A glasshouse screening procedure for identifying citrus hybrids which restrict chloride accumulation in shoot tissues

Abstract

Twelve-month-old citrus rootstock hybrids, from crosses made during springs 1980 and 1981, were screened for chloride accumulation in leaves following a short-term salt test under glasshouse conditions. Seedlings were grown in nutrient solution cultures containing 50 mM NaCl for 56 days. Individual hybrids were selected for further evaluation, mainly on the basis of low leaf chloride concentrations but also on visual symptoms of salt damage. The reliability and accuracy of the screening procedure for identifying new hybrids which restrict chloride accumulation in shoots were evaluated in four replicated glasshouse experiments. These were conducted with plants propagated from cuttings taken from selected hybrids. The first of these experiments compared four hybrids selected from two crosses, Rangpur lime x Trifoliate orange and Cleopatra mandarin x Carrizo citrange, with seedlings of parent cultivars. Plants were grown in coarse river sand irrigated with nutrient solution ¦ NaCl (50 mM) over a 56-day period. Two Rangpur lime x Trifoliate orange hybrids and one Cleopatra mandarin x Carrizo citrange hybrid accumulated similar chloride concentrations in shoots as Rangpur lime and Cleopatra mandarin. The other three experiments were conducted using solution cultures as in the original screening experiments (i.e. 50 mM NaCl, 56 days). Within each experiment there was a significant positive correlation between mean leaf chloride concentration of replicated hybrids and those measured for each hybrid in original screening experiments. Although there were a few escapes, results demonstrated that the original screening experiments were for the most part reliable and accurate.