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Susceptibility to black spot [caused by Mycosphaerella pinodes (Berk. and Blox.) Vestergr.] and weak stem strength in field pea (Pisum sativum L.) are major restrictions to yield, seed quality, and ease of harvest. Previous studies have established that additive genetic variance is present for both traits, and that stem strength is strongly associated with a field test of compressed stem thickness at the base of the stem. This study aimed to improve these two complex traits simultaneously by recurrent selection. Heritabilities and responses to selection for resistance to black spot and stem strength were evaluated during two cycles of recurrent selection after intercrossing diverse genotypes. Response to selection was indicated by a reduction of 10% in the mean black spot leaf disease in the [F.sub.2] of cycle 2 compared with the [F.sub.2] of cycle 1, when considered as a percentage of the mean of cycle 1 parents in the same trials. Likewise, there was a 15% increase in stem strength, based on the mean compressed stem thickness in the [F.sub.2] of cycle 2 compared with the [F.sub.2] of cycle 1. Broad sense heritability for resistance to black spot leaf disease was moderate (H = 0.63 [+ or -] 0.35 across cycles 1 and 2) and for compressed stem thickness was also moderate (H = 0.66 [+ or -] 0.34). Genetic gains were realized for both traits simultaneously in the first two cycles and were predicted to be rapid over the next five to six cycles based on a random mating quantitative genetics model.

In feeding, aphids inject saliva into plant tissues, gaining access to phloem sap and eliciting (and sometimes overcoming) plant responses. We are examining the involvement, in this aphid-plant interaction, of individual aphid proteins and enzymes, as identified in a salivary gland cDNA library. Here, we focus on a salivary protein we have arbitrarily designated Protein C002. We have shown, by using RNAi-based transcript knockdown, that this protein is important in the survival of the pea aphid (Acyrthosiphon pisum) on fava bean, a host plant. Here, we further characterize the protein, its transcript, and its gene, and we study the feeding process of knockdown aphids. The encoded protein fails to match any protein outside of the family Aphididae. By using in situ hybridization and immunohistochemistry, the transcript and the protein were localized to a subset of secretory cells in principal salivary glands. Protein C002, whose sequence contains an N-terminal secretion signal, is injected into the host plant during aphid feeding. By using the electrical penetration graph method on c002-knockdown aphids, we find that the knockdown affects several aspects of foraging and feeding, with the result that the c002-knockdown aphids spend very little time in contact with phloem sap in sieve elements. Thus, we infer that Protein C002 is crucial in the feeding of the pea aphid on fava bean. aphid-plant interaction | saliva | RNAi | electrical penetration graph | immunohistochemistry

Resistance to Mycosphaerella pinodes in field pea (Pisum sativum L) is a quantitative trait, and expression of resistance is substantially influenced by environment. The disease reaction to mycosphaerella blight of four crosses ([F.sub.2:4] and [F.sub.2:5] populations) was assessed in field trials at Vegreville, AB, Canada. Broad-sense heritability of resistance was quite high (0.62-0.81). Narrow-sense (realized) heritability was moderate (0.43-0.57), indicating that additive genetic factors contributed substantially to the resistance phenotype. Significant improvement in resistance among the lines developed from selected individuals indicates that genetic improvement based on progeny testing would be effective. This study demonstrated that resistance to M. pinodes can be improved through progeny selection from crosses of the most resistant lines.

A study of the spatial pattern differences between Pseudomonas fluorescens strains 2-79RN(sub 10) and 2-79-B46 on the rhizoplane of pea seedlings is given. Strain 2-79RN(sub 10) is a biological control agent while 2-79-B46 is phenazine-deficient Tn5 mutant. The study was undertaken to find out if changes in spatial patterns of colonization leads to a loss of phenazine production by mutation. The study employed geostatistical analysis in quantifying the spatial patterns.

Four Bacillus thuringiensis [delta]-endotoxins, Cry3A, Cry4Aa, Cry11Aa, have displayed low to moderate toxicity on the pea aphid, Acyrthosiphon pisum, in terms both of mortality and growth rate. Cry1Ab is essentially nontoxic except at high rates and these effects are shown by using exhaustive buffer-based controls.

The ability of widespread agricultural pest, pea aphids to vector the phytopathogen Pseudomonas syringae pv. syringae B728a (PsyB728a) is described. The less virulent feature of strain Pseudomonas syringae pv. Tomato DC3000 compared to PsyB728a in the pea aphid indicated that PsyB728a possess strain-specific pathogenicity factors that allow it to exploit aphids as hosts.

Several tests are conducted to compare the performance, performance differentiation and genetic variation observed in pea aphid clones of eight different host-plant genera. The analysis proves that the host plant is a site of gene flow that takes place between different populations, limiting further host-related divergence.