One hundred and sixty accessions representing global germplasm of guinea grass (Panicum maximum Jacq.), an important apomictic (aposporous) fodder crop, were subjected to study on reproductive diversity in apomictic seed development utilizing ovule clearing and Xow cytometric seed screen (FCSS). Single seed FCSS of selected 14 tetraploid and Wve hexaploid lines demonstrated uncoupling between the three apomixis components, viz. apomeiosis, parthenogenesis and functional endosperm development, in natural as well as experimental populations, though it diVered across ploidy levels and genotypes. Reconstruction of reproductive pathways yielded a total of eight diVerent pathways of seed development, arising by uncoupling/recombination between apomixis components. Amongst these, two pathways involving modiWcations in embryo-sac (ES) (presence of two polar nuclei in aposporous ES that fuse prior to fertilization) and fertilization process (fusion of only one polar nucleus in a sexual ES) have been reported for the Wrst time. Some of the combinations, such as M I (haploids arising from parthenogenetic development of reduced egg cell), were found viable only in hexaploid background.Germplasm lines with higher expression of individual components were also identiWed. These components (including autonomous endosperm development) were also experimentally partitioned in hexaploid progenies (derived from a tetraploid parent viz. accession IG 04-164) that showed segregation in their reproductive capacities, and are reported for the Wrst time. Occurrence of several apomixis recombinants (phenotypic) in guinea grass lines suggested their hybrid origin, favors a multigene model for apomixis, with their penetrance aVected by modiWers and epigenetic mechanisms, in contrast to earlier reports of single locus control. Implications of partitioning components on apomixis research are discussed.

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SummaryThe Egyptian clover or berseem (Trifolium alexandrinum L.) is widely cultivated as a winter season forage crop in about two million hectare of land in India. It is widely accepted because of its multicut nature, high yield and nutritional value. A plausible approach for increasing yield could be through increasing photosynthetically active leaf area and consequently the biomass. The present investigation deals with induction of polyploidy and evaluation of tetraploids vis-à-vis diploids lines of Egyptian clover for multifoliate leaf formation. Immersing of pre-hydrated seeds, from diploid multifoliate plants, in colchicine followed with seedlings immersed in 0.1 and 0.2% colchicine solution for 24 and 48 h, respectively, was effective in inducing tetraploidy. Distinct characteristic features observed among induced pentafoliate tetraploid plants were presence of serrate leaflet margin, prominent rachis and bold seeds. Leaves were thick, succulent, and hairy with apical notch characterized by presence of pigmentation on the outer margin. The autotetraploids had better expression of pentafoliate trait than in diploid plants.Key words Colchicine, Multifoliate, Pentafoliate, Polyploidy, Tetraploid, T. alexandrinum, Egyptian clover, Fodder.The Egyptian clover or berseem (Trifolium alexandrinum L.) is a diploid species (2n=16) commonly cultivated as a winter annual fodder crop in tropical and subtropical countries. It is cultivated as a winter season forage crop in about two million hectare of land in India. It is widely accepted because of its multicut nature, high yield and nutritional value. In the past, efforts have been made to induce genetic variability through mutation, polyploidization and selection but the results were not very encouraging. A plausible approach for increasing yield could be through increasing photosynthetic area, i.e. leaf area, which will help in increasing the photosynthetically active leaf area and consequently the biomass yield. The number of leaves per plant and leaflets per leaf in the Egyptian clover contribute to higher leaf-stem ratio (Bakheit 1996). Cultivars of Egyptian clover possess trifoliate leaves in general. However, occasional occurrence of multifoliate plants in natural population is reported (Shukla and Malaviya 1986). The frequency of multifoliate plants in the natural population of berseem was 0.004% only. Such multifoliate plants possessed only 1 to 2% multifoliate leaves. Likewise, white clover occasionally produces a leaf with four (or more) leaflets. The genetics underlying this phenomenon has been partly worked out (Tashiro et al. 2010). One such reference to multifoliolate leaves in white clover (Trifolium repens L.) is in the registration of FL-ML white clover germplasm (Baltensperger et al. 1991). Knight (1969) in Trifolium incarnatum and Jaranowski and Broda (1978) in Trifolium pratense also reported multifoliate leaf formation. However, there is no report of developing pure pentafoliate in any

Background The genus Trifolium is characterized by typical trifoliolate leaves. Alterations in leaf formats from trifoliolate to multifoliolate, i.e., individual plants bearing trifoliolate, quadrifoliolate, pentafoliolate or more leaflets, were previously reported among many species of the genus. The study is an attempt to develop pure pentafoliolate plants of T. alexandrinum and to understand its genetic control. Methods The experimental material consisted of two populations of T. alexandrinum with multifoliolate leaf expression, i.e.,interspecific hybrid progenies of T. alexandrinum with T. apertum, and T. alexandrinum genotype Penta-1. Penetrance of the multifoliolate trait was observed among multifoliolate and trifoliolate plant progenies. In vitro culture and regeneration of plantlets from the axillary buds from different plant sources was also attempted. Results The inheritance among a large number of plant progenies together with in vitro micro-propagation results did not establish a definite pattern. The multifoliolate leaf formation was of chimeric nature, i.e., more than one leaf format appearing on individual branches. Reversal to normal trifoliolate from multifoliolate was also quite common. Penetrance and expression of multifoliolate leaf formation was higher among the plants raised from multifoliolate plants. Multifoliolate and pure pentafoliolate plants were observed in the progenies of pure trifoliolate plants and vice-versa. There was an apparent increase in the pentafoliolate leaf formation frequency over the years due to targeted selection. A few progenies of the complete pentafoliolate plants in the first year were true breeding in the second year. Frequency of plantlets with multifoliolate leaf formation was also higher in in vitro axillary bud multiplication when the explant bud was excised from the multifoliolate leaf node. Conclusion Number of leaflets being a discrete variable, occurrence of multifoliolate leaves on individual branches, reversal of leaf formats on branches and developing true breeding pentafoliolates were the factors leading to a hypothesis beyond normal Mendelian inheritance. Transposable elements (TEs) involved in leaf development in combination with epigenetics were probably responsible for alterations in the expression of leaflet number. Putative TE’s movement owing to chromosomal rearrangements possibly resulted in homozygous pentafoliolate trait with evolutionary significance. The hypothesis provides a new insight into understanding the genetic control of this trait in T. alexandrinum and may also be useful in other Trifolium species where such observations are reported.

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