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The bean weevil Acanthoscelides obtectus is one of the world’s main pests of stored beans. The heterogeneous inbred family (HIF) population of near-isogenic lines (NILs) could be an exceptional strategy to study the inheritance of the resistance against A. obtectus. We developed a HIF population of 148 NILs of R-bufa-80-12. The objectives of this research were as follows: (1) to study and understand the genetics of the attack resistance to A. obtectus in a HIF population and (2) to identify the best lines to provide weevil resistance. The pure lines of the HIF population showed a great variability for all the analyzed traits. The traits studied in this research have a normal distribution showing continuous variation, so they are considered to be quantitatively inherited. The heritabilities for resistance traits were low and very low, ranging from 0.09 to 0.17. The heritability for 100 seed weight was the highest, with a significant value of 0.90. The best lines of the HIF population for resistance to A. obtectus comprised Line-45, Line-129, Line-124, Line-142 and Line-47. In general, these lines presented lower preference of adults, and lower consumption in grams and in percentages. However, lines 45 and 129 are the most interesting from a commercial point of view because they combine resistance and seed weight.

Sitophilus zeamais (Motsch.) (Coleoptera: Curculionidae) has a global distribution and is one of the most important post-harvest pests of maize (Zea mays L.). Some Mexican maize races could be a novel source of resistance against S. zeamais to improve commercial maize, generating lines, varieties, and hybrids with resistance to the pest. These are original races from the center of origin of maize and have been exposed to selection pressure from S. zeamais and other pests for thousands of years, which probably resulted in some type of resistance. We studied the resistance of Mexican maize races to S. zeamais focusing on antixenosis, antibiosis, and tolerance. Antibiosis reduces the survival and reproduction of the insect or prolongs the time between generations, whereas antixenosis reduces the rate of initial and successive accumulation of the insect population. Obligate-antibiosis and free-choice bioassays were performed, and in those experiments, resistance traits and the consumption by S. zeamais were measured. The most resistant accession showed high adult mortality and fewer adults in the 1st generation, where the number of emerged adults is an ideal trait to evaluate the level of maize resistance to the pest. Net consumption (in grams) is the most economically important trait because it indicates the gross amount lost in a store, while yield losses (percentage of consumption) allow for studying tolerance. The type of endosperm did have an influence on the resistance/tolerance to S. zeamais. The flint varieties showed significantly higher mortality of adults before entering the seed, a lower quantity of emerged adults of the first generation in the obligate-antibiosis bioassay, and lower net consumption and percentage in both bioassays. In general, the varieties of the races Cristalino de Chihuahua, Apachito, and Azul showed high levels of resistance, with the Cristalino-079 (flint) and Azul (floury) accessions also being tolerant, and low levels of consumption

Sitotroga cerealella (Oliv.) (Lepidoptera: Gelechiidae) is one of the most important post-harvest pests of maize Zea mays L. Some Mexican maize races (Z. mays) could be a novel source of resistance against S. cerealella to improve commercial maize varieties, lines and hybrids. We studied the resistance of Mexican maize races, recollected at Chihuahua State to S. cerealella. We focused on antibiosis and tolerance of maize to S. cerealella. Cristalino-079 maize race shows low level of consumption in grams and percentage, increased larvae mortality before to entering the seed. In addition, Cristalino-079 reduced first adult’s generation and show the largest biological cycle. Due to the small number of emerged adults, there was very little grain weight loss in resistant maize race. The compound that causes high mortality of larvae before to entering the grain is in the pericarp of resistant maize races. The compound that causes longest development time is in the endosperm and embryo. Cristalino-079 show the better level of resistance to S. cerealella infestation in almost all traits studied and this can be used as source of resistance for maize breeding.