Population Dynamics and Clonal Comparisons of Cowpea Aphid (Homoptera: Aphididae) on Resistant and Susceptible Cowpea Cultivars

Abstract

Survivorship, growth, and reproductive performance of cowpea aphid, Aphis craccivora Koch, were studied on whole plants and excised plant tissues of aphid-resistant ('ICY-12') and aphid-susceptible ('ICY-I') cultivars of cowpea, Vigna unguiculata (L.) Walp. In a greenhouse study, clonal populations derived from individuals that were originally collected from 5 different locations were studied on plants of the 2 cultivars to assess possible development of aphid biotypes. In the laboratory, performance of 1 clone was studied on excised leaves, flowers, and pods to assess tissue localization and effect of injury on ICV-12 resistance. Aphid life table parameters measured included survivorship, reproductive period, intrinsic rate of increase, net rate of reproduction, number of generations and generation time. Aphid reproductive performance and life table parameters were significantly reduced on seedlings and excised tissues of ICY-12 plants compared with ICY-I. Survivorship, intrinsic rate of increase and net rate of reproduction of populations were most adversely affected. Antibiosis appeared to contribute to aphid resistance in ICY-12. Effects of excised ICY-12 foliage were stronger than those of flowers or pods. Thus, the resistant factor in ICY-12 apparently was based in seedling foliage. However, there were no differences among excised tissues of ICY-I. Trends in the results indicated that there was no variability among the different populations in their demographic statistics on each cultivar. Thus, there did not seem to be biotype development or breakdown of ICY-12 resistance in any of the A. craccivora populations.

Life table and population parameters of cowpea aphid, Aphis craccivora Koch (Homoptera: Aphididae) on five cowpea Vigna unguiculata (L. Walp.) varieties

“…This is a promising variety that needs to be evaluated further and can constitute a useful genetic resource for cowpea breeding programs aimed at developing resistant varieties against A. craccivora. Our results like those of Annan et al (1997), Ruggle and Gutierrez (1995), Guldemond et al (1998), Laamari et al (2008) show that studies of life tables and population dynamics are useful tools in characterizing aphid resistance in crop plants. Since environmental factors (such as temperature) significantly influence aphid population dynamics (Diaz and Fereres 2005;Ruggle and Gutierrez 1995), future work will test the interaction between environment and genotypic resistance of cowpea varieties against A. craccivora.…”

“…The adverse effect of IT835-720-20 plants on aphid life history parameters may suggest that antibiosis (Painter 1951) is the modality of resistance against the cowpea aphid. Similar studies using other varieties (Annan et al 1997;Givovich et al 1988;Ofuya 1988) found that antibiosis and antixenosis were mechanisms of resistance to A. craccivora. However, further studies that include examination of biochemical and morphological characteristics of IT835-720-20 that mediate its resistance to cowpea aphids need to be carried out.…”

Interspecific and intraspecific variation in the performance of three pest aphid species on five grain legume hosts

“…Previous comparisons among CPA clones showed no significant variation in host preference between susceptible and resistant cowpea lines (Annan et al, 1997), nor between different host species (Jones, 1967).…”

“…Biotypes of BGA have been described with differing abilities to feed on resistant lucerne cultivars (Mackay & Lamb, 1988). To date, no evidence has been found for host races or feeding biotypes in CPA (Jones, 1967;Annan et al, 1997).…”

Sources of black aphid resistance in the cowpea

“…Even in non-choice trials, such as those performed by Silva and Bleicher (2010), with two of the standards used here, TVu 408 P 2 and VITA 7, the response was found to be influenced by the confined nature of the experimental environment. Therefore, under the current methodology the resistance to adult aphids reported here (Table 2) cannot be attributed to a single mechanism of resistance, antixenosis or antibiosis, since these two mechanisms may be involved simultaneously, but in different proportions (ANNAN et al, 1997;OBOPILE;OSILILE, 2010 ). médias separadas em grupos pelo teste de Scott-Knott a 5% de probabilidade.…”