Difference In Waterlogging Tolerance Among Peanut Varieties And Their Mechanisms

Peanut (Arachis hypogaea L.) is a worldwide important oil and protein crop. Drought and Waterlogging occur alternately in semi-arid and humid peanut production regions. In peanut regions of China, waterlogging takes place at high frequency in summer and spring seasons in southern parts, while often in summer and autumn seasons in northern parts. As one of the two water stress factors in peanut crop,therefore, waterlogging should be researched imperatively. Focusing on the responses of morphologic formation, yield components, photosynthesis and root physiology, endogenous hormones and protective enzymes, the present paper had preliminarily researched the issue of waterlogging in peanut with eighteen vatieties selected by several years of breeding practices. The main results were as follows:1 Based on field experiments jointed with indoor simulation, methods for evaluating waterlogging tolerance difference among vatieties had been established.(1) Screening for tolerant vatieties A field experiment with three treatments i.e. normal irrigation (NI), short-term waterlogging (10d, W10) and long-term waterlogging (88d, W88) was conducted under plastic rain-proof shelter condition to setup database of 18 vatieties responded to different water condition and target functions, i.e. Waterlogging Tolerance Coefficient(WTC) and Actual Yield (AY) , which were used as basis for evaluation of availability of other index. The indoor screening experiments were conducted at germination and seedling stages. The germination test consisted of shallow and deep water treatments which simulated field and ultimate conditions respectively, and the tolerant ability to the water stresses was estimated with indexes of protruding and germinating ratio. While the seedling test was conducted under waterlogging condition after normal germination so as to estimate tolerance difference according to seedling development and biochemical indexes.(2) Tolerant mechanism experiment Two typical vatieties i.e. Yuhua 15 and Hua 269, with remarkable difference in waterlogging tolerance, were subjected to NI and W10 at their main developmental phases to find out the relationship between some morphologic, physiological and, biochemical changes and waterlogging tolerance.2 Some tolerance mechanisms were revealed and a tolerant evaluating system aimed at WTC and AY and meanwhile based on serial indexes had been established.(1) There were extensive difference of responses of yields to waterlogging among vatieties The difference among varieties amount to 2.9 and 3.8 times under W10 and W88 respectively. In contrast to NI, W10 and W88 caused decrease of yield by 2.5~48.6% or increase by 5.5~ 56.7%. Among the 18 varieties, the yields of seven vatieties always increased, while five ones decreased, five and one only increased under W88 and W10 respectively. Seven tolerant types were classified with short and long-term WTC, whereas six tolerant types were classified with WTC and AY combined by cluster analysis. In addition, it was inferred that deviations would occured when WTI (waterlogging tolerant index) was used as comprehensive index to combine WTC and AY.(2) Morphological and agronomic characteristics The plant height increased in major vatieties under W10, while increased of all vatieties under W88. The draft vatieties possessed higher yield. As a whole, the number of total pod decreased under W10, while increased slightly under W88. The number of full pod of major vatieties with higher WTC increased by a big margin under W10, while most vatieties increased under W88. The rate of full pod of most vatieties increased whereas the shelling rate varied slightly under the waterlogging conditions. The 100-pod mass, 100-kernel-mass and ratio of plump pod and kernel of major vatieties raised under W10, while reduced under W88. Therefore, the decrease of total pod contributed to yield decreasing under W10, while the increase of total and full pod jointly contributed to yield increasing under W88. This provided evidence on the respect of yield components for yield increasin...