The Effect of Cultivar and Environment on Alfalfa Seed Quality Characteristics

S.R. Smith, R. Gjuric and F. Katepa-Mupondwa
Department of Plant Science, University of Manitoba
Winnipeg MB R3T 2N2 CANADA

Development of an establishment year seed production system would allow contract multiplication of non-winterhardy cultivars in western Canada, but may have a negative effect on seed quality as these cultivars are removed from their area of adaptation. The objective of this research was to study the effect of cultivar and environment on the following alfalfa seed quality characteristics: seed weight/size, seed colour, percentage germination, hard and non-viable seed. Nine alfalfa cultivars covering the whole range of fall dormancy classes were included in a series of field experiments at three locations in Manitoba over the period 1992-1994. Differential success in establishment and winter survival resulted in seed being harvested in only seven location-years (four establishment year stands and three second year stands). Seed harvested from these experiments were tested for seed quality using standard germination tests and by using a computer Digital Image Analysis (DIA). Measurements of plant seasonal development showed that the most fall dormant cultivars, 'Rangelander' and 'Algonquin', had slower early spring growth and development, but these differences diminished later in the season.

Variable environmental conditions (cool temperatures and high rainfall) negatively influenced pollinator activity and seed development during all years of this study. Over the range of location-years the cultivars 'Arrow', 'Algonquin', 'Cimmaron VR', 'Rangelander' and 'Florida 77' produced higher seed yields than 'Wilson', 'Moapa 69' 'Nitro' and 'CUF101'. The top five cultivars also showed a consistent, though nonsignificant, ranking for seed yield even though yields ranged from 1 to 350 kg ha^-1 over all location-years. All seed quality characteristics were under a strong influence of the environment. There were also significant cultivar differences for seed weight and percentage hard seed. Even the non-dormant cultivars showed hard seed development above 45% in 5 out of 7 location years.

The most fall dormant cultivar, Rangelander, consistently developed the highest percentage hard seed and the lowest seed weight. The measurements of seed characteristics through DIA (size and colour) were strongly correlated with measurements of seed quality through standard tests and showed potential for development of alternative or supplementary methods to measure seed quality.

In conclusion, the potential for seed production during the establishment year is unpredictable in western Canada, but successful winter survival suggests that contract multiplication may be possible of medium dormancy cultivars (2 to 3 year stands). Hard seed content was controlled by both genotype and environmental conditions, but the environment had the strongest influence on percentage hard seed.

1995 Central Alfalfa Improvement Conference Proceedings