VARIABILITY OF SEED AND PLANT DEVELOPMENT IN PEA

Pea (Pisum sativum L.) yields are generally highly dependent on seed number. The objective of the present study was to investigate seed and plant development of 10 contrasting genotypes of pea with differences in seed size (0.1-0.3 g seed(-1)), foliage type (semi-leafless and leafed), and number of branches. The periods of seed set and seed filling were studied in the field for 2 yr at two sowing dates. Seed water content (WC) was closely related to seed development. Seed water content at beginning of seed filling and at physiological maturity corresponded to 0.85 and 0.55 g g(-1) fresh weight, respectively. The progression of flowering, beginning of seed filling, and physiological maturity along the stem were linearly related to cumulative degree days from the beginning of flowering. The rates of progression of flowering and of beginning of seed filling were not dependent on environmental conditions, but they were significantly different among genotypes. Conversely, the duration of the lag phase, time between flowering and beginning of seed filling at the first node, remained stable in spite of differences in seed size. The onset of physiological maturity was more variable. Duration of seed filling varied among environments, but genotypes had similar durations in spite of differences in seed size. Seed number on the main stem was fixed when the seeds of the last reproductive node began to bd. The delimitation of the seed set period showed genetic variability for the beginning of the period, depending on the first reproductive node number, and its duration.