Breeding for pea weevil resistance

[William S.]

I have problematic pea weevils. Thanks to Andrew I have quite a bit of pea diversity, but I don't know for sure if any resistance is evident. Timing does seem to matter a bit. I'd be a good test site for resistant material.

[Andrew Barney]

I Like the jar test idea,  but I do think one should not ignore the pods. Perhaps if one could find resistant seed AND resistant or deterrent pods that would be the ideal combination.

I suspect the resistant ones might be more shelling, soup, or field peas with lots of tannins. Snow and snap might be out of the question.

[Andrew Barney]

Andrew: In some sense, I breed for pea weevil resistance every time I plant peas. Because those that are most susceptible are the least likely to produce viable seed.

Haha,  true,  but I thought you hadn't been planting them at all as of late.

Let me know if you want more random germplasm to try. I have jars of what I have labeled as "unknowns", which are mostly probably unknown hybrids and crosses. Very diverse.

I also have unusual seed colors like deep black seeds, purple seeds,  and more red seeds (bred from biskopens). Who knows,  maybe the black seeds are from p. fulvum and may have traits that resist bugs.

[Andrew Barney]

https://dl.sciencesocieties.org/publications/cs/abstracts/42/6/2167?access=0&view=pdf

The pea weevil, Bruchus pisorum (L.) (Coleoptera: Bruchidae), is one of the most intractable pest problems of cultivated pea, Pisum sativum L. The availability of resistant cultivars would give growers more pest management options. Searches for plant resistance to pea weevil were expanded to the Pisum secondary gene pool (P fulvum Sm.) because seed resistance had not been located in P sativum and subspecies. The objectives of this study were to determine the extent of pod and seed resistance to pea weevil in P fulvum, and to use the life table format to characterize weevil stage-specific mortality and survivorship on different P fulvum accessions. Mortality of first instar larvae on pods, mortality of all weevil stages within seed, adult emergence from seed, and seed damage levels were quantified. In two greenhouse trials, more larvae died (14 to 50% averages) on pods of P fulvum accessions than on pods of ‘Alaska 81’ (6% average), and mortality of first instar larvae entering seed of P fulvum accessions averaged 83.7%. Seed damage ratings (1 = feeding scar on seed testa, 0-1% cotyledon tissue eaten, dead first instar larva; 5 = extensive damage, live adult) averaged <3.0 for 26 P fulvum accessions, compared with mean ratings of 4.9 for Alaska 81. Using weevil mortality and survivorship values in life tables and adult emergence rates, entries were classified as susceptible (two controls and five accessions), moderately resistant (14 accessions), and resistant (12 accessions). Antibiosis resistance was based on the death of weevil larvae on pods and seed testa and cotyledon tissues. The results identify sources of natural weevil resistance in the Pisum genome (26 moderately resistant and resistant accessions of P fulvum) to endow pea cultivars with pod and/or seed resistance to B pisorum

[Lauren]

To select for seed based resistance, it would be easy to put a bunch of seeds on a jar and let the weevils do their thing over the winter.  (Hard to watch, but effective!). Freeze in the Spring (rather than early in the Fall) and plant the debris.  Of course, you need to make sure the weevils don't escape!

I did this a few years, in a sense. I put the peas in a closed jar after they were dried out. The weevil that hatched headed for the top of the jar, presumably to be closer to any oxygen. I sorted out the peas that had holes and planted the rest.

I do it differently now. I sort for those with holes and then fumigate the seeds. If I was breeding for this I'd divide the seeds by plant and plant those that had the fewest weevil.

[PhilaGardener]

I did this a few years, in a sense. I put the peas in a closed jar after they were dried out. The weevil that hatched headed for the top of the jar, presumably to be closer to any oxygen. I sorted out the peas that had holes and planted the rest.

I do it differently now. I sort for those with holes and then fumigate the seeds. If I was breeding for this I'd divide the seeds by plant and plant those that had the fewest weevil.

Nifty to hear someone has tried this!  After several years, any impact on the extent of infestation?

[Lauren]

Last year I found no pea weevils among those I kept for seed, but can't prove causation. It wasn't deliberate.

[Andrew Barney]

If this line is indeed resistant I'll need someone with pea weevil who can evaluate it. I do not have pea weevils here.

[Garrett Schantz]

If this line is indeed resistant I'll need someone with pea weevil who can evaluate it. I do not have pea weevils here.

 Doesn't Joseph have a big weevil problem?

[Andrew Barney]

https://grdc.com.au/research/reports/report?id=646

1. Pea weevil resistance is a polygenic trait, controlled by a minimum of three major recessive genes.

Breeding populations should ideally be kept large enough to include a sufficient chance of selecting resistant lines in the population. For example, only one in 64 plants will be 100% pea weevil resistant if the hypothesis that the trait is controlled by three major recessive genes is correct. For example, in a population of 6,500 F2 plants, 100 of these will theoretically carry all three resistance genes and be 100% resistant.

'By the completion of the project, a minimum of one resistant field pea to BC3 generation will be produced and made available to breeders'.

[Andrew Barney]

Ok! Just found some interesting information!

Pea weevil (Bruchus pisorum L.) resistance and genetic diversity in field pea (Pisum sativum L.)

https://pub.epsilon.slu.se/12535/1/teshome_a_260815.pdf

Among different seed colour groups,
creamy coloured seeds were the most susceptible, which suggest the presence of a different chemical signal
produced by genotypes with creamy seed colour that strongly attract this pest. Such trend of higher
susceptibility in creamy coloured seeds was also the case when different coloured seeds exist within an
accession. For example, when PSD of green and creamy seeds within the same accessions were compared,
the green seeds were unattacked in most accessions while creamy seeds scored a minimum of 45% mean
PSD (Fig. . A possible explanation for high susceptibility in these groups (creamy coloured seeds) could
be a thinner seed coat (testa) and/or a larger cotyledon which can play role in the fecundity of the larvae.
For example, seeds of wild relatives of cow pea have smaller size and a darker seed coat colour than
cultivated varieties which is correlated with higher tannin content (Chang et al., 1994). Tannins are
secondary metabolites that are directly or indirectly involved in the deterrence of herbivory by making
protein digestion hard to attain. Previous studies reported antibiosis and antixenosis capacities of pods of P.
fulvum against pea weevil (Byrne et al., 2008). Interestingly, seeds of P. fulvum are small in size with a
relatively stark dark seed coat colour, which makes them different from most cultivated varieties of P.
sativum.

Another interesting observation related to pea weevil infestation was the gradual change in seed coat
colour of infested seeds. In most infested seeds, the green and variegated-green seed coat colour gradually
turns into brown and variegated brown, respectively, upon infestation (Fig. 9). Such alteration was not
observed in creamy coloured seeds which remained the same before and after infestation. When the mean
PSD of green and brown coloured seeds within accessions was compared, it was easy to see the high PSD
score in the brown coloured seeds (Fig. 10). The fact that pea weevil infestation causes a change in seed
coat colour and that specific colours of seeds are more susceptible, imply the importance of seed coat
colour in relation to pea weevil susceptibility or resistance. According to Ceballos et al. (2002), seeds of
Sesbania drummondii undergo changes in seed coat colour and physiology following attack by the nymph
of Hyalymenus tarsatus. Our findings indicate the need to consider seed coat colour and seed coat thickness
in search for pea weevil resistance in field pea.