RESUMO
Lettuce is an important cool-temperature crop, and its principal abiotic stress is low heat tolerance. Lettuce production has become more challenging in the context of global warming changes. Hence, the main objective of this research was to investigate the relationship between stability and lettuce heat tolerance. Field and greenhouse trials were run in 2015 (summer) and 2016 (fall and spring). The environments were composed of a combination of season and place (field, glass, and plastic greenhouse), and the assessed genotypes were BRS Leila and Mediterrânea, Elisa, Everglades, Simpson, and Vanda. Statistical analysis showed a significant effect (p < 0.05) of environments (E), genotypes (G), and the GEI. BRS Leila, Elisa, and BRS Mediterrânea showed the greatest means to the first anthesis in suitable environments (milder temperatures). Among these cultivars, BRS Mediterrânea was the most stable and adapted to hot environments. The environmental conditions studied in this research, mainly high temperatures, could become a reality in many lettuce-producing areas. Therefore, the results can help indicate and develop lettuce varieties with greater heat tolerance.
RESUMO
Sweetpotato is a staple crop in Brazil presenting a smaller number of pathogens and diseases in comparison with other root and tuberous crops. Root-knot nematodes are among the most serious sweetpotato root pathogens. The impact of these pathogens also extends to succeeding crops. Because in Brazil, it is common to cultivate more than one crop per season, this problem is rapidly disseminated. The aim of this study was to assess the resistance of two sweetpotato clones and four commercial sweetpotato genotypes to three different Meloidogyne species. Assays were performed under greenhouse and field conditions. 'CIP BRS Nuti' and 'Canadense' were resistant to Meloidogyne incognita, M. javanica, and M. enterolobii under greenhouse conditions. This finding was obtained based on the reproduction factor < 0.2, meaning that the initial population of 5,000 nematodes was reduced to <1,000 individuals after 90 days of inoculation. Tomato and sweetpotato cultivar Beauregard, known to be susceptible to the three nematode species, were highly damaged by the pathogens. Similar results were also observed under field conditions. To our knowledge, 'CIP BRS Nuti' and 'Canadense' are the first South American commercial cultivars with triple nematode resistance.