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.

The stand longevity of 13 alfalfa varieties was evaluated 3 years after planting. The number of crowns per acre ranged from 71,000 to 163,000.

Ten alfalfa varieties, ranging from very non- dormant to moderately dormant cultivars, have been grown and yields compared over a four year period No significant differences were noted in the yields for 1989; all varieties yielded over 8 tons per acre in 6 cuttings. Interesting changes are taking place, however, with the very non -dormant varieties continuing their productivity and the more dormant varieties productivity declining.

Yields by cutting are given for 22 varieties of alfalfa grown at the Safford Agricultural Center. Yields were good in 1989 with 9 of the varieties yielding over 10 tons per acre in 7 cuttings and the top variety yielding 12 tons per acre. Graphs are shown comparing yields by cutting between sister varieties of differing fall dormancy classes.

No description available.

Moisture loss from stacked alfalfa was measured at various times of the year and at various baling moistures. Total moisture loss over two month time periods varied from 4.5% to 8.3% with considerable fluctuation occurring due to environmental conditions.

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.

Cercospora summer black stem and leaf spot, a fungal disease of alfalfa, has been associated with a stand decline problem in La Paz County. In a continuation of a study initiated in 1987, we examined the ability of three fungicides to control the disease and decline problem. Bravo, Funginex, and Kocide significantly reduced the severity of Cercospora summer black stem and leaf spot. In addition, significant increases in yield were recorded on plots treated with fungicides.

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.