Increased Water-Use Efficiency in Alfalfa by Selection for Two Key, HeritablePhysiological Traits

摘要

Physiological breeding to improve crop water-use efficiency is one of severalcomplementary approaches to problems of agricultural water use, such as competition with other end-users and soil salinization, and to problems of declining or erratic water supplies for agriculture itself. In previous work, a physiologically based model was developed which predicted that breeding for two specific traits might confer 10% increases in water-use efficiency (WUE) on alfalfa in large-field growth over the whole season, while only modestly depressing yield. The predictions apply to other crops, while the focus is on alfalfa as a major crop economically and in southwestern water use. More detailed tests of the hypothesis about WUE gains and their cost in reduced yield is reported. The tests, in both controlled and field environments, also provided evidence that the two traits (C sub i = CO2 concentration maintained in the leaf interior, and SLM = specific leaf mass or mass per area) are usable for breeding because they are (1) heritable, (2) stable in expression between repeated growth cycles and between modestly different growth environments, and (3) measurable for selection by accurate, cost-effective methods.