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Abstract Drought and heat stress are two critical threats to crop growth and sustainable agriculture worldwide. In the last decade, many studies focused on the response of crops to a single stress, nevertheless studying the response of plants to a combination stress may be critical to our understanding of stress tolerance in plants and the development of tolerant genotypes. Buffel grass (Cenchrus ciliaris L.) is a warm-season grass known in arid and semiarid regions for its tolerance to heat and drought stress, productivity, and forage quality. However, in our previous works, several accessions have exhibited different responses to abiotic stresses. Therefore, the objective of this work was to evaluate the effects of combination of drought and heat stresses on biochemical parameters and plant growth and to compare the impacts of the stresses separately and when combined. We found that sensitive genotype exhibited higher lipid peroxidation content, lower total reducing power values and reduced catalase and superoxide dismutase activities than tolerant under drought or heat stress or combination stress. In this study, heat stress had a predominant effect on buffel grass genotypes over drought stress, which explained why simultaneous application of heat and drought revealed similar biochemical and growth responses to the heat stress. Antioxidant metabolism seems to be critical for tolerate abiotic stress. This study may provide useful information to perform a rapid and low-cost characterization in new buffel grass germplasm and to identify genotypes with better growth performance under drought and heat conditions. Highlights • Changes in oxidative damage and growth performance were observed between genotypes. • Drought, heat and combined stress enhanced lipid peroxidation in sensitive genotypes. • The sensitivity of genotypes may be related with a decreased activity of CAT and SOD. • Catalase activity in tolerant genotypes appears to play an important role in all stress conditions. • Heat stress had a predominant effect on buffel grass genotypes subjected to combined stress [ABSTRACT FROM AUTHOR]

Abstract: Four somaclonal mutants (S1, S4, S6 and M10) and their parental Cenchrus ciliaris L. cultivar Biloela were characterized under salinity conditions at germination and vegetative growth stages. Seeds of all somaclonal mutants had higher germination percentages than cv. Biloela seeds in the control and salt treatments. At 150mM, germination was significantly higher in M10, S6 and S4 (72.3%, 66.3% and 61.8%, respectively) than in cv. Biloela (35.5%). Mutants grown under salinity along with cv. Biloela for 35days had a different relative growth rate. S6 had the highest growth rate, indicating its potential tolerance to salt stress, whereas M10 was the most sensitive, with Bi, S4 and S1 being intermediate tolerant genotypes. Catalase enzyme activity (CAT) in M10 decreased in response to salt stress and was significantly associated with malondialdehide content, suggesting salt injury, whereas higher levels of CAT activity in S6 during salt stress were associated with increased salinity tolerance. The present results indicate that somaclonal variation and in vitro mutagenesis offer an effective tool for improvement of C. ciliaris because the somaclonal mutants showed differential tolerance to salt stress with respect to their parental and could be a better choice for use in a breeding program. [Copyright &y& Elsevier]

Buffel grass ( Cenchrus ciliaris L.) is an important forage grass in arid and semiarid regions. As part of a genetic improvement programme, four genotypes [Biloela (Bl), Americana (Am), Texas (Tx) and Sexual (Sx)] were categorized by tolerance to heat stress in a greenhouse experiment. At 30 d after sowing, half of the plants (control plants) were transferred to growth chambers (28°C day per night), and the other half (pre-treated plants, Prt) were exposed to heat stress treatment (0, 24, 48 and 72 h; 45°C day per night). Malondialdehyde (MDA) content, an indicator of oxidative damage, was determined from foliar samples. During heat stress, Sx showed the earliest increase in MDA (at 24 h) followed by Tx (48 h) and Am and Bl (72 h). Results were compared with heat-stress tolerance evaluated as morphological traits at the end of recuperation (60 d after sowing). Fresh weight and aerial plant height were lowest in the Prt-Sx genotype and highest in Am and Bl genotypes; Tx showed intermediate tolerance. Results suggest that tolerance to heat stress in C. ciliaris genotypes could be related to the capacity for regulating the oxidative damage increase. Foliar MDA content might therefore be used in a genetic improvement programme of C. ciliaris as a potential biochemical indicator for a rapid, simple and low-cost identification of heat-stress tolerant genotypes. [ABSTRACT FROM AUTHOR]

Damage produced by salt stress (300 mm NaCl) under hydroponic greenhouse conditions in seedlings of eight Buffel grass ( Cenchrus ciliaris L. Syn. Pennisetum ciliare Link) genotypes was estimated through different component characters of total fresh weight damage (DTFW). Coefficient of genetic determination (CGD) was estimated for each character as well as their direct and indirect contribution to damage to total fresh weight, considered as biomass production loss. Americana and Biloela were the most salt-tolerant cultivars, whereas sexual line and Texas 4464 were the genotypes most susceptible to salt stress. Damage to fresh weight of aerial part (DFWA) was the only component with a direct effect on DTFW and with a high CGD. Therefore, DFWA could be used in breeding programmes as an indirect selection criterion for tolerance and better productivity. [ABSTRACT FROM AUTHOR]

Buffel grass ( Cenchrus ciliaris L.) is an apomictic species that is widely adapted to arid and semi-arid, tropical and warm climates. Six apomictic cultivars used as male parents, one sexual line used as the female parents and 15 putative F1 genotypes were studied using the amplified fragment length polymorphism (AFLP) technique for their evaluation and recognition. The NTSYS programme and Jaccard's Index were used to establish the genetic similarity; and a phenogram was constructed. A total of 152 bands was recorded. Three primer combinations were sufficient to identify the genotypes. The maximum proportion of polymorphisms was 0·835, and 0·510 of the polymorphisms consisted in individual bands that strictly diagnosed unique genotypes. Texas 4464 and Americana cultivars were the most different from the sexual line, indicating that they might be the best genotypes for future crossing. Two hybrids were identified among F1 material to demonstrate the usefulness of the AFLP technique in characterizing genotypes and recognizing hybrids in Buffel grass for breeding purposes. [ABSTRACT FROM AUTHOR]

Buffel grass ( Cenchrus ciliaris L.) is an important apomictic grass used as forage for ruminant livestock. Biotechnological methods provide opportunities for producing new germplasm. Mature embryos of fourteen buffel grass apomictic cultivars (2 n = 4 x = 36) were used to induce embryogenic callus formation using a basal medium supplemented with 3% sucrose and with the testing of five concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) and four concentrations of 6-benzylaminopurine (BAP). The effects of cultivar and culture medium on callus induction and plant regeneration were evaluated. Significant differences were observed among the fourteen cultivars and the five concentrations of 2,4-D ( P < 0·01). Values for embryogenic callus production varied from 0 to 86·7. Most cultivars showed the highest level of embryogenic callus production on the medium with the concentration of 3 mg L−1 2,4-D. The addition of different BAP concentrations in combination with 2,4-D in the medium inhibited embryogenic callus growth and did not permit plant regeneration. The data clearly demonstrated that the genotype and concentrations of 2,4-D had significant effects both on the frequency of embryonic callus formation from mature embryos and on the subsequent efficiency of plant regeneration of apomictic cultivars of buffel grass. Cultivars Biloela and Nunbank showed the greatest efficiency in in vitro culture response. [ABSTRACT FROM AUTHOR]

The objective was to evaluate the crude protein content in materials previously selected from the three pastures. Six apomictic cultivars and an introduced sexual race were evaluated in buffel grass; eight diploid clones and two tetraploids tolerants to salinity stress (600 and 800 mM CINa, respectively) were tested in grama rhodes and nine improved clones of closed and open structure plants regarding varietal phenotype coloratum, and six clones to makarikari were used in P. coloratum. In buffel grass, the clones differed in both cuttings for the leaves and the stems; the Nunbank and Americana cultivars showed the highest CP level. Among different ploidies of grama rhodes only significant differences were observed in the stems. There were significant differences among the diploid clones and in both cutting moments, in leaves as well as in stems. The tetraploid clones only differed between leaves and stems. In P. coloratum the variety types differed in the leaves for ND and the coloratum type presented the major value of CP. It is concluded that the three species studied showed a wide variability regarding CP content. This encourage the possibility to obtain improved germplasm for this character, adapted to productive limitations of the argentine semiarid Chaco. [ABSTRACT FROM AUTHOR]

Abstract: Buffel grass (Cenchrus ciliaris L. syn. Pennisetum ciliare (L.) Link) is a species that is highly tolerant to drought and is used primarily as forage in drier regions throughout the subtropics and tropics. It reproduces mainly by apomixis and the acquisition of obligate sexual genotypes or facultative apomicts with high levels of sexuality is required for performing crosses and plant improvement. The aim of this study was to obtain sexual genotypes from controlled crosses using obligate apomictic cultivars and a sexual line. Twelve putative hybrid F1 plants were selected morphologically and two of them were identified as sexual genotypes by PCR using specific primers for reproductive mechanism. Cytoembryological analysis showed 65.5 and 71.3% meiotic embryo sacs in these plants and their hybrid nature was corroborated by AFLP. Both highly sexual genotypes could be used as female parents in crosses for obtaining improved cultivars of buffel grass. [Copyright &y& Elsevier]