The nonselective nature of a modified single-seed descent breeding procedure

The objectives of this study were to determine (i) if selection for barley yellow dwarf virus (BYDV) tolerance occurred under a modified single-seed descent (MSSD) procedure when used in conjunction with BYDV inoculation, and (ii) if changes in nuclear DNA content occurred during MSSD. Plants from four intraspecific spring oat (Arena sativa L.) crosses were proven in the green/house under a MSSD procedure and were infected with BYDV by inoculation with viruliferous aphids. These populations were compared with populations grown without exposure to BYDV. BYDV tolerance was evaluated in the field in the F(4:5) and F(4:5) generations. Inoculation with BYDV under the MSSD method did not selectively eliminate BYDV susceptible genotypes. To determine if the MSSD procedure induced selection for a particular nucleotype, seeds harvested from the parents (grown under the MSSD procedure) were tested for nuclear DNA content. No difference in DNA content was observed among progeny grown from seeds of stressed plants compared with progeny grown from seeds of nonstressed plants. These results suggest that even the most BYDV susceptible plants produced seeds during MSSD, and the MSSD method does not seem to induce directed changes in nuclear DNA content.