Physical Sciences and Mathematics Commons^™

Advances In Breeding Apomictic Brachiaria In Tropical America, J W. Miles, C B. Do Valle

IGC Proceedings (1997-2023)

Prior to 1988 Brachiaria improvement was based exclusively on the collection, introduction, and evaluation of natural germplasm from Africa. Breeding programs in Brachiaria have been possible only in the past 10 years with the creation of a sexual, tetraploid B. ruziziensis cross-compatible with B. decumbens and B. brizantha. Applied Brachiaria breeding projects are underway both in Colombia (International Center for Tropical Agriculture, CIAT) and Brazil (National Centre for Beef Cattle Research - Brazilian Corporation for Agricultural Research, CNPGC/EMBRAPA). These seek to combine the broad edaphic adaptation and other desirable agronomic attributes of B. decumbens cv. Basilisk with spittlebug resistance. An …

Apomixis And The Reproductive Dynamics Of Eastern Gamagrass Tripsacum Dactyloides L., B Kindiger, C L. Dewald

IGC Proceedings (1997-2023)

Studies were conducted to determine the reproductive characteristics of Tripsacum, a perennial, native pasture species and to identify methods for breeding agronomically superior cultivars. Reproductive methods and types of individuals generated were evaluated with triploid and hexaploids possessing a novel method for transferring sexual germplasm into apomictic tetraploids and tetraploid germplasm into sexual diploids. Triploids and hexaploids are demonstrated to be useful materials for introgressing and transferring desirable alleles across ploidy levels and reproductive barriers.

Selection Of Interspecific Hybrids Of Brachiaria-A Tropical Forage Grass, C B. Do Valle

IGC Proceedings (1997-2023)

The aim of the breeding program at the National Beef Cattle Research Center (CNPGC) of the Brazilian Corporation for Agricultural Research (EMBRAPA), is to produce vigorous apomictic hybrids with wide edaphic adaptation, good production and nutritive value combined with spittlebug (Homoptera:Cercopidea) resistance. Fiftysix superior hybrids were selected based on visual estimates of vigor, leafiness, tolerance to drought and natural spittlebug infestation in the field. These were characterized for mode of reproduction, spittlebug reaction under controlled conditions and for morphological diversity using nine selected traits. Multivariate analysis classified the population into seven groups where the hybrids were clearly intermediate in plant …

Phylogenetics Of Apomictic Common Dallisgrass (Paspalum Dilatatum), B L. Burson, M A. Hussey

IGC Proceedings (1997-2023)

Common dallisgrass, Paspalum dilatatum Poir., an important warm season forage grass, is an obligate apomict with 50 chromosomes which associate as 20 bivalents and 10 univalents during meiosis. Because efforts to improve the grass have not been successful, a phylogenetic investigation was initiated to identify the progenitors of common dallisgrass in an effort to circumvent the apomictic barrier to improvement. The genomic composition has been determined for four dallisgrass biotypes: yellow-anthered (2n=4x=40) IIJJ; common (2n=5x=50) IIJJX; Uruguayan (2n=6x=60) IIJJXX; and Uruguaiana (2n=6x=60) IIJJXX. While the source of the X genome is unknown, the genes controlling apomixis are on at least …

Fitness Of Apomictic And Sexual Buffelgrass Germplasm, M A. Hussey, Yue-Wen Wang, B L. Burson

IGC Proceedings (1997-2023)

Breeding apomictic grasses is based on either the direct selection of apomictic landraces or the hybridization of sexual and apomictic types and selection of apomictic F1 hybrids. Little is known about the potential of sexual hybrids as cultivars in apomictic species. To determine if method of reproduction (MOR) was related to plant vigor, parental, S1, and F1 hybrids of buffelgrass differing in method of reproduction (apomictic or sexual) were established in a common garden in 1994 and 1995. In both years severe inbreeding depression was observed in the S1 progeny as they were shorter, produced less biomass, and had low …

Preliminary Performance Of Panicum Maximum Accessions And Hybrids In Brazil, Liana Jank, Rosangela M. S. Resende, S. Calixto, M. M. Gontijo Neto, V. A. Laura, Manuel C. M. Macedo, Cacilda B. Do Valle

IGC Proceedings (1997-2023)

Due to the lack of high quality forages adapted to the distinct ecosystems in Brazil, a national network to evaluate 14 accessions, 4 hybrids and 5 commercial standards of Panicum maximum was established in 2002, in 5 regions of Brazil (states of Mato Grosso do Sul, Acre, Rondônia, Minas Gerais and in the Federal District). Staff of the Embrapa Beef Cattle group co-ordinated the network and pre-selected the accessions and hybrids (Jank, 1995; Jank et al., 2001; Resende et al., 2004). We present their performance as to leaf dry matter yield (LDMY) and leaf percentage (LP) obtained from …

Development Of Simple Sequence Repeat (Ssr) Markers And Their Use To Assess Genetic Diversity In Apomictic Guineagrass (Panicum Maximum Jacq.), M. Ebina, Kaori Kouki, S. Tsuruta, M. Takahara, M. Kobayashi, T. Yamamoto, K. Nakajima, H. Nakagawa

IGC Proceedings (1997-2023)

Guineagrass is an important and widely grown tropical forage grass. Despite its importance and increasing popularity, only little is known about its genetic diversity (Ebina et al., 2001). Such information is useful for the selection of diverse parents in breeding programmes. Moreover, no simple sequence repeat (SSR) markers have been reported in any apomixis species. In this study SSR markers were developed and used to investigate genetic diversity in germplasm of apomictic guineagrass.

Grass And Forage Plant Improvement In The Tropics And Sub-Tropics, Liana Jank, C. B. Do Valle, Rosangela M. S. Resende

IGC Proceedings (1997-2023)

1. The majority of tropical and subtropical forage grass genera and/or species have not yet been collected, or need further collection to be representative of their natural distribution.
2. New biotechnological techniques will only result in the release of superior forage cultivars if supported by strong breeding programs.
3. More funding and investment in the formation of strong public research teams in forage conservation and improvement are needed to guarantee the sustainability of tropical and subtropical pasture-based livestock systems in the future.
4. The creation of a permanent international working group on tropical and subtropical forages is essential to assist the International Plant Genetic …

Grass And Forage Plant Improvement In The Tropics And Sub-Tropics, Liana Jank, Cacilda B. Do Valle, Rosangela M. S. Resende

IGC Proceedings (1997-2023)

Key points

1. The majority of tropical and subtropical forage grass genera and/or species have not yet been collected, or need further collection to be representative of their natural distribution.

2. New biotechnological techniques will only result in the release of superior forage cultivars if supported by strong breeding programs.

3. More funding and investment in the formation of strong public research teams in forage conservation and improvement are needed to guarantee the sustainability of tropical and subtropical pasture-based livestock systems in the future.

4. The creation of a permanent international working group on tropical and subtropical forages is essential …

Evaluation Of Guineagrass (Panicum Maximum Jacq) Hybrids In Brazil, Liana Jank, Cacilda B. Do Valle, J. De Carvalho, S. Calixto

IGC Proceedings (1997-2023)

Guineagrass (Panicum maximum Jacq.) is responsible for a high percentage of cattle finishing and milk production in Brazil, but presents problems of pasture degradability due to high soil fertility requirements and uneven production distribution. In order to search for new varieties to reduce these problems, over four hundred apomictic accessions of guineagrass and several sexual plants were introduced to Brazil in 1982. Agronomic evaluation took place at the National Beef Cattle Research Center of the Brazilian Agricultural Research Corporation (Embrapa Beef Cattle), in Campo Grande, MS, Brazil. Breeding of the apomictic species began in 1990 using sexual x apomictic …

Breeding Perennial Warm-Season Grasses For The Subtropical Belt In South America, Carlos A. Acuña

IGC Proceedings (1997-2023)

Perennial warm-season grasses share several agronomic characteristics, such as marked seasonal growth, cold susceptibility and photoperiod sensitivity. Breeding efforts in South America have been focused on attempting to improved cool-season growth, cold tolerance and also adaptation to the alternation of flooding and drought periods. Warm-season grasses also have in common that most of them are polyploid and some have very low fertility. Apomixis is also a common trait among these species. For polyploid species with limited seed yield, which commonly have stolons or rhizomes, F₁ hybrids are created and released as cultivars. Acroceras macrum and Hemarthria altissima will be …

Genetic Control Of Parthenogenesis In Kentucky Bluegrass: Results From A Sexual X Apomictic Cross, E. Albertini, G. Barcaccia, A. Porceddu, D. Rosellini, Mario Falcinelli

IGC Proceedings (1997-2023)

Apomixis, as it exists in Poa pratensis L., permits to combine genotype fixation with propagation by seed. The process of apomictic seed production involves the formation of embryo sacs without meiotic reduction (apospory) and embryos without egg cell fertilization (parthenogenesis). Further information on the genetic control of apomixis was obtained by analyzing aposporous parthenogenesis and the segregation of molecular markers in a progeny resulting from a “sexual” (S) x “apomictic”(A) cross. Data from the 35 F₁ plants examined so far have shown that parthenogenesis segregated 1:1, confirming control by a dominant gene, simplex in the parthenogenetic parent. Analysis of …

Preliminary Evaluation Of Brachiaria Humidicola Hybrids, Cacilda B. Valle, G. A. Bitencourt, A. Q. Arce, Lucimara Chiari, Liana Jank, Rosangela M. S. Resende, S. Calixto

IGC Proceedings (1997-2023)

No abstract provided.

Polyploidization Of Sexual Diploid Brachiaria Decumbens For Intraspecific Hybridization, Cacilda B. Valle, C. Simioni, Liana Jank, Rosangela M. S. Resende

IGC Proceedings (1997-2023)

No abstract provided.

Breeding Apomictic Bahiagrass (Paspalum Notatum Flügge) In Southeastern Usa, C. A. Acuña, A. R. Blount, C. L. Mackowiak, K. H. Quesenberry

IGC Proceedings (1997-2023)

No abstract provided.

Down Regulation Of Receptor Like Kinase Gene In Apomictic Cenchrus Ciliaris, Shashi, Anuj Dwivedi, Vishnu Bhat

IGC Proceedings (1997-2023)

Apomixis is a potential technology for agriculture to fix heterosis or hybrid vigor in hybrid plants. Cenchrus ciliaris which is a popular forage crop reproduces predominantly through apomixis and has been used as a model plant to understand genetic and molecular mechanisms controlling apomixis. A partial receptor like kinase gene (CcRLK) was isolated from apomictic C. ciliaris which showed exclusive expression in the embryo sacs of apomictic flowers compared to sexual embryo sacs during in situ hybridization analysis. This gene showed kinase and LRR domains implying its putative role in signaling pathways. In order to understand its …

Transcriptome Analysis Of Differentially Expressed Genes At Pre-Meiotic Developmental Stage In Pennisetum Hybrids With Contrasting Modes Of Reproduction, Krishna Kumar Dwivedi, Auji Radhakrishna, D. R. Malaviya, Ajoy K. Roy, P. Kaushal

IGC Proceedings (1997-2023)

Apomixis is an asexual reproduction through seeds where embryo develops without meiosis and fertilization. It is widely distributed throughout plant kingdom, but is more prevalent in families like Asteraceae, Rosaceae and Poaceae (Carman, 1997). This trait is highly desirable for fixing heterosis in F1 hybrids with significant implications for crop improvement (Dwivedi et al., 2007). Therefore it is necessary to unravel the molecular and genetic basis of apomixis to tap its potential. Pennisetum is an important genus of the Poaceae family which contains a wide range of species exhibiting wide variability in morphological, molecular, and reproductive traits (Jauhar, …

A New Candidate Cultivar Of Brachiaria Grass 'Br-203' Developed With Apomixis Marker Assisted Selection, Through A Collaborative Breeding Activity Of Thailand And Japan, Ganda Nakamanee, Masumi Ebina, Katsuhisa Shimoda, Sarayut Thaikua, Wattanawan Srisomporn, Chalermpon Patipan, Kazuhiro Suenga, Sada Ando, Kaori Kouki, Genki Ishigaki, Ryo Akashi, Yasuhiro Kawamoto

IGC Proceedings (1997-2023)

Brachiaria grass (Brachiaria spp.) is one of most important tropical forage grass which belongs to family Poaceae, subfamily Panicoideae, tribe Paniceae, genus Brachiaria. Brachiaria grass has attracted attention because of a leading ‘Green Revolution’ over tens of millions of hectares in the Central Brazilian Cerrado in the 1970s. Breeding programs for Brachiaria grass have been conducted mainly by the International Center for Tropical Agriculture (CIAT) and the Brazilian Agricultural Research Corporation (EMBRAPA). Careful and effective recurrent selection of tetraploid sexual lines for vigor, growth habit, leafiness, and spittlebug resistance have spawned several successful hybrid cultivars: ‘Mulato’, …

In Vitro Plant Regeneration Via Callus Induction In A Rare Sexual Plant Of Buffelgrass (Cenchrus Ciliaris L.), Suresh Kumar, Neha Sahu, Archana Singh

IGC Proceedings (1997-2023)

Buffelgrass (Cenchrus ciliaris L.) is one of the most important perennial forage grasses of the world. It is a polyploid forage grass suited to pastures, range-lands, tropics and sub-tropics of Australia, South Africa, and India. It reproduces predominantly through apomixis which provides a means of clonal propagation through seeds. In many of the plants apomixis shows dominance over sexuality, hence occurrence of obligate sexual plant in natural population is rare and over the time apomictic individuals outnumber sexuals. Being protogynous in nature, cross pollination from neighbouring apomictic plants leads to the production of either facultative or obligate apomictic genotypes. …

Scar Markers Linked With Mode Of Reproduction In Eight Cenchrus Species, Suresh Kumar, Sheena Saxena, M. G. Gupta

IGC Proceedings (1997-2023)

The genus Cenchrus comprises of forage grasses of tropical and sub-tropical regions. Some of the Cenchrus species were introduced into India from Australia, Africa and they are now important component of Dichanthium-Cenchrus-Lasiurus grasslands of India. Eight Cenchrus spp. are available in India but only four (C. ciliaris, C. glaucus, C. pennisetiformis and C. setigerus) species are used in sown pastures. The remaining four (C. biflorus, C. preiurii C. echinatus and C. myosuroides) species are grown in limited pockets and maintained as genetic resources for basic and applied studies (Chandra and Dubey, 2010). Number of Cenchrus species …

Status And Role Of Antioxidant Enzymes In Sexual And Apomictic Species Of Boechera, Manoj Kumar Srivastava, Mayelyn Mateo De Arias, David A. Sherwood, John G. Carman

IGC Proceedings (1997-2023)

Enzymatic and non-enzymatic antioxidation systems provide protection against the toxic effects of activated oxygen species including scavenging H₂O₂. It is evident that during stress plants produce different ROS which play a negative role in regulating the antioxidant system and a positive role in signaling events that regulate ion channel activity and gene expression Microarray data indicate that ovules and pistils from apomictic Boechera differ in gene expression from those of sexual Boechera. Specifically, these differences involve genes responsible for stress response, RNA processing, ribosome synthesis and function, photosynthesis and cell cycle regulation. Thus, in the …

Seasonal Expression Of Apospory In Bahiagrass, Esteban F. Rios, Ann R. Blount, Kevin E. Kenworthy, Carlos A. Acuña, Kenneth H. Quesenberry

IGC Proceedings (1997-2023)

Flowering plants can reproduce sexually (outcrossing and/or selfing) and/or asexually. Sexual reproduction implies the successful completion of meiosis and double fertilisation for the formation of both the embryo and the endosperm. In contrast, gametophytic apomixis is an asexual mode of reproduction through seeds that involves parthenogenetic embryo development from a cytologically unreduced egg cell (2n). Apospory is the process by which unreduced gametophytes are formed after a series of mitotic divisions of somatic cells (2n) in the ovary. This occurs independently from the sexual meiotic process; and therefore, both sexual and apomictic pathways may coexist simultaneously. Apospory is inherited in …

Breeding Strategies For Brachiaria Spp. To Improve Productivity–An Ongoing Project, Geovani F. Alves, Ulisses J. De Figueiredo, Antônio D. Pandolfi Filho, Sanzio C. L. Barrios, Cacilda B. Valle

IGC Proceedings (1997-2023)

Two strategies have been used in the breeding of Brachiaria (syn. Urochloa) to produce new cultivars. The first involves exploring the natural variability existing in nature, which is the selection of ecotypes, mostly apomicts, from the diversity in germplasm banks. This strategy proved efficient originally and the cultivars in use in Brazil were derived in this way, but progress with this strategy is limited in the medium to long term.

Agronomic Evaluation Of 324 Intraspecific Hybrids Of Brachiaria Decumbens In Brazil, Rogério G. Mateus, Sanzio C. L. Barrios, Ulisses J. De Figueiredo, Cacilda B. Valle

IGC Proceedings (1997-2023)

Brachiaria decumbens cv. Basilisk is the most planted pasture grass in the tropics owing to its adaptation to poor and acid soils, typical of the tropics, plus good animal performance. This cultivar was responsible for a radical change of scenario in central Brazil in the early 1970s and is the only cultivar available commercially. Efforts to breed this species have been recent, as the successful somatic chromosome duplication of sexually reproducing diploid plants of B. decumbens was accomplished only in 2009 (Simioni and Valle 2009). Subsequently, intraspecific crosses with natural apomictic tetraploid accessions were carried out. Breeding is needed since …

Agronomic And Nutritional Evaluation Of Intraspecific Crosses In Brachiaria Decumbens, Simony A. Mendonça, Sanzio C. L. Barrios, Ulisses J. De Figueiredo, Geovani F. Alves, Cacilda B. Valle

IGC Proceedings (1997-2023)

Brachiaria decumbens cv. Basilisk is the single most important forage grass used for pastures in the tropics. This cultivar has exceptional adaptation to acid soils, vigorous growth, ease of establishment, and good forage value throughout the year, but these favourable characteristics are counteracted by its susceptibility to insect pests such as spittlebug. Breeding to produce improved cultivars within this species was impossible until 2009 due to the lack of compatible sexual ecotypes. With the success of somatic chromosome duplication of sexually reproducing diploid plants of B. decumbens (Simioni and Valle 2009), intraspecific crosses with natural apomictic tetraploid accessions were finally …

Reciprocal Recurrent Selection In The Breeding Of Brachiaria Decumbens, Sanzio C. L. Barrios, Cacilda B. Valle, Geovani F. Alves, Rosangela M. Simeão, Liana Jank

IGC Proceedings (1997-2023)

Pastures of Brachiaria decumbens cv. Basilisk radically changed the scenario of livestock production in central Brazil in the early 1970s and in fact, promoted the development of this vast region. However, despite the reasonable biomass yields and nutritional value when grown on these tropical acid soils, its susceptibility to grassland spittlebugs has limited its use. The breeding of B. decumbens in Brazil has been restricted to interspecific crosses using cv. Basilisk as a pollen donor due to the lack of compatible sexual ecotypes within this species. Recently, the successful chromosome duplication of a sexually reproducing diploid accession produced 3 successful …

Genomic Approaches For Dissecting Complex Traits Related To Quality Production Of Range Grasses, Masumi Ebina

IGC Proceedings (1997-2023)

Tropical grasses have been widely used as warm-season forage grasses in the warm temperate zone since the early 20th century because of their high yields; they have also been used as perennial forages in their native tropical areas. Increasing demand for animal production sparked by economic development in tropical countries is requiring breeders to improve native forage grasses in these countries. Considerable efforts have been made to breed accessions with improved characteristics and to develop new cultivars. However, cross-breeding is not common, owing to a lack of genetic information and to complexities related to polyploidy, high sterility rates, outcrossing, and …