New Zealand Journal of Botany abstracts

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Limiting factors of reproductive success in Bromus auleticus (Poaceae). 2. Fruit set under different pollination regimes, pollen viability, and incompatibility reactions

Hugo F. Gutiérrez

Cátedra de Botánica Sistemática Agronómica
Facultad de Ciencias Agrarias
Universidad Nacional del Litoral (UNL)
Luis Kreder 2805
(3080) Esperanza, provincia de Santa Fe, Argentina
hgutierr@fca.unl.edu.ar

Diego Medan

Cátedra de Botánica Agrícola
Facultad de Agronomía UBA
Av. San Martín 4453
(1417) Buenos Aires, Argentina

José F. Pensiero

Cátedra de Botánica Sistemática Agronómica
Facultad de Ciencias Agrarias
Universidad Nacional del Litoral (UNL)
Luis Kreder 2805
(3080) Esperanza, provincia de Santa Fe, Argentina

Abstract  Several aspects related to the reproductive biology of the valuable Argentinian native forage grass Bromus auleticus were studied in three populations to identify its reproductive system and the factors that limit its reproductive success. In vitro pollen fertility and germinability were measured, and the behaviour of pollen tubes under self-pollination was compared with that of cross-pollen. Fruit set under different pollination conditions was also determined. Pollen amount and pollen fertility do not per se limit fruit set, and pollen fertility was not impaired by bagging; however, in vitro pollen germination was low (22.5%) which may limit reproduction. The differential behaviour of pollen tubes under selfing and crossing, as well as the high pollen:ovule ratio, indicate allogamy. Substantial fruit set (38.3%) occurred only when stigmas received nonself pollen in adequate amounts. Treatments providing only self- or no pollination drastically reduced or suppressed fruit set, which suggests lack of apomixis and, at the same time, the operation of a self-incompatibility mechanism. The limited reproductive success of a natural population of this species may be the consequence of self-incompatibility coupled with reduced genetic variation for incompatibility alleles.

Keywords  reproductive success; fruit set; Bromus auleticus; Poaceae; self-incompatibility

B05032; Received 25 July 2005; accepted 6 January 2006; Online publication date 2 March 2006
New Zealand Journal of Botany, 2006, Vol. 44: 57–63
0028–825X/06/4401–0057 © The Royal Society of New Zealand 2006

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