Detection of Maternal and Cytoplasmic Effects on Resistance to Zymoseptoria tritici in Durum Wheat

Field Evaluation of Experimental Maize Hybrids for Resistance to the Fall Armyworm (Lepidoptera: Noctuidae) in a Warm Temperate Climate

The polyphagous fall armyworm (FAW), Spodoptera frugiperda, has become an invasive pest worldwide in recent years. To develop maize germplasm with multiple pest resistance and understand genetic inheritance, 12 experimental hybrids (six pairs of reciprocal crosses) with diverse genetic backgrounds and four commercial checks were examined for FAW resistance in 2013 and 2014. The experiment utilized a randomized complete block design with four replications as the block factor. FAW injury on maize plants was assessed at 7 and 14 d after the artificial infestation at the V6 stage, and predatory arthropod taxa and abundance on maize seedlings were recorded 7 d after the infestation. Spodoptera frugiperda resistance varied significantly among the 16 hybrids. Two reciprocal crosses ('FAW1430' × 'Oh43' and 'CML333' × 'NC358') showed the least FAW injury. Eleven arthropod predators [i.e., six coleopterans, three hemipterans, earwigs (dermapterans), and spiders (or arachnids)] were also recorded; the two most common predators were the pink spotted ladybeetle, Coleomegilla maculata, and the insidious flower (or minute pirate) bug, Orius spp. Predator abundance was not correlated to FAW injury but varied greatly between 2013 and 2014. Principal component analysis demonstrated that, when compared with FAW resistant (or Bt-transgenic) checks ('DKC69-71', 'DKC67-88', and 'P31P42'), five pairs of the reciprocal crosses had moderate FAW resistance, whereas a pair of reciprocal crosses ('NC350' × 'NC358' and NC358 × NC350) showed the same FAW susceptibility as the non-Bt susceptible check 'DKC69-72'. Both parents contributed similarly to FAW resistance, or no maternal/cytoplasmic effect was detected in the experimental hybrids.

ZmCCT haplotype H5 improves yield, stalk-rot resistance, and drought tolerance in maize

The ZmCCT locus underlies both stalk-rot resistance and photoperiod sensitivity in maize (Zea mays L.). We previously introduced nine resistant ZmCCT haplotypes into seven elite but susceptible maize inbred lines (containing the haplotype H1) to generate 63 backcross families. Here, we continued backcrossing, followed by selfing, to develop 63 near-isogenic lines (NILs). We evaluated 22 of these NILs for stalk-rot resistance and flowering time under long-day conditions. Lines harboring the haplotype H5 outperformed the others, steadily reducing disease severity, while showing less photoperiod sensitivity. To demonstrate the value of haplotype H5 for maize production, we selected two pairs of NILs, 83B28 ^H1 /83B28 ^H5 and A5302 ^H1 /A5302 ^H5 , and generated F₁ hybrids with the same genetic backgrounds but different ZmCCT alleles: 83B28 ^H1 × A5302 ^H1 , 83B28 ^H1 × A5302 ^H5 , 83B28 ^H5 × A5302 ^H1 , and 83B28 ^H5 × A5302 ^H5 . We performed field trials to investigate yield/yield-related traits, stalk-rot resistance, flowering time, and drought/salt tolerance in these four hybrids. 83B28 ^H5 × A5302 ^H1 performed the best, with significantly improved yield, stalk-rot resistance, and drought tolerance compared to the control (83B28 ^H1 × A5302 ^H1 ). Therefore, the ZmCCT haplotype H5 has great value for breeding maize varieties with high yield potential, stalk-rot resistance, and drought tolerance.