Linkage analysis was used to determine the genetic map location of er-1, a recessive gene conditioning resistance to powdery mildew, on the Pisum sativum genome. Genetic linkage was demonstrated between er-1 and linkage group 6 markers after analyzing the progeny of two crosses, an F2 population and a set of recombinant inbred lines. The classes of genetic markers surrounding er-1 include RFLP, RAPD and allozyme markers as well as the morphological marker Gty. A RAPD marker tightly linked to er-1 was identified by bulked segregant analysis. After DNA sequence characterization, specific PCR primers were designed to convert this RAPD marker into a sequence characterized amplified region (SCAR).
In 1991, 1992, and 1994, 2,936 accessions of Pisum sativum from the USDA Plant Introduction collection were screened under field conditions for resistance to Mycosphaerella pinodes without replication due to seed supply. These trials were conducted at the Oak Park Research Station at Carlow, Ireland, where conditions are highly favorable for disease expression. In 1995, the 157 most resistant accessions were again screened at Carlow and at the Food and Crops Research Station at Gore, New Zealand, in replicated trials. At both locations, disease was severe and ranged from 20 to 100% foliar blight. Five accessions were as resistant as the commercial cultivar Radley at both locations: PI 142441, PI 142442, PI 381132, PI 404221, and PI 413691. No accessions were more resistant than the cultivar Radley.
ABSTRACfAt Lincoln eight haricot bean cultivars were grown at 2 in. and 4 in. spacing in 18 in. rows in 1969-70. The cultivars Small White Commercial, White Navy, Sanilac, and Seaway were superior in yield and seed size for processing. On average, plots with 2 in. spacing yielded 9.8% more than plots with 4 in. Cultivars did not differ significantly in their yield response to different plant spacings.The cultivars differed in flowering date, growth habit, pod clearance from the ground, and seed size.The plot-to-plot correlation of yield with number of pods per plant was positive and significant at the wider spacing. Yield was not associated with number of seeds per pod, and showed a significant negative correlation with lOO-seed weight. Inverse relationships among components of yield were observed, but number of pods per plant and I DO-seed weight were not significantly correlated.Standardised partial regression coefficient analysis indicated that number of pods was the main component determining yield. Selection for high yield can be based on number of pods per plant when grown at wider plant spacing.Heritability estimates for components of yield were very high.
Transformed pea (Pisum sativum L.) lines were produced with two chimeric gene constructs encoding the coat protein (CP) of alfalfa mosaic virus (AMV) strain NZ1. To determine whether transformed lines have improved AMV resistance, progeny of independently derived transgenic lines were tested in the greenhouse and five lines with improved virus resistance were identified. Resistance was observed only in individual plants that accumulated detectable CP product from the transgene, suggesting that resistance is CP mediated. Plants that accumulated detectable amounts of transgene CP product yet were susceptible to AMV were found among the progeny of most lines, indicating that these lines are only partially resistant to the challenging AMV strains, 425 and NZ1(Lincoln). A field test was conducted with the progeny of four independently derived transgenic lines. To test for improved virus resistance under field conditions, plots of transgenic lines and nontransgenic controls were inoculated with two AMV strains, NZ1(Lincoln) and NZ34. Analysis of disease severity in seedlings in inoculated plots confirmed that partial virus resistance can be produced by genetically modifying peas with AMV CP sequences.
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