Alfalfa resistance to post-harvest Aspergillus species: Response to selection

2000 ◽  
Vol 80 (4) ◽  
pp. 755-763
Author(s):  
C. A. Kimbeng ◽  
S. R. Smith Jr. ◽  
V. Babij ◽  
K. M. Wittenberg
Keyword(s):  
Medicago Sativa ◽  
Leaf Area ◽  
Forage Yield ◽  
Fungal Resistance ◽  
Aspergillus Species ◽  
Response To Selection ◽  
Post Harvest ◽  
Species Response ◽  
Sib Families ◽  
Selection For

Alfalfa (Medicago sativa L.) cultivar development programs routinely incorporate resistance to fungal diseases that limit forage yield, quality and stand longevity. "Hay molding", caused by saprophytic fungi, reduces forage quality during the post-harvest period, but genetic resistance has not been reported. The objective was to determine the response to selection for post-harvest fungal resistance in alfalfa. Initially, 1144 genotypes from 22 alfalfa cultivars were screened for post-harvest fungal resistance with a combination of Aspergillus species. Forty resistant and 40 susceptible genotypes were selected by measuring percentage of leaf area with fungal coverage. The selected genotypes and their maternally derived half-sib families were screened for resistance to Aspergillus repens. Mean leaf area with fungal coverage was significantly (P < 0.05) lower for resistant than susceptible parental genotypes and maternal half-sib families. Percent leaf area with fungal coverage ranged from 13.2 to 70.5% (mean, 41.7 ± 1.7) among resistant and 28.2 – 83.4% (mean, 50.2 ± 1.7) among susceptible parental genotypes. Among the maternal half-sib families, resistant families ranged from 14.0 to 51.3% (mean, 32.1 ± 1.8) and susceptible families from 18.8 to 60.1% (mean, 40.3 ± 1.9). These results show a positive response to selection for post-harvest fungal resistance in alfalfa. Key words: Alfalfa, Medicago sativa, post-harvest fungi, Aspergillus species, breeding, divergent selection

Screening methodology for post-harvest fungal resistance in alfalfa

1998 ◽  
Vol 78 (3) ◽  
pp. 481-488
Author(s):  
K. M. Wittenberg ◽  
S. R. Smith ◽  
F. Katepa-Mupondwa ◽  
J. F. Yang
Keyword(s):  
Leaf Area ◽  
Economic Loss ◽  
Fungal Resistance ◽  
Screening Procedure ◽  
Fungal Colonization ◽  
Soluble Carbohydrate ◽  
Equal Proportion ◽  
Adaxial Side ◽  
Post Harvest ◽  
And Storage

Forage deterioration due to field and storage fungi represents a major economic loss for hay producers. A series of experiments was conducted to develop a methodology for screening alfalfa plants for resistance to post-harvest fungal colonization. Pure cultures of Aspergillus glaucus, Aspergillus repens, Aspergillus flavus, Aspergillus versicolor and Aspergillus fumigatus, isolated from alfalfa forage sampled during field wilting and storage, were established and maintained to produce a 105 spore mL−1 suspension containing an equal proportion of spores from each Aspergillus spp. Alfalfa leaves were dipped in concentrations of propionic acid solution to simulate levels of resistance to fungal activity. Fully-developed trifoliate leaves were placed adaxial side down onto petri plates containing a dichloran (2 mg mL−1) and glycerol (18% vol/vol) agar. The Aspergillus spp. spore suspension was sprayed onto each petri plate and the plates were incubated under dark conditions at 25 °C and 70% relative humidity. Plates were monitored daily for percent of leaf area colonized. The random screening of a small population of cloned alfalfa genotypes using this screening procedure indicated that variation in post-harvest resistance to fungal attack does exist for greenhouse and field-grown plants harvested at an early vegetative stage. Leaf dry matter was not related to genotype variation in post-harvest susceptibility to fungal colonization; however, leaf soluble carbohydrate level was negatively correlated (P < 0.05) with leaf area colonized. The screening procedure did not detect consistent differences among genotypes when dried leaves were used. Key words: Alfalfa, genotype, post-harvest fungi, Aspergillus spp., resistance, screening

Effect of divergent selection for root size in field-grown alfalfa

1999 ◽  
Vol 79 (1) ◽  
pp. 93-95 ◽  
Author(s):  
O. Chloupek ◽  
M. Skácel ◽  
J. Ehrenbergerova
Keyword(s):  
Medicago Sativa ◽  
Root System ◽  
Selection Criterion ◽  
System Size ◽  
Forage Yield ◽  
Electrical Capacitance ◽  
Root System Size ◽  
Medicago Sativa L ◽  
Selection For ◽  
Root Size

The size of the root system as measured by its electrical capacitance was evaluated on two alfalfa (Medicago sativa L.) cultivars (Zuzana, Palava) for 3 yr. Plants with root system size (RSS) significantly larger or smaller than the cultivar mean were selected and their open-pollinated progenies were evaluated in the following 3 yr. Progenies of plants with large RSS tended to have larger RSS and higher forage yield than progenies of plants with small RSS. The differences for both parameters were significant (P < 0.05) in the case of Zuzana. It is concluded that RSS is a useful selection criterion in alfalfa breeding. Key words: Medicago sativa L., root system size, selection, yield, survival

Response of alfalfa to bidirectional selection for root bark area and xylem vessel diameter

1991 ◽  
Vol 71 (2) ◽  
pp. 427-435
Author(s):  
Shaoke Wang ◽  
M. A. Brick ◽  
C. E. Townsend
Keyword(s):  
Medicago Sativa ◽  
Vessel Diameter ◽  
Xylem Vessel ◽  
Root Bark ◽  
Response To Selection ◽  
Vessel Area ◽  
Medicago Sativa L ◽  
Selection For ◽  
Bidirectional Selection ◽  
Root Size

Development of alfalfa [Medicago sativa L. ssp. sativa and M. sativa ssp. falcata (L.) Arcangeli] germplasm with contrasting root bark area and xylem vessel area could be useful to evaluate relationships between anatomical root characteristics and plant functions such as drought tolerance. This study was conducted to determine the response of alfalfa to bidirectional selection for root bark area and xylem vessel area of the largest vessels as viewed in cross section. Bidirectional selection for large and small root bark area and for large and small xylem vessel area was conducted for two cycles. Selection for high root bark area resulted in an increase in root bark area in cycle one (C1), but no further response occurred in cycle two (C2). Response to selection for low bark area resulted in no response in the C1, but a response occurred in the C2. Response to selection for large xylem vessel area increased xylem area in the C1 but no further response occurred in the C2. There was no response to selection for small vessel area in either of the two cycles of selection. Asymmetrical responses to bidirectional selection were found. Root size increased significantly over the two cycles of selection and was probably due to indirect selection for large root size. Key words: Medicago sativa L., ssp. sativa and M. sativa ssp. falcata (L.) Arcangeli, root bark area, xylem vessel diameter

scholarly journals Development of more productive and persistent lucerne by selection under frequent cutting

1994 ◽  
pp. 113-116
Author(s):  
R.G. Purves ◽  
R.B. Wynn-Williams
Keyword(s):  
Medicago Sativa ◽  
Grazing Management ◽  
Response To Selection ◽  
Selected Lines ◽  
Breeding Method ◽  
Breeding Lines ◽  
Selection Cutting ◽  
Cutting Frequency ◽  
Medicago Sativa L ◽  
Selection For

The area of luceme (Medicago sativa L.), regarded as the best adapted legume for dry areas of New Zealand, has declined by 67% over the last 2 decades. The major reason for the decline has been the effect of pests, diseases and poor grazing management on productivity and persistence. The development of disease- and pest-resistant cultivars has allowed plant breeders to investigate methods for developing grazing-tolerant lucernes. It has been suggested that frequent cutting is harder on plants than grazing and that it could be used to rapidly identify the survival characteristic of breeding lines. Lines surviving cutting every 4 m weeks for 2 seasons have been selected at Lincoln. To evaluate the breeding method these selected lines were compared with their parents, under 4- weekly cutting (frequent), 8-weekly cutting (infrequent) and frequent grazing. Frequent grazing was less severe on plants than frequent cutting and evaluation by this treatment was discontinued after 3 years. There was a trend towards increased production through selection under both frequent and infrequent cutting and there appeared io be line differences in response to selection. Persistence of lines after 7 years of frequent and infrequent cutting was significantly improved by selection for most lines. The different degrees of improvement between lines indicate that lines responded differently to selection. Cutting frequency had little effect on the final plant numbers of lines. The differences between cultivars and lines can be attributed to disease and pest resistance and adaptability of lines. The trial showed that selecting plants tolerant of frequent cutting can improve production and persistence. Keywords: frequent cutting, grazing, Medicago sativa, persistence, production, selection

Correlated response to selection for litter size in pigs: II. Carcass, meat, and fat quality traits

2002 ◽  
Vol 80 (10) ◽  
pp. 2566 ◽  
Author(s):  
J. Estany ◽  
D. Villalba ◽  
M. Tor ◽  
D. Cubiló ◽  
J. L. Noguera
Keyword(s):  
Litter Size ◽  
Correlated Response ◽  
Quality Traits ◽  
Response To Selection ◽  
Fat Quality ◽  
Selection For
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