The mushroom, Agaricus bisporus (Lange) Imbach, has been in cultivation since 1650 and is now a major protected crop with a value world-wide in excess of £2,OOOm. Despite its importance as a crop species and long history of cultivation, little work has been done on genetics and strain improvement. The mushroom is 2-spored and single-spore cultures are usually fertile. Studies of the breeding system of the mushroom are described based on the behaviour of cultures derived from aberrant 3- and 4-spored basidia. It is shown to be a secondarily homothallic species with a single mating-type factor. Methionine and proline auxotrophs are identified and two morphological markers are characterised, the first resulting in the constitutive production of fruit-body initials in culture and the second in altered gill morphology. Studies of 4-spored wild Agaricus species are described. A. bitorguis, ~ macrosporus and A. nivescens are shown to be unifactorially heterothallic. Nuclear numbers in homokaryons and heterokaryons of these species are determined and compared with A. bisporus. A scheme is proposed for the evolution of the secondary homothallism seen in ~ bisporus from a 4-spored heterothallic ancestor. Approaches to mushroom strain improvement are considered in detail and a breeding strategy based on the use of induced fungicide resistance is described. Following this strategy mutants resistant to the fungicides carboxin, benodanil and tridemorph have been obtained and evaluated in vitro and in vivo. Four of these mutants are the subject of a patent under the aegis of the British Technology Group. Finally, the mechanism regulating secondary homothallism has been studied. A predictive hypothesis, the random migration of nuclei in pairs from the basidium into the spores, has been tested in the model 2-spored organism Coprinus bilanatus nom. provo

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This investigation examined the efficiency of various screening procedures which could be used in breeding for increased production of root-proliferating (RP) genotypes of alfalfa (Medicago sativa L. s. l.). Also investigated were relationships between RP and winter growth characteristics in populations derived from crosses between dormant, RP clones and nondormant, non-RP clones. In addition, this investigation also considered the inheritance of the RP habit. Plants from an 11-month F₁ progeny test containing 3508 offspring were qualitatively analyzed for RP expression using three pairs of screening procedures. Procedures compared included: (1) direct-seeding vs. transplanting; (2) use of characterized parental clones (known RP-expressing genotypes selected from field nursery) vs. uncharacterized parental clones (genotypes derived from RP seed lots with no prior knowledge of their ability to express the RP habit) in RP x nondormant crosses; and (3) low vs. high harvest frequencies. A low frequency (3.3%) of F₁ plants exhibited adventitious shoot formation. No differences were observed in the frequency of RP-expressing genotypes between the direct-seeded and transplanted treatments or between the low and high harvest frequency treatments. Characterized RP parents produced a hybrid population with a significantly higher frequency of RP-expressing genotypes than did the F₁ population derived from uncharacterized RP parents. Average winter forage production of the F₁ hybrids were similar in magnitude to the midparent value. Plant height was significantly and positively correlated with forage yield and could be used as an accurate indicator of winter forage yield in analyses of RP segregants. Estimates of components of genetic variance for RP expressivity indicated a predominance of additive effects and narrow sense heritability of 8.4%. Family selection and progeny testing are suggested for maximum breeding progress.

Curly mesquite (Hilaria belangeri (Steud.) Nash) is a palatable, nutritious range grass in the southwestern United states. A research project was initiated in 1988 on plant material collected within Arizona to determine the value of this species as a turfgrass, if sufficient genetic variation existed in vegetative , reproductive, and germination traits to allow for improvement of the turfgrass value by breeding, and if this species could be successfully established by seeding. curly mesquite can withstand the rigors of turfgrass cultural practices (mowing and fertilizing), while maintaining an attractive, healthy appearance. Plant material from five separate geographic origins was subjected to 5 cm and 10 cm heights of cut, and a no cut treatment, along with nitrogen applications of 0, 48, and 96 kg ha⁻¹ yr⁻¹ in a randomized complete block split-split plot design. cutting at 10 cm, and application of 96 kg N ha⁻¹ yr⁻¹ produced the best color and highest ground cover. Control (uncut) plots exhibited low vigor and color. Broad-sense (h²(b)) and narrow-sense (h²(n)) heritability estimates were computed for measured and rated characters on clones and their open-pollination progeny grown at Safford (S) and Tucson (T), AZ. Estimates of h²(b) of measured characters were: leaf length 0.29 (S) and 0.45 (T), stature 0.83 (S) and 0.71 (T), and flowers•spike⁻¹ 0.40 (S) and 0.36 (T). Significant variation was not observed in leaf width. Significant h2 n estimates of 0.31, 0.51, and 0.30 were obtained for leaf length, stature, and flowers•spike⁻¹ , respectively. Broad-sense heritability estimates ranged from 0.46 to 0.79 for color, and 0.47 to 0.69 for density ratings. Cumulative germination percentages had h2 b estimates ranging from 0.45 to 0.61. Hard seed (%) and seed weight (mg 100 seed-l) had h²(b). estimates of 0.83 and 0.95, respectively. Successful seedling establishment occurred after June, July and August sowings. Ground cover at the close of the season was greatest for the June seeding. A significant difference did not exist between the ground cover means of seeding rates (1 and 2 gm m⁻²). The results of these investigations clearly warrant further efforts in the development of curly mesquite into a low maintenance turfgrass.

The cytological and breeding behavior of barley with 8 pairs of chromosomes, of which 2 pairs are interdependent were evaluated. The 8II material originated from selfed progeny of a Balanced Tertiary Trisomic 57a msg16. Chromosome interdependence was established after a naturally occurring reciprocal translocation between the normal chromosome 5 and the extra interchanged 57a chromosome. The interdependent chromosomes are fragment chromosomes. A Male Sterile Facilitated Recurrent Selection Population (MSFRSP) of 8II plants was developed. Eight chromosome paired plants were crossed onto male sterile plants from barley Composite Cross XXXII. The F₁ plants from the 7II x 8II crosses carried a characteristic 15-chromosome cytotype. In the F₂ of this cross, 5 different cytotype classes of progeny were isolated by root-tip chromosome and microsporocyte analyses: 7II, F₁, 8II, tertiary trisomic where the extra chromosome is a fragment chromosome and a Unique-16 chromosome cytotype which consisted of 6 normal pairs, one pair of fragments, one normal chromosome 5 and one fragment chromosome from the other pair of fragments. The F₂ population was approximately 30% 7II, 50% F₁ and 20% 8II cytotype progeny. Microsporocytes observed from F₂ cytotype plants indicated that the 7II and 8II progeny went through normal meiosis. The F₁ cytotypes produced functional gametes with 7 normal chromosomes, 8 chromosomes equivalent to gametes produced by 8II plants and gametes with 7 normal chromosomes plus a fragment chromosome. The tertiary trisomic progeny produced functional gametes with 7 normal chromosomes and gametes with 7 normal chromosomes plus a fragment chromosome. The Unique-16 cytotype produced functional gametes with 7 normal chromosomes, 8 chromosomes equivalent to gametes produced by 8II plants, 7 chromosomes plus a fragment chromosome and 9-chromosome gametes with 6 normal chromosomes plus 3 fragment chromosomes, two of which are a pair. Crosses and their reciprocals between 7II plants and plants of each F₂ cytotype indicated that the cytological stabilty of an 8II or 7II population would be disrupted if contaminated by pollen from 7II or 8II plants respectively. Growing the populations in physical isolation from each other is a must in order to maintain the cytotype of the population homozygous

Regrowth and yield of 23 Middle Eastern (ME) cultivars and the elite cultivar Lew were evaluated for twelve regrowth harvests in pure stands and 50:50 mixtures with Lew in 1988 at Tucson, Arizona. Stem elongation rate and crown shoot development were measured on selected ME cultivars and Lew in the spring of 1988. No significant differences in yield were observed between mixtures and monocultures. Few significant differences were observed over all yields among ME cultivars and Lew. Cultivars from Saudi Arabia and Egypt produced more forage than Lew in spring harvests. These cultivars developed crown shoots precociously and had high stem elongation rates during the first week of regrowth. Most ME cultivars had higher leaf area and leaf:stem ratio than did Lew. These findings suggest that ME cultivars may be useful in improving forage yield during the winter and spring and forage quality in elite nondormant cultivars.

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