Simultaneous selection for seed and forage production in cocksfoot (Dactylis glomerata): application of drought tolerance and susceptibility indices

An experiment was conducted to estimate drought tolerance of some cocksfoot genotypes based on seed and forage yield and related indices (including tolerance index, mean productivity, geometric mean productivity, reduction percentage index, stress tolerance index and stress susceptibility index) and to identify relationships between measured traits. Twenty‐five genotypes were evaluated in the field under control and drought‐stress environments over 2 years. The results revealed a high variation for seed yield and forage yield and the measured indices under both moisture conditions. No correlation was observed between seed yield and forage yield under the control treatment, but this correlation was positively significant under the water‐stress treatment. Drought‐tolerant and susceptible genotypes were identified based on seed and forage yield performance. Genotypes 2, 4 and 7 had high seed yield, while genotypes 7 and 10 had high forage yield under both stressed and non‐stressed conditions and were identified as the most tolerant genotypes in each category. The results also revealed that genotypes 1, 2, 4, 6, 7, 8 and 24 had relatively high seed and forage yield in both control and drought‐stressed conditions. These genotypes can be used for further studies to improve both seed and forage yields concurrently.     

Genetic variation among populations of wild safflower, <Emphasis Type="Italic">Carthamus oxyacanthus</Emphasis> analyzed by agro-morphological traits and ISSR markers

Wild species of safflower, Carthamus oxyacanthus Bieb., is highly crossable with cultivated species, C. tinctorius L. and could be directly exploited in broadening safflower gene pool and improving the crop for biotic and abiotic stress environments. In this study, genetic diversity among accessions of C. oxyacanthus and their relationships with cultivated safflower were evaluated using agro-morphological traits and polymorphic inter-simple sequence repeats (ISSR) markers. Significant variation was observed among accessions particularly for seeds per capitulum, seed yield per plant, harvest index and capitula per plant. Cluster analysis based on agro-morphological traits classified the wild accessions in two groups according to their geographical regions, and separated them from the cultivated genotypes. ISSR marker also revealed a high genetic variation among the accessions, and cluster analysis based on this marker divided genotypes into four groups, with cultivated ones in a separate clade. Genetic variation observed among the wild safflower germplasm at the DNA level was higher than the agro-morphological traits, indicating that ISSR is an effective marker system for detecting diversity among safflower genotypes and their genetic relationships. Accessions of C. oxyacanthus with high genetic relationship to cultivated species could be used for interspecific hybridization in breeding programs of safflower.     

Neotyphodium endophytes trigger salt resistance in tall and meadow fescues

Infection with Neotyphodium spp. endophytes increases resistance to drought stress and soil mineral imbalances in tall fescue (Festuca arundinacea Schreb. = Lolium arundinaceum (Schreb.) S. J. Darbysh.) and meadow fescue (Festuca pratensis Huds. = Lolium pratense (Huds.) Darbysh.). We hypothesized that resistance of these grasses to salinity stress may also be attributed to endophyte infection. Two tall fescue genotypes, Fa75 and Fa83, and one meadow fescue genotype, Fp60, infected (E+) with their endophytic fungi, Neotyphodium coenophialum (Glenn, Bacon and Hanlin) and N. uncinatum (Glenn, Bacon and Hanlin), respectively, and their noninfected counterparts (E–) were cultured in nutrient solution at three salinity levels of 0, 85, and 170 mM NaCl. Except for genotype Fa75, E+ plants exhibited higher leaf survival rates than E– clones at a high salinity level (170 mM). Root dry matter was higher in E+ than in E– plants, but shoot dry matter was not affected by endophyte infection. This resulted in a lower shoot‐to‐root ratio in E+ plants (1.63) compared with E– plants (2.40). Sodium (Na⁺) and chloride (Cl^–) concentrations were greater in roots of E– than in E+ clones. In shoots, Na⁺ and Cl^– concentrations were not affected by the endophyte. In contrast, E+ plants accumulated more potassium (K⁺), which resulted in a greater K⁺ : Na⁺ ratio in shoots of E+ than in those of E– plants. Our results show that endophyte infection reduced Na⁺ and Cl^– concentrations in tall fescue and meadow fescue roots but increased K⁺ concentrations in the shoots. Based on these results, we conclude that endophyte‐infected grasses may thrive better in salinity‐stress environments.     

Allele sequencing of the barley stem rust resistance gene Rpg1 identifies regions relevant to disease resistance

The stem rust resistance gene Rpg1 has protected North American barley cultivars from significant yield losses for over 65 years. The remarkable durability of this gene warrants further study as to its possible origin and allelic variation. Eight Swiss barley (Hordeum vulgare) landraces and eight wild barley (H. vulgare subsp. spontaneum) accessions from diverse geographic regions were analyzed to uncover new alleles of Rpg1 and learn about its possible origin. The two germplasm groups included accessions that were resistant and susceptible to Puccinia graminis f. sp. tritici pathotype MCCF. Allele-specific primers were utilized to amplify 1 kbp overlapping fragments spanning the Rpg1 gene and sequenced if a polymerase chain reaction (PCR) fragment was generated. Variation among the PCR products revealed significant polymorphisms among these Hordeum accessions. Landraces and wild barley accessions susceptible to pathotype MCCF exhibited the highest degree of Rpg1 polymorphism. One resistant landrace (Hv672) and one resistant wild barley accession (WBDC040) yielded all seven Rpg1-specific PCR fragments, but only landrace Hv672 coded for an apparently functional Rpg1 as determined by comparison to previously characterized resistant and susceptible alleles and also resistance to HKHJ, a stem rust pathotype that can specifically detect Rpg1 in the presence of other resistance genes. Accessions resistant to stem rust pathotype MCCF, but completely lacking Rpg1-specific PCR amplification and hybridization with an Rpg1-specific probe, suggested the presence of stem rust resistant gene(s) different from Rpg1 in the Hordeum germplasm pool. Some Rpg1 alleles that retained the ability to autophosphorylate did not confer resistance to Puccinia graminis f. sp. tritici pathotype MCCF, confirming our previous observations that autophosphorylation is essential, but not sufficient for disease resistance. Thus, the RPG1 protein plays a complex role in the stem rust disease resistance-signaling pathway.     

Wild safflower species (Carthamus oxyacanthus): A possible source of resistance to the safflower fly (Acanthiophilus helianthi)

Safflower (Carthamus tinctorius L.) is an important oil seed crop with growing importance in many countries around the world. However, safflower fly (Acanthiophilus helianthi Rossi) is one of the main limiting factors to expand the production area of the crop in several countries. Since host plant-resistance is the most efficient method for pest management, we evaluated a germplasm of wild accessions (Carthamus oxyacanthus Bieb.) with mostly brown–black seed coat color along with some white-seeded cultivated safflower genotypes for resistance to safflower fly. The results showed that there was a significant difference between two species for safflower fly damage with all cultivated genotypes being susceptible. However, for the accessions of C. oxyacanthus, a wide range of resistance was observed. In a choice experiment and natural infestation, 35.3–78.9 percent of heads per plant were infested in genotypes of C. tinctorius while for the accessions of C. oxyacanthus this was much smaller and ranged from 1.6 to 13.6%. In addition, percentage of seed yield loss per infested plant was more drastic in cultivated safflower (29.0–72.8%) than the wild accessions (0.0–21.4%). In the no-choice experiment, fly population was dramatically decreased in the wild accessions due to larval mortality and possibility of antibiosis. There was a strong relationship between brown–black seed coat color and resistance to safflower fly indicating the possibility of using this trait in breeding programs of safflower to develop fly-resistant cultivars.     

Enumeration of lactobacilli in the fecal flora of infant using two different modified de-Man Rogosa Sharpe media under aerobic and anaerobic incubation

Regarding the importance of the presence of intestinal lactobacilli and their population in infants, four different treatments were evaluated for Lactobacillus isolation efficiency via reduction in the growth of other groups of bacteria capable of growing on de-Man Rogosa Sharpe (MRS) medium from fecal samples of 11 Iranian infants. MRS-Vancomycin (1 mg L(-l)) was used as a base medium and application of lactic acid and aerobic incubation of inoculated plates were performed as selective factors. Each fecal sample was cultivated as duplicate on to the base medium with or without lactic acid to reduce the pH to 5.4 +/- 0.2. Half of the plates were incubated aerobically and the rest of them incubated under 10% CO2 concentration. Total count and Lactobacillus count of all samples were recorded according to the age differences of infants. The counts of false positive colonies were recorded with respect to their cell morphology and gram reaction in all treatments. Anaerobic incubation of lactic acid modified MRS-Vancomycin gave the most Lactobacillus percentage coverage, about 93% among the Lactobacillus positive samples. Using this treatment, the median Lactobacillus count yielded 8.29 log10 cfu g(-1) in the younger and 5.70 log10 cfu g(-1) in the elder group. It could be concluded that lactic acid might be a proper pH reducing agent when enumeration of lactobacilli from fecal samples is of interest.     

Root characteristic system improves drought tolerance in orchardgrass

Plant genotypes with higher drought tolerance through improved root characteristics are poorly studied in orchardgrass. In the current research, 30 orchardgrass genotypes were polycrossed and the resulting half‐sib families evaluated under both normal and water stress environments. Under water stress conditions, values for most root traits decreased at 0–30 cm soil depth, while at 30–60 cm depths, the root length (RL), root area (RA), root volume, percentage of root dry weight (RDW) and the ratio of root to shoot were increased. We identified drought‐tolerant genotypes with a high combining ability for root characteristics and a high yield potential. High estimates of heritability as well as genetic variation for root traits indicated that phenotypic selection would be successful in order to achieve genetic progress. Indirect selection to improve dry matter yield was most efficient when selecting for RL and RDW under water stress conditions. Significant associations between a drought tolerance index and RL, RA and root volume confirmed the importance of these traits in conferring drought tolerance of orchardgrass.     

Genetic analysis of seed‐related traits in smooth bromegrass (Bromus inermis) under well‐watered and water‐stressed conditions

In forage grasses, knowledge about the genetic basis of seed production and its association with related traits under water stress is very limited. Half‐sib families derived from the polycross of twenty five smooth bromegrass genotypes were evaluated in the field in well‐watered and water‐stressed environments during 2012 and 2013. Results showed that drought stress had a negative effect on seed yield and reduced phenotypic variation for seed yield and agro‐morphological traits. High genotypic variation was observed among families for seed yield and its components. Narrow‐sense heritabilities (h²) ranged from 0·22 (flag leaf weight) to 0·81 (days to anthesis). These moderate‐to‐high heritability estimates for seed yield and its components indicate that phenotypic selection can be successful to achieve genetic progress for these traits. Seed yield had a positive correlation with 1000‐seed weight, number of ears per plant, number of seeds per panicle, seed weight per panicle and panicle length.     

Physiological traits related to drought tolerance in tall fescue

The physiological basis of genetic variation in drought response and its association with yield and related indices is not clear in tall fescue. In this study thirty genotypes of tall fescue (Festuca arundinacea Schreb.) were sampled from a polycross population and evaluated under two levels of irrigation in 2010 (normal and intense stress) and 2011 (normal and mild stress). Physiological traits including relative water content (RWC), total chlorophyll (TChl), chlorophyll a (Chla), chlorophyll b (Chlb), Chla/Chlb, carotenoids (Car), TChl/Car and proline content along with forage yield, agro-morpholgical traits and selection indices (stress tolerance index, STI and drought susceptibility index, DSI) were studied. Large variation and moderate to high heritability was estimated for most of the studied traits. Intense drought condition decreased chlorophyll content while mild stress significantly increased it. In the other hand intense drought stress increased Chla/b while mild stress didn’t change it. Under mild drought stress condition STI was positively correlated with RWC while under intense drought stress condition STI was positively correlated with chlorophyll content. Although proline content was significantly increased in both intense and mild drought stress conditions, no relationship was found between proline accumulation with forage yield and STI. Applications of principle component analysis for screening suitable genotypes are also discussed.     

Genotype selection for physiological responses of drought tolerance using molecular markers in polycross hybrids of orchardgrass

The present study aimed to assess the effect of contrasting levels of molecular and phenotypic diversity among polycross parents of orchardgrass on the performance of synthetic progeny with respect to physiological responses and drought tolerance. Four polycross groups each composed of six parental plants were evaluated under normal irrigation and drought stress conditions. A number of 923 inter simple sequence repeats and sequence related amplified polymorphism markers and several phenotypic traits were used to select contrasting levels of diversity (high and low) in parental genotypes. Highly significant correlation was observed between molecular distance and progeny performances at both normal irrigation and drought stress conditions. High molecular diversity among polycross parents led to a significant yield advantage of first generation progeny with averages of 34.40% for normal irrigation and 48.10% for drought stress conditions. Also crosses between genetically distant parents produced progeny with considerable drought tolerance and yield stability. Positive associations between phenotypic distance of parents and progeny performance were found for most physiological traits at both moisture regimes but phenotypic distances had weak association with forage yield, stress tolerance index and yield stability of progeny. Significant associations between drought tolerance index and some physiological traits confirmed the importance of these traits in conferring drought tolerance of orchardgrass. Our results underscore the effectiveness of marker‐assisted polycross breeding to improve drought tolerance and yield stability through physiological traits in orchardgrass.