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Oat is an important fodder crop high in lysine rich protein. Various species differ in their morphological, physiological and growth attributes. Knowledge of the inheritance of the qualitative characters help the plant breeder to increase the efficiency of selection. The present study was done to identify the introgression of morphological traits from tetraploid wild species in amphiploid progenies of A. sativa x A. maroccana inA14 to A16 generations and to isolate the progenies with introgressed traits from wild progenitor to cultivated A. sativa.

The objectives of the present study were to analyze the impact of A. maroccana genome in increasing the forage production and related traits when introgressed in the background of A sativa and to estimate the extent and range of genetic diversity and character association and to isolate the progenies with introgressed traits from wild progenitors to the cultivated background in A14 – A16 generations.

Oat protein is nearly equivalent to the quality of soy protein, as has been shown by the World Health Organization it is equal to meat, milk and egg protein (Ahmad et. al. 2013). To increase the productivity per unit area there is a need to develop varieties having higher crop yield potential and quality (Ahmad et. al., 2020). The genus Avena incorporates diploid tetraploid and hexaploid species with a basic chromosome number of n=7. The restricted germplasm base of cultivated hexaploid oat (A. sativa L. 2n = 6x = 42) has been a limiting factor in the improvement programme (Choubey et al 1996). The use of wild relatives like A. maroccana (A wild progenitor of cultivated oat) is recommended to enrich the cultivated oat as it is an important source of certain desirable traits such as high protein (up to 30%) content, high tillering ability and resistance to various biotic and abiotic stress situations.

The interspecific hybridization followed by backcrossing to recurrent parent has been a potent tool for transferring the desirable traits from wild to cultivated species without affecting the general agronomic features of the later. Interspecific hybridization has been aptly used in the genus Avena which constitutes cultivated hexaploid (2n = 6x = 42) and a wide array of wild species at diploid, tetraploid and hexaploid levels.

The objectives of the present study were to analyze the impact of A. maroccana genome in increasing the forage production and related traits when introgressed in the background of A sativa and to estimate the extent and range of genetic diversity and character association and to isolate the progenies with introgressed traits from wild progenitors to the cultivated background in A₁₄ – A₁₆ generations.

The material of the present study comprised of A14 amphiploid A sativa L. (UPO 94) X A maroccana Gdgr. The original cross was attempted in the Oat Improvement Programme of IGFRI way back (Choubey et al 1985). The fertility of sterile pentaploid hybrid was restored through chromosome duplication giving rise to fertile decaploid (2n=10x=70) hybrids. Over the generations of selfing, there has been a progressive loss of chromosomes and various lines have stabilized at hexaploid levels (2n=6x=42) of the female plant incorporating various morphologically visible characters from the pollen parent also.

The observations for non-metric qualitative characters were recorded and analyzed in 91 plants per generation for nine traits viz leaf colour, panicle size, glume size, lemma colour, lemma pubescence, frequency and type of awns, spikelet separation and caryopsis shape for three successive generations (A₁₄, A₁₅, A₁₆).

A. sativa (UPO 94)

Single plant selection from American material having erect growth, tall stature, medium tillering, semi-erect green foliage, panicle long with large number of spikelets, lemma creamish non-hairy and awnless, mid-long and mid plump seeds.

A. maroccana

Short stature, profused tillering and prostrate growth habit but becomes semi-erect at flowering, dark-green leaves, dropping with hairy margins and pubescent leaf sheath, spikelets less in number/panicle, very hairy lemma with greyish brown colour and strong twisted double awns seeds long and plump.

Often wild species are a valuable source of useful traits for broadening the genetic base of the cultivated ones (Kumar and Gupta,2019, Singh et.al.2013, Singh et.al.,2017). The genetic distinctness between crossed species often prevents the formation of desired hybrids but also enables obtaining superior genotypes with traits exceeding the parental forms (Koroluk et al 2020).

Table 1: Variation of qualitative characters in amphiploid progenies (A₁₄, A₁₅ and A₁₆) generations

The data on various qualitative traits such as panicle size, leaf colour, glume size, floret per spikelet, spikelet separation, lemma hairiness, basal lemma hairs etc. indicates introgression of traits from wild to the cultivated background.

The large size of panicle along with dark-green leaves and large glume size, semi abscission and abscission type of floret separation lemma hairiness indicate that these traits have been incorporated from wild parent A. maroccana to the cultivated background of A. sativa. Distribution of awns reveals the predominance of wild character (strong twisted double awns) over the cultivated ones (awnless or single weak awn) as nearly one-third of the progenies studied indicate strong awns.

The presence of A. maroccana characters like strong awns, lemma colour, pubescence and high tillering potential in progenies indicate that introgression of genes from A. maroccana to A. sativa has not only taken place but also have established over the generations. Such observations for morphological traits were also reported by Ladizinsky and Feinstein (1977), Thomas et. al. (1980), and Premchandran et.al. (1988). But these studies were carried out at very earlier generations mostly up to F2 or F3 in contrast to the present study which is carried out in a highly advanced generation. The finding, therefore, confirms that these traits are not only transferable but also could be stabilized in the progenies. Data on various qualitative traits were recorded in all three generations of study. The results were compared with the parents.

The study indicates the introgression of traits from wild tetraploid parent to cultivated female (hexaploid) some of which were also reported to be continuing in the following generations. Many progenies were marked for having large-sized panicles and glume along with dark green leaves, semi-abscission and abscission type of floret separation and lemma hairiness. This indicated that these traits have been incorporated from wild parent A. maroccana to the cultivated background of A. sativa and are governed by different sets of genes as segregation of characters was observed over the generations. The genetic inheritance of different morphological traits is essential for selection of superior desirable transgressive segregants for genetic improvement.

A. sativa parent used in this hybridization programme was having medium size glume, fructure type of floret separation, medium awn with absence of lemma and basal lemma hairs. In comparison to this, the wild parent A. maroccana (pollen parent) had large glume size, abscission type of floret separation, dark green leaves and dense hairs on the lemma and base of the floret, brown lemma colour, two strong twisted black awns. About one-third of the progenies were noticed for having wild characters (strong black twisted double awns) over the cultivated ones. Similar findings for some of these traits have also been reported by several earlier workers. However, earlier studies were carried out in early generations i.e., F2 or F3 (Ladizinsky 1974) The present study indicates that these traits are stable in the progenies even up to A16 generation.

Some of the marked qualitative traits of the wild pollen parent were predominant in the progenies. About one-third of the progenies show large panicle size in all three generations. The distribution of progenies with large sizes of glume was observed to vary from 6.59 to 18.68% progenies in different generations. Abscission type of spikelet separation was observed in 36.26%, 30.76% and 34.06% of progenies in all three generations. Similarly, a large size of lemma was observed in 23.07%, 18.68% and 19.78% of progenies in successive generations. Very dense lemma hair, a typical wild parent character was observed in 14.28%, 17.58% and 15.38% of progenies in A14, A15 and A16 generations respectively. Progenies having sparse hairiness and those without hairs were 27.48% and 37.36% in A15 generation and 37.36 and 35.16 in A16 generation. For basal lemma hair trait, 24.17% of progenies with very dense hair and 23.07% with dense hair were observed in A14 generation. In two subsequent generations, 32.96% and 35.16% with dense hairs and 17.58% and 15.38% progenies with very dense hairs were observed. This pattern of distribution clearly indicates the predominance of wild parent characters (profuse hairs) over cultivated ones.

The cream lemma colour (maternal cultivated trait) was observed in 37.36%, 52.74% and 39.56% progenies in three successive generations. The remaining progenies showed some shades of brownies and blackish lemma.

The double geniculate awn traits, a marked character of wild pollen parent was found in 46.15% 42.85% and 49.45% progenies respectively in the successive generations of which strong and very strong twisted black awns were found in 63.73%, 57.13% and 68.12% progenies in A14, A15 and A16 generations respectively. This again reveals the predominance of wild character over cultivated ones. The number of awns also shows an intermediate character indicating it to be a polygenic trait.

The study indicates that sufficient homology exists among the two species and they are cross-compatible. The findings, therefore, confirm that these traits are not only transferable but also could be stabilized in the progenies.

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