The effect of hybridisation on seed vigour of continental and Mediterranean tall fescue (Festuca arundinacea Schreb.) crosses : A dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Science with Honours [Lincoln University]

Abstract

Continental and Mediterranean tall fescue (Festuca arundinacea Schreber) crosses were transplanted in August 2005 after parent plants were covered with pollen-proof sacs. As part of a larger programme run by AgResearch Lincoln, representative seed heads were hand harvested in January and February 2006. There were 20 continental x Mediterranean crosses, 20 Mediterranean x continental crosses and 7 control lines (4 continental lines and 3 Mediterranean lines). In March 2006, 9 lines of each cross plus the 7 control lines were selected based on strong growth. Seed was hand threshed and blown at 2 settings; working seed samples were obtained and scored for the fungus ergot (Claviceps purpurea (Fr.) Tul.). Seed was subjected to standard germination testing and accelerated ageing.

The ability to germinate depended on continental and Mediterranean parental lines. There were differences in germination among and within lines. Germination of hybrids was reduced by the presence of ergot and low seed weight. Ergot reduced seed weight and the amount of pure seed that could be selected for germination testing. Generally, as ergot increased, seed weight and germination decreased. Seed weight of 5 seed heads of continental x Mediterranean lines was 0.31 to 1.76g and was 0.22 to 1.18g in Mediterranean x continental tall fescue lines. Seed weight of control lines was 0.73 to 2.77g.

There was a positive relationship between seed weight and germination, especially in continental x Mediterranean tall fescue crosses (r² = 0.644: p < 0.01). The relationship was not as strong in Mediterranean x continental tall fescue crosses (r² = 0.277: p < 0.01). Germination was 0 to 44.5% for continental x Mediterranean hybrids and 0 to 34.7% for Mediterranean x continental hybrids.

Seed vigour was measured by accelerated ageing. Germination after accelerated ageing was 2.6 to 91.2% for continental x Mediterranean hybrids and 2.8 to 12.2% for Mediterranean x Continental hybrids. Although higher than the standard germination results, this was because missing plants or plants that failed to germinate were not subjected to accelerated ageing. Therefore only seed of high performing lines was subjected to accelerated ageing.

Some lines with high ergot, and low seed weight and germination exhibited strong winter/early spring growth. Visual assessment of morphological characteristics showed these lines were intermediate between the parental lines. It is possible that these plants were hybrids between continental and Mediterranean tall fescue. Lines with low ergot and high seed weight and germination were unlikely to be hybrids.