Location: Crop Genetics Research Unit
2013 Annual Report
Isolates of Phomopsis (P.) longicolla were collected from seed harvested in past years in different states, and from lower stems of soybean plants grown in two fields in Arkansas and one field in Mississippi. Stem sections were collected from 100 locations in each field using a 20 X 20 m grid. Hundreds of isolates have thus far been collected. Efforts have been made to purify and single-spore those isolates. Selected isolates have been sequenced at internal transcribed spacer (ITS) region to confirm the pathogen identity. Identification of simple sequence repeat (SSR) markers based on the draft genome sequence of a P. longicolla from Mississippi is in progress.
For breeding and genetics purposes, the following plant populations are being advanced in Fayetteville, AR, for breeding/mapping purposes: F4 generation: 5002T x PI 417479, 5002T x PI 417050, and R03-984 x PI 417050. F3 generation: R07-R07-10244 x PI 424324B, R04-1268RR x PI 594858A, and R07-10231 x PI 235335. F2 Generation: PI 567635 x R01-976. F1 generation: PI 506647 x R05-3239, PI 567381B x Osage, and PI 567635 x UA 5612.
In addition, 41 new lines were selected from sudden death syndrone crosses (12 from 5002T x PI 417050, 12 from 5002T x PI 417479, and 16 from R03-984 x PI 417050). These lines are being evaluated for yield and PSD in Stuttgart, AR.
In Illinois, hand pollinations were made in the greenhouse to cross elite Midwestern lines with the PSD-resistant accessions PI 209908, PI 279088, and PI 360841. Although only a low percentage of those were successful, a few pods with putative F1 seeds have been found. Additional crosses will be made in the field in Urbana this summer. PSD-resistant accessions from maturity groups (MGs) II through IV have been planted outdoors, and PIs from higher MGs have been or will soon be planted in the greenhouse for this purpose. Putative F1 seeds that should have PSD resistance will be planted to the extent that this is possible.