varieties, we made clear the geographicaldistribution of soybean varieties in different MGs. MG0000was mainly distributed in the northand northeast part of Daxing’anling Mountains, on Heilongjiang River coast to the north of Huma county, and in the high altitude area of Xiaoxing’anling Mountains (Huma-Heihe-Sunwu);MG000was mainly distributed in the area crossed between Xiaoxing’anling Mountains andDaxing’anling, Heilongjiang River coast to Huma-Heihe and the lower-elevation areas; MG00was mainly distributed in the low-elevation area in the north of Oroqen Autonomous Banner andsoutheast of Daxinganling Mountains, in the low-elevation area in the south and north ofXiaoxing’anling Mountains, south ridge of Zhang Guangcailing Mountains and in the area ofLaoyeling Mountains; MG0was mainly along Heilongjiang River coast in Heihe and Yichun,transitional area between Xiaoxing’an mountains and Songnen plain.