Characterization of core collection of lentil germplasm for phenology, morphology, seed and straw yields
Increasing and maintaining crop residues in predominantly cereal-based rotations of the US Pacific Northwest is critical to controlling soil erosion. The core collection of lentil (Lens culinaris Medik.) germplasm comprising 287 accessions was evaluated for variation in phenological, morphological and growth parameters including seed yields and residue amounts over a two-year period under conventional tillage and no-till conditions. The objectives of this study were (i) assess lentil genetic variation in germplasm for variation in biomass production and seed yield, (ii) assess the relationship of phenological and morphological traits with biomass and seed yield and (iii) identify high biomass producing germplasm for use as parents in the breeding program. Days to flowering and days to maturity ranged from 31 to 78 and from 71 to 106 days, respectively. Time to flowering in terms of cumulative heat units was a more efficient measurement than days to flowering. Plant height and plant canopy width had a significant association with total biomass, seed yield and residue amounts. Total biomass ranged from 788–6389 kg ha−1 under conventional tillage, while the range under no-till conditions was 1045–6195 kg ha−1. Most of the lines with higher biomass also produced the highest seed yields and residue amounts. Overall, only one accession produced more residue than `Laird'. In the more favorable environment of 1997, six accessions exceeded the control cultivars, `Laird' and `Indianhead', for residue amounts, and seven and twenty-four accessions exceeded control cultivars, `Pardina' and `Brewer', for seed yield. Results indicated that plant height, canopy width at maturity and seed yield explained most of the variation in biomass and residue production. Large seeded germplasm consistently had a longer reproductive growth period than small seeded accessions and had 17%, 7% and 21% more biomass, seed yield and residue, respectively. Our data indicated significant variation in lentil germplasm for biomass, seed yield and residue amounts to warrant their use in the breeding program.
Physiological Aspects of Peanut Yield Improvement 1
Development of new peanut (Arachis hypogaea L.) cultivars over the past 40 years has more than doubled yield potential. The purpose of this paper is to identify and evaluate the physiological changes made in the course of this varietal improvement that are responsible for the great increase in yield potential. Weekly harvests of large samples of four Florida cultivars, a Spanish peanut type, and one soybean (Glycine max (L.) Merr.) cultlvar gave the information needed to show the progressive changes in dry weights of all plant parts throughout the growing season. Other weekly samplings and observations gave numbers of pegs, flowers, and fruits as well as fruit weights, root length, shoot length, and leaf areas. Quantitative estimates of the physiologlcal factors responsible for the dry weight differences were made by computer simulation using the PENUTZ model. Differences in three physiological processes explain most of the yield variation among the five peanut cultivars; the partitioning of assimilate between vegetative and reproductive parts, the length of the filling period, and the rate of fruit establishment. Of these, the partitioning of assimilate had the greatest effect on fruit yield. Estimates of partitioning to fruit ranged from 41% in the first cultivar released to 98% in the most recently released cultivar. Crop growth rates did not differ significantly among peanut cultivars but all were much higher than the crop growth rate of soybeans
The potential vorticity flux through the Yucatan Channel and the Loop Current in the Gulf of Mexico
Two‐year‐long time series of current and density structure measurements across the Yucatan Channel's main section allow the calculation of the time‐dependent potential vorticity flux between the Gulf of Mexico and the Caribbean Sea, which is characterized by alternating periods of positive (cyclonic) and negative (anti‐cyclonic) vorticity influx. Periods of negative cumulative vorticity influx are related to the Loop Current extending into the Gulf of Mexico, whereas periods of positive cumulative vorticity influx relate to a Loop Current retraction, sometimes coincident with the shedding of an anti‐cyclonic eddy.