Increasing crop salt tolerance can mean higher yields on irrigated farmland and salt -affected soils. Three cycles of selection were made for growth of alfalfa seedlings under 7500 ppm NaCl. Comparison of parent and selected populations was made for yield and germination under saline conditions. Yield of the last cycle was significantly improved. Germination of the last two cycles was higher than that of the parent and cycle 1.

Alfalfa which is extremely salt tolerant during germination has been developed by researchers at the University of Arizona Carbohydrates were analyzed in the original parental gemiplasm 'Mesa- Sirsa' and Cycle₅Syn₂ and Cycle₈Syn₂ seed to determine why this seed could germinate in extremely saline conditions. Raffinose and sucrose were both significantly higher in the salt -tolerant germplasm compared to the parental germplasm; however, the magnitude increase of these free sugars was not sufficient to explain the increased ability of the seed to absorb water in a stress environment. The galactomannan content was not different among the alfalfa germplasms.

Salinity is a persistent problem for alfalfa growers in Arizona that will likely worsen over time. Plant breeding may offer a relatively low-cost short-term solution: varieties bred to remain productive in the presence of moderate levels of salinity. We have developed and released AZ-9ONDC-ST, a broad - based, nondormant alfalfa population with increased forage yield in greenhouse trials under moderate NaCl stress. AZ-90NDC-ST was derived from two cycles of selection for increased forage yield under NaCl stress from AZ-88NDC a composite nondonnant population previously released by the experiment station. AZ-90NDC-ST was developed to provide a source of alfalfa with increased forage production under moderate salt stress and is the only population with these characteristics in existence. This population, which has been made available to the alfalfa breeding community, will provide the basis for improved high yielding and pest- resistant varieties for use in areas in subject to salinity stress.

Genetic variability must exist for a selection program to be successful. Alfalfa seedlings were selected for salt tolerance after six weeks growth at 7500 ppm NaCl. The selection criteria considered plant height and survival. Variability for each factor within a population of alfalfa was shown. Both criteria were important and facilitated selection from those parents which contributed most to the salt tolerance of the population.

The nondormant alfalfa cultivars now grown in Arizona trace largely to a small number of alfalfas introduced from the Middle East. Middle Eastern alfalfas regrow rapidly primarily from crown shoots following harvest and produce high yields during late fall, winter and early spring. Harvest management may have a significant effect on the persistence and yields of Middle - Eastern alfalfas under Arizona conditions. In the Middle East, alfalfa is frequently harvested at the bud stage and little stubble is left. In this experiment we compared the yield and persistence of Middle Eastern alfalfa ecotypes under traditional Middle - Eastern (bud stage + 2 cm stubble) and Southwestern harvest management (10% bloom + 10-15 cm stubble), and a regime with elements of both primary systems (bud stage + 10-15 cm stubble). Only slight differences in yield or persistence were observed between the management systems in the most nondormant entries, however, some ecotypes produced significantly more forage than Lew. No apparent advantages were noted for harvest leaving 2 cm stubble. Elevated yields of high quality forage would be produced with bud stage harvest and 10-15 cm stubble in most Middle Eastern ecotypes.

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Improving the germination salt tolerance of alfalfa will help this crop endure both increasingly saline irrigation water and salt build -up in the soil. Seven previous cycles of selection for salt tolerance at germination plus the parental line, Mesa-Sirsa, were evaluated for percentage germination under various levels of NaCI solutions. Germination improved linearly from the earliest to the latest cycle of selection. Germination salt tolerance can be improved through recurrent selection techniques.

Deposition of salts from irrigation water is an increasing concern for Arizona farmers and agronomists. Selection for salt tolerance during the seedling stage has been undertaken over the past three years. Yield tests were conducted in greenhouses and a significant increase in dry matter production was shown in the selected material.

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There has been limited research on the rooting patterns of alfalfa. This information would be important in developing new germplasm sources that are more water efficient, salt tolerant and drought tolerant. Ten alfalfa varieties were evaluated for possible genetic control of rooting traits. Seedlings were grown hydroponically in a growth chamber. The cultivars evaluated showed a significant statistical difference for width of lateral root system and number of lateral roots. The variation in seedling rooting patterns is sufficient to warrant a selection program for improved lateral rooting patterns.