Demographic parameters of cowpea aphids on advanced semi-erect cowpea lines

Abstract

The objective of this work was to evaluate the resistance of advanced semi-erect cowpea (Vigna unguiculata) lines, by means of a screening assay for resistance and the elaboration of fertility-life tables of Aphis craccivora (Hemiptera: Aphididae). The experiments were carried out in a screenhouse. For the resistance trial, 15 advanced cowpea lines were used, as well as two standard genotypes for resistance and two for susceptibility, which were arranged in six blocks. After resistance was determined, two lines with the highest and lowest resistance were selected for the development of the fertility-life tables which were used to estimate demographic parameters. The MNCO4-762F-03 and MNCO4-762F-09 cowpea lines were classified as resistant, for which cowpea aphids showed the lowest values (in parentheses, respectively) for: net reproductive rate (RO = 3.0 and 2.5), intrinsic rate of increase (rm = 0.16 and 0.15), and finite rate of increase (λ = 1.18 and 1.16). The highest values were obtained for the 'Vita-7', MNCO4-795F-168, and 'BRS Tumucumaque' genotypes. The MNCO4-762F-03 and MNCO4-762F-09 lines show antibiosis-type resistance, which directly affects the reproductive potential of the cowpea aphid population.

Preferences and demographic parameters of cowpea aphid on advanced lines of semiprostrate cowpea

“…The genotypes MNCO4-795F-158, MNCO4-768F-21, MNCO4-769F-26, MNCO4-769F-49, MNCO4-769F-31, MNCO4-769F-45, MNCO4-769F-55, MNCO4-768F-16, MNCO4-774F-90, MNCO4-768F-25, 'BR 17-Gurguéia', MNCO4-769F-46, MNCO4-782F-108 and 'Vita 7' were all classified as susceptible to cowpea aphid (Table 2). From these, 'BR 17-Gurguéia' and 'Vita 7' had already been reported as susceptible to cowpea aphid (Moraes & Bleicher, 2007;Silva & Bleicher, 2010;Silva et al, 2018b). Therefore, the number of advanced lines showing susceptibility to cowpea aphid is high, that is, out of the 16 tested genotypes there was a total of 12 lines.…”

“…MNCO4-792F-123 had the smallest sum of rank (Σr) value (Table 3). Thus, among the evaluated lines, MNCO4-792F-123 is the least susceptible line to the pest, using an antibiosis resistance mechanism that reduces female fecundity and increases mortality in the nymph phase (Silva et al, 2018a(Silva et al, , 2018b.…”

“…There are reports on the susceptibility of several cowpea cultivars (released to the market) to cowpea aphid (Melville et al, 2016;Silva et al, 2018a). A study on the resistance to cowpea aphid in fifteen semi-erect cowpea lines, developed for the medium and large farmer, the authors observed that only two genotypes were resistant to the insect (Silva et al, 2018b). If one of these lines was to be launched without a full knowledge of its aphid-resistance capacity, purchasing farmers could end up making costly applications of insecticides, with a consequent reduction of profit and increase of local agrotoxicity.…”