Euphytica

The distribution of vegetative and fruit characters among a large population of parent and F1 hybrid tomato cultivars is described and heritability estimates are given. Comparison of parent and offspring subpopulations revealed higher overall values in the F1 hybrids for vegetative characters and lower overall values for fruit characters than in the parents. A general Galtonean feature of higher offspring values for cross combinations with low parent means and lower offspring values for cross combinations with high parent mean is evident in all traits studied. The predictive value of the data given is evaluated.

In order to analyse the genetic control of anther culture response in barley, a doubled-haploid (DH) population from the cross between a medium responsive cultivar ‘Dobla’ and the model cultivar ‘Igri’ was produced. A linkage map was constructed with 91 markers. A sub-population of 41 lines was characterised for different components of the anther culture response, and was used for quantitative trait loci (QTL) analysis. The vrs1 locus region on chromosome 2H, which determines inflorescence row type, was coincident with the largest putative QTL for number of embryos (nEMB) and albino plants. A region of chromosome 6H was associated with QTLs for nEMB and green plants. QTLs for number and percentage of green plants were located on the long arm of chromosome 5H. Therefore, new QTLs for main components of barley anther culture response were identified on chromosomes 2H, 5H and 6H, indicating that anther culture response in barley could be controlled by relative few genes of large effect. This work is a useful step towards the identification of new regions on the barley genome that could be associated with fundamental biological process implicated in the anther culture response.

The erectophile plant architecture in maize is responsible for high plant density tolerance, yet the genetic basis for this relationship remains elusive, especially for how canopy architecture and plant height related traits at different positions respond to plant density. In this study, nine canopy traits and six plant height (PH) traits were evaluated across four environments under low plant density (57,000 plants/ha, LD) and high plant density (114,000 plants/ha, HD), using a set of 301 recombinant inbred lines originating from two foundation parents in China, the inbred lines YE478 and 08-641. In total, 176 quantitative trait loci (QTLs) for plant architecture related traits (94 only in LD, 44 only in HD and 38 under both densities) and 36 QTL clusters were detected via combined analysis. We identified 21 sharing QTL regions associated with plant height, leaf width and leaf angle at different positions. These results suggest that plant architecture-related traits were greatly influenced by density-specific and environment-specific alleles, and epistasis, QTL × environment interaction and QTL pleiotropy also play essential roles for plant architecture via complex interactions. Though PH-related traits, leaf widths and leaf angles at different positions could be partially affected by several common QTLs, there are still different genetic mechanisms of plant architecture response to plant density. Furthermore, elite line YE478 provided most of the favorable plant architecture alleles for high-density tolerance. Five QTL clusters containing six major QTLs, were useful for further studies of plant architecture and will provide helpful information for ideal plant type, high-density tolerance and marker-assisted selection.

An account is given of Mendel's activities concerning pear breeding. Especially pulp quality and time of ripening were his points of interest. His work resulted in the breeding of some pear varieties.

A commercial horticultural industry that establishes plant-breeding nurseries for an exotic species throughout a regional economy will expand until the marginal profit of the last nursery established is zero. However, a regional government concerned with social welfare will take into account not only the profits of the horticultural industry but also any expected costs of an accidental invasion. The latter costs will consist of the discounted expected social damages due to an increase in the rate of invasion over time and the increase in expected damage cost per hectare caused by an additional nursery. A government can employ an “introducers' pay” tax equal to the latter social costs to ensure that the plant breeding industry establishes the optimal number of nurseries. We illustrate this outcome with the example of purple loosestrife (Lythrum salicaria) in North America. In the absence of any tax, the horticultural industry will establish n = 3528 nursery operations, and the expected damages from invasion are US$ 28.2 million per year. With the tax, only n = 300 nurseries are established but the expected damages from invasion are reduced to US$ 1.3 million per year. Although profits for the horticultural industry are lower from the tax, the net gains in overall social welfare more than offset the losses. Although these results are illustrative only, they show that the problem of plant invasives initiated by commercial operations is amenable to standard economic analysis and solutions, such as implementation of an “introducers' pay tax”.

The effect of gamma rays on parameters such as chlorophyll mutation frequency and spectrum, mutagenic effectiveness and efficiency and viable mutation frequency and spectrum were studied in M2 generation of Rhodes grass employing nine doses of gamma rays. The chlorophyll mutation frequency increased in a linear fashion at low and medium doses and was erratic at higher doses. The chlorophyll mutant spectrum ineluded albina, xantha, chlorina, viridis, tigrina, striata, albo-xantha and albo-viridis. The frequency of these mutants varied with treatments. A dose rate of 60 krad was found to be effective as well as efficient both on M1 and M2 plant basis in inducing chlorophyll mutations. The highest frequency of viable mutations was found in 50 krad treatment. Viable mutants found were: nodal variant, peduncle variant, lax ears, coxcomb ears, earhead proliferation, level of fingers, incurved fingers, gappy ears, apical sterility, partial sterility and high sterility.

A survey of the genetic control of seven aspects of wheat quality shows the presence of complex genotype x environment interactions. The demonstration of these interactions emphasises the need for an effective sampling of environments during the testing of breeding material and the importance of consistency of performance of selections over the range of environments.