Convergence of Probability Measures. By P. Billingsley. Chichester, Sussex, Wiley, 1968. xii, 253 p. 9 1/4“. 117s.

Convergence of Probability Measures

In this paper, for right censored competing risks data, a class of tests developed for comparing the cumulative incidence of a particular type of failure among different groups. The tests are based on comparing weighted averages of the hazards of the subdistribution for the failure type of interest. Asymptotic results are derived by expressing the statistics in terms of counting processes and using martingale central limit theory. It is proposed that weight functions very similar to those for the $G^p$ tests from ordinary survival analysis be used. Simulation results indicate that the asymptotic distributions provide adequate approximations in moderate sized samples.

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A Class of $K$-Sample Tests for Comparing the Cumulative Incidence of a Competing Risk

One of the most successful means of controlling plant diseases has been the development of varieties with major or vertical resistance genes. This type of resistance is easily manipulated in a breeding program and is efIec­ tive until strains of the pathogen to which it does not confer resistance be­ come established. Then, if another gene that conditions resistance to the new strains of the pathogen is available, this resistance gene may be incorporated into the variety by the plant breeder. In doing this, the breeder either con­ sciously or unconsciously is applying the principle of the gene-far-gene hypothesis. Plants resistant to races that are virulent on old varieties possess the new resistance gene. With the diseases of some crops, this process has becn repeated at relatively frequent intervals (4D, 42, 82). However, in some instances a single gene has conferred adequate resistance for many years 80,82). In plant diseases caused by living organisms, the same phenomena: in­ fection type in rusts, percent of infected plants in smuts of cereals, fleck or lesion in apple scab, are criteria of both the reaction of the host and the pathogenicity of the parasite. They indicate the relative resistance or sus­ ceptibility of the host and the relative avirulence or virulence of the para­ site. The gene-for-gene hypothesis was proposed (20,25) as the simplest ex­ planation of the results of studies on the inheritance of pathogenicity in the .flax rust fungus, M elampsora lini. On varieties of flax, Linum usitatissimum that have one gene for resistance to the avirulent parent race, F 2 cultures of the fungus segregate into monofactorial ratios. On varieties having 2, 3, or 4 genes for resistance to the avirulent parent race, the F2 cultures segregate into bi-, trio, or tetra factorial ratios (20-22) respectively. This suggests that for each gene that conditions reaction in the host there is a correspond­ ing gene in the parasite that conditions pathogenicity. Each gene in either member of a host-parasite system may be identified only by its counterpart in the other member of the system.

Current Status of the Gene-For-Gene Concept

This survey of sexual practices in the United States has been combed by the media for items of interest to the public: monogamous sex is much more widespread in this country than has been thought; infidelity is less frequent than presumed; vaginal intercourse is the defining experience of heterosexual behavior; watching one's partner undress is stimulating to many people; married couples have more sex than single people (unmarried, cohabiting couples have the most sex of all); the majority of couples experience sex twice a week to several times a month; 2.8% of men identify themselves as homosexual and 1.4% of women do so, but a higher percentage of people consider a same-gender experience to have some appeal; 75% of men always experience orgasm compared with 28.6% of women, but more nearly equal numbers of men and women declare themselves satisfied with their sexual experiences. The book is, in fact, a

The Social Organization of Sexuality: Sexual Practices in the United States

Maize silage is a significant energy source for animal production operations, and the efficiency of the conversion of forage into animal mass is an important consideration when selecting cultivars for use as feed. Fiber and lignin are negatively correlated with digestibility of feed, so the development of forage with reduced levels of these cell-wall components (CWCs) is desirable. While variability for fiber and lignin is present in maize germplasm, traditional selection has focused on the yield of the ear rather than the forage quality of the whole plant, and little information is available concerning the genetics of fiber and lignin. The objectives of this study were to map quantitative trait loci (QTLs) for fiber and lignin in the maize stalk and compare them with QTLs from other populations. Stalk samples were harvested from 191 recombinant inbred lines (RILs) of B73 (an inbred line with low-to-intermediate levels of CWCs) x De811 (an inbred line with high levels of CWCs) at two locations in 1998 and one in 1999 and assayed for neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL). The QTLs were detected on nine chromosomes, mostly clustered in concordance with the high genetic correlations between NDF and ADF. Adjustment of NDF for ADF and ADF for ADL revealed that most of the variability for CWCs in this population is in ADF. Many of the QTLs detected in this study have also been detected in other populations, and several are linked to candidate genes for cellulose or starch biosynthesis. The genetic information obtained in this study should be useful to breeding efforts aimed at improving the quality of maize silage.

Quantitative trait loci for cell-wall components in recombinant inbred lines of maize (Zea mays L.) I: stalk tissue.

Pleiotropism and the Genetic Variance and Covariance

Multitype Branching Processes.

The genetics of disease resistance in plants has been studied by numerous investigators since Biffen first reported in 1905 that host resistance to plant pathogens was a Mendelian character. Although a considerable literature on the . genetics of disease resistance has accumulated through the years, the work of Flor, Briggs, and his associates is particularly notable in that a concerted effort has been made to explore the genetic structure of a species in terms of disease resistance. In the present paper, the genetic systems uncovered by the work of Flor, Briggs, and his associates will be briefly reviewed and their evolutionary significance will be interpreted from the standpoint of population genetics.

Charles J. Mode

Papers

Pleiotropism and the Genetic Variance and Covariance

Multitype Branching Processes.

A mathematical model for the co‐evolution of obligate parasites and their hosts

A general age-dependent branching process. II

Stochastic Processes in Demography and Their Computer Implementation