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identify physiological races of P. capsici for phytophthora root rot and phytophthora foliar blight syndromes in pepper using a set of different cultivars of Capsicum annuum as host differentials. Phytophthora capsici is a heterothallic species with
Capsicum annuum , a vegetable crop of international importance, has rich genetic diversity for fruit traits. Much of this diversity has been exploited to develop sweet, blocky peppers that are most popular in commercial production and typically
Inheritance of 10 quantitative traits related to plant and fruit development was studied in an intraspecific cross between a bell-type `Maor' [Capsicum annuum L. var. annuum (Grossum Group) `Maor'] and a small-fruited pungent chilli line `Perennial' [C. annuum var. annuum (Longum Group) `Perennial']. Estimates of broad- and narrow-sense heritabilities, coefficients of genetic variance, and genotypic correlations were obtained from the segregation of 120 F3 families in 2 years. Three of the traits analyzed, days to first ripened fruit, plant height, and pedicel length, exhibited heterosis and transgressive segregation. Days to first ripened fruit and total soluble solids had low narrow-sense heritabilities. The other traits studied had moderate to high narrow-sense heritability estimates. Most of the genetic variation associated with traits that affect the size of the fruit and its shape was additive. The highest genetic correlation coefficients among pairs of traits were found between fruit weight and each of the three width characters: fruit diameter, pericarp thickness, and pedicel diameter. In contrast, fruit weight had a low correlation coefficient with fruit length, indicating that the size of the pepper fruit in this cross was determined primarily by its width.
The inheritance of multiple flowers and leaf pubescence resulting from the crosses between accessions from pepper species Capsicum annuum L. and C. chinense Jacq. was examined. Hand cross- and self-pollinations were made in a glass greenhouse. Only eight normal F1 plants were obtained from crosses between the two species when C. annuum L. was the female parent. F2 and backcross generations obtained from the F, and the two parents were grown in the field. Two field studies indicated that multiple flowers and leaf pubescence were controlled by dominant genes. A three-gene model leading to an F2 segregation ratio of 45:9:10 and a two-gene model leading to an F2 segregation ratio of 13:3 were suggested for the inheritance of multiple flowers and leaf pubescence, respectively. Epistasis was evoked in the interpretation of the data. No linkage was found between the two characters. The inconsistencies between F2 and backcross data might be due to selective elimination of genes from one or the other parent in an Interspecific hybridization. Segregation ratios from intraspecific crosses for leaf pubescence supported a two-gene model and gave an F2 ratio of 13 pubescent leaf : 3 glabrous leaf progeny.
Despite extensive breeding efforts, no pepper (Capsicum annuum L. var. annuum) cultivars with universal resistance to phytophthora root rot and foliar blight (Phytophthora capsici Leon) have been commercially released. A reason for this limitation may be that physiological races exist within P. capsici, the causal agent of phytophthora root rot and phytophthora foliar blight. Physiological races are classified by the pathogen's reactions to a set of cultivars (host differential). In this study, 18 varieties of peppers were inoculated with 10 isolates of P. capsici for phytophthora root rot, and four isolates of P. capsici for phytophthora foliar blight. The isolates originated from pepper plants growing in New Mexico, New Jersey, Italy, Korea, and Turkey. For phytophthora root rot, nine of the 10 isolates were identified as different physiological races. The four isolates used in the phytophthora foliar blight study were all determined to be different races. The identification of physiological races within P. capsici has significant implication in breeding for phytophthora root rot and phytophthora foliar blight resistance.
Several inheritance experiments with bentazon herbicide-tolerant Capsicum annuum `Bohemian Chili' (BCH P1) and susceptible `Keystone Resistant Giant' (KRG, P2) and `Sweet Banana' (SB, P2) were conducted. Populations of plants at the three- to five-leaf stage were treated with a bentazon rate of 4.5 kg·ha-1. Tolerance expression was affected by environment and varied across experiments. F2 and BCP2 generations from both susceptible parent crosses fit the expected ratios for a single, dominant gene conferring tolerance. Reciprocal F1s showed a maternal effect on tolerance intensity not consistently observed in reciprocal BCP2s or at all in reciprocal F2s. Segregation ratios of reciprocal crosses, however, were not heterogeneous, based on x2 tests of observed ratios in seven of eight cases. Variable tolerance expression in expected homogeneous populations (P1, P2, and F1) and lower tolerance in BC3 families suggested that modifying factors affected tolerance. Analysis of genetic components of shoot height and fresh weight generation means showed significant digenic epistasis, primarily additive × dominance. Modifying genes that affect the major gene controlling tolerance in BCH are, therefore, present. The simple inheritance of bentazon tolerance, even though modifying factors were present, facilitated transfer of bentazon tolerance into KRG via backcrossing. Chemical name used: 3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide (bentazon).
Abstract
In the paper, Effect of growth regulators on branching, flowering, and fruit development of ornamental pepper (Capsicum annuum L.), by M. Khademi and M. Khosh-Khui (J. Amer. Soc. Hort. Sci. 102(6):796-798. 1977), the description for Figure 1 should read … C1 is control and C2 to C4 represent 300, 600, 900 ppm ethephon, 400, 800, 1200 ppm BA, and 50, 100, 150 ppm IAA, respectively.
Abstract
Concentrations of O2 greater than 21% stimulated germination rate of Capsicum annuum L. (sweet pepper) at 25°C but inhibited germination rate at 15°. At a 10% O2 concentration, germination rates were reduced at both temperatures. Gibberellins A4A7 (GA4+7) increased germination rates at 15° and 25° in air. At 25° in 100% O2, germination rates of GA-treated and nontreated seeds were the same. At 15° and 100% O2, germination rates were increased slightly by GA4+7 application; however, the rates were slower than in air. Total respiratory activity at 25° was higher in 100% O2 than in air. High O2 concentrations did not affect the proportion of respiration which was in the cyanide-sensitive and -resistant pathways. Cyanide-resistant respiration comprised only a small percentage of total respiratory activity. At 15°, total respiration and the cyanide-sensitive and -resistant components were similar regardless of O2 treatment. The addition of GA increased respiratory activity only after radicle emergence occurred. Thus, germination rate of pepper seed can be increased by increasing temperature, higher O2 concentrations at the higher temperature, and GA4+7 at normal and low temperatures. GA appears to affect germination through metabolic events which occur before radicle emergence and which do not include alteration of respiratory activity.
Abstract
Indoleacetic acid (IAA), benzyladenine (BA) and (2-chloroethyl)phosphonic acid (ethephon) were applied to pinched and non-pinched ornamental peppers (Capsicum annuum L. cv. Teno) before, after, or at the time of pinching. Ethephon increased the number of lateral branches, but reduced growth, delayed flowering, reduced the number of flowers per branch thus reducing fruit production. Ethephon applied at 300 ppm 2 weeks post-pinching substituted for hand pinching. BA and IAA had no desirable effect on ornamental characteristics of treated plants.
Two isogenic sets of bell pepper (Capsicum annuum L.) lines (differing at the N root-knot nematode resistance locus) were characterized for resistance to Meloidogyne arenaria (Neal) Chitwood races 1 and 2, M. hapla Chitwood, and M. javanica (Treub) Chitwood in greenhouse and growth chamber tests. The isogenic sets of C. annuum were `Charleston Belle' (NN) and `Keystone Resistant Giant' (nn-recurrent parent), and `Carolina Wonder' (NN) and `Yolo Wonder B' (nn-recurrent parent). Meloidogyne arenaria race 1 is pathogenic to C. annuum. `Charleston Belle' and `Carolina Wonder' exhibited high resistance to M. arenaria race 1. Their respective recurrent backcross parents, `Keystone Resistant Giant' and `Yolo Wonder B', were susceptible to M. arenaria. Meloidogyne arenaria race 2 and M. javanica are not highly pathogenic to pepper. However, `Charleston Belle' and `Carolina Wonder' both exhibited higher (P≤0.05) resistance to M. arenaria race 2 and M. javanica than `Keystone Resistant Giant' and `Yolo Wonder B'. Meloidogyne hapla is pathogenic to pepper. Both `Charleston Belle' and `Carolina Wonder' and their respective recurrent parents, `Keystone Resistant Giant' and `Yolo Wonder B', were susceptible to M. hapla. We concluded that the N gene confers resistance to M. arenaria races 1 and 2, and M. javanica in C. annuum, but the N gene does not condition resistance to M. hapla.