Cagnola Juan I, Parco Martín, Rotili Diego H, Ploschuk Edmundo L, Curin Facundo, Amas Juan I, Luque Sergio F, Maddonni Gustavo A, Otegui María E, Casal Jorge J
Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA), Facultad de Agronomía, Buenos Aires, Argentina.
Universidad de Buenos Aires, Facultad de Agronomía, Cátedra de Fisiología Vegetal, Av. San Martín 4453, C1417DSE Ciudad Autónoma de Buenos Aires, Argentina.
J Exp Bot. 2021 May 4;72(10):3902-3913. doi: 10.1093/jxb/erab119.
Identifying the physiological traits indirectly selected during the search for high-yielding maize hybrids is useful for guiding further improvements. To investigate such traits, in this study we focused on the critical period of kernel formation because kernel number is the main yield component affected by breeding. Our results show that breeding has increased the number of florets per ear and ear growth rate but not the vegetative shoot growth rate, suggesting localised effects around the ear. Consistent with this possibility, breeding has increased the net CO2 exchange of the ear leaf in field-grown crops grown at high population densities. This response is largely accounted for by increased light interception (which increases photosynthesis) and by reduced rates of respiration of the ear leaf in modern hybrids compared to older ones. Modern hybrids show increased ear-leaf area per unit leaf dry matter (specific leaf area), which accounts for the reduced respiratory load per unit leaf area. These observations are consistent with a model where the improved ear leaf CO2 exchange helps the additional florets produced by modern hybrids to survive the critical period of high susceptibility to stress and hence to produce kernels.
识别在高产玉米杂交种选育过程中间接选择的生理特性，有助于指导进一步改良。为了研究这些特性，在本研究中，我们聚焦于籽粒形成的关键时期，因为籽粒数量是受育种影响的主要产量构成因素。我们的结果表明，育种增加了每穗小花数量和穗生长速率，但未提高营养枝的生长速率，这表明在穗周围存在局部效应。与此可能性相符的是，育种提高了高密度种植的田间作物穗叶的净二氧化碳交换量。这种响应很大程度上是由于现代杂交种相比老品种增加了光截获量（从而增加光合作用）以及降低了穗叶的呼吸速率。现代杂交种单位叶干物质的穗叶面积（比叶面积）增加，这解释了单位叶面积呼吸负荷的降低。这些观察结果与一个模型相符，即改良的穗叶二氧化碳交换有助于现代杂交种产生的额外小花在对压力高度敏感的关键时期存活下来，从而形成籽粒。
