Pollination behaviour among different breeding populations of Egyptian clover

Abstract

Pollination behaviour and the extent of self-compatibility were studied in Trifolium alexandrinum, commonly known as Berseem or Egyptian clover, an important fodder legume cultivated in Egypt, the Mediterranean basin and the Indian subcontinent. Four treatments were imposed on 16 populations comprising three diploid exotic, three diploid advanced breeding, five induced tetraploid and five diploid pentafoliate lines. The different treatments were open pollination, caging, hand tripping and controlled bee visits. Compared with the open pollinated condition, reduction in seed set in different populations ranged from 12.3 to 99.2% under caged condition. Eight of 16 populations registered more than 90% reduction in seed set. Hand tripping and/or controlled bee visits improved seed set considerably in a few populations, whereas, in one population, no significant effect of these four treatments was observed. The results indicated considerable variation for self-compatibility, together with a requirement of tripping for pollination and seed set, even in self-compatible lines.The genus Trifolium comprises approximately 290 species. While T. repens, T. pratense, T. nigrescens, etc. are important constituents of temperate pastures, T. alexandrinum and T. resupinatum are cultivated as winter annual fodder in the tropical and sub-tropical belt. Trifolium alexandrinum, commonly known as Berseem or Egyptian clover is an important winter annual fodder legume cultivated in Egypt, the Mediterranean basin and the Indian subcontinent.For an effective genetic improvement programme, it is imperative to have an adequate knowledge of the breeding system. Identification of self-compatible populations and the development of inbreds is likely to expose the hidden variability among populations of Berseem. The breeding method entails the development of inbreds and the production of hybrid seed. The advantage of this method in an allogamous species is to increase homozygosity, select for traits with additive heritability and identify the plants which are tolerant of selfing (Busbice 1968, Rotili 1993. Controversy exists about the pollination mechanism and compatibility, hence, the present study was undertaken to estimate the extent of selfcompatibility among different populations of Berseem (Egyptian clover) based on seed set per inflorescence under different treatments. Materials and MethodsPlant materials: Sixteen populations of Egyptian clover, Trifolium alexandrinum L., comprising three diploid exotic, three diploid advanced breeding, five induced tetraploid and five diploid pentafoliate (usually T. alexandrinum has trifoliate nature) populations were selected for the present study. These populations represent diverse origins, distinct morphological traits and two different ploidy levels (Table 1). Fifteen populations represented the ÔMescaviÕ and one exotic population represented the ÔSaidiÕ ecotype. The crop was sown in the month of October in 3 m rows spaced at 50 cm and with a plantto-plant distance of 15 cm. The different treatments ...

Overexpression of HARDY, an AP2/ERF gene from Arabidopsis, improves drought and salt tolerance by reducing transpiration and sodium uptake in transgenic Trifolium alexandrinum L.

“…T. alexandrinum is largely self-incompatible and more than 90% cross-pollinated (Frankel and Galun 1977;Roy et al 2005). In our study, the reduced fertility and seedling vigour could have resulted from the limited efficiency of hand tripping in achieving self-pollination and/or genetic barriers (Roy et al 2005) in addition to inbreeding depression (Hallauer and Miranda 1981). However, variation in fertility and seedling vigour indicates variability in self-compatibility and tolerance of T. alexandrinum to inbreeding depression.…”

“…Because T. alexandrinum is predominantly self-incompatible, hand tripping of the flower heads was performed every 2 days to improve seed set (Roy et al 2005). The seeds (T1) were collected from each plant separately and stored in paper bags for 2 months.…”

Interspecific compatibility barriers, development of interspecific hybrids through embryo rescue and lineage ofTrifolium alexandrinum(Egyptian clover)—important tropical forage legume

“…This can be attributed to the climatic conditions. T. alexandrinum populations also exhibit a range of genotypes from self‐incompatible to self‐compatible (Roy et al., ). Although information on allelic control of self‐incompatibility is not available in T. alexandrinum , Lawrence () concluded the presence of 100 to 200 alleles for self‐incompatibility in T. repens and T. pratense and 17 alleles that in T. hybridum .…”

Fast versatile regeneration of Trifolium alexandrinum L.

“…It is grown in the winter for forage in the Mediterranean basin, the Indian subcontinent, central Asia and parts of the United States (Knight 1985;Roy et al 2005). In Egypt, it is the only forage crop grown during the winter.…”